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Heavy metal contamination is a primary concern worldwide and it is discharged from the industrial wastewater to a large amount of heavy metal receiving environments. In recent years, the effective use of agricultural by-products is definitely a major challenge in waste management. The fact that agricultural residues are more easily obtained and cheaper than commercial adsorbents makes it attractive. In this study, removal of zinc from industrial wastewater using natural and thermally modified (biochar) walnut shells as biosorbent was investigated. It was tried to remove zinc in aqueous solutions with different concentrations by using walnut shells at different rates. The effects of initial concentration, contact time, adsorbent dosage. In addition, adsorption isotherms and kinetics were also studied. With the modified form of the walnut shell, up to 98% zinc removal efficiency was obtained. Also, adsorption was observed to be consistent with pseudo-second kinetics and Freundlich isotherm. The results showed that the modified walnut shell in zinc removal was a potential adsorbent. The adsorption of zinc, onto walnut shells was found to fit Freundlich isotherm. The results obtained in the tests with wastewater showed the potential use of walnut shells for the removal of zinc., Ağır metal kirliliği dünya çapında endişe kaynağıdır ve endüstriyel atık sulardan büyük miktarda ağır metal alıcı ortamlara deşarj edilmektedir. Son yıllarda, tarımsal yan ürünlerin etkin kullanımı, atık yönetiminde kesinlikle büyük bir zorluktur. Tarımsal kalıntıların ticari adsorbentlere göre daha kolay elde edilmesi ve daha ucuz olması onları cazip kılmaktadır. Bu çalışmada, biyosorbent olarak doğal ve biyokömür haline getirilmiş ceviz kabukları kullanılarak endüstriyel atık sudan çinkonun giderimi araştırılmıştır. Ceviz kabukları farklı oranlarda kullanılarak farklı konsantrasyonlardaki sulu çözeltilerdeki çinko giderilmeye çalışılmıştır. Başlangıç konsantrasyonunun etkileri, temas süresi, adsorbent dozu araştırılmıştır. Ayrıca adsorpsiyon izotermleri ve kinetiği de incelenmiştir. Ceviz kabuğunun modifiye edilmiş şekli ile %98'e varan çinko giderimi elde edilmiştir. Ayrıca the pseudo-second kinetiği ve Freundlich izotermiyle uyumlu olduğu gözlemlenmiştir. Sonuçlar, çinko gideriminde modifiye edilen ceviz kabuğunun potansiyel bir adsorban olduğunu göstermiştir. Ceviz kabukları üzerine çinko adsorpsiyonunun Freundlich izotermine uyduğu bulunmuştur. Atık su ile yapılan testlerde elde edilen sonuçlar, çinkonun giderilmesi için ceviz kabuklarının potansiyel kullanımının uygun olduğunu göstermiştir.

This work aimed on the adsorption of safranin dye from wastewater using activated groundnut pods (AGP). The raw pods were collected, crushed into particle size of about 400 - 550 μm and modifiedin-situwith ZnCl2to prepare AGP which was characterized using analytical technique; Fourier Transform Infra-Red (FTIR), Energy Dispersive X-ray (EDX) spectroscopy, Thermo gravimetric analyser (TGA) and Scanning Electron Microscopy (SEM). The absorbance of the dye solution was monitored at 530 nm with UV-Visible spectrophotometer. FTIR analysis showed the vibration frequency for C‒H, O‒H, C=O and C‒O stretches at 2900, 3420, 1730, and 1100 cm-1respectively. SEM results revealed the AGP has a porous surface with heterogeneous pores which became compact after dye adsorption. EDX confirmed the presence of C, O, Zn and Cl in the adsorbent. The suitability of the pseudo-first, pseudo second and Elovich kinetic models for the sorption of safranin onto AGP was examined. The equilibrium data were subjected to Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich isotherm models. Adsorption factors were optimized by Box-Behnken design using response surface methodology (RSM). The pseudo-second order kinetic model provided the best correlation and was found to be more statistically significant. Langmuir model was found to fit well based on the high values of the coefficient of regression R2and low % standard error values. The monolayer adsorption capacity Qmaxwas found to be 45.45 mgg-1. Thermodynamic adsorption processes showed the spontaneous, endothermic and randomness of the systems with free energy change less than zero, enthalpy change (∆H) of 66.43 kJmol-1and entropy change (∆S) of 145.37 Jmol-1K-1. Response Surface Methodology (RSM) showed that 0.55 g was the optimum dosage with 92.50 % removal of safranin dye concentration of 200 mgL-1at pH 10.&nbsp

The study focused on fabricating a novel magnetic Fe3O4 loaded and EDTA modified brewed tea waste (TW-Fe3O4-EDTA) as a cheap, environmentally friendly, and efficient adsorbent for the removal of Cr(VI) ions from aqueous medium in a batch system. Characterization of the prepared adsorbent was performed with different techniques. Adsorption experiments were implemented at different conditions including initial solution pH (1.0-7.0), equilibrium time (1-480 min), adsorbent dosage (1.0-20.0 g L-1), and initial Cr(VI) concentration (50-1000 mg L-1). The optimum adsorption performance was observed at pH 2.0 with 120 min of contact time. Maximum adsorption capacity of 114.9 mg g(-1) was acquired for TW-Fe3O4-EDTA which is much higher than the recently developed adsorbents for Cr(VI) removal. Adsorption process was well explicated by Freundlich isotherm model and the adsorption rate is described in accordance with pseudo-second order kinetic model. It was observed that common salts did not have a notable influence on Cr(VI) adsorption. The results of the study indicated that TW-Fe3O4-EDTA can be applied as an effective adsorbent in heavy metal removal as an alternative to many expensive adsorbents available in the literature. Karadeniz Teknik Üniversitesi Bilimsel Araştırma Projeleri Birimi 000889424900002

© 2022 Published by ISRES.Today, various methods are used to remove the dye pollution in the increasing water. Adsorption is a fast and effective method that has been used since the past. The value of the obtained adsorption capacity varies according to the type of biosorbent material used. The seeds of the fruit of Sophora Japonica (SJfs), a tree commonly found in nature, were pyrolyzed at 450°C to produce biochar (SJfsB) in this study. Iron nanoparticles were immobilized into the SJfsB structure to form a more active biosorbent matrix. The obtained SJfsB and nM-SJfsB were used in the removal of methyl blue, an anionic dye. SJfsB and nM-SJfsB used for dye removal were characterized by FT-IR and SEM instruments. The obtained results revealed that the adsorption process occurred in the pseudo-second-order and was consistent with the Langmuir model. The maximum adsorption capacity for MB removal was 434.783 mg/g for nM-SJfsB and 76.923 mg/g for SJfsB, respectively.

Published in Separation Science and Technology. Free download:https://www.tandfonline.com/eprint/53FUC2EGMEBGGK2E6SWU/full?target=10.1080/01496395.2022.2097093

Methylene blue (MB) adsorption was performed on a natural material powder of Cynara scolymus as a new inexpensive adsorbent identified by Cs. To analyze the Cs material, FTIR, SEM, isoelectric point (pHpzc) analysis, TGA, and DRX were used. The maximum experimental adsorption capacity of the Cs material was 203.333, 192.187, and 179.380 mg•g−1 at 298, 303, and 313 K, respectively. The correlation coefficients (R2) and average percentage errors APE (%) values for the kinetic and isotherms models indicated that the adsorption kinetics followed a pseudo-nth order model and that the traditional isotherm model Redlich–Peterson (R–P) correctly described the experimental data obtained at 298, 303, and 313 K, respectively. The steric, energetic, and thermodynamic characteristics of the most relevant advanced model (double-energy single-layer model (AM 2)) were analyzed in detail. The number of active sites for the first receptors (n1) was determined to be 0.129, 0.610, and 6.833, whereas the number of second active sites (n2) was determined to be 1.444, 1.675, and 2.036 at 298, 303, and 313 K, respectively. This indicated the presence of both multi–docking and multimolecular modes for the first style of MB ions (n1), while only a multimolecular mode for the second style of MB ions (n2). Thermodynamic characteristics demonstrated that MB adsorption onto the Cs adsorbent is spontaneous and feasible.

The quest for organic products globally has necessitated the appropriate use of organic wastes that are nutrients-enriching and safe. Hence, this study evaluated the use of four amendments (raw, composted and pyrolyzed oil palm empty fruit bunch as modified forms and NPKMg fertilizer), applied at the rate of 75 kg K ha-1 and their effects on the nitrogen release characteristics in three soil types (Lixisol, Plinthosol and Acrisol). The research was carried out at the Ohosu experimental station of Nigerian Institute for Oil Palm Research (NIFOR), Edo State, Nigeria between November 2018 and December 2019. The field experiment was arranged in a randomized complete block design with three replicates. Oil Palm seedlings of ages 3 and 12 months were planted, soil samples were collected and analyzed for NO3- and NH4+ - nitrogen release monthly. Data collected were subjected to kinetics models (Lagergren pseudo first order, Pseudo second order and Elovich), Analysis of Variance and regression analysis. Treatment means were separated using Least Significant Difference (p≤0.05). Results showed that Acrisol treated with compost had the highest NO3- and NH4+ - N release of 1400 mg/kg. The kinetics of NO3- , NH4+-N -release fitted most to the pseudo second order model for Lixisol and Plinthosol treated with compost, and Lixisol treated with biochar. The kinetics followed pseudo first order model for Acrisol treated with compost. The study observed that treatments and fertilizers had significantly increased the concentration of mineral nitrogen (NH4+ and NO3- nitrogen) in soil due to net mineralization.

The field of soft matter teems with molecules and aggregates of molecules that have internal size-modulating degrees of freedom. Proteins, peptides, microgels, polymers, micelles, and even some colloids can exist in multiple—often just two dominating—states with different effective sizes, where size can refer to the volume or to the cross-sectional area for particles residing on surfaces. The size-dependence of their accessible states renders the behavior of these particles pressure-sensitive. The Bragg–Williams model is among the most simple mean-field methods to translate the presence of inter-particle interactions into an approximate phase diagram. Here, we extend the Bragg–Williams model to account for the presence of particles that are immersed in a solvent and exist in two distinct states, one occupying a smaller and the other one a larger size. The basis of the extension is a lattice–sublattice approximation that we use to host the two size-differing states. Our model includes particle–solvent interactions that act as an effective surface tension between particles and solvent and are ignorant of the state in which the particles reside. We analyze how the energetic preference of the particles for one or the other state affects the phase diagrams. The possibility of a single phase-two phases-single phase sequence of phase transitions as a function of increasing temperature is demonstrated.

The removal of hazardous heavy metals that have been released into the environment due to industrial activities has become an important issue in recent years. The presented study concerned the removal of copper(II) ions from aqueous solutions using dolomites. Dolomite is a very attractive adsorbent due to its wide availability, low cost, good adsorption, and environmental compatibility. The paper describes the properties of D-I and D-II dolomites from two different open-cast mines in Poland. The properties of natural adsorbents were determined based on point of zero charges (PZC), elemental analysis of the adsorbent composition, FT-IR, XRD, and SEM spectra analysis. Depending on the initial concentration of the solution used, the adsorption efficiency of copper(II) ions was 58–80% for D-I and 80–97% for D-II. The adsorption mechanism in the case of D-II dolomite was mainly based on ion exchange, while chemisorption dominated the D-I dolomite surface. Considering the possibility of the regeneration and reuse of the adsorbent, dolomite D-II is a better material (the desorption efficiency of copper(II) ions was 58–80%). The adsorption behavior of dolomites has been described using six adsorption isotherms. The best fit was obtained for the Redlich–Peterson, Jovanović, and Langmuir isotherms, indicating that monolayer adsorption occurred. The maximum adsorption capacity for copper(II) was 378 mg/g of D-I and 308 mg/g of D-II.

A basic urea technique was successfully used to synthesize Mg/Al-Layered double hydroxides (Mg/Al LDHs), which were then calcined at 400 °C to form Mg/Al-Layered double oxides (Mg/Al LDOs). To reconstruct LDHs, Mg/Al LDOs were fabricated with different feeding ratios of Ni by the co-precipitation method. After synthesis, the Ni/Mg/Al-layered double hydroxides (NMA-LDHs) with 20% and 30% Ni (S1 and S2) were roasted at 400 °C and transformed into corresponding Ni/Mg/Al-layered double oxides (NMA-LDOs) (S1a and S2b, respectively). The physiochemical properties of synthesized samples were also evaluated by various characterization techniques, such as X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR), and Brunauer, Emmett, and Teller (BET). The adsorption behavior of methyl orange (MO) onto the synthesized samples was evaluated in batch adsorption mode under varying conditions of contact time, adsorbent quantity, and solution pH. As the dosage amount increased from 0.01–0.04 g, the removal percentage of MO dye also increased from 83% to 90% for S1, 84% to 92% for S1a, 77% to 87% for S2, and 93% to 98% for S2b, respectively. For all of the samples, the adsorption kinetics were well described by the pseudo-second-order kinetic model. The equilibrium adsorption data were well fitted to both Langmuir and Freundlich models for methyl orange (MO). Finally, three adsorption-desorption cycles show that NMA-LDHs and NMA-LDOs have greater adsorption and reusability performance for MO dye, signifying that the design and fabrication strategy can facilitate the application of the natural hydrotalcite material in water remediation.

The toxicity of metal ions on ecosystems has led to increasing amounts of research on their removal from wastewater. This paper presents the efficient application of a carbon magnetic nanocomposite as an adsorbent for the elimination of metal ions (copper, lead and zinc) from aqueous solutions. A Box–Behnken factorial design combined with the response surface methodology was conducted to investigate the effect and interactions of three variables on the pollutant removal process. Highly significant (p < 0.001) polynomial models were developed for each metal ion: the correlation coefficient was 0.99 for Cu(II) and Pb(II), and 0.96 for Zn(II) ion removal. The experimental data were in agreement and close to the theoretical results, which supports the applicability of the method. Working at the natural pH of the solutions, with a quantity of carbon magnetic nanocomposite of 1 g/L and a metal ions’ concentration of 10 mg/L, for 240 min, removal efficiencies greater than 75% were obtained. The kinetic study indicated that a combination of kinetic models pseudo-second order and intraparticle diffusion were applied appropriately for copper, lead and zinc ion adsorption on carbon magnetic nanocomposite. The maximum adsorption capacities determined from the Langmuir isotherm model were 81.36, 83.54 and 57.11 mg/g for copper, lead and zinc ions. The average removal efficiency for five adsorption–desorption cycles was 82.21% for Cu(II), 84.50% for Pb(II) and 72.68% for Zn(II). The high adsorption capacities of metal ions, in a short time, as well as the easy separation of the nanocomposite from the solution, support the applicability of the magnetic carbon nanocomposite for wastewater treatment.

Heavy metal ion pollution poses severe health risks. In this study, a kappa-carrageenan/cellulose (κ-CG/CL) hydrogel was prepared using a facile one-step method to remove Pb2+ ions from aqueous solutions. The functional groups and crystallinity nature of κ-CG/CL hydrogel have been identified via Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). In contrast, the porous morphology and size distribution on the surface of κ-CG/CL hydrogel with a pore size of 1–10 μm were identified using scanning electron microscope (SEM) and Brunauer–Emmett–Teller (BET) surface area analysis. The as-prepared κ-CG/CL hydrogel effectively removed Pb2+ ions, primary environmental pollutants. The effects of pH and contact time on Pb2+ adsorption were studied along with the adsorption isotherms and kinetics of Pb2+ adsorption onto the hydrogels from aqueous solutions. Notably, the aqueous solutions were effectively treated with the prepared κ-CG/CL hydrogels to remove Pb2+ ions. The adsorption results fit well with pseudo-first- and second-order kinetic, Elovich, intra-particle diffusion, and Langmuir and Freundlich isotherm models. Based on the fitting results, the maximum adsorption capacity was obtained with the Freundlich isotherm model of κ-CG/CL hydrogel found to be 486 ± 28.5 mg/g (79%). Reusability studies revealed that the κ-CG/CL hydrogel could remove Pb2+ ions with more than 79% removal efficiency after eight adsorption–desorption cycles. In addition, its mechanism for efficiently adsorbing and removal of Pb2+ ions was analyzed. These findings imply that the κ-CG/CL hydrogel has substantial potential for application in removing and recycling heavy metal ions from aqueous solutions.

In this research, the adsorption of gallium onto natural zeolite (clinoptilolite) and two mesoporous-activated carbons were compared and evaluated. The clinoptilolite was treated with HCl (HCPL), while mesoporous-activated carbons (MCSG60A and MCO1) were synthesized by replica method, using sucrose as the carbon precursor and silica gel as the template. These carbonaceous materials showed large pore sizes and mesoporous surface, as well as a suitable surface chemistry for cation adsorption, which promotes a high negative charge density. On the other hand, zeolites have narrower pore sizes, which hinders the material diffusion inside the particle; however, its strength is their ion exchange capacity. Regarding the gallium kinetic studies, it is described by Pseudo-second order model for both sorts of adsorbents. MCO1 is the best carbonaceous adsorbent studied, with a capacity of 4.58 mg/g. As for zeolites, between the two zeolites studied, HCPL showed the best results, with a gallium adsorption capacity of 3.1 mg/g. The gallium adsorption mechanism onto MCO1 material is based on physisorption, while HCPL is mainly retained due to an ion-exchange process. Regarding the Giles classification, MCO1 isotherm described an H-4 pattern of high affinity and characteristic of multilayer adsorption. The Double-Langmuir model fits properly within these experimental results. In the case of zeolites, HCPL adsorption isotherm followed an L-2 pattern, typical of monolayer adsorption—the Sips model is the one that better describes the adsorption of gallium onto the zeolite.

The removal of pharmaceutical contaminants from wastewater has gained considerable attention in recent years, particularly in the advancements of hydrogel-based adsorbents as a green solution for their ease of use, ease of modification, biodegradability, non-toxicity, environmental friendliness, and cost-effectiveness. This study focuses on the design of an efficient adsorbent hydrogel based on 1% chitosan, 40% polyethylene glycol 4000 (PEG4000), and 4% xanthan gum (referred to as CPX) for the removal of diclofenac sodium (DCF) from water. The interaction between positively charged chitosan and negatively charged xanthan gum and PEG4000 leads to strengthening of the hydrogel structure. The obtained CPX hydrogel, prepared by a green, simple, easy, low-cost, and ecological method, has a higher viscosity due to the three-dimensional polymer network and mechanical stability. The physical, chemical, rheological, and pharmacotechnical parameters of the synthesized hydrogel were determined. Swelling analysis demonstrated that the new synthetized hydrogel is not pH-dependent. The obtained adsorbent hydrogel reached the adsorption capacity (172.41 mg/g) at the highest adsorbent amount (200 mg) after 350 min. In addition, the adsorption kinetics were calculated using a pseudo first-order model and Langmuir and Freundlich isotherm parameters. The results demonstrate that CPX hydrogel can be used as an efficient option to remove DCF as a pharmaceutical contaminant from wastewater.

The wood-water interactions of welded bond-lines of European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.) were in this paper studied for the first time with dynamic vapour sorption equipment. The aim of this study was to characterize the water sorption in the welded bond-line and to define to which extent it deviates from water sorption of the unwelded wood. The objective was to provide deepened knowledge about water sorption of the welded bond-line, which could be used to improve the moisture resistance of welded wood in the future. The welded wood generally had lower equilibrium moisture contents than the unwelded wood. The welded bond-lines of beech and pine showed greater hysteresis than the unwelded wood from 0 to 55 % relative humidity. All specimens showed faster adsorption than desorption. However, the welded wood showed slower adsorption but faster desorption than unwelded wood. The time to complete half of the fractional change in moisture content (E(t) = 0.5) increased as the moisture content increased. The adsorption diffusion coefficients of beech and welded beech were higher than those of pine and welded pine up to 50 % and 40 % RH, respectively. In desorption, pine had a higher diffusion coefficient than beech in the whole range of 85-0 % RH. Analogously, welded pine had a higher diffusion coefficient than welded beech in the range of 85-5 % RH. In contrast to the desorption, the welded wood always had lower adsorption diffusion coefficients than the corresponding unwelded wood. The diffusion coefficients showed irregular patterns in some ranges of the RH. Therefore, it was hard to make a clear conclusion about the water-sorption behaviour of the specimens based on the defined diffusion coefficients., Holzforschung, 77 (7), ISSN:0018-3830, ISSN:1437-434X

One of the solutions to deal with water crisis problems is using agricultural residue capabilities as low-cost and the most abundant adsorbents for the elimination of pollutants from aqueous media. This research assessed the potential of activated carbon obtained from rice husk (RHAC) to eliminate caffeine from aqueous media. For this, the impact of diverse parameters, including initial caffeine concentration (C0), RHAC dosage (Cs), contact time (t), and solution pH, was considered on adsorption capacity. The maximum caffeine uptake capacity of 239.67 mg/g was obtained under the optimum conditions at an RHAC dose of 0.5 g, solution pH of 6, contact time of 120 min, and initial concentration of 80 mg/L. The best fit of adsorption process data on pseudo-first-order kinetics and Freundlich isotherm indicated the presence of heterogeneous and varying pores of the RHAC, multilayer adsorption, and adsorption at local sites without any interaction. Additionally, modeling the adsorption by using statistical and mathematical models, including classification and regression tree (CART), multiple linear regression (MLR), random forest regression (RFR), Bayesian multiple linear regression (BMLR), lasso regression (LR), and ridge regression (RR), revealed the greater impact of C0 and Cs in predicting adsorption capacity. Moreover, the RFR model performs better than other models due to the highest determination coefficient (R2 = 0.9517) and the slightest error (RMSE = 2.28).

International audience; Aim: In the face of ongoing climate warming, we wanted to quantify impacts on vegetation at one of the major climatic and biogeographical boundaries of Europe, the limit between the Mediterranean and Eurosiberian biogeographical regions. We analyse temperature and moisture requirements of plants along altitudinal gradients at regional scale in the period 1980–2020 and we explore if changes coincide with observedchanges in the same regions in terms of measured climatic data.Location: Southern France.Time period: 1980–2020.Taxa: Vascular plants.Methods: We calculated shifts in plants’ temperature and moisture requirements for a large floristic database from south-eastern France (SIMETHIS) during the period 1980–2020 along altitudinal gradients by using ecological indicator values (EIV). Additionally, we analysed standardized weather station data from the same area and period, to investigate whether floristic changes are synchronized with climatechanges.Results: Vegetation data suggest a linear increase in temperature requirements of plant communities from 1980 to 2020 with a greater change at low altitudes. Upward shifts in temperature requirements coincided with observed climate change although warming did not show a general trend towards greater increases at low altitudes. Data on vegetation and climate suggest an upward shift of respectively 150 and 300 m for the boundary between Mediterranean and temperate belts. Moisture requirements of vegetation indicate an increase of the frequency of dry adapted species at low altitudes but an increase towards higher moisture requirements at high altitudes. Comparing vegetation responses with climate data suggests that responses are faster at low altitudes.Main conclusions: Our analyses show that strong general changes in vegetation are underway and highlight faster responses of vegetation to warming in low altitudes compared to high altitudes and demonstrate the need for reliable data on vegetation and climate changes, especially on water balance.

Currently, heavy metal-contaminated groundwater is an environmental concern. This study investigated the use of bamboo biochar, chitosan-impregnated biochar, and iron-impregnated biochar for arsenic, iron, and manganese removal from groundwater. Isotherms of arsenic, iron, and manganese adsorption by bamboo derived biochar were compared with those of commercial activated carbon in simulated groundwater composed of single and trinary heavy metal solutions. The binding of heavy metals by virgin and loaded bamboo biochar and activated carbon was also investigated by sequential extraction. Chitosan and iron-impregnated biochar had enhanced arsenic adsorption, but these sorbents turned the pH of solution acidic, while it was alkaline for activated carbon. Adsorption equilibrium times of arsenic and iron were faster for single than trinary heavy metal systems because less ion competition occurred at active sites. The Langmuir model fitted the adsorption data well. The maximum adsorption capacities of arsenic, iron, and manganese by bamboo biochar in trinary heavy metal system were 2.2568, 0.6393, and 1.3541 mg g−1, respectively. The main mechanism for arsenic removal was precipitation with iron. Bamboo biochar bound iron in organic and sulfide fractions and manganese with iron-oxide. Bamboo biochar can replace activated carbon as a more efficient and sustainable carbonaceous sorbent material for removal of mixed heavy metals from groundwater within acceptable pH ranges.

This study includes the characterization and exploitation of an abundant agricultural waste in Algeria, Alfa (Stipa tenacissima L.) leaf powder (ALP) as a biosorbent for the removal of hazardous triphenylmethane dyes, malachite green (basic green 4) and crystal violet (basic violet 3), from aqueous media under various operating conditions in batch mode. The effect of experimental parameters such as initial dye concentration (10–40 mg/L), contact time (0–300 min), biosorbent dose (2.5–5.5 g/L), initial pH (2–8), temperature (298–328 K), and ionic strength on dye sorption was investigated. The results of both dyes show that the increase in initial concentration, contact time, temperature, and initial pH of solution leads to an increase in biosorbed quantity, unlike the effect of ionic strength. The biosorption kinetics for triphenylmethane dyes on ALP was analyzed by pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models proposed by the Weber–Morris equation. Equilibrium sorption data were analyzed by six isotherms, namely the Langmuir, Freundlich, Harkins–Jura, Flory–Huggins, Elovich, and Kiselev isotherms. The thermodynamic parameters were evaluated for both dyes. The thermodynamic results suggest that both dyes’ biosorption is a typical physical process, spontaneous and endothermic in nature.

This study examines the treatment of bagasse fly ash (BFA), a solid waste generated from boilers in the sugar industry, using acid (HCl, H2SO4 and HNO3) treatment and carbonization under N2 atmosphere. The obtained adsorbents were characterized for their porous properties including BET surface area, total pore volume and average pore size. The treated fly ash with the highest surface area (TFA) was studied in detail for its physicochemical properties and the adsorption of methylene blue (MB) dye from aqueous solutions, and was compared with untreated BFA and a commercial activated carbon (CAC). The physicochemical characterization indicated that BFA and TFA represent adsorbents with low and moderate surface area (26 and 239 m2/g, respectively) with functional groups on their surface, while CAC has a high surface area (1130 m2/g) with weak surface functional groups. For all three adsorbents, the MB adsorption equilibrium was attained within 90 min and the kinetic data were best described by pseudo-second order and intra-particle diffusion kinetic models. The adsorption isotherms followed the Langmuir equation with a maximum MB adsorption capacity of 27.2, 39.0 and 42.1 mg/g for BFA, TFA and CAC, respectively. The comparable adsorption capacities of TFA and CAC suggest that the MB adsorption involves both surface area and surface functional groups on the adsorbents. Thus, this study demonstrates that BFA, a low cost solid waste, can be converted by simple treatment into an effective adsorbent for MB removal from aqueous solution with performance comparable to that of high surface area CAC.

A batch system investigated the application of two types of chemically modified biosorbents derived from spent grated coconut (Cocos nucifera) powder to adsorb methylene blue (MB) from aqueous solutions. The biosorbents were characterised by spectroscopic and quantitative analyses. The assessment of MB adsorption onto the investigated biosorbents was studied at different experimental conditions with different pHs (2–9) and different initial concentrations of MB (10–400 mg/L) at three different temperatures (298, 308, and 318 K). The maximum adsorption capacity (qmax) of xanthated spent grated coconut (XSGC) was higher than that of hexane-washed spent grated coconut (HSGC). The thermodynamic study indicated that the MB adsorption process was spontaneous for both biosorbents. Desorption of MB-loaded biosorbents was carried out using HCl, NaOH, and Na2EDTA solutions. A desorption ratio of more than 90% was obtained over three adsorption/desorption cycles for HSGC. However, XSGC demonstrated poor MB desorption, implying a stronger MB interaction with XSGC, which could be attributed to H-bonding, Yoshida H-bonding, n-π, and π-π bonding. The study showed that HSGC and XSGC could be applied as biosorbents to remove low MB concentrations from aqueous solutions.

It was found that date seeds are suitable for biochar production due to their low moisture content 8.92 %, low ash yield 1.05%, and high organic matter content 78.3%. The biochar was produced by pyrolysis at 350, 450 and 550oC. The effect of pyrolysis temperature on the physicochemical characteristics of biochar was investigated. It was found that the porosity, water holding capacity, ash content, pH, organic matter, fixed carbon, and the elemental content of Na, K, Ca, Mg, Fe, Mn, P, Zn, Ba, Cr, Cu, Ni, Pb, Ti, and V were increased along with pyrolysis temperature. Meanwhile, the biochar yield, bulk density, and the total content of N and S were decreased. The biochar was tested as a sustainable adsorbent to investigate the adsorption of Cd from contaminated water. The adsorption isotherms of Cd on biochar were determined based on Langmuir equation. The maximum adsorption of Cd at 25oC and pH 7 were 667, 714, and 833 mg/Kg for the biochars produced at 350, 450, and 550oC, respectively. On the basis of the physicochemical characteristics of the biochar and the findings from Langmuir equation that showed the biochar produced at 550oC has the highest adsorption capacity for Cd, the desorption/adsorption experiment was carried out using the biochar produced at 550oC. The adsorption of Cd by biochar was directly proportional to the Cd concentrations. It was increased from 0.009 mmol/0.5g at 0.01 mmol Cd to 0.12 mmol/0.5g at 0.2 mmol Cd concentration. The desorption of Cd from biochar was increased proportionally to cadmium concentrations from 0.01 to 0.05 mmol and became constant above 0.05 mmol, regardless of the increment of cadmium concentrations. High retention potential for the cadmium that adsorbed within the biochar was proven in this study with desorption/adsorption percentage of 16%. These findings provide a successful example of date seeds converting into the sustainable adsorbent for Cd removal from aquatic environment to achieve the conception of eco-friendly production, which should be studied further.

Purpose: In this study, the effects of pH, biosorbent dosage, contact time and initial lead concentration on the treatment of lead ion by using pepper seeds were examined. The removal of lead from both synthetic and real wastewater was studied. Various isotherm and kinetic models were used to clearly identify the biosorption process. The performance of this biomass on storage battery industry wastewaters was exhibited. Theory and Methods: Peppers used in this study were purchased from a local market in Dikili, Izmir, Turkey. Seeds were disassociated from the body of pepper and then cleaned down by using tap water, pure and ultra-pure water, respectively before the drying process. Dried seeds were crushed and sifted between the range of 125-250 mu m. The reagent Pb(NO3)2 was used to prepare synthetic wastewater. Storage industry wastewaters containing 2.0 and 4.3 mg/L were used in real wastewaters tests. Experimental studies were conducted in Erlenmeyer flasks of 250 mL using lead-containing solutions (100 mL). Known biosorbent doses were inserted to these flasks including 100 mL of contaminated solution. The final suspensions were mixed at 150 rpm shaking rate and 25 degrees C'in an incubator shaker for different test periods. After proper treatment time, suspensions were centrifuged for 8 minutes at 5000 rpm by using a centrifugal machine. The lead ion concentrations in the solutions separated from the biomass were analyzed with photometer using lead test kits. Results: The optimum pH for this biosorption system was 5.0 at 25 degrees C. The system was reached equilibrium in nearly 90 minutes. The biosorbent amount of 0.6 g/L gave the maximum uptake capacity of this Capia pepper residual. The maximum uptake capacity of biosorbent and the R2 value according to Langmuir model were determined to be 29.67 mg/g and 0.99, respectively. The mostly suitable kinetic model was found to be pseudo-second order kinetic model (0.99). It was shown in the studies that intraparticle diffusion was not the only mechanism limiting the rate in biosorption of lead by capia pepper residual. Storage battery industry wastewater containing very low lead concentrations was treated with an efficiency of 71%. Conclusion: Lead ions were successfully removed from synthetic and storage battery industry wastewaters by capia pepper residuals. As a cost-effective and novel biosorbent, the capia pepper residual carries an important potential for further biosorption tests of lead ions in real wastewaters. Consequently, it has been demonstrated that this residual material can be brought into the economy to be used for treatment purposes.

The manufacturing of fiber-reinforced plastics has been linked to the discharge of volatile organic compounds (VOCs), particularly toluene and benzene, which have been identified as posing substantial risks to human health and the environment. To counteract this issue, activated carbons have been suggested as a means of reducing VOC emissions through adsorption. The objective of this study was to investigate the adsorption characteristics of toluene and benzene onto activated carbons produced from coal (AC) and coconut shells (CAC). The study was carried out in an aqueous medium. The findings revealed that the AC sample with higher surface characteristics exhibited a higher adsorption capacity (toluene: 196.0784 mg g−1 and benzene: 181.8182 mg g−1) in comparison to the CAC sample (toluene: 135.1351 mg g−1 and benzene: 116.2791 mg g−1). The superior adsorption performance of AC on both VOCs can be attributed to its higher surface characteristics. The Langmuir model was found to be more appropriate than the Freundlich model, as indicated by the higher coefficient of determination (R2) value of the Langmuir isotherm (avg. R2 = 0.9669) compared to that of the Freundlich isotherm (avg. R2 = 0.9654), suggesting the use of a monolayer adsorption mechanism. The adsorption kinetics of the samples were analyzed using the pseudo-first-order and pseudo-second-order models, and the former was found to be more fitting, indicating that the rate of adsorption is directly proportional to the concentration difference between the solution and the sample surface. The adsorption process was found to be spontaneous and favorable based on the positive value of ΔG_ads. Furthermore, the adsorption process was endothermic and disordered, as indicated by the positive values of ΔH_ads and ΔS_ads. The regeneration efficiency of all the samples was secured more than 95% upon the fifth cycle.

The presence of dyes and pharmaceuticals in natural waters is a growing concern worldwide. To address this issue, the potential of montmorillonite (MMT), an abundant clay in Colombia, was assessed for the first time for the removal of various dyes (indigo carmine (IC), congo red (CR), methylene blue (MB) and crystal violet (CV)) and pharmaceuticals (levofloxacin and diclofenac) from water. Initially, the MMT was characterized. TGA and FTIR showed OH groups and water adsorbed onto MMT. XRD showed an interlayer spacing of 11.09 Å and a BET surface area of 82.5 m2g−1. SEM/EDS revealed a typical flake surface composed mainly of Si and O. Subsequently, the adsorbent capacity of MMT was evaluated for the removal of the pollutants. Adsorption isotherms showed a fit to the Langmuir model, which was confirmed by the Redlich–Peterson isotherm, indicating a monolayer-type adsorption. Furthermore, adsorption kinetics were best described by the pseudo-second-order model. Adsorption capacity (for dyes CV > MB > CR > IC) was associated with the attractive forces between the contaminants and MMT (PZC 2.6). Moreover, the findings evidenced that MMT can remove MB, CR, CV, and levofloxacin by electrostatic attractions and hydrogen bonding, while for IC and diclofenac only hydrogen bonding takes place. It was shown that MMT was most cost-effective at removing CV. Additionally, the material was able to be reused. Finally, the MMT efficiently removed CV in textile wastewater and levofloxacin in urine due to the positive charge of the pollutants and the low PZC of MMT.

Water quality is under constant threat worldwide due to the discharge of heavy metals into the water from industrial waste. In this report, we introduce a potential candidate, chitosan, extracted and isolated from shrimp shells, that can adsorb heavy metals from polluted water. The waste shrimp shell chitosan was characterized via Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The adsorption capacity of heavy metals on the modified shrimp shell was measured using an inductively coupled plasma mass spectrometry before and after adsorption. The highest adsorption of arsenic, nickel, and cobalt was 98.50, 74.50, and 47.82%, respectively, at neutral pH, whereas the highest adsorption of chromium was 97.40% at pH 3. Correspondingly, the maximum adsorption capacities of MSS for As, Cr, Ni, and Co were observed to be 15.92, 20.37, 7.00, and 6.27 mg/g, respectively. The application of Langmuir and Freundlich isotherm models revealed that the adsorption processes for the heavy metals were statistically significant (r2 > 0.98). The kinetic studies of metal adsorption, using modified shrimp shell, were well explained by the pseudo-second-order kinetic model with linear coefficients (r2) of >0.97. The presence of a greater number of functional groups on the adsorbent, such as N–H coupled with H–O, –COO−, C–H, N–N, and C–O–C, was confirmed by FTIR analyses. Furthermore, SEM-EDX analysis detected the presence of elements on the surface of modified shrimp shell chitosan. This noteworthy adsorption capacity suggests that MSS could serve as a promising, eco-friendly, and low-cost adsorbent for removing toxic heavy metals including Cr, Ni, As, and Co and can be used in many broad-scale applications to clean wastewater.

The study of the adsorption efficiency of new carbon/CNT composites was undertaken to remove a cationic dye, Rhodamine B (RhB), from dye-contaminated wastewater. Indeed, we investigated the effect of different experimental parameters such as time, initial concentration of dye and temperature on the adsorption of RhB by the carbon composites (KS44-0 and KS44-20). The results showed that the adsorption uptake increased with the initial concentration and solution temperature while maintaining a relatively constant pH. The presence of the carbon nanotubes provided more active sites for dye removal and improved the adsorption behavior of Rhodamine B dye. The analysis of the experimental data was conducted using model equations, such as Langmuir, Freundlich and Temkin isotherms. As regards the Freundlich isotherm model, it was the best fit for the equilibrium data obtained from the experiments. The applicability of the pseudo-second-order equation could be explained assuming that the overall adsorption rate is limited by the rate of adsorbate transport that occurs on the pore surfaces of adsorbents. Furthermore, the intraparticle diffusion and Bangham models were used to investigate the diffusion mechanism of RhB absorption onto carbon composites. They showed that multiple adsorption stages occurred simultaneously via pore surface diffusion. Concerning the thermodynamic parameters (∆G°, ∆H°, and ∆S°), they were calculated and explained in the mean of the chemical structure of the adsorbate. Negative standard Gibbs free energy change values (ΔG°ads) at all temperatures suggested that the adsorption process was spontaneous, and the positive values of the standard enthalpy change of adsorption (∆H°ads) revealed the reaction to be endothermic. The values of standard enthalpy (ΔH°ads) and activation energy (Ea) indicated that the adsorption process corresponds to physical sorption. The mechanisms for the removal of Rhodamine B dye from wastewater using carbon composite were predicted. RhB is a planar molecule that is readily adsorbed, in which adsorbed molecules are bound by hydrophobic or other weak interactions due to the π-π interactions between the dyes’ aromatic backbones and the hexagonal skeleton of graphite and carbon nanotubes. Thus, the graphite carbon/carbon nanotube composite is believed to play a major role in organic pollutant reduction.

In the present research, zeolite is used for the removal of toxic Congo red dye from water solution. The effects of different operating conditions such as hydrogen potential (pH), contact time (time), zeolite dose (D), initial dye concentration (C0), and ionic strength (I) are investigated for Congo red adsorption under batch mode. It was found that the adsorption process was greatly affected by the initial pH of the dye solution. The removal efficiency decreased from 97.68 to 5.22% when the pH varied from 3 to 5; thus, acidic conditions clearly improve Congo red adsorption on zeolite. At pH 3, an increase in C0 and I and decrease in D resulted in an increase in the adsorption capacity qe. The effects of these three parameters and their interactions were also investigated using the 23 full factorial design experiments approach where qe was chosen as the response. The results obtained from this method followed by the analysis of variance and the Student’s t-test show that, the influence of these parameters on dye adsorption process are in the order I < C0 < D. The kinetic studies revealed that adsorption follows a pseudo-second-order kinetic model. The adsorption isotherms experimental data were analyzed using the Langmuir, Freundlich, and Temkin isotherms models. The Freundlich isotherm was the best-fit model to the experimental data. The fitting of kinetics and isotherm models was evaluated by using non-linear modeling, R2, MSE, and RMSE.

Mason pine-derived hydrochar (MPHC), cedarwood-derived hydrochar (CHC), bamboo-derived hydrochar (BHC), coconut shell-derived hydrochar (CSHC), pecan shell-derived hydrochar (PSHC), wheat straw-derived hydrochar (WSHC), maize straw-derived hydrochar (MSHC), and rice straw-derived hydrochar (RSHC) were synthesized by hydrothermal carbonization (HTC). The physicochemical properties of these hydrochars were characterized by various techniques, and the adsorption behavior of methylene blue (MB) on hydrochars from an aqueous solution was also investigated. The characterization results suggested that the hydrochars possessed various oxygen-containing functional groups (e.g., ether and hydroxyl groups, etc.). Thermodynamic parameters demonstrated that adsorption was spontaneous for all produced hydrochars. The adsorption was endothermic for CHC, BHC, CSHC, PSHC, WSHC, MSHC, RSHC, and exothermic for MPHC. The Langmuir model best described the adsorption process. MB adsorption capacity is ranked as MPHC > PSHC > CSHC > CHC > MSHC> WSHC > RSHC > BHC. The saturated adsorption value for MB on these hydrochars at 15 degrees C was 155.14, 109.24, 93.15, 91.71, 88.11, 86.36, 70.01, and 64.43 mg/g, respectively; the difference in adsorption value indicates that the type of biomass affects MB adsorption. This high adsorption capacity for MB suggests that the produced hydrochars could be utilized as a promising new adsorbent in wastewater treatment.

In this study, Box-Behnken design (BBD) in response surface methodology (RSM) was employed to optimize As(V) removal from an aqueous solution onto synthesized crosslinked carboxymethylchitosan-epichlorohydrin/Fe3O4 nanaocomposite. The factors like solution pH, adsorbent dose, contact time and temperature were optimized by the method which shows high correlation coefficient (R2 = 0.9406), and a predictive quadratic polynomial model equation. The adequacy of the model and parameters were evaluated by analysis of variance (ANOVA) with their significant factors of Fischer’s F-test (p < 0.05). Seven significant parameters with interaction effects in the experiment with p-value < 0.0001 was observed, having a maximum removal efficiency of As(V) is 95.1%. Optimal conditions of dosage, pH, temperature, initial ion concentration and contact time in the process were found to be 0.7 g, pH 6.5, 308K, 10 mg/L and 60 min respectively. Langmuir isotherm model fitted better than the Freundlich model having a maximum adsorption capacity of 28.99 mg/g, a high regression value of 0.9988, least chi-square value of 0.1781. The process was found to follow monolayer adsorption and pseudo-second-order kinetics. Thermodynamic parameters indicate the process is spontaneous, endothermic and physisorption in nature. Successful regeneration of the adsorbent implies its applicability to the removal of arsenic from real life wastewater.

Introduction: Toluene is considered as a group of chemical contaminants, causing problems for people’s health. Due to the high rate of evaporation and rapid emission in the surrounding environment, it leads to the exposure of many employees and people at risk and, subsequently, its irreparable effects on their health in different jobs. Therefore, its removal is very important. In the present study, this contaminant was removed using the copper metal-organic framework (MOF) under different operating conditions. Material and Methods: In this study, the copper MOF was synthesized using the one-pot and in situ method. Physical and morphological properties of the adsorbent were investigated using BET, XRD, FTIR and SEM techniques. The efficiency of the adsorbent in removing toluene from the air stream under the dynamic adsorption system was investigated by examining the effect of the variables of adsorbent mass, pollutant concentration and humidity. Isotherm, thermodynamics and kinetics equations were used to evaluate the data. Results: The results of experiments determining the properties of the metal-organic framework showed the formation of pure Cu-BDC crystals with mean and particle size distribution of 1.95 nm. The specific surface area calculated by the BET method for the mentioned sample was 686 m2 g-1 and the total volume of structural pores was 0.335 g3 cm3. The presence of micropores increased the dynamic adsorption capacity of toluene. The findings follow the Langmuir isotherm model and the Pseudo-second order kinetic model. Based on the results of thermodynamic studies, entropy change (ΔS°) and enthalpy change (ΔH°) were equal to -0.44 kJ mol-1 K-1 and -15.67 kJ mol-1, respectively. Gibbs free energy change (ΔG°) was also calculated negatively, indicating that the adsorption process was spontaneous and exothermic. The regeneration of the adsorbent was 77% after three cycles. Conclusion: According to the results of this study, the microporous copper MOF can be used as a result of cheapness, high access, high adsorption capacity and appropriate regeneration rate in different operating conditions for adsorption of toluene.

In this study, magnetic Mg/Fe hydrotalcite calcined material (M-CHT) was synthesized through the co-precipitation and calcination method, and was used to effectively remove nitrate and nitrite from water. M-CHT can restore its original layered structure after the adsorption of nitrate or nitrite, and can be easily separated by an applied magnetic field. The first-order and pseudo-second-order kinetic models (R2 ≥ 0.97) can better describe the adsorption kinetic process. The equilibrium isotherm showed that the Langmuir model provided a better fit to the experimental data than the Freundlich model for nitrates and nitrites. With temperature increased from 298 to 308 K, the maximum adsorption capacity obtained by the Langmuir model increased from 10.60 to 16.90 mg-N/g for nitrate and 7.89 to 14.28 mg-N/g for nitrite, respectively. The adverse effect of coexisting anions ranked in the order of ClO4− > Cl− > SO42− > F− > CO32− > PO43−. The actual Fe2+/Fe3+ value of M-CHT (0.56) is nearly consistent with the theoretical value of 0.5, and the saturation magnetic strength value of M-CHT is 9.15 emu/g, greatly contributing to the solid–liquid separation. Overall, M-CHT with features of magnetic properties and satisfactory adsorption capacity exhibits great promise for application in wastewater purification. HIGHLIGHTS Magnetic Mg/Fe hydrotalcite was synthesized by the co-precipitation method.; Magnetic Mg/Fe hydrotalcite subjected to calcination at 500 °C (M-CHT) recovered its original double layer after the adsorption of nitrate and nitrite.; The adsorption capacity was 16.90 mg-N/g for nitrate and 14.28 mg-N/g for nitrite at 35 °C.

Diazepam has been detected in water sources around the world affecting the quality of drinking water. Even in small quantities, recent studies have proven the negative effects of the drug on human body. Since traditional water and sewage treatment do not remove this type of contaminant, it became interesting to evaluate forms to remove them from water sources. A cheap and eco-friendly alternative to remove this drug from the water is through adsorption using the natural clinoptilolite zeolite as an adsorbent. This work goal was to study the characterizations of clinoptilolite, such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometer (XRD), and Fourier transform infrared spectroscopy (FTIR) and analyze the potential of this material as an adsorbent. Kinetic studies and isotherm analysis were performed in batch. The results showed the potential of the natural zeolite to remove the pollutant in an aqueous medium reaching a maximum adsorption capacity of 8.25 mg g−1. The adsorption process followed a pseudo-second-order kinetics indicating that the adsorption was based on a chemisorption process. The isotherms curves shown favorable adsorption and the Langmuir isotherm model fit the experimental data better. Supplementary Information The online version contains supplementary material available at 10.1007/s11356-021-17452-z.

In this work, natural and thermally modified Chocolate B clays were used for batch adsorption of Pb2+ and Zn2+ from an aqueous solution. The materials were characterized by X-ray diffraction, X-ray fluorescence spectroscopy, nitrogen adsorption, and cation exchange capacity. The tests were performed in a finite bath following a 22 factorial design, with the variables: pH and initial concentrations of metal. Results revealed that the thermal treatment caused alterations on the Chocolate B clay structure and decreased the specific surface area. Affinities between Pb2+ or Zn2+ and Chocolate B clay were found with adsorption capacities up to 3.36 and 3.72 mg.g-1, respectively. The maximum adsorption capacities were 6.79 mg.g-1 for Pb2+ and 3.35 mg.g-1 for Zn2+ using thermally activated clay. The Langmuir and Freundlich models were used for the adsorption equilibrium analysis, and the Langmuir model provided the best fit for sorption isotherms. The adsorption kinetics was evaluated by two models: pseudo-first-order and pseudo-second-order. The pseudo-first-order kinetic model represented well the mechanism of interaction involved during Pb2+ adsorption into the pores of the clay. However, the two models represented well the mechanism of interaction of Zn2+ adsorption into the pores of the clay.

A novel arginine-modified Heliotrope leaf (Arg@HL) was used as adsorbent for the crystal violet (CV) dye adsorption in a batch process. The physicochemical and morphological composition of Arg@HL were characterized by field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The experiments were carried out to investigate the factors that influence the dye uptake by the adsorbent, such as the contact time under agitation, adsorbent amount, initial dye concentration, temperature and pH of dye solution. The optimum conditions of adsorption were found on the batch scale as followed: CV concentration of 20 mg·L−1, an amount of 0.75 g·L−1 of the adsorbent, 90 min contact time, 6 pH and 25 °C temperature for Arg@HL. The results confirmed a second-order model explaining the dye crystal violet's adsorption's kinetics by Arg-Heliotrope leaves. The Langmuir model effectively defines the adsorption isotherms. The results revealed that the Arg@HL has the potential to be used as a low-cost adsorbent for the removal of CV dye from aqueous solutions. HIGHLIGHTS The first effort to use a low-cost arginine-modified Heliotrope leaves material as an adsorbent for crystal dye elimination by adsorption procedures.; CV dye was efficiently removed using Arg@HL.; Arg@HL exhibited high adsorption capacity for CV dye.; Adsorption process follows the Langmuir isotherm.

The current study focused on utilizing cobalt oxide to eliminate hazardous Eriochrome Black T (EBT) dye. The impact of pH (2, 4, 7, 8, and 10) and temperature (45, 50, and 55 °C) was examined for EBT removal. The results show that the maximum sorption occurred at pH = 2 and that the removal percentage increased with increasing temperature. Five non-linear regression methods were used to predict the best isotherm and kinetic models. A coefficient of non-determination, K2, was very helpful for selecting the RMSD function as a preferable error function among the five methods. Isothermal models to illustrate equilibrium sorption information, the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models were used. The results showed that the Langmuir model (R2 = 0.99) was the most favorable, indicating monolayer sorption of EBT occurred. The kinetics models were analyzed using pseudo-first-order and pseudo-second-order whereas the sorption information was well described by the pseudo-second-order model (R2 = 0.99). The results of the thermodynamic study appeared that the adsorption of EBT was endothermic, feasible, spontaneous, and physical adsorption.

With increasing walnut production in California, walnuts are stored for longer times. It is increasingly important to optimize storage conditions, wherever possible, to reduce quality degradation. We examined the effects of temperature (5, 15, and 25 °C) and relative humidity (20%, 40%, and 60% in year 1 and 40%, 60%, and 80% in year 2) on the rate of quality degradation of four walnut varieties. The relationship between water activity and moisture content was investigated for each variety. In addition, the effects of harvest timing (early vs. late) and storage as shelled or in-shell product were investigated. Later harvested walnuts had darker kernel color (P < 0.001), and walnuts stored as kernels (shelled) had higher rates of peroxide formation and free fatty acid development than walnuts stored in-shell. Temperature had a significant effect on quality with faster degradation at higher temperatures. There was a significant interaction between temperature and relative humidity effects on quality. The effects of relative humidity were often not significant at storage temperatures of 5 °C but were apparent at 15 °C and at 25 °C. Managing relative humidity during walnut storage is difficult under typical commercial storage conditions; however, when low temperature storage is used, quality is preserved even when relative humidity is not controlled, although storage at 80% relative humidity should be avoided. To reduce the rate of color darkening and rancidity development during commercial storage, operators should emphasize storage at lower temperatures, at least below 15 °C.

In this study, it was aimed to remove malachite green, a cationic dye, from aqueous solutions by the adsorption method under various experimental conditions by using red clay. Red clay was used because it is abundant in nature and easily accessible in our region. In addition, it has been preferred as an adsorbent because it is used economically without any pre-treatment. The effects of initial malachite green concentration, temperature, adsorbent amount, and contact time on the adsorption process were evaluated. To examine the percent dye removal effect of the initial malachite green concentration, five different amounts of 25-150 ppm were examined. In order to examine the effect of the amount of red clay on the percentage of dye removal, five different amounts, in the range of 0.5-2 grams, were examined. In order to find the optimum time for the adsorption process, studies were carried out at four different values, 30-120 minutes. In the adsorption process of red clay and malachite green, experiments were carried out at three different degrees as 298, 313 and 333 K. After reaching equilibrium in the adsorption process, the data obtained were analyzed and studies were carried out by applying them to isotherm models. The results obtained from the adsorption process were compared with Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. It has been determined that the experimental studies are more compatible with the Dubinin-Radushkevich model. According to the results, it is incompatible with the Langmuir model. Accordingly, it can be said that the adsorption takes place in a multilayer and heterogeneous form.

The detrimental consequences of excessive levels of heavy metal contamination on living things served as the motivation for this study. Adsorption of Pb(II) ions was investigated on synthetic magnetite (MG), baobab fruit shell (BB) and magnetite-baobab composite (MB). The batch equilibrium technique was used to investigate the adsorption of Pb(II) ions. The effects of initial metal concentrations (15-500 mg/L), adsorbent dose (0.05-0.3 g), contact time (5-150 min), pH (2-8) and temperature (303-343 K) on the adsorption capacity of the adsorbent were studied. Langmuir, Freundlich and Temkin isotherms were used to describe the adsorption of Pb(II) ions. The maximum adsorption capacity, qmax, of MB, MG and BB was 249.86, 227.45 and 34.67 mg/g respectively at a concentration of 500 mg/L of Pb(II) ions. Freundlich model was shown to have the best fit for the adsorption data in the following order: BB > MG > MB, with R2 values of 0.9954, 0.980 and 0.9797 respectively. Freundlich adsorption intensity for MG, BB and MB are 1.590, 1.339 and 1.761 respectively. The kinetic and thermodynamic investigations revealed that the adsorption followed pseudo-second-order kinetics and endothermic process. The amount of Pb(II) ions adsorbed after each stage of the desorption process varied between the different acid concentrations, according to sorption-desorption studies using spent adsorbents. The highest stepwise adsorptions of Pb(II) ions were observed when 0.5 M HCl was utilized as a stripping agent for BB while 0.1 M HCl favoured MG and MB.

Methylene blue (MB) immobilized onto a sulfonated poly(glycidyl methacrylate) (SPGMA) polymer composite has been developed as a novel adsorbent for water treatment applications. The MB adsorptions onto sulfonated poly(glycidyl methacrylate) polymer characters have been studied. The adsorption isotherms, namely Langmuir and Freundlich, have been investigated. Other isotherm models. As a compromise between the Freundlich and Langmuir isotherm models, such as the D–R isotherm and the Temkin isotherm, have been compared. The results indicated that the adsorption process followed the Freundlich isotherm model, indicating heterogeneous surface site energies and multi-layer levels of sorption. This study selected three linear kinetic models, namely pseudo-first order, pseudo-second order, and Elovich, to describe the MB sorption process using SPGMA negatively charged nanoparticles (430 nm). The obtained data revealed that the adsorption process obeyed the pseudo-second-order kinetic model, suggesting that the rate-limiting step in these sorption processes may be chemisorption. Furthermore, the thermodynamic parameters have been evaluated. Moreover, the interaction of the MB molecules with SPGMA nanoparticles has been simulated using the governing equation that describes ion exchange resin derived from Nernst—Plank equations between two ion species. Finally, the developed MB-SPGMA composite adsorbent (27 mg/g) wastested for the first time for the removal of Cr6+ ions and Mn7+ metal ions from dichromate and permanganate-contaminated waters under mild adsorption conditions, opening a new field of multiuse of the same adsorbent in the removal of more than one contaminant.

Emerging dye pollution from textile industrial effluents is becoming more challenging for researchers worldwide. The contamination of water by dye effluents affects the living organisms in an ecosystem. Methylene blue (MB) and malachite green (MG) are soluble dyes with a high colour intensity even at low concentration and are hazardous to living organisms. The adsorption method is used in most wastewater plants for the removal of organic pollutants as it is cost-effective, has a high adsorption capacity, and good mechanical stabilities. In this study, a composite adsorbent was prepared by impregnating iron modified silica (FMS) onto polyurethane (PU) foam to produce an iron modified silica/polyurethane (FMS/PU) composite. The composite adsorbent was utilised in batch adsorption of the cationic dyes MB and MG. The effect of adsorption parameters such as the adsorbent load, pH, initial dye concentration, and contact time were discussed. Adsorption kinetics and isotherm were implemented to understand the adsorption mechanism for both dyes. It was found that the adsorption of MB and MG followed the pseudo-second order model. The Langmuir model showed a better fit than the Freundlich model for the adsorption of MB and MG, indicating that the adsorption occurred via the monolayer adsorption system. The maximum adsorption capacity of the FMS/PU obtained for MB was 31.7 mg/g, while for MG, it was 34.3 mg/g. The thermodynamic study revealed that the adsorption of MB and MG were exothermic and spontaneous at room temperature. In addition, the regeneration of FMS/PU was conducted to investigate the composite efficiency in adsorbing dyes for several cycles. The results showed that the FMS/PU composite could be regenerated up to four times when the regeneration efficiency dropped drastically to less than 20.0%. The impregnation of FMS onto PU foam also minimised the adsorbent loss into the environment.

This study aims to investigate the application of two calix[4]arene derivatives named 5,11,17,23-tetra-(t-butyl)-25,26,27,28-tetrahydroxycalix[4]arene (TBCA) and 5,11,17,23-tetra-(t-butyl)-26,27,28-tribenzoyloxycalix[4]arene (TBMTCA) as adsorbents of Pb(II) from aqueous solution in a batch system. Adsorption was carried out by varying pH solution, exposure time, and concentration. The kinetics was evaluated based on the adsorption in various exposure times using the Lagergren and Ho equations, while the isotherms were analyzed based on the adsorption in various Pb(II) concentrations using the Langmuir and Freundlich equations. Furthermore, the isotherm model showed the Pb(II) adsorption of TBCA and TBMTCA followed Langmuir model with a capacity of 137.29 and 128.46 mg/g, respectively. Based on the adsorption capacity, both adsorbents are the potential for the removal of heavy metal cations from polluted water.

The reuse and separation of nanomaterials from an aquatic solution is always challenging and may cause nanotoxicity if not separated completely. Nanomaterial immobilization on the surface of a macro-size material could be an effective approach to developing an efficient composite for groundwater purification. Herein, polyaniline and graphene oxide nanosheet immobilized granular tea waste (PANI/GO@GTW) has been synthesized to remove the anionic and cationic contaminants from groundwater. The synthesized materials were characterized by SEM, XRD, XPS, and FTIR spectroscopies. The optimization of experimental conditions was tested for bromide (Br−) removal from synthetic water. The results revealed that Br− adsorption behavior onto the synthesized materials was as follows: PANI/GO < PANI/GTW < PANI < PANI/GO@GTW. The optimum removal of Br− ions was observed at pH 3 with 90 min of saturation time. Br− adsorption onto PANI/GO@GTW followed the pseudo-first-order kinetic and Langmuir isotherm model, and electrostatic interaction was involved in the adsorption process. The optimum adsorption of Br− onto PANI/GO@GTW was found to be 26.80 m/g. The application of PANI/GO@GTW on real groundwater treatment demonstrated the effective removal of anion pollutants such as F−, Cl−, Br−, NO3−, and PO43−. This study revealed that PANI/GO@GTW successfully reduced Br− concentrations in synthetic and real groundwater and can be used for large-scale applications.

This study focuses on developing a novel foam material with ionic functional groups using the most abundant natural resource, cellulose, for the removal of heavy metals. Ionic functionalities were introduced to cellulose-based foam for increased affinity towards heavy metals. Based on the type of cellulose polymer used in the synthesis, four different cellulose based foam material batches were obtained, these are, activated cellulose, cellulose acetate, carboxymethyl cellulose, and acetylated carboxymethyl cellulose based foam materials. Heavy metal removal capacity of each foam material was tested using cobalt as the model heavy metal. At pH of 6.5, foam dose of 10 g/L, and initial Co2+ concentration of 100 mg/L, heavy metal removal capacities of the foam samples varied between 2% to 36 %, while foam material produced by cellulose acetate revealed the highest removal efficiency, 36%. Co2+ removal efficiency of cellulose acetate based foam increased to 50% when 15 g/L of foam sample was used under otherwise the same experimental conditions. Adsorption behavior of the cellulose acetate based foam material was also studied, which suggested Sips isotherm model as the most suitable adsorption mechanism.

This research focused on the removal of Fe(III) ions from an aqueous solution of wastewater through an adsorption process using biosorbents of natural palmyra palm fruit fibres (N–PPF) and chemically modified palmyra palm fruit fibres (C–PPF). BET was used to determine the pore volume and pore size of the biosorbents; the C–PPF was more than N–PPF at 0.01069 cm3/g and 450.2094 Å, respectively. The initial concentration of Fe(III), the adsorbent dosage, solution pH, and contact time for optimal adsorption were investigated for adsorption, and it was found that the dosage of the adsorbent was 2.0 g, pH 4, and 300 min for adsorbent dosage, solution pH, and contact time, respectively. The adsorption data were consistent with the three models, though the Freundlich model provided the best fit. The characteristics for both before/after adsorption were examined by FT–IR, which showed that hydroxyl groups were involved in adsorption. SEM–EDX analysis confirmed the successful increase of containing functional groups during adsorption. Adsorption proceeded according to a pseudo–first–order kinetic model for N–PPF, while the adsorption of C-PPF was according to both kinetic models. It was revealed that Fe(III) adsorption is an exothermic process that occurs on the surface of heterogeneous adsorbents and physisorption. The intra-particle diffusion model is appropriate to explain the rate-controlling step in the Fe(III) adsorption process of natural fibres.

The development of the industry has resulted in a proportional increase in waste materials. Waste industrial products play a major role in the pollution of nature along with seas, lakes, and various water resources around the world. Organic dyes, which do not degrade in nature and have carcinogenic effects, are important industrial wastes. The improvement of wastewater is a research topic that has gained importance in recent years. In this study, the biosorption of Congo red dye from aqueous solution with dried mint leaves was investigated. The experiments were carried out at 20 °C and the natural pH of the dye. The process was optimized by examining the parameters of initial dye concentration, amount of biosorbent and contact time. It was determined that the biosorption equilibrium conformed to the Langmuir isotherm (R2=0.9815) and the maximum biosorption capacity (qmax) was 60.24 mg/g. In addition, the process conforms to the pseudo-second-order (R2=0.9946) kinetic model. As a result of the process, the removal of the Congo red dye from the dried mint leaves from the aqueous solution was achieved at a level of approximately 70%.

The paper investigates the physicochemical regularities (kinetics and isotherm) of phosphorus and beryllium recovery by sorbents based on polyacrylonitrile (PAN) fiber and Fe(OH)3 obtained by various methods: PAN or pre-hydrolyzed PAN with precipitation of FeCl3 with ammonia, using ready-made or electrochemically generated Na2FeO4, pre-hydrolyzed PAN treated with an alkaline solution of Na2FeO4, as well as their comparison with granular aluminum oxide. The Langmuir, Freudlich and Dubinin–Radushkevich models show high performance of materials for sorption of stable P and Be used as tracers for the release of 7Be, 32P, and 33P from seawater. The obtained kinetic data are processed using kinetic models of intraparticle diffusion and the pseudo-first-order, pseudo-second-order, and Elovich models. Optimal conditions for obtaining sorbents are established, namely, the effect of NaOH concentration at the stages of preparation on the properties of sorbents based on the PAN fiber and Fe(OH)3 obtained by various methods.

In this work, pseudo-stem banana (Musa acuminata) (PBF) fiber was utilized as a potential low-cost natural adsorbent to uptake methylene blue (MB) dye from synthetic wastewater by batch adsorption process. Different adsorption factors like contact time, pH, initial concentration, and adsorbent dosage were explored and found that the separation process is strongly pH dependent. Additionally, the adsorption data were fitted with various adsorption isotherms like Langmuir, Freundlich, Temkin, and Dubinin–Radhushkevich models to detect the adsorption equilibrium phenomena. Reaction kinetics was inspected using pseudo-first-order and second-order kinetic models. Mass transfer and intra-particle diffusion analyses indicate the adsorption mechanism of the system described particularly in the context. Furthermore, scanning electron spectroscopy (SEM) and Fourier transformed infrared spectroscopy (FTIR) were conducted to get the morphology and surface properties of the adsorbent, respectively. As a result, the as-prepared banana fiber can be proposed as a cheap suitable adsorbent to separate dyestuffs from industrial wastewater.

This study investigated the adsorption capacity of the elements Chromium (Cr), Manganese (Mn) and Zinc (Zn) to marine algae Lithothamnium calcareum by means of adsorption kinetics and batch adsorption tests, with a view to the development of a simple technique for the treatment of effluents that have a high concentration of metal ions. The algae was sieved, washed and subjected to treatment. In the adsorption kinetics, 0.2 g of algae was weighed, an amount transferred to 125 mL Erlenmeyer flasks, to which was added 15 mL of solution with a concentration of 5 mg L-1 of the metal ion. The flasks were stirred at 60 rpm for 240 minutes. In batch adsorption, 0.2 g of algae was weighed, amount transferred to 125 mL Erlenmeyer flasks, to which was added 15 mL of solution with concentrations of 5, 10, 20, 50, 100, 250 e 500 mg L-1 of the metal ion. The flasks were stirred at 60 rpm for 24 hours. In the two tests, the supernatant solutions collected were centrifuged at 2000 rpm for 5 minutes and the equilibrium concentrations of metal ions were determined by atomic absorption spectrometry. It was found that, in 240 minutes of contact, the Lithothamnium calcareum removed 15.5% of Cr, 33.0% of Mn and 8.0% of Zn in solution; and that in 24 hours of contact, at a concentration of 5 mg L-1, it removed 0.4% of Cr, 52.5% of Mn and 92.6% of Zn; and, at a concentration of 500 mg L-1, it removed 20.0% of Cr, 22.6% of Mn and 40.8% of Zn. The results showed that the Lithothamnium calcareum submitted to thermochemical treatment presented potential for use in the adsorption of Cr, Mn and Zn. Resumo Objetivou-se investigar a capacidade adsortiva dos elementos Cromo (Cr), Manganês (Mn) e Zinco (Zn) à alga marinha Lithothamnium calcareum por meio de ensaios de cinética de adsorção e adsorção em batelada, tendo em vista o desenvolvimento de uma técnica simples para o tratamento de efluentes que apresentam elevada concentração de íons metálicos. A alga foi peneirada, lavada e submetida a tratamento. Na cinética de adsorção, pesou-se 0,2 g de alga, quantidade transferida para frascos Erlenmeyer de 125 mL, aos quais adicionou-se 15 mL de solução em concentração de 5 mg L-1 do íon metálico. Os frascos foram agitados a 60 rpm, por 240 minutos. Na adsorção em batelada, pesou-se 0,2 g de alga, quantidade transferida para frascos Erlenmeyer de 125 mL, aos quais adicionou-se 15 mL de solução em concentrações de 5, 10, 20, 50, 100, 250 e 500 mg L-1 do íon metálico. Os frascos foram agitados a 60 rpm, por 24 horas. Nos dois ensaios, as soluções sobrenadantes coletadas foram centrifugadas a 2000 rpm, por 5 minutos, e as concentrações de equilíbrio dos íons metálicos foram determinadas por espectrometria de absorção atômica. Verificou-se que, em 240 minutos de contato, a Lithothamnium calcareum removeu 15,5% do Cr, 33,0% do Mn e 8,0% do Zn em solução, e que, em 24 horas de contato, em concentração de 5 mg L-1, removeu 0,4% de Cr, 52,5% de Mn e 92,6% de Zn, e, em concentração de 500 mg L-1, removeu 20,0% de Cr, 22,6% de Mn e 40,8% de Zn. Os resultados mostraram que a Lithothamnium calcareum submetida ao tratamento termoquímico apresentou potencial de uso na adsorção de Cr, Mn e Zn.

Most of dyes cause various environmental and health problems due to their toxic, mutagenic, and even carcinogenic properties. Therefore, several treatment methods are used to remove dyes from wastewater. Adsorption is one of the most preferred methods due to its easy application and high efficiency. The aim of this study is to prepare and characterize KOH-activated pine cone (APC) biochar and use it as adsorbent for removal of anionic diazo dye, Congo red (CR) from aqueous solution. The various operating parameters such as pH, contact time, temperature, initial dye concentration, and adsorbent dosage are optimized in batch adsorption system. Experimental results showed that the prepared APC biochar has a surface area of 1714.5 m(2)/g and was achieved 94.62% CR removal efficiency at an adsorbent dosage of 2 g/L. The Freundlich, Langmuir, and Temkin adsorption models were used for the mathematical description of the adsorption equilibrium. Experimental data showed the best compatibility with the Freundlich isotherm. Batch adsorption models, based on the assumption of the pseudo first-order, pseudo second-order, and intra particle diffusion mechanisms, were applied to examine the kinetics of the adsorption. Kinetic data fitted the pseudo second-order kinetic model. Calculated thermodynamic parameters indicated the spontaneous, endothermic, and the increased randomness nature of CR adsorption. Structural and morphological changes of APC biochar after adsorption process were determined by using Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) analysis. The prediction of the CR adsorption capacity of the APC biochar using artificial neural network (ANN) algorithm was modeled. For this purpose, many different ANN models have been developed. Among them, ANN10 gave the best results. According to ANN10 results, root-mean-squared error (RMSE), mean bias error (MBE), mean absolute error (MAE), and correlation coefficient (R-2) were estimated as 0.770, 0.310, 0.037, and 0.999, respectively. Consequently, the prediction results showed well agreement with experimental results. Hitit UniversityHitit University The authors would like to thank Hitit University for its support and also would like to thank to Assoc. Prof. Dr. Yunus Onal for his support in the preparation of activated biochar product. WOS:000692311200001 2-s2.0-85114141621