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The use of commercial activated carbon (AC) to remove organic micropollutants from aqueous solution is expensive and unsustainable. In this study, coconut shell activated carbon (CSAC) was synthesized and applied for the removal of ibuprofen, ketoprofen and naproxen from aqueous solutions. The effects of carbonization and acid activation on the CSAC were studied using Fourier-transform infrared spectroscopy, scanning electron microscope, proximate and ultimate analyses. The influence of initial concentration (200–1000 mg/L), contact time (10–200 min), and temperature (30–60°C) was also investigated. The adsorptive capacity of CSAC for various pollutants was found to increase with concentration up to 150 min. Ibuprofen, ketoprofen and naproxen removal obeyed Langmuir (R2 = 0.9978), Temkin (R2 = 0.9551) and Freundlich (R2 = 0.9879) isotherm, respectively. The kinetic data obtained for various pollutants are best described by the pseudo-first-order model with correlation coefficient values in the range 0.96–0.99. The free energy ( G) values ranged between 1.0 and 9.0 kJ/mol for all the pollutants investigated. The mechanism of adsorption is physical, endothermic, and non-spontaneous. This study shows that CSAC is an effective alternative adsorbent for sequestering mixture of organic pollutants from aqueous solution.

The substrate N1, N3, N5-tris(2-hydroxyphenyl)benzene-1,3,5-tricarboxamide (Sensor A) was prepared in the reaction of 1,3,5-benzenetricarboxylic acid (trimesic acid) and o-aminophenol in ethanol. The prepared organic sensor fulfills the chemiluminescent requirements including a luminophore, spacer, and suitable binding receptor that distress the probe’s luminescent features, providing selective and sensitive detection of mercury and iron ions in aqueous solutions. The sensor selectively detects mercury and iron ions in a water matrix containing various metal ions, including sodium, calcium, magnesium, zinc, and nickel. Strong and immediate binding was observed between mercury ions and the substrate at pH 7.0 with a binding affinity toward Hg2+ 9-fold higher than that observed for iron sensor binding affinity, which makes the substrate a distinctive luminescence sensor for mercury detection at ambient conditions. The sensor shows a linear response toward Hg2+ in the concentration range from 50 ppb to 100 ppm (2.0 × 10−8 to 4.2 × 10−5 M) with a limit of detection of 2 ppb (1.0 × 10−8 M). Further, Sensor A provides linear detection for iron ions in the range from 10 ppb to 1000 ppm (1.5 × 10−8 to 1.5 × 10−3 M). The measured adsorption capacity of Sensor A toward mercury ions ranged from 1.25 to 1.97 mg/g, and the removal efficiency from water samples reached 98.8% at pH 7.0. The data demonstrate that Sensor A is an excellent probe for detecting and removing mercury ions from water bodies.

Growing pollution is making it necessary to find new strategies and materials for the removal of undesired compounds from the environment. Adsorption is still one of the simplest and most efficient routes for the remediation of air, soil, and water. However, the choice of adsorbent for a given application ultimately depends on its performance assessment results. Here, we show that the uptake of and capacity for dimethoate adsorption by different viscose-derived (activated) carbons strongly depend on the adsorbent dose applied in the adsorption measurements. The specific surface areas of the investigated materials varied across a wide range from 264 m2 g−1 to 2833 m2 g−1. For a dimethoate concentration of 5 × 10−4 mol L−1 and a high adsorbent dose of 10 mg mL−1, the adsorption capacities were all below 15 mg g−1. In the case of high-surface-area activated carbons, the uptakes were almost 100% under identical conditions. However, when the adsorbent dose was reduced to 0.01 mg mL−1, uptake was significantly reduced, but adsorption capacities as high as 1280 mg g−1 were obtained. Further, adsorption capacities were linked to adsorbents’ physical and chemical properties (specific surface area, pore size distribution, chemical composition), and thermodynamic parameters for the adsorption process were evaluated. Based on the Gibbs free energy of the adsorption process, it can be suggested that physisorption was operative for all studied adsorbents. Finally, we suggest that a proper comparison of different adsorbents requires standardization of the protocols used to evaluate pollutant uptakes and adsorption capacities.

A polyamine special ion exchange resin was used to adsorb Mo from ammonium tungstate solutions. The effects of adsorption time, S2− concentration, adsorption temperature, CO32− concentration, mass ratio of WO3 to Mo, and Mo concentration on the Mo and WO3 adsorption capacities were investigated. Energy dispersive spectrometer plane scans were used to study the distributions of Mo, W, S, and Na on the loaded polyamine special ion exchange resin and the desorbed polyamine special ion exchange resin. The results showed that the polyamine special ion exchange resin performed well during adsorption and desorption. Under the optimum conditions for the static adsorption experiments, the adsorption capacities for Mo and WO3 were 99.29 mg/mL and 31.97 mg/mL, respectively, and the desorption rates for Mo and WO3 were 99.35% and 99.43%, respectively. Adsorption and desorption of molybdenum and tungsten on the polyamine special ion exchange resin were investigated by dynamic adsorption experiments with an ammonium tungstate solution containing 125.0 g/L WO3, 12.50 g/L Mo, 15.65 g/L S2−, and 0 g/L CO32−. The adsorption capacities for Mo and WO3 were 53.48 mg/mL and 9.79 mg/mL, and the adsorption rates for Mo and WO3 were 99.05% and 1.81%, respectively. The loaded polyamine special resin was desorbed with a 45 g/L sodium hydroxide solution, and the dynamic desorption rates for Mo and WO3 were 99.02% and 99.29%, respectively.

The rod-like nano-MoS2/graphene oxide (GO) nanocomposite was fabricated by a facile hydrothermal method, which was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and N2 adsorption–desorption isotherms, respectively. It was used as adsorbent to remove heavy metal contaminate, such as Cr(VI), from aqueous solution. The investigations on adsorption kinetics and isotherms showed that the pseudo-second-order kinetic and Langmuir isotherm model could well fit the experimental data. The adsorption rate was controlled by both exterior and interior surface diffusion steps. Further investigations on the activation energy and thermodynamics of the adsorption process elucidated that the Cr(VI) adsorption on MoS2/GO was an endothermic and spontaneous chemi-sorption process. The maximum adsorption capacity was 43.95 mg·g-1 and the adsorption efficiency of Cr(VI) was enhanced significantly with the coexistence of organic contamination. After recycling five times, the decline of adsorption capacity of MoS2/GO wasno more than 8.0 %, which indicated that the adsorbents could be reused in Cr(VI) removal practically. The MoS2/GO nanocomposite has been proved to be a low-cost, efficient and promising adsorbent used for heavy metal ions removal from wastewater.

Efforts to reduce the concentration of heavy metal cations in the environment have become a matter of concern due to their potential impact and widespread pollution in the waters. This study aims to examine the adsorption capacity of Pb(II) and Fe(III) cations using 5,11,17,23-tetra-(t-butyl)-25,26,27,28-tetra-hydroxycalix[4]arene compounds (TBKA) with various pH variations. The synthesis product of TBKA was characterized using FTIR and 1H-NMR spectroscopy. TBKA has functioned as an adsorbent or pollutant absorbent for Pb(II) and Fe(III) cation with an immersion system. The results showed that variations in pH affect the adsorption capacity of the adsorbent TBKA on Pb(II) and Fe(III) cations. The adsorption capacity of the adsorbent of TBKA on Pb(II) cations at pH 2; 3; 4; 5; and 6 was 6.32; 2.16; 4.14; 10.52; and 2.88 mg/g, respectively, while the adsorption capacity of TBKA on Fe(III) cations at pH 1.5; 3; 4; 5 and 6 was 8.4; 13.32; 11.6; 14.18; and 6.66 mg/g, respectively. Keywords: TBCA, Batch system, pH variations, Adsorption capacity ABSTRAK Upaya untuk mengurangi konsentrasi kation logam berat di lingkungan telah menjadi perhatian sehubungan dengan dampak yang dapat ditimbulkan dan masih adanya pencemaran logam berat di perairan. Penelitian ini bertujuan untuk mengkaji kapasitas adsorpsi kation Pb(II) dan Fe(III) menggunakan senyawa 5,11,17,23-tetra-(t-butil)-25,26,27,28-tetra-hidroksikaliks[4]arena (TBKA) dengan berbagai variasi pH. Karakterisasi hasil sintesis TBKA dilakukan dengan menggunakan spektroskopi FTIR dan 1H-NMR. TBKA difungsikan sebagai adsorben atau penjerap polutan kation Pb(II) dan Fe(III) dengan sistem perendaman. Hasil penelitian menunjukkan bahwa variasi pH berpengaruh terhadap kapasitas adsorpsi daya jerap antara adsorben TBKA terhadap kation Pb(II) dan kation Fe(III). Kapasitas adsorpsi daya jerap antara adsorben TBKA terhadap kation Pb(II) pada pH 2; 3; 4; 5; dan 6 secara berturut turut adalah 6,32; 2,16; 4,14; 10,52; dan 2,88 mg/g, sedangkan kapasitas adsorpsi terhadap daya jerap antara TBKA terhadap kation Fe(III) pada pH 1,5; 3; 4; 5 dan 6 secara berturut turut adalah 8,4; 13,32; 11,6; 14,18; dan 6,66 mg/g. Kata kunci: TBKA, Rendam, Variasi pH, Kapasitas adsorpsi

Fruit peels, which are common agricultural byproducts, have been extensively used as abandoned or low-cost biosorbents to remove heavy metals. In this study, dragon fruit peel (DFP), rambutan peel (RP), and passion fruit peel (PFP) were used to remove Cu(II) ions from an aqueous solution. Concentrations of the adsorbed metal ions were determined using the atomic absorption spectroscopic method. Adsorption experiments were performed with different adsorbent dosages, pH values, contact times, and initial copper concentrations. The optimum set of conditions for biosorption of Cu(II) ions was found to be an adsorbent dosage of 0.25 g, a contact time of 180 min, an initial concentration of 100 mg/L, a pH value of 4 for RP and PFP, and a pH value of 5 for DFP. The adsorption conformed with the pseudo-second-order kinetic model. The adsorption data were consistent with the Langmuir and Freundlich isotherm models, but the best fit was with the Langmuir model. The Langmuir monolayer adsorption capacity values of DFP, RP, and PFP were calculated to be 92.593, 192.308, and 121.951 mg/g, respectively. RP showed a higher adsorption capacity of Cu(II) ions than PFP and DFP for all parameters. The results indicate that these biosorbents might be used to effectively adsorb Cu(II) ions from wastewater treatment plants.

Aerobic digestion is the final stage of biological treatment systems employed for treating Palm Oil Mill Effluent (POME). The presence of phenolic compounds in POME inhibits the performance of aerobic microbes. To mitigate the inhibitory effect, removing phenolic compounds at the early stage of aerobic treatment could be a workable solution. In this study, the performance of biochar from oil palm frond (OPF-BC) prepared using steam pyrolysis was investigated for the efficient removal of phenolic compounds. Adsorption kinetics and equilibrium tests were performed to assess the time required to reach adsorption equilibrium and uptake capacity for phenol, catechol and gallic acid spiked in water and facultatively treated POME. Adsorption of the phenols onto OPF-BC attained equilibrium within 2 h irrespective of the water matrix. In the water maximum adsorption capacities of 38.7, 28.2 and 26.2 mg/g were obtained for phenol, catechol, and gallic acid, respectively. The presence of background organic matter in facultatively treated POME reduced the adsorption capacities by 3-folds. The simplified equivalent background model estimated dosage to achieve 80% removal ranged between 14.4 and 18.8 g/L. The OPF-BC demonstrated efficient phenolic compounds removal performance, making it a promising and economical adsorbent for the hybrid adsorption-aerobic treatment system. &nbsp

Supplementary Materials: The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/molecules27228073/s1, Acknowledgments: E.E. is grateful to the Government of the Basque Country for the predoctoral fellowship and R.F.M for the Junior Research Position CEECIND/ 00553/2017. S.R. acknowledges the Juan de la Cierva Incorporación Fellowship (grant agreement no. IJC2019-038894-I). The authors thank for technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF) and also wish to acknowledge the terrific help of all reviewers of the present manuscript, whose comments helped to improve the quality of the work., Funding: This work was developed within the scope of the projects given by the University of the Basque Country (GIU 20/028 Junta de Andalucía (B-FQM-734-UGR20, ProyExcel_00386 and FQM-394), the Spanish Ministry of Science, Innovation and Universities (MCIU/AEI/FEDER, UE) (PGC2018-102052-B-C21) and the CICECO-Aveiro Institute of Materials (UIDB/50011/2020 and UIDP/50011/2020)., Due to the fast, emerging development of antibiotic-resistant bacteria, the need for novel, efficient routes to battle these pathogens is crucial; in this scenario, metal-organic frameworks (MOFs) are promising materials for combating them effectively. Herein, a novel Cu-MOF—namely 1—that displays the formula [Cu3L2(DMF)2]n (DMF = N,N-dimethylformamide) is described, synthesized by the combination of copper(II) and 3,4-dihydroxybenzoic acid (H3L)—both having well-known antibacterial properties. The resulting three-dimensional structure motivated us to study the antibacterial activity, adsorptive capacity and processability of the MOF in the form of pellets and membranes as a proof-of-concept to evaluate its future application in devices., Government of the Basque Country for the predoctoral fellowship and R.F.M for the Junior Research Position CEECIND/00553/2017, Juan de la Cierva Incorporación Fellowship (grant agreement no. IJC2019-038894-I), SGIker of UPV/EHU, European funding (ERDF and ESF), University of the Basque Country (GIU 20/028 Junta de Andalucía (B-FQM-734-UGR20, ProyExcel_00386 and FQM-394), Spanish Ministry of Science, Innovation and Universities (MCIU/AEI/FEDER, UE) (PGC2018-102052-B-C21), CICECO-Aveiro Institute of Materials (UIDB/50011/2020 and UIDP/50011/2020)

With the rapid development of urbanization, the problem of environmental pollution is becoming more and more serious. As a major pollutant, heavy metals have caused serious contamination in soil and groundwater. In order to prevent the diffusion of heavy metals in the soil from industrial sewage, the concept of hybrid-fill layer construction improved by red mud was proposed in this study. This study examines the adsorption capacities of lead and zinc ions and engineering characteristics on red mud-amended soils by direct shear, permeability, adsorption, desorption batch and column tests. Two mixing methods, full particle size displacement mixing and partial particle size displacement mixing, were adopted. The results showed that red mud effectively increased the adsorption capacity of soil to heavy metal ions, and the desorption rate of ions after adsorption was less than 3%, which had good anti-desorption ability. The optimum content of red mud in hybrid-fill material can be determined as 20%. The direct shear test showed that the internal friction angle of hybrid-fill material was 38.9°, and the cohesive force was 30.3 kPa, which met the engineering strength requirements of foundation materials. Based on the test results, red mud can be used as a barrier material to prevent heavy metal contamination in industrial sewage from diffusion, which controls not only heavy metal contamination but also consumes industrial by-products.

Phosphorus is a non-renewable resource. Supplies are limited and much phosphorus is currently wasted during the production and utilization process, causing concerns about future supplies and widespread environmental problems. To solve these problems, a new type of NiFe-LDH/rGO electrically switched ion-selective (ESIX) film is designed, based on the dominant mechanism of inner-sphere complexation. An ESIX process allows the NiFe-LDH/rGO hybrid film to achieve a controllably selective uptake and release of the phosphate anions. This route involves tuning potential steps to regulate the redox states of the composite film and the variable metal (e.g., Ni, Fe (II)/(III)) in coordination centers, as the inner- sphere complexation of the metals to phosphate anions is combined with the assistance of the outer elec- tric field. A high absorption capacity (270 mg g 1) and regeneration rate (>85%) were achieved, together with good cycle stability.

Ammonia (NH3) emissions during agricultural production can cause serious consequences on animal and human health, and it is quite vital to develop high-efficiency adsorbents for NH3 removal from emission sources or air. Porous metal–organic frameworks (MOFs), as the most promising candidates for the capture of NH3, offer a unique solid adsorbent design platform. In this work, a series of MOFs with different metal centers, ZnBTC, FeBTC and CuBTC, were proposed for NH3 adsorption. The metal centers of the three MOFs are coordinated in a different manner and can be attacked by NH3 with different strengths, resulting in different adsorption capacities of 11.33, 9.5, and 23.88 mmol/g, respectively. In addition, theoretical calculations, powder XRD patterns, FTIR, and BET for the three materials before and after absorption of ammonia were investigated to elucidate their distinctively different ammonia absorption mechanisms. Overall, the study will absolutely provide an important step in designing promising MOFs with appropriate central metals for the capture of NH3.

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.

It is rather essential to design glorious system with high CO2 adsorption capacity and electron migration efficiency for improving selective and effective CO2 reduction into solar fuels. Here, as-synthesized phenolic resin spheres via suspension polymerization were carbonized and activated by water vapor to obtain activated carbon spheres (ACSs). Subsequently, Bi2MoO6/ACSs were prepared via hydrothermal-impregnated method. The systematical characterizations of samples, including XRD, XPS, SEM, EDX, DRS, BET, PL, CO2 adsorption isotherm, EIS and transient photocurrent, were analyzed. The results clearly demonstrated that Bi2MoO6 with suitable oxidation reduction potentials and bandgap and ACSs with admirable CO2 adsorption and electrical conductivity not only enhanced separation efficiency of photoindued electron-hole pair, but also displayed as 1.8 times CO2 reduction activity to CO as single Bi2MoO6 sample under Xe-lamp irradiation. Finally, a concerned photocatalytic CO2 reduction mechanism was proposed and investigated. Our findings should provide innovative guidance for designing a series of photocatalytic CO2 reduction materials with highly efficient and selective ability.

Adsorptive properties for Cd(II), Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) onto amidoxime-functionalized polyacrylonitrile (APAN) micro/nanofibers were systematically investigated in a hexahydroxy metallic solution system using batch experiments. The interactive effect of multi-metal ions in multi- metal systems was antagonistic in nature, and the adsorption capacity in a multi-metal system was lower than that in a single-metal system. The Langmuir isotherm model could explain respectively the isotherm and kinetic experimental data for the hexahydroxy metallic system with much satisfaction. The maximum adsorption capacity in hexahydroxy metallic for Cd(II), Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) was calculated to be 98 mg/L, 158 mg/L, 80 mg/L, 76, 312 and 58 mg/L individually. The APAN micro/nanofibers possessed good selectivity toward Pb(II) and Cr(III), over Cd(II), Cu(II), Ni(II), and Zn(II), having the highest selectivity coefficients at 17.52 and 6.07 in the test range. The five adsorption-desorption cycle experiments exhibited that APAN micro/nanofibers adsorbent are readily reusable, and have potential for heavy metal removal from wastewater. The adsorption behavior in multi-metal systems was shown to be complex, including surface complexation, antagonistic competition and displacement reactions. The diversity and selectivity in metal ion adsorption onto the micro/nanofibers relate mainly to the stability constants, and the microscopic coupling mechanism between the heavy metal ions and the functional groups on the fiber surface. This interaction mechanism between the favorable component and other metal ions could contribute significantly to the direct displacement impact illustrated schematically. HIGHLIGHTS Amidoxime-functionalized polyacrylonitrile micro/nanofibers were prepared.; Competitive adsorption behavior of hexahydroxy metallic system was investigated.; APAN micro/nanofibers had a better selective adsorption for Pb(II) and Cr(III).; The mechanisms included surface complexation, antagonistic competition and displacement reaction.

One of the most important environmental challenges in the world is environmental pollution with toxic and dangerous heavy metals, which causes various environmental effects. Lead is a heavy metal that can be removed in a variety of methods. In this study, graphene oxide adsorbent was prepared by modified Hummers method and functionalized with aminomethyl phosphonic acid and its application for the adsorption of lead ions from aqueous solutions in a batch sorption process was investigated. The effect of several batch adsorption parameters such as contact time, pH, adsorbent dose, initial concentration and temperature were investigated. The kinetic data were analyzed by Pseudo-first-order, Pseudo-second-order and Double- exponential kinetic models. The results showed that experimental data was fitted well by Pseudo-second-order kinetic model. The Freundlich and Langmuir isotherm models were applied to describe the equilibrium data. The maximum adsorption capacity of lead ions with graphene oxide and functionalized-graphene oxide adsorbents was found to be 187.80 and 209.41 mg/g at a pH of 2.0 and temperature of 45 ºC, respectively. Furthermore, the graphene oxide and functionalized-graphene oxide adsorbents were regenerated by HCl/HNO3 solution and the adsorption capacity did not change remarkably after seven adsorption-desorption cycles.

Interactions with dietary fibers in the gastrointestinal tract might affect the potential bioactivities of phenolic compounds. In this study, the interactions between apple phenolic compounds and β-glucan (a dietary fiber) were studied by studying the adsorption process in simulated gastric and intestinal fluid electrolyte solutions. Phenolic compounds were extracted from apples, adsorbed onto β-glucan (2 h, 37 °C, in gastric or intestinal fluid electrolyte solutions), and determined using high performance liquid chromatography. Phenolic compounds (flavan-3-ols, flavonols, phenolic acids, and dihydrochalcone) were stable in the gastric fluid (pH 3). In the intestinal fluid (pH 7), flavan-3-ols were not found and chlorogenic acid isomerized. Polyphenols from the apple peel (up to 182 and 897 mg g−1) and flesh (up to 28 and 7 mg g−1) were adsorbed onto β-glucan in the gastric and intestinal fluids, respectively. The adsorption was affected by the initial concentration of the polyphenols and β-glucan and by the environment (either gastric or intestinal fluid electrolyte solution). By increasing the initial polyphenol amount, the quantity of adsorbed polyphenols increased. Increasing the amount of β-glucan decreased the amount adsorbed. The results can be helpful in explaining the fate of phenolic compounds in the gastrointestinal tract.

Experimental assessment of the hydrogen (H2)-adsorption capacities of metal-doped carbon nanostructured materials were investigated in this study. Given their intrinsic characteristics, nanostructured carbonic materials show great potential for different applications that require H2, one such being their use as hydrogen carriers in the automotive sector. The current paper considers two types of carbonic substrates (carbon nanotubes and polyaniline) functionalized and doped with platinic metals: Pt, Ru and Ir. The H2-adsorption capacities of the materials were assessed at 293 K and at relatively low pressures (10, 20 and 30 bar). Thus, nanostructured polyaniline (p-C6H5NH2) and multi-walled carbon nanotubes (MW-CNTs) were subject to noble-metal doping in order to assess their physical H2-adsorption capacities. The two types of substrates have different structures and characteristics, one being a “synthetic metal” and the other an amorphous carbon substrate. The metals used for doping were Platinum (Pt), Iridium (Ir) and Ruthenium (Ru), and the doping procedure consisted of chemical reaction between the metals’ salts and the carbonic substrate after the latter’s physical activation. Physical H2-adsorption capacity was determined with equipment designed to measure porous materials’ adsorption capacities at pressures ranging from 1 to 200 bar. The obtained results showed an increase inH2-adsorption capacity of 293% from 10 to 30 bar for Ru, 270% for Ir and 256% for Pt doping in the case of the MW-CNTs, and 296% for Ru, 282% for Ir and 251% for Pt from 10 to 30 bar in the case of p-C6H5NH2. As the main conclusion, even though Pt is known to be the main metal used in reactions involving H2, Ru and Ir showed better potential for this application, namely, as hydrogen-carrier materials for use in the automotive sector.

In this study, the response surface methodology (RSM) and artificial neural network (ANN) were employed to study the adsorption process of 2,4-dichlorophenoxyacetic acid (2,4-D) by using modified hydrogel, i.e., activated carbon poly(dimethylaminoethyl methacrylate) (AC/PDMAEMA hydrogel). The effect of pH, the initial concentration of 2,4-D and the activated carbon content on the removal of 2,4-D and adsorption capacity were investigated through the face-centered composite design (FCCD), optimal design and two-level factorial design. The response surface plot suggested that higher removal of 2,4-D and adsorption capacity could be achieved at the higher initial concentration of 2,4-D and lower pH and activated carbon content. The modeling and optimization for the adsorption process of 2,4-D were also carried out by different design methods of RSM and different training methods of ANN. It was found that among the three design methods of RSM, the optimal design has the highest accuracy for the prediction of 2,4-D removal and adsorption capacity (R2 = 0.9958 and R2 = 0.9998, respectively). The numerical optimization of the optimal design found that the maximum removal of 2,4-D and adsorption capacity of 65.01% and 65.29 mg/g, respectively, were obtained at a pH of 3, initial concentration of 2,4-D of 94.52 mg/L and 2.5 wt% of activated carbon. Apart from the optimization of process parameters, the neural network architecture was also optimized by trial and error with different numbers of hidden neurons in the layers to obtain the best performance of the response. The optimization of the neural network was performed with different training methods. It was found that among the three training methods of the ANN model, the Bayesian Regularization method had the highest R2 and lowest mean square error (MSE) with the optimum network architecture of 3:9:2. The optimum condition obtained from RSM was also simulated with the optimized neural network architecture to validate the responses and adequacy of the RSM model.

Ammonia (NH3) is a common pollutant mostly derived from pig manure composting under humid conditions, and it is absolutely necessary to develop materials for ammonia removal with high stability and efficiency. To this end, metal–organic frameworks (MOFs) have received special attention because of their high selectivity of harmful gases in the air, resulting from their large surface area and high density of active sites, which can be tailored by appropriate modifications. Herein, two synthetic metal–organic frameworks (MOFs), 2-methylimidazole zinc salt (ZIF-8) and zinc-trimesic acid (ZnBTC), were selected for ammonia removal under humid conditions during composting. The two MOFs, with different organic linkers, exhibit fairly distinctive ammonia absorption behaviors under the same conditions. For the ZnBTC framework, the ammonia intake is 11.37 mmol/g at 298 K, nine times higher than that of the ZIF-8 framework (1.26 mmol/g). In combination with theoretical calculations, powder XRD patterns, FTIR, and BET surface area tests were conducted to reveal the absorption mechanisms of ammonia for the two materials. The adsorption of ammonia on the ZnBTC framework can be attributed to both physical and chemical adsorption. A strong coordination interaction exists between the nitrogen atom from the ammonia molecule and the zinc atom in the ZnBTC framework. In contrast, the absorption of ammonia in the ZIF-8 framework is mainly physical. The weak interaction between the ammonia molecule and the ZIF-8 framework mainly results from the inherent severely steric hindrance, which is related to the coordination mode of the imidazole ligands and the zinc atom of this framework. Therefore, this study provides a method for designing promising MOFs with appropriate organic linkers for the selective capture of ammonia during manure composting.

Chitin is mentioned as the second most abundant and important natural biopolymer in worldwide scale. The main sources for the extraction and exploitation of this natural polysaccharide polymer are crabs and shrimps. Chitosan (poly-β-(1 → 4)-2-amino-2-deoxy-d-glucose) is the most important derivative of chitin and can be used in a wide variety of applications including cosmetics, pharmaceutical and biomedical applications, food, etc., giving this substance high value-added applications. Moreover, chitosan has applications in adsorption because it contains amino and hydroxyl groups in its molecules, and can thus contribute to many possible adsorption interactions between chitosan and pollutants (pharmaceuticals/drugs, metals, phenols, pesticides, etc.). However, it must be noted that one of the most important techniques of decontamination is considered to be adsorption because it is simple, low-cost, and fast. This review emphasizes on recently published research papers (2013–2021) and briefly describes the chemical modifications of chitosan (grafting, cross-linking, etc.), for the adsorption of a variety of emerging contaminants from aqueous solutions, and characterization results. Finally, tables are depicted from selected chitosan synthetic routes and the pH effects are discussed, along with the best-fitting isotherm and kinetic models.

A novel struvite–humic acid composite (S–HA) was derived from an anaerobic digestate and evaluated for the adsorption and reduction of chromium [Cr (VI)] in this study. The results indicated that the struvite–humic acid composite (S–HA) contains higher contents of oxygen-containing and aromatic functional groups (47.05% and 34.13%, respectively) and a higher specific surface area (19.3 m2 g−1). These special characteristics of S–HA contributed to its higher adsorption capacity (207.69 mg g−1 and 254.47 mg g−1 for pseudo-first and second-order kinetic models, respectively) for chromium. Furthermore, XPS analysis showed that a portion of the bonded Cr (VI) was reduced to Cr (III) by carboxyl and hydroxyl functional groups, which oxidized and changed into ketone and phenol functional groups. Based on the findings, it was concluded that the phosphate–humic acid composite has an outstanding chromium adsorptive and reduction capacity. However, more research is needed to fully understand the potential of the struvite–humic acid composite for chromium adsorption and reduction.

The occurrence and migration of coalbed methane (CBM) is inseparably associated with the pore structure within the coal seams. Three Permian Longtan Formation tectonic coal samples (QL, XL, XT) from Guizhou Province were studied to determine pore size distribution and characteristics, as well as factors that influence adsorption. Adsorption test results show that all samples generally have “ink bottle”-type pores, with large pore capacity but poor connectivity. Furthermore, the fractal dimension Df, the tortuosity “τ”, and tortuous fractal dimension DT of samples were calculated. Among the studied tectonic coals, moisture, ash, tortuosity, and volatile fraction have a positive effect on the maximum adsorption capacity (VL), whereas intact coals’ tortuosity volatile has a negative correlation with the maximum adsorption capacity (VL).

Final properties of unfired earth are influenced by composition of earth mixtures. Methylene blue test could be useful method for analysis of earth composition. This would facilitate of designing unfired earth building structures because composition of natural earth is various. Principle of methylene blue test is measure of amount of adsorbed methylene blue dye by clay. The essential component of earth mixtures is clay because clay fulfils a function of binder. Experimental measure of adsorption capacity of individual kind of clay is described in this paper. Adsorption capacity was investigated in montmorillonite, kaolinite, illite-kaolinite and illite clays. The obtained results show that the adsorption capacity of clays is significantly different.

Nowadays, there is an extensive production and use of plastic materials for different industrial activities. These plastics, either from their primary production sources or through their own degradation processes, can contaminate ecosystems with micro- and nanoplastics. Once in the aquatic environment, these microplastics can be the basis for the adsorption of chemical pollutants, favoring that these chemical pollutants disperse more quickly in the environment and can affect living beings. Due to the lack of information on adsorption, three machine learning models (random forest, support vector machine, and artificial neural network) were developed to predict different microplastic/water partition coefficients (log Kd) using two different approximations (based on the number of input variables). The best-selected machine learning models present, in general, correlation coefficients above 0.92 in the query phase, which indicates that these types of models could be used for the rapid estimation of the absorption of organic contaminants on microplastics. Ministerio de Universidades | Ref. FPU2020/06140

The novel [Cuphen(VBA)2H2O] complex (phen: phenanthroline, VBA: vinylbenzoate) was prepared and used as a functional monomer to preorganize a new ion-imprinted polymer (IIP). By leaching the Cu(II) from the molecular imprinted polymer (MIP), [Cuphen(VBA)2H2O-co-EGDMA]n (EGDMA: ethylene glycol dimethacrylate), the IIP was obtained. A non-ion-imprinted polymer (NIIP) was also prepared. The crystal structure of the complex and some physicochemical, spectrophotometric techniques were also used for the MIP, IIP, and NIIP characterization. The results showed that the materials are nonsoluble in water and polar solvents, which are the main features of polymers. The surface area of the IIP is higher than the NIIP demonstrated by the blue methylene method. The SEM images show monoliths and particles smoothly packed together on spherical and prismatic-spherical surfaces in the morphology of MIP and IIP, respectively. Moreover, the MIP and IIP could be considered as mesoporous and microporous materials, shown by the size of the pores determined by the BET and BJH methods. Furthermore, the adsorption performance of the IIP was studied using copper(II) as a contaminant heavy metal. The maximum adsorption capacity of IIP was 287.45 mg/g at 1600 mg/L Cu2+ ions with 0.1 g of IIP at room temperature. The Freundlich model was found to best describe the equilibrium isotherm of the adsorption process. The competitive results indicate that the stability of the Cu-IIP complex is higher than the Ni-IIP complex with a selectivity coefficient of 1.61.

Rapid industrialization has led to huge amounts of organic pollutants and toxic heavy metals into aquatic environment. Among the different strategies explored, adsorption remains until the most convenient process for water remediation. In the present work, novel cross-linked chitosan-based membranes were elaborated as potential adsorbents of Cu2+ ions, using as cross-linking agent a random water-soluble copolymer P(DMAM-co-GMA) of glycidyl methacrylate (GMA) and N,N-dimethylacrylamide (DMAM). Cross-linked polymeric membranes were prepared through casting aqueous solutions of mixtures of P(DMAM-co-GMA) and chitosan hydrochloride, followed by thermal treatment at 120 °C. After deprotonation, the membranes were further explored as potential adsorbents of Cu2+ ions from aqueous CuSO4 solution. The successful complexation of copper ions with unprotonated chitosan was verified visually through the color change of the membranes and quantified through UV-vis spectroscopy. Cross-linked membranes based on unprotonated chitosan adsorb Cu2+ ions efficiently and decrease the concentration of Cu2+ ions in water to a few ppm. In addition, they can act as simple visual sensors for the detection of Cu2+ ions at low concentrations (~0.2 mM). The adsorption kinetics were well-described by a pseudo-second order and intraparticle diffusion model, while the adsorption isotherms followed the Langmuir model, revealing maximum adsorption capacities in the range of 66–130 mg/g. Finally, it was shown that the membranes can be effectively regenerated using aqueous H2SO4 solution and reused.

Because of its priority to remove anions, nano-layered double hydroxide (LDH) was incorporated to improve the sulfate attack corrosion resistance of cement-based materials. Herein, the synthesis of high-efficiency LDH for removal of SO 4 2 − {\text{SO}}_{4}^{2-} is necessary. In this study, LDH with different Mg/Al ratios was synthesized under different dual solvent systems (water and ethylene glycol/ethanol/tetrapropylammonium hydroxide). Based on the adsorption experimental results, the LDH synthesized with n(Mg:Al) = 2:1 under water and ethanol solvent systems (ET2.0) exhibits the best adsorption capacity. The d (003) of LDH synthesized with n(Mg:Al) = 2:1 under different dual solvent systems are 0.7844, 0.7830, and 0.7946 nm, respectively. Three LDH belong to LDH- NO 3 − {\text{NO}}_{3}^{-} . The results indicated that their surface charges show obvious difference synthesized under different dual solvent systems, which leads to differences in adsorption performance. The adsorption experimental results show that ET2.0 followed pseudo second-order kinetics and Langmuir model. The ET2.0 removed SO 4 2 − {\text{SO}}_{4}^{2-} through anion substitution and electrostatic interaction and exhibited excellent adsorption rate with the maximum adsorption capacity of 95.639 mg/g. The effects of pore solution anion (OH−, Cl−, and CO 3 2 − {\text{CO}}_{3}^{2-} ) on the removal of SO 4 2 − {\text{SO}}_{4}^{2-} by the ET2.0 are limited.

Hydrometallurgical leaching solutions are often rich in iron, which was traditionally considered a major impurity. However, iron can be selectively separated and recovered by applying appropriate solvent extraction and stripping techniques, and the resulting solutions can be valorized for the synthesis of high-added-value products, such as magnetic iron oxide nanoparticles (mIONPs). The aim of this study was to synthesize high-quality mIONPs from solutions simulating the composition of two alternative stripping processes. The precursor solutions consisted of Fe(II) in an acidic sulfate environment and Fe(III) in an acidic chloride medium. The Fe(II)-SO4 solution was treated with a mixture of KNO3-KOH reagents, and the product (M(II)) was identified as pure magnetite with a high specific magnetization of 95 emu·g−1. The treatment of Fe(III)-Cl solution involved the partial reduction of Fe(III) using metallic iron and the co-precipitation of iron cations with base addition combined with microwave-assisted heating. The product (M(III)) was a powder, which consisted of two phases, e.g., maghemite (75%) and magnetite (25%), and also had a high magnetic saturation of 80 emu·g−1. The nanopowders were evaluated for their effectiveness in removing Cr(VI) from contaminated waters. The maximum adsorption capacity was found to be equal to 11.4 and 17.4 mg/g for M(II) and M(III), respectively. The magnetic nanopowders could be easily separated from treated waters, a property that makes them promising materials for the water treatment sector.

The impact of urbanization and modern agricultural practice has led to accelerated eutrophication of aquatic ecosystems, which has resulted in the massive development of cyanobacteria. Very often, in response to various environmental influences, cyanobacteria produce potentially carcinogenic cyanotoxins. Long-term human exposure to cyanotoxins, through drinking water as well as recreational water (i.e., rivers or lakes), can cause serious health consequences. In order to overcome this problem, this paper presents the synthesis of completely new activated carbons and their potential application in contaminated water treatment. The synthesis and characterization of new active carbon materials obtained from waste biomass, date-palm leaf stalks (P_AC) and black alder cone-like flowers (A_AC) of reliable physical and chemical characteristics were presented in this article. The commercial activated carbon (C_AC) was also examined for the purpose of comparisons with the obtained materials. The detailed characterization of materials was carried out by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), low-temperature N2 physisorption, and Field emission scanning electron microscopy (FESEM). Preliminary analyzes of the adsorption capacities of all activated carbon materials were conducted on water samples from Aleksandrovac Lake (Southern part of Serbia), as a eutrophic lake, in order to remove Cyanobacteria from water. The results after 24 h showed removal efficiencies for P_AC, A_AC, and C_AC of 99.99%, 99.99% and 89.79%, respectively.

The value-added utilization of waste resources to synthesize functional materials is important to achieve the environmentally sustainable development. In this paper, the biochar supported graphene oxide (BGO) materials were prepared by using navel orange peel and natural graphite. The optimal adsorption parameters were analyzed by response surface methodology under the conditions of solution pH, adsorbent dosage, and rotating speed. The adsorption isotherm and kinetic model fitting experiments were carried out according to the optimal adsorption parameters, and the mechanism of BGO adsorption of Pb2+ was explained using Scanning Electron Microscope (SEM-EDS), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). Compared with virgin biochar, the adsorption capacity of Pb2+ on biochar supported graphene oxide was significantly increased. The results of response surface methodology optimization design showed that the order of influence on adsorption of Pb2+ was solution pH > adsorbent dosage > rotating speed. The optimal conditions were as follows: solution pH was 4.97, rotating speed was 172.97 rpm, and adsorbent dosage was 0.086 g. In the adsorption–desorption experiment, the desorption efficiency ranged from 54.3 to 63.3%. The process of Pb2+ adsorption by BGO is spontaneous and endothermic, mainly through electrostatic interaction and surface complexation. It is a heterogeneous adsorption process with heterogeneous surface, including surface adsorption, external liquid film diffusion, and intra-particle diffusion.

Iron oxyhydroxides (FeOOHs) appear to be the optimal group of materials among inorganic adsorbents for the removal of phosphates from water, providing significant adsorption capacities. This research work presents a thermodynamic study of phosphate adsorption by examining five different FeOOHs sorbent nanomaterials. The otablebtained results indicated that the adsorption process in these cases was spontaneous. When the experiments were performed using distilled water, akageneite (GEH), schwertmannite, and tetravalent manganese feroxyhyte (AquAsZero), displaying ΔH° values of 31.2, 34.7, and 7.3 kJ/mole, respectively, presented an endothermic adsorption process, whereas for goethite (Bayoxide) and lepidocrocite, with ΔH° values of −11.4 and −7.7 kJ/mole, respectively, the adsorption process proved to be exothermic. However, when an artificial (according to NSF) water matrix was used, GEH, schwertmannite, lepidocrocite, and AquAsZero presented ΔH° values of 13.2, 3.3, 7.7, and 3.3 kJ/mole, respectively, indicative of an endothermic process, while only for Bayoxide, with ΔH° of −17 kJ/mole, the adsorption remained exothermic. The adsorption enthalpy values generally decreased with the NSF water matrix, probably due to the competition for the same adsorption sites by other co-existing anions as well to the possible formation of soluble phosphate complexes with calcium; however, an overall positive effect on the uptake of phosphates was observed.

The emission of acid gases such SO2 and NOx have detrimental effects on human beings and the environment hence, removing them from flue gas in a dry adsorption process is desirable. In this work, carbon monolith was synthesized with various metals consisting of CeO2, Co3O4, V2O5, and CuO by deposition precipitation, hydrothermal and wet pore volume impregnation synthesis techniques. The fixed bed adsorption activity test was carried out with flue gas production by coal burning. Furthermore, the breakthrough curves of the adsorbents were investigated where the adsorbent developed via hydrothermal technique with Co3O4 metal oxide termed as HM-Co3O4 /CM displayed higher adsorption capacity for both SO2 (103.9 mg/g) and NOx and (106.6 mg/g). The Langmuir model can best describe the experimental data based on the correlation coefficient and separation factor results. These results implied that the developed adsorbent can be potentially used in the industry for flue gas cleaning. &nbsp

The discharging of ammonium from industrial, domestic, and livestock sewage has caused eutrophication of the water environment. The objectives of this study are to synthesize magnetic zeolite (M-Zeo) by an eco-friendly, economical, and easy procedure and to investigate its suitability as an adsorbent to remove ammonium from an aqueous solution. Based on characterization from XRD, BET, and SEM-EDS, Fe3O4 was proved to successfully load on natural zeolite. The effect of pH, temperatures, reacting times, initial ammonium concentrations, and regeneration cycles on ammonium adsorption was examined by batch experiments. The ammonium adsorption process can be best described by the Freundlich isotherm and the maximum adsorptive capacity of 172.41 mg/g was obtained. Kinetic analysis demonstrated that the pseudo-second-order kinetic model gave the best description on the adsorption. The value of pH is a key factor and the maximum adsorption capacity was obtained at pH 8. By using a rapid sodium chloride regeneration method, the regeneration ratio was up to 97.03% after five regeneration cycles, suggesting that M-Zeo can be recycled and magnetically recovered. Thus, the economic-efficient, great ammonium affinity, and excellent regeneration characteristics of M-Zeo had an extensively promising utilization on ammonium treatment from liquid.

Acetaminophen (ACT), an antipyretic analgesic, is one of the emerging pollutants that has been found in high concentrations in domestic and hospital wastewaters. This study compared the adsorption capacity of sugarcane bagasse (SB) and corn cob (CC) for the ACT removal through the dynamic simulation of the adsorption column using Aspen Adsorption® V10. The effects of flow rate (1.5–3.0 mL min− 1), ACT initial concentration (40–80 mg L− 1), and bed height (20–35 cm) on the breakthrough curves were studied. Finally, the simulation results were validated with experimental studies, and analyzed by error functions, sum of squared errors (SSE), absolute average deviation (AAD), and coefficient of determination (R2). Based on the predicted breakthrough curves, ACT is adsorbed in greater quantity on CC, with saturation times and adsorption capacity greater than SB in all simulations. The maximum adsorption capacity was 0.47 and 0.32 mg g− 1 for CC and SB, respectively, under condition of flow rate of 1.5 mL min− 1, bed height of 25 cm, and ACT initial concentration of 80 mg L− 1. Breakthrough and saturation times were higher when the column operated at low flow rates, large bed height, and low ACT concentrations, for both adsorbents. The predicted and experimental breakthrough curves satisfactorily coincided with R2 values greater than 0.97, SSE and AAD values ​​less than 5% and 0.2, respectively, for all studies. The experimental adsorption capacity was greater for CC than for SB, thus confirming that the software is able to predict which adsorbent may be more effective for ACT removal. The results of this study would speed up the search for effective materials to remove ACT from wastewaters.

Technetium-99m (99mTc) plays a major role in diagnostic nuclear medicine and has not yet been replaced with any other radionuclides. It is available through the 99Mo/99mTc generator. The use of low-specific-activity 99Mo for 99Mo/99mTc generator application requires high adsorptive capacity sorbents. This study focused on the determination of 99Mo adsorption capacity of several zirconia materials, namely monoclinic nanozirconia, orthorhombic nanozirconia, sulfated zirconia, and phosphated zirconia. These materials were synthesized by using the sol-gel method and characterized using FT-IR spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDS). The determination of 99Mo adsorption capacity of these materials was carried out by soaking the materials in a Na299MoO4 solution with pH of 3 and 7, at temperatures ranging from room temperature to 90 °C, for 1 and 3 hours. The results indicated that monoclinic nanozirconia has a 99Mo adsorption capacity of 76.9 mg Mo/g, whereas orthorhombic nanozirconia, sulfated zirconia, and phosphated zirconia have 99Mo adsorption capacities of 150.1 mg Mo/g, 15.58 mg Mo/g, and 12.74 mg Mo/g, respectively. It appears that orthorhombic nanozirconia has the highest 99Mo adsorption capacity among the synthesized materials and can be applied as a candidate material for the 99Mo/99mTc generator.

The adsorption process was adopted to separate SO2 from surface modified haematite / III-ferric oxide with highly positive nano-particles. Ferric oxide was produced by precipitation at a different temperature rate. Adsorption of SO2 was performed in a dual packed bed column with different process parameters such as temperature, adsorbate rate to achieve balance of isotherm. Characteristics of adsorption have been studied such as concentration gradient, exhaustion time T0.95, mass transfer zone length (LMTZ), breakthrough time T0.05 and constant rate. Chemisorption between the surfaces of ferric oxide activated and the targeted adsorbate SO2 were strongly influenced between 45 and 50 °C. The adsorbent was analysed before and after the adsorption process using the X-Ray Diffraction Method (XRD), Atomic Adsorption Spectroscopy (AAS) to investigate adsorption properties such as porosity, specific surface area (152 m2g−1), adsorption capacity and characterization. The study showed that the activated ferric oxide surface affects the adsorption process capacity more than other metal oxide surfaces. Higher specific surface area (558 m2g−1) of ferric oxide activated adsorbed more SO2 than non-activated ferric oxide at room temperature.

Three valsartan metal (tin, nickel, and magnesium) complexes were examined as capture and storage media for methane under high temperature (323 K) and pressure (50 bar) conditions. The surface morphology of the complexes were examined using Field emission scanning electron microscopy and displayed porous structures comprising particles of different shapes and sizes. The narrow pore-size distribution of metal complexes makes them suitable materials for methane capture. The methane adsorption–desorption isotherms of the metal complexes were reversible. The tin(IV) and nickel(II) complexes exhibited type-III physisorption isotherms, while the magnesium(II) complex displayed a type-IV physisorption isotherm. Both types of isotherms are typical for mesoporous materials. The magnesium(II) complex was more efficient compared with the tin(IV) and nickel(II) complexes. It exhibited a remarkable methane uptake capacity of 71.68 cm3/g under optimized conditions.

High-temperature calcination was used to modify garnet media. Brunauer–Emmett–Teller (BET) measurements, X-ray diffractometer (XRD), scanning electron microscopy (SEM), zeta potential analysis, and a static adsorption experiment on humic acid removal were carried out to compare unmodified garnet and traditional quartz sand. Fitting adsorption isotherm of the media before and after modification was conducted to determine the adsorption type, and a dynamic filtration experiment was performed to treat micro-polluted water. Results of the characterization analysis and the static adsorption experiment revealed that, compared with the smooth surface of unmodified garnet, the surface of modified garnet media was covered with Fe2O3, which showed a rough concave-convex structure with a specific area that was 2.44 times larger than that of unmodified garnet. The removal efficiency of organic matter after modification increased from 2.5–4.5% to 51.7–63.1%, and the adsorption capacity increased 11–24 times. The adsorption type of the modified garnet media belongs to the Langmuir and Freundlich adsorption mode, while that of the original media belongs to the Freundlich adsorption mode. Results of the dynamic filtration experiment revealed that the effect of modified garnet media on turbidity, CODMn, and UV254 removal was better than that of unmodified garnet and traditional quartz sand.

Background and aims: The large amounts of the dyestuffs used in industries are toxic and whenever are released into wastewaters can lead to environmental and health problems. One of the most commonly used dyes in industries is Rhodamine B. It is widely used in printing, leather, paper and textile industries and is harmful to both human beings and animals. Thus, it is necessary to treat contaminated wastewater prior to discharging into water streams. Among all conventional physical, chemical and biological methods, adsorption is a very simple and effective method for removing dyes from wastewater even at low concentration. Activated carbons (ACs) are among the most widely used efficient absorbents which can remove these pollutants from aqueous phase and cause to prevent damages to the environments. Specific surface area, pore volume, pore-size distribution and the nature of surface are the main factors that influence AC performance. The surface modifications result in the change in the surface reactivity, chemical, physical and structural properties. Based on the type and chemical nature of the dyes, the surface of AC can be modified to enhance the affinity toward the desired contaminants. Depending on the application, there are different methods to modify AC, which can be classified as chemical, physical and biological modification. Plasma treatment is an environmental friendly method, which can introduce functional groups onto material surfaces without changing the bulk properties of the substrate. Methods: Modification of AC surfaces by means of plasma is a well-known method to enhance its adsorption capacity. Hence, in this research AC was prepared using chemical activation method from sound (SBAC) and rotted (RBAC) beech wood (Fagus orientalis) as precursors. The impregnation was carried out by ZnCl2 with the ratio of 75 percent to precursor mass and carbonization was performed at activating temperature of 400 ºC. The potential of AC treatment by plasma was then examined to introduce oxygen-containing groups onto AC surfaces and to enhance its efficiency to remove a basic dye, Rhodamine B, from aqueous solution. After carbonization step, surface modification of activated carbons was then conducted by dielectric barrier discharge (DBD) plasma in a parallel- plate reactor under different conditions of voltages (2, 4, and 6 kv) and treatment time(20, 30, and 40 min). Specific surface area, average pore diameter and pore volume of ACs were characterized from the results obtained by N2 adsorption at 77 K. In order to evaluate structure changes in plasma modified-ACs the FT-IR spectroscopy and scanning electron microscopy (SEM) were also used. Then, the capability of modified-ACs in removing of Rhodamine B was assessed and was compared with untreated ones. The batch adsorption tests have been carried out in the laboratory by contacting a 100 ml of dye aqueous solution with 0.1g of AC. The adsorption capacity of Rhodamine B in aqueous solution was measured using UV-Vis spectrometer at 555 nm. Results: The results indicated that the iodine number of ACs prepared from sound wood (SBAC) was less than RBAC that indicate more development of micropores in RBAC. Activated carbons from sound wood exhibited more specific surface area (1538 m2g-1), total pore volume (0.649 cm3g-1) and less average diameter (1.69 nm) in comparison with RBAC. As it was expected, chemical activation of precursors by ZnCl2 could successfully develop micropores through dehydrating reactions. It was found that adsorption capacity of untreated ACs prepared from rotted beech wood was higher in comparison with sound wood ACs. This may be attributed to differences in chemical compositions of precursors, which results in different pore structures at the same preparing conditions. It was also revealed that the adsorption capacity of ACs for removal of Rhodamine B can be improved by the surface modification of ACs using plasma treatment. Although, voltage changes showed no significant influence on ACs adsorption capacity, but maximum gain of 20% obtained at 2 kv with plasma treatment time of 2 min. Destruction of micropores walls and probable blocking of pores due to developing new functional groups may be a main cause of adsorption capacity loss in ACs, which modified by high voltage plasma. Raising heat of plasma because of increasing treatment time up to 30 min impaired dye removal by plasma modified ACs. The results of FTIR spectroscopy showed that oxygen-containing groups on ACs surfaces increased due to cold plasma treatment and changed slightly in acidic nature. A few bands were observed at around 1250, 1570, 1750 and 3440 cm-1 for each spectrum which indicated qualitatively that these carbon surfaces contains a mass of phenols, carboxylic anhydrides and a small quantity of carboxylic acids. This confirms the role of surface acid oxygen containing groups in contributing adsorption of Rhodamine B from aqueous medium. The enrichment of surfaces with hydroxyl groups results in improved interaction between Rhodamine B and adsorbent surfaces via electrostatic attraction and Van der Waals forces. In addition, a comparison of spectra of treated ACs with unmodified AC showed that use of cold plasma in presence of air to modify the carbon surface could not generate new types of surface chemical groups. It is proposed that adsorption of Rhodamine B on plasma-modified ACs is based on physisorption. The results of analyzing SEM images showed significant degradation of wood microstructure during impregnation with ZnCl2 as well as carbonization process under N2 inert atmosphere. However, it was observed from SEM images that morphology of ACs remained unchanged during plasma treatment. Although, in some cases the deposits effect of plasma caused to smooth surface of ACs sample. Conclusion: It is concluded from this research that both rotted and sound beech wood as a lignocellulosic materials has good potential in preparing ACs with great performance using ZnCl2 as activation agent. The results demonstrated that any variations in structure and compositions of lignocellulosic precursors with the same sources due to biological degradation result in different adsorption behavior of activated carbons. It was also found that cold plasma treatment under optimum conditions of voltage and treatment time could be a good surface modification method to enhance the adsorption capacity of ACs without any significant morphological changes to remove dyes such as Rhodamine B from aqueous phase.

The removal of brilliant green dye (BGD) from aqueous solution by using Salix alba leaves (SAL) was carried out via batch studies. The maximum removal efficiency was found to be 95.2% with initial dye concentration 50 mg/L at 0.15 g adsorbent dosage, pH = 6, and 298 K temperature, and the equilibrium was observed within 3½ hours. The adsorption capacity increased (2.21–15.89 mg/g) from 10 to 50 mg/L of dye concentration. Kinetic and isotherm studies were also carried out. The results showed that pseudo-second order model better describes the adsorption mechanism. The isotherm equilibrium data analysis was carried out by using Freundlich and Langmuir models and the sorption process was observed to conform with the Langmuir isotherm with linear correlation coefficient (R2 = 0.99). The thermodynamic properties ΔG°, ΔH°, and ΔS° delineated that BGD adsorption over SAL was feasible, spontaneous, and endothermic between 303 and 323 K temperature.

Industrial/technological growth is directly connected with environmental pollution, but its influence can be minimized through pollution abatement approaches such as the treatment of industrial wastewater. In this study, novel porous amine-functionalized silicate minerals, specifically, cordierite was investigated for the removal of toxic heavy metals from industrial wastewaters. Cordierite supports were synthesized by mixing MgO, Al2O3, and SiO2 powders in 2:2:5 molar ratios, and mechanically activated via ball milling in ethanol for 10, 40, or 80 min. Pellets were sintered by heating in air at 20 degrees C min(-1) to 1,350 degrees C, for 2 h. Porous supports were produced by coarsely crushing the sintered pellets and mixing the crushed and sieved cordierite powder with 20 wt.% of a pore-forming agent, either nanocellulose or yeast. The resulting pellets were sintered by heating at 5 degrees C min(-1) to 700 degrees C in air. The synthetic cordierite support was modified by treatment in poly-ethylenimine. Activated supports were then tested for the removal of Ni2+ and Cd2+ ions. The phase composition of the cordierite supports was analyzed by the X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Analysis of adsorption isotherms, kinetics, and thermodynamic parameters indicated that adsorption was a spontaneous, endothermic process with a maximum adsorption capacity of 36 mg g(-1) for Cd2+ and 43 mg g(-1) for Ni2+. This work has shed light on the mechanism of heavy metal removal from the aquatic medium using the novel hybrid functionalized cordierite-based ceramic.

In this study, a carbon molecular sieve (CMS) was synthesized from walnut shells, followed by physical activation of the carbon content of the CMS. Adsorption of CO2 and CH4 onto raw and acid treated adsorbents were investigated using two sizes, 300?600 and 600?1180 ?m. The adsorbents were impregnated with two solvent mixtures of waste engine oil with kerosene and with thinner at a proportion of 1:1 at 25?C. The highest adsorption for CO2 and CH4 was obtained at the suitable size of a group of CMS(A) adsorbents, with acid treated adsorbents being more efficient than the raw adsorbents. The acid treated CMS(A-3) sample adsorbed 0.925 mol CO2 g-1 and 0.353 mol CH4 g-1. The results indicated that by decreasing the granulation size of group CMS(R) adsorbents, the adsorption capacities for CO2 and CH4 were reduced while increasing the granulation size of group CMS(A) adsorbents resulted in an enhancement in the adsorption capacity for CO2 and CH4. Moreover, acid treated adsorbents achieved enhanced adsorption capacity for CO2 and CH4. Further modifications reduced the adsorption capacity for CO2 and CH4 in impregnated adsorbents, due to a decrease in surface area, pore volume and pore size of the adsorbent.

The influence of Al2O3 content in refining slag on the cleanliness and fatigue property of ultra-low-carbon (ULC) automotive steel were investigated based on the industrial experiments. The inclusion-adsorption capacity of the refining slag was calculated and the total [O] (T.O) content of ULC automotive steel was measured. The number density, size distribution and morphology of inclusions were analyzed and their effects on the cleanliness and fatigue property of ultra-low-carbon (ULC) automotive steel were investigated. The results showed that as the Al2O3 content in refining slag increased from 19.92% to 39.73%, the inclusion-adsorption capacity of ULC automotive steel decreased from 210.30 down to 57.12, and the fatigue life from 1.4x104 down to 0.9x104 cycles, while the T.O content of steel increased from 12 up to18 ppm and the inclusion number density from 4 up to 9 per mm2.

Science & Technology Asia, 27, 2, 84-97

This paper demonstrates that intercalating Na+ homoionic vermiculite with Fe3+ polyhydroxy cations (1:1 molar ratio OH− to Fe3+) significantly improved the affinity of the clay mineral-based sorbent toward phosphate. Kinetic experiments revealed that adsorption is fast, approaching an equilibrium within about 200 min of contact time, and that the rate-limiting step is the intraparticle diffusion. Adsorption isotherms fitted to the Freundlich equation and a two-site Langmuir model, consistent with the heterogeneity of adsorption sites. The separation factor derived from the Langmuir constant revealed that the adsorption was favorable and even irreversible for high-affinity minor adsorption sites. The adsorption capacity was 299 ± 63 μmol g−1 (9.3 ± 2.1 mg P g−1), a value similar to several other clay-based phosphate adsorbents. Application to reservoir water spiked with 10 mg L−1 in P removed about 71% of the available phosphate.

In this work, the inverse fluidized-bed bio-adsorption column is applied for the first time and is demonstrated using the torrefied rice husk (TRH) for the removal of methylene blue from the solution. The bio-adsorbents were characterized by BET, FI-IR, and SEM. The inverse fluidized-bed adsorption column using TRH becomes saturated in the 95-min continuous adsorption, during which the breakthrough time is 22 min, the overall MB removal (R) is 84%, and the adsorption capacity (Qexp) on the TRH is 6.82 mg g−1. These adsorption characteristics are superior to those in the fixed-bed adsorption column (R of 52% and Qexp of 2.76 mg g−1) at a lower flow rate (100 vs. 283 cm3 min−1). Torrefaction of RH significantly increases the surface area (28 vs. 9 m2 g−1) and enhances the surface functional groups, leading to an improved maximum equilibrium adsorption amount from 21.5 to 38.0 mg g−1 according to Langmuir model in the batch adsorption system. Besides, the increased Qexp on the TRH is also obtained in the inverse fluidized-bed (5.25 vs. 2.77 mg g−1, 89% higher) and the fixed-bed (2.76 vs. 1.53 mg g−1, 80% higher) adsorption columns compared to that on the RH.

As one of the most promising groups of microbes, lactic acid bacteria (LAB) can synthesize metabolites that can be used in different industries over the world, mainly in the pharmaceutical, food, and dairy industries. In this study, a novel exopolysaccharide was extracted and isolated from the probiotic strain Lactobacillus reuteri B2, and assessed on biological activity and its possible application as a biosorbent for the removal of Ni2+ ions from contaminated water. New exopolysaccharide was characterized using FTIR, SEM, XRD, NMR, MALDI-TOF MS, and TGA/DTG analysis. Biological assays included antioxidative activity, cytotoxic assay, and adhesion assay of L. reuteri B2 to HT29 cells. Our hypothesis was that if this exopolysaccharide is nontoxic, it can be used as a novel biomaterial for the possible application of the removal of Ni2+ ions from contaminated water. The scavenging effect of nontoxic exopolysaccharide was 76% at 2 mg/mL using ABTS assay, in biological assays, while the removal efficiency of nickel from the aqueous solution was 92.96% in biosorption study. According to these results, this exopolysaccharide can be considered a very promising biomaterial for potential application in different industries, from pharmacy to wastewater treatments.

Activated carbons are widely used especially in the removal of harmful contents of gases and liquids. Activated carbons constitute one of the important import items for our country. It is foreseen that the production of activated carbons from cheap, easily available and abundant raw materials of various organic origins will make significant contributions to the country's economy. In this study, it is aimed to evaluate semi-bituminous coals (Gediz-Kütahya) containing high sulfur as an alternative area of use in the production of activated carbon. In the study where ZnCl2 was used as the activation chemical, the effects of different working parameters (chemical/coal ratio, impregnation time and grain size) on activated carbon production were investigated. Various properties such as BET surface area, pore distribution, SEM surface properties, adsorption capability etc. of the obtained activated carbon were determined. Comparisons of the obtained activated carbon with the imported activated carbons still used commercially were made, and it was determined that there were significant similarities in properties.Optimum production operating parameters, 1/1 ZnCl2/coal mixture ratio, 24 hours impregnation time and +2 mm particle size coal is treated at 650 oC for 60 minutes under N2 atmosphere, with 733 m2/g BET surface area, micro and meso porosity activated carbon with a total pore volume of 0.460 cm3/g was obtained. As a result of the adsorption tests of the obtained activated carbon, it was determined that 99.2% of the Cu2+ ions in the solution could be removed. It has been understood that the obtained activated carbon can be used in many sectors. © 2023 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.

В данной работе представлены результаты исследования адсорбирующей способности адсорбентов в нативной и модифицированной формах, полученных на основе отходов растительного сырья Кыргызстана. Для достижения поставленных задач использованы химические (гравиметрия, экстракция, титриметрия) и физико-химические методы (спектрофотометрия). Концентрацию МС в растворе определяли спектрофотометрическим методом на UV-спектрофотометре Specord 50 в длине волны 190-110. Результаты исследования позволили установить, что модифицированные 0,8% раствором NaOH сорбенты, полученные из хлопчатника и полынь эстрагона, обладают высокой адсорбционной способностью по сравнению с нативной формой, например, по йоду (стебли хлопчатника с 12,63 до 24,44%, коробки хлопчатника - 11,43 до 24,01%, стебли полынь эстрагона - 11,21- 24,07%, при этом объём макропор также увеличивается в два раза (2,20-4,23, 1,32-3,08 и 2,28-4,20 см3 /г), а по метилен голубому наибольшей адсорбционной способностью обладают те же объекты., This paper presents the results of a study of the adsorption capacity of adsorbents in native and modified forms obtained on the basis of waste plant raw materials of Kyrgyzstan. Chemical (gravimetry, extraction, titrimetry) and physico-chemical methods (spectrophotometry) were used to achieve these tasks. The concentration of MS in the solution was determined by spectrophotometric method on a Specord 50 UV spectrophotometer at a wavelength of 190-110. The results of the study allowed us to establish that sorbents modified with 0.8% NaOH solution obtained from cotton and tarragon wormwood have a high adsorption capacity compared to the native form. For instance, by iodine (cotton stems from 12.63 to 24.44%, cotton boxes - 11.43 to 24.01%, wormwood tarragon stems - 11.21- 24.07%, at the same time, the volume of macropores also doubles (2.20-4.23, 1.32-3.08 and 2.28-4.20 cm3/g), and the same objects have the greatest adsorption capacity for methylene blue., НАУКА, НОВЫЕ ТЕХНОЛОГИИ И ИННОВАЦИИ КЫРГЫЗСТАНА, Выпуск 4 2022, Pages 118-121