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This paper proposes an easy and sustainable method to prepare high-sorption capacity biobased adsorbents from wood waste. A biomass wood waste (spruce bark) was employed to fabricate a composite doped with Si and Mg and applied to adsorb an emerging contaminant (Omeprezole) from aqueous solutions, as well as synthetic effluents loaded with several emerging contaminants. The effects of Si and Mg doping on the biobased material's physicochemical properties and adsorptive performance were evaluated. Si and Mg did not influence the specific surface area values but impacted the presence of the higher number of mesopores. The kinetic and equilibrium data presented the best fitness by the Avrami Fractional order (AFO) and Liu isotherm models, respectively. The values of Qmax ranged from 72.70 to 110.2 mg g−1 (BP) and from 107.6 to 249.0 mg g−1 (BTM). The kinetic was faster for Si/Mg-doped carbon adsorbent, possibly due to different chemical features provoked by the doping process. The thermodynamic data showed that the adsorption of OME on biobased adsorbents was spontaneous and favorable at four studied temperatures (283, 293, 298, 303, 308, 313, and 318 K), with the magnitude of the adsorption correspondent to a physical adsorption process (ΔH° < 2 kJ mol−1). The adsorbents were applied to treat synthetic hospital effluents and exhibited a high percentage of removal (up to 62%). The results of this work show that the composite between spruce bark biomass and Si/Mg was an efficient adsorbent for OME removal. Therefore, this study can help open new strategies for developing sustainable and effective adsorbents to tackle water pollution. [ABSTRACT FROM AUTHOR]

• Diatomite is a highly efficient adsorbent of Nd3+, Ce3+, and La3+. • At pHs 2–6, the REEs removal efficiency practically did not change. • The uptaken percentages were La3+ (50%), Ce3+ (77%), and Nd3+ (92%). • Diatomite could be reused 8 times without losing performance. This study addresses the application and evaluation of diatomite as a low-cost, natural, abundant, and highly efficient adsorbent of Nd3+, Ce3+, and La3+ rare earth elements (REEs). The results revealed that the diatomite was porous and cylindrical, with a specific surface area of 150 m2/g. The diatomite displayed a point of zero charge equal to 1.8, maintaining its surface negatively charged at pH values higher than 1.8, which was beneficial for cationic REEs uptake. At pH 1, all three REEs had their lowest uptake values; at pHs 2–6, the REEs removal efficiency practically did not change. The uptaken percentage increased in the order of La3+ (50%), Ce3+ (77%), and Nd3+ (92%), influenced by the electronegativity of the ions. The Avrami-fractional order (AFO) and Liu isotherm model better fit the kinetic and equilibrium process (q max = La3+ (22.8 mg g−1), Ce3+ (56.2 mg g−1), and Nd3+ (100.9 mg g−1)). Since the diatomite is highly porous, pore filling/pore-surface diffusion was the main mechanism for REEs adsorption, as well as ion exchange and chelation. The reusability tests revealed that the diatomite could be reused 8 times without losing performance. This research shows that diatomite is an efficient strategy for designing effective, low-cost, sustainable adsorbents to recover REEs from synthetic and real effluents. [ABSTRACT FROM AUTHOR]

Over the last decade, adsorption has exhibited promising and effective outcome as a treatment technic for water and also for wastewater contaminated with many types of pollutants such as metals, dyes, pharmaceutical products in solutions. To achieve such effectiveness, a number of efficient adsorbents have been synthesized and applied in the process. In recent years, significant efforts have been achieved in the development of highly efficient adsorbent materials. However, despite these achievements, researchers are now focused on developing the materials that are non-toxic, cost effective and efficient at the same time. Among the most well-known adsorbents, activated carbon is the most popular, due to its excellent adsorption characteristic, porous structure and high specific surface area, despite the fact that it is expensive, and does not possess good mechanical strength etc. Based on this context, the silicate based materials such as clays, zeolites; sand, etc constitute a large resource and low-cost material which could be used as an alternative raw material for producing low cost and efficient adsorbent materials. However, due to the poor performance exhibited by natural silicate based materials in pollution withdrawal, amine grafted silicate based material was considered for long years as a promising approach for both adsorption of inorganic and organic pollutants. This review’s goal is to make a comprehensive discussion about the preparation, the use of amine grafted silicate based materials and their adsorption behaviour under diverse conditions. The literature survey presented in this paper provides evidence of the good potential of amine grafted silicate based materials to remove several contaminants from aqueous solution. [ABSTRACT FROM AUTHOR]

Hybrid adsorbents were prepared by reacting tannin with different amounts of 3-aminopropyltriethoxysilane (APTES). The materials were characterized by SEM, TEM, FTIR, CHN, N 2 adsorption/desorption isotherms and vapor sorption (water and n-heptane adsorptions–for determination of the hydrophobicity-hydrophilicity ratio). The modified materials were utilized as adsorbents for the removal of Acid Red 1 (AR-1) dye from aqueous solutions. The N 2 isotherm results showed low porosities of the modified materials, however they presented high efficient adsorption of AR-1 dye. To find a proof of hybridization between tannin and APTES, the materials were characterized by Diffuse Reflectance Ultraviolet-Visible Absorption (DRUV) spectroscopy. The results indicate that the electronic structure of the final materials was changed, and was related to a hybrid formation between tannin and APTES. For the adsorption experiments, the best experimental conditions were reached at pH 2.0, contact time of 8 h and at 50 °C. The equilibrium and kinetics adsorption data were well represented by the Liu isotherm and the General order kinetic models, respectively. The maximum adsorption capacity of 418.3 mg g −1 was obtained at 50 °C for a tannin-APTES material at ratio 1:1 (Tan-Ap-1.0). Based on experimental data it was found that electrostatic interactions and hydrogen bonds between adsorbent and AR-1 dye played the most important role in the adsorption process. Effect of temperature and thermodynamic studies revealed that the adsorption processes of AR-1 onto tannin materials are dependent on temperature and are exothermic and spontaneous. With regards to the applicability of the adsorbents for treating simulated effluents, they showed an excellent outcome confirming their high-efficiency for dye adsorption. [ABSTRACT FROM AUTHOR]

Preparing sustainable and highly efficient biomass-based carbon materials (BBPM) as adsorbents remains a challenge for organic pollutant management. In this work, novel biobased carbon material has been synthesized via facile, sustainable, and different single-step pyrolysis chemical methods (KOH, ZnCl 2 , ZnSO 4, and MgCl 2) using a Norway spruce bark as suitable and efficient carbon precursor. The effects of each chemical activator on the physicochemical structure of synthesized were thoroughly investigated as well as its performance on the acetaminophen adsorption. The results showed that the use of different chemical activation provoked remarkable differences in the BBPM physicochemical characteristics. The KOH activation generated material with the highest specific surface area (2209 m2 g−1), followed by ZnCl 2 (1019 m2 g−1), ZnSO 4 (446 m2 g−1), and MgCl 2 (98 m2 g−1). The chemical characterization of the carbon materials indicated that the activation of MgCl 2 yielded a material around three times more hydrophobic when compared with the other activation methods. The acetaminophen removal showed to be ultrafast, not only due to the BBPM's microstructure but also to the abundant active sites provided by the different chemical activation methods. The adsorption equilibrium times were reached at 1 min for BBPM-KOH and BBPM-MgCl 2 and 15 min for BBPM-ZnSO 4 and BBPM-ZnCl 2. The adsorption process suggests that the pore-filling mechanism mainly dominates the acetaminophen removal but also some physical-chemical interactions such as hydrogen bonding between the amide group of acetaminophen and oxygenated or nitrogenated groups of biochar, π-π interactions between the aromatic ring of the pharmaceutical and the aromatics of biochar, n-π interaction, van der Waals interactions. The BBPM regeneration studies showed very good cyclability; in the 3rd cycle, the removal was approximately 70% for all four samples. The samples were also used to treat two synthetic effluents, which attained a removal percentage up to 91.9%. [Display omitted] • Porous carbons were prepared by simple methods using MgCl 2 , ZnSO 4 , ZnCl 2, and KOH. • KOH activation yielded a porous carbon with a specific surface area of 2209 m2 g−1. • Compared to other chemicals, MgCl 2 yielded an extremely hydrophobic material. • Ultrafast acetaminophen adsorption times were reached for all activation methods. • Regeneration studies showed good cyclability at around 70% in the 3rd cycle. [ABSTRACT FROM AUTHOR]

In this work, Norway spruce bark was used as a precursor to prepare activated biochars (BCs) via chemical activation with potassium hydroxide (KOH) as a chemical activator. A Box–Behnken design (BBD) was conducted to evaluate and identify the optimal conditions to reach high specific surface area and high mass yield of BC samples. The studied BC preparation parameters and their levels were as follows: pyrolysis temperature (700, 800, and 900 °C), holding time (1, 2, and 3 h), and ratio of the biomass: chemical activator of 1: 1, 1.5, and 2. The planned BBD yielded BC with extremely high SSA values, up to 2209 m2·g−1. In addition, the BCs were physiochemically characterized, and the results indicated that the BCs exhibited disordered carbon structures and presented a high quantity of O-bearing functional groups on their surfaces, which might improve their adsorption performance towards organic pollutant removal. The BC with the highest SSA value was then employed as an adsorbent to remove Evans blue dye (EB) and colorful effluents. The kinetic study followed a general-order (GO) model, as the most suitable model to describe the experimental data, while the Redlich–Peterson model fitted the equilibrium data better. The EB adsorption capacity was 396.1 mg·g−1. The employment of the BC in the treatment of synthetic effluents, with several dyes and other organic and inorganic compounds, returned a high percentage of removal degree up to 87.7%. Desorption and cyclability tests showed that the biochar can be efficiently regenerated, maintaining an adsorption capacity of 75% after 4 adsorption–desorption cycles. The results of this work pointed out that Norway spruce bark indeed is a promising precursor for producing biochars with very promising properties. [ABSTRACT FROM AUTHOR]

Concrete slurry is an abundant, cheap, and commonly found waste all over the world where construction activities take place; concrete slurry, which is rich in calcium and metallic oxides, could be successfully employed in the phosphate (P) removal from aqueous media. For the first time, the effect of the carbonation process on concrete adsorbent properties and how it can influence on the removal of phosphate ions in aqueous media are studied. Besides, the potential applicability of P loaded concrete adsorbent is also evaluated. The results showed that a non-carbonated sample was more effective in the P removal, due to higher releasing of calcium (Ca2+) in comparison to carbonated sample. The dissolved Ca2+ from the dissolution of calcium hydroxide (Ca(OH) 2), calcium carbonate (CaCO 3), and calcium oxide (CaO) are preferably precipitated by phosphates in high pH solution, reflecting in a high initial adsorption rate. General order kinetic and Liu isotherm provided better-fitting models for the adsorption behavior of P onto both non-carbonated and carbonated concrete samples. Phosphate removal was mainly ruled by chemical adsorption through inner-sphere complexation and P precipitation on the surface of the adsorbent containing Ca2+ as an essential ion in the adsorption mechanism. Compared with other phosphate adsorbents, both non-carbonated and carbonated concrete showed to be economical and efficient adsorbent. The non-carbonated sample gave a high adsorption capacity of P (47.6 mg g−1) and presenting fast and high initial adsorption, reaching 72% of P removal within 5 min (min) at 22 °C, while carbonated showed adsorption capacity of 30.6 mg g−1, at the same experimental conditions. Therefore, concrete slurries can be used widely as an inexpensive phosphate-recovery adsorbent. Besides, the application of these P loaded waste as potential fertilizers in soil can be an exciting and environmentally approach for reusing this solid-waste. The environmental analysis highlighted that the adsorbents did not leach out chemicals above the allowable limits, preconized by The Food and Agriculture Organization of the United Nations (FAO) for irrigation waters. However, aspects related to monitoring the presence and mobility of heavy metals on soil must be better addressed and monitored. Image 1 • The effect of the concrete carbonation on adsorption properties was investigated. • Non-carbonated concrete presented better adsorption properties. • The dissolved Ca2+ played an important role in the phosphate adsorption. • Non-carbonated and carbonated were efficient adsorbents for phosphate adsorption. • The P loaded concrete could be applied as potential fertilizers in soil. [ABSTRACT FROM AUTHOR]

The PVSDM model was used for single and binary dye adsorption systems. This model is commonly used for adsorption in single systems, but this is the first time used in a binary mixture of dyes in the literature. To that end, a new adsorbent derived from Bauhinia forficata waste was created and described for eventual use in the treatment of a dye combination (methylene blue and crystal violet). The single and binary isotherms revealed that increasing the temperature decreases the methylene blue adsorption capacity while increasing the crystal violet adsorption capacity. The Langmuir and extended Langmuir models described the single and binary systems, respectively. Maximum adsorption capacities of 229.13 mg g−1 at 298 K for methylene blue and 324.12 mg g−1 at 328 K for crystal violet were obtained. The thermodynamic parameters showed that the adsorption process for both dyes is spontaneous, being exothermic for the methylene blue and endothermic for the crystal violet. Similar decay curves for the single and binary systems were observed. The PVSDM was able to describe both single and binary adsorption systems. The external mass transfer and the surface diffusion change according to the initial dye concentration and the system type (single or binary). [Display omitted] • The capacity of the single systems was 190.9 and 267.7 mg g−1, for the MB and CV. • The capacity for the mixture was 185.51 and 266.6 mg g−1 for the MB and CV. • The PVSDM model was able to describe the adsorption of single and binary systems. • The external mass transfer and surface diffusion changed according to the system. [ABSTRACT FROM AUTHOR]

Textile dyes are one of the most commonly found pollutants in water, and it is necessary to remove them before textile industry effluents are released into the environment. In this study, cellulose-based adsorbents were prepared by grafting N1-(3-trimethoxysilylpropyl)-diethylenetriamine (TMSPDETA) on microcrystalline cellulose surface for the adsorption of reactive dyes from aqueous solution. Characterization of the produced adsorbents [Cel@TMSPDETA 10 ; composite of cellulose + TMSPDETA (10% weight)] and the experimental and modeling studies were thoroughly investigated. Based on ΔBIC analysis (Bayesian Information Criterion), the fractal-like pseudo-first-order model (FPFO) was the model with the highest degree of adequacy to describe the kinetic behavior for RR-35 (Reactive Red 35) and RG-19 (Reactive Green 19) dye adsorption on Cel@TMSPDETA 10. It was observed that the values of t 0.95 (time necessary to attain 95% saturation) of RG-19 dye were 1.81 times slower than those of RR-35. This difference in times to attain 95% saturation of RG-19 with RR-35 could be assigned to the larger size of the RG-19 molecule. Based on the ΔBIC values, the Liu isotherm was better fitted to the experimental data. At 30 °C, the highest Q max (Liu model) value was 197.0 mg g−1 for RR-35 dye. For RG-19, the highest value of Q max (Liu model) was 210.5 mg g−1 at 45 °C. Alternatively, a statistical physics model that represents the general case of the Langmuir model was adopted to provide new insights into the adsorption mechanisms of RR-35 and RG-19 dyes on the adsorbents. Interestingly, this new approach showed that RR- 35 was adsorbed via a partial aggregation process, contrary to the RG-19 dyes. [Display omitted] • Increase in the sorption capacity of up to 8 times Cel@TMSPDETA 10 to Cel • Cel@TMSPDETA 10 was employed to remove RR-35 and RG-19 dyes from wastewater. • The FPFO and Liu models were fitted to describe the kinetic and equilibrium experiments. • Statistical physics data shows that RR-35 was adsorbed with a lower aggregation degree. • Statistical physics data shows that RG-19 was adsorbed with a higher aggregation degree. [ABSTRACT FROM AUTHOR]

[Display omitted] • H 2 O 2 was successfully used to modify the surface of the clay mineral in the preparation of a novel adsorbent. • The treated sample (MMT-H 2 O 2) showed a high oxygen content and adsorption capacity compared to the untreated one (MMT). • The maximum adsorption capacity (Q max) value obtained with the best-fitted model was 1178.5 mg g−1. • Temperature-dependent adsorption energy levels were found to be less than 40 kJ mol−1. The water contamination problem caused by dyes and the understanding of their adsorption mechanism in aqueous media is still significant nowadays. This study investigates the adsorption performance of natural montmorillonite clay treated with H 2 O 2 (MMT-H 2 O 2) and employed as an adsorbent to remove Acid Red 114 (AR-114) from aqueous solutions. MMT-H 2 O 2 and the natural clay without treatment (MMT) were analysed using different analytical techniques such as XRF, XRD, FESEM, EDS, FTIR, TGA/DTG, N 2 -adsorption/desorption curves, CHNS/O analysis, hydrophobicity Index (HI). It also provides a theoretical analysis of the adsorption phenomenon utilising Statistical Physics methods to understand the adsorption mechanism between AR-114 and MMT-H 2 O 2 adsorbent associated with batch adsorption conditions and adsorption equilibrium. The treated clay with H 2 O 2 showed a higher oxygen content and a better adsorption capacity than the untreated one. The maximum adsorption capacity (Q max) values obtained with the best-fitted model (Liu) ranged from 421.9 and 1178.5 mg g−1. This high adsorption capacity for AR-114 dye can be explained by considering the remarkable characteristics of the MMTH 2 O 2 material, such as high oxygen content, variety of surface functional groups, porous interlayer structure, and hydrophilicity. The computational adsorption results suggest that the AR-114 molecules adsorbed onto the surface site of the MMTH 2 O 2 adsorbent in a perpendicular orientation. This indicates that the n 2 values increased as the operating temperature was raised, demonstrating the endothermic accumulation of dye molecules on the treated clay mineral surface. Moreover, the temperature-dependent adsorption energies (E 1 and E 2) levels were less than 40 kJ mol−1, highlighting the primary physical interactions between AR-114 and MMTH 2 O 2 clay mineral by electrostatic attraction and hydrogen bonding. [ABSTRACT FROM AUTHOR]

Natural clay was grafted with 3-aminopropyl-trietoxisilane (APTES) for obtaining an organic-inorganic hybrid material. This material was successfully used as adsorbent for removal of Acid Red 1 (AR-1) and Acid Green 25 (AG-25) anionic dyes from aqueous solutions. This work demonstrates the effect of APTES concentration on the hydrophobic/hydrophilic characteristics and optical properties of the amino-functionalized materials. The adsorption capacity of the resultant hybrid materials were studied using anionic dyes. The physico-chemical properties of the materials was determined by several analytical techniques. It appears that the modified samples were more hydrophilic than the natural clay for ratios from 1.0 up to 2.0, due to the presence of amino group (—NH 2 ) located at the end of the chain. The characterization data showed that APTES was successfully grafted on to the external as well as interlayer and broken edges of montmorillonite. Transmission electron microscopic images confirmed that the morphology of amino-functionalized material changed from sheet-like in the natural clay material to a conglobulated structure. The amino-functionalized material exhibited a surface area 6-times (S BET = 13.31 m 2 /g) lower than natural clay (S BET = 86.10 m 2 g −1 ; V tol = 0.126 cm 3 g −1 and D p = 4.72 nm). The total pore volume (V tol = 0.041 cm 3 g −1 ) and average pore diameter (D p = 10.2 nm) was found to be 2-times lower than clay. Adsorption followed the general-order kinetic model for both dyes. Liu isotherm model was observed to be best fit and it displayed Q max as 364.1 and 397.0 mg g −1 for AR-1 and AG-25, respectively at 50.0 °C. Electrostatic interaction was the main mechanism involved in the adsorption process. The Mrt-APTES 0.5 seemed to be a good adsorbent for the treatment of synthetic effluents. The removal percentage of effluent A and B were 97.94% and 95.94%, respectively. [ABSTRACT FROM AUTHOR]