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• Sustainable strategy to synthetize selenium-doped biochar materials. • High surface area Se-doped biochar (1300 m2/g) with mesopore features was synthetized. • Selenium-doped biochar showed effective removal of selected dye and drug. • High-performance adsorbents for treating different synthetic effluents. In this study, for the first time, a selenium-doped mesoporous biochar was prepared and efficiently employed for sodium diclofenac and reactive orange 16 dye adsorption. The characterization results indicated that selenium doping had a remarkable impact on Biochar-Se morphological and physicochemical structures. The efficacy of developed biochar samples on reactive orange 16 (RO-16) and diclofenac (DCF) removals was fully investigated. For both molecules (DCF and RO-16), Liu's equilibrium model offered the best fitness with maximum adsorption capacity values of 355 mg g−1 for DCF and 538 mg g−1 for RO-16 for Biochar-Se. Multiple mechanisms including pore filling, π-π interaction, and hydrogen bonding between the Biochar-Se and DCF/RO-16 molecules were involved in the adsorption process. Se-nanoparticles formed metal–oxygen bonds, which boosted the adsorption of DCF and RO-16 molecules. The current work offered a feasible approach for the development of Se-doped biochar adsorbent that is incredibly effective in treating wastewater. [ABSTRACT FROM AUTHOR]

Drinking water containing high fluoride concentrations may lead to serious health problems. Thus, aiming at water defluoridation through adsorption, several adsorbent materials have been studied worldwide. Due to its low cost and selectivity for fluoride ions, activated alumina (AA) is one of the most applied materials. At the same time, AA has low adsorption capacity, the pH of the aqueous solution must be less than 6.0 for fluoride adsorption, and it requires a long contact time to reach adsorption equilibrium. This study investigated the use of ozone to enhance the defluoridation property of AA. For this purpose, AA was treated under various ozonation conditions. Subsequently, the ozone-treated AA (OAA) samples were applied to adsorb fluoride from an aqueous solution. The influence of some ozonation parameters (AA concentration, pH, and contact time) was evaluated by carrying out adsorption experiments under fixed conditions. As a result, by full-factorial central composite rotational design (CCRD) and response surface methodology (RSM), it was found that the effect of initial pH during the ozonation is negligible on improving the defluoridation property of AA. At the same time, the decrease of AA concentration in the ozonation system significantly enhances the defluoridation property of AA. For example, the ozonation of 10 g L−1 of AA at a pH of 7.0 increased the fluoride removal efficiency of this material from 77.4% to 98.3%. Finally, the analysis of the ozonation time (0–120 min) showed that 90 min are sufficient to promote a significant rise in the fluoride removal efficiency of AA (from 78.3% to 97.4%). AA was characterized by FTIR, SEM, EDX NMR, and N 2 physisorption methods to elucidate factors responsible for the increased fluoride removal efficiency when the material is ozonized. [Display omitted] • A new approach to the use of the ozonation technique was studied. • Ozone increased the number of hydroxyl groups on the activated alumina surface. • The ozonation of activated alumina improved its defluoridation property. • The ozone-activated alumina can remove up to 99% of the fluoride ions from water. [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]

This article investigated the recovery of Gd3+ from real leachate of phosphogypsum (PG) using natural bentonite clay. Firstly, a detailed adsorption study was performed using synthetic Gd3+ solutions. Then, it was investigated the clay performance in the real PG leachate. The characterization results indicate classical bentonite characteristics, such as rugosity and an S BET 91.3 m² g−1, with meso (D p =3.82 nm) and macroporous (D p =52.6 nm). In addition, it was identified that the major functional groups are hydroxyl and silicate, with the presence of organic matter. The initial pH solution effect indicates that the optimum removal of Gd3+ is at pH (6), attributing to the pH pzc being at 5.75 and the negatively charged surface above the pH pzc. The Avrami fractional order model was the most suitable for describing the experimental kinetic data. The Langmuir was the proper model for describing the adsorption isotherms, indicating that the Gd3+ forms a monolayer at the surface of the bentonite. The maximum adsorption capacity at pH 6.0 was 121.5 mg g−1. The thermodynamic parameters indicate that the adsorption is spontaneous, with a standard enthalpy change of − 92.30 kJ mol−1, indicating an ionic exchange, where the Gd3+ tends to be organized at the surface, according to the standard entropy change of − 206.0 J K−1 mol−1. The fixed bed adsorption test showed that Gd3+ could be adsorbed for up to 200 min without regeneration. Regeneration results show that the citric acid is more efficient in desorbing the Gd3+ from the bentonite, reaching up to 8 cycles without efficiency loss. Finally, the bentonite clay could selectively recover Gd3+ from the real PG leachate. • Selective adsorption of gadolinium from leachate using bentonite. • The specific ion-exchange mechanism between bentonite and Gd+3. • Bentonite could be used for 8 adsorption-desorption cycles. • Bentonite could selectively recover 90% of Gd3+ from the leachate. [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]

The challenge nowadays still to find an economical way for the production of biochar materials with specific characteristics, rich in nitrogen, sulfur, or other surface functional groups for a specific purpose, as well as providing a clear understanding of the mechanisms occurring in the process preparation, when it is used different chemical agents, and, produce highly porous materials. This study displays the influence of different zinc salts (Cl-, SO 4 2-, PO 4 3- and NO 3 -) at the different quantities on the physical-chemical and adsorptive properties of the biochar materials produced via conventional heating. The biochar materials (ZnACs) are characterized by FTIR spectroscopy, DRX, X-Ray Fluorescence, nitrogen-adsorption/desorption analyses, FESEM-EDS, TGA/DTG, CHNS elemental analysis, pH zpc , hydrophobic properties, total basicity, and acidity groups. The Adsorption studies of emerging organic contaminants, pharmaceutical molecules, and anionic and cationic dyes on the ZnACs carbons were carried out at the following conditions: C 0 = 300.0 mg L−1, T = 25 °C, adsorbent mass = 30.0 mg and t = 20 h. It appeared that although all the salts have zinc and even in the same molar amounts, the preparation process led to biochar materials with different textural characteristics and surface functional groups. The biochars also presented good adsorption capacities for removing pharmaceuticals, EOCs, and dyes from aqueous media. Notwithstanding, the biochar prepared with Zn(NO 3) 2 and ZnCl 2 show the best textural characteristics and adsorption performance for all tested classes of adsorbates. The adsorbed amount (q e) is > 200 mg g−1 for ZnNAC 2 and ZnCAC 1. [Display omitted] • Different zinc salts were employed as activating agents in the preparation of the biochar materials. • The smaller the number of valence electrons in the counterions is, the greater is the S BET and V p. • High surface area for ZnCl 2 (1220 m2 g−1) and Zn(NO 3) 2 (323 m2 g−1) was obtained. • The preparation process leads to biochars with different textural characteristics and functional groups. • Zn(NO 3) 2 and ZnCl 2 based biochars show good adsorption performance and Q e > 200 mg g−1 for ZnNAC 2 and ZnCAC 1. [ABSTRACT FROM AUTHOR]

Four magnetic biochars (MBs) were prepared from two mixtures of Sappeli sawdust with NiCl 2 solution or Sappeli sawdust with NiCl 2 plus ZnCl 2 solutions. These mixtures formed two pastes that were dried and further pyrolyzed at 700 °C under nitrogen flow. The pyrolyzed material was leached out with 0.1 M HCl under conventional reflux (AL- 80 °C, 2 h) or assisted by ultrasound-leaching (US- 15 min, 600 W), obtaining four biochars: SNiAL, SNiUS, SNiZnAL, SNiZnUS. The biochars were characterized by VSM, XRD, FTIR, isotherms of adsorption and desorption of nitrogen, pH pzc , hydrophobically characteristics (HI), TGA, elemental analysis (CHN/O). The data show that using the leaching process assisted by ultrasound can obtain biochars that present good magnetization saturation, with a lower leaching time than conventional leaching. The four biochar were tested as adsorbents to remove ten emerging contaminants and four dyes of aqueous effluents. It was observed that the impregnation of zinc chloride in the samples led to an increase in the surface areas of the magnetic biochars, which influenced the most of sorption capacities of the adsorbents for the different sorbing species. Making a ratio of sorption capacities of SNiAL/SNiZnAL and SNiUS/SNiZnUS, it was obtained the values, respectively, of 0.9761, and 0.9710 (Acid Red 1), 2.057, and 3.030 (Reactive Blue 4), 4.192, and 1.971 (Basic Violet 3), 3.359, and 1.129 (Basic Green 1), 1.673, and 1.835 (Paracetamol), 3.612, and 3.779 (Propranolol), 5.871, and 5.171 (Sodium Diclofenac), 1.457, and 1.607 (Nicotinamide), 1.094 and 1.093 (Caffeine), 1.167, and 2.398 (4-chloroaniline), 1.009 and 0.9965 (2-nitrophenol), 1.156 and 1.341 (Resorcinol), 1.299 and 1.331 (Hydroquinone), 0.9975 and 1.019 (4-bromophenol). [Display omitted] [ABSTRACT FROM AUTHOR]

• Removal of captopril pharmaceutical from synthetic pharmaceutical-industry wastewaters. • ZnCl 2 -activated carbon (ABc-600) prepared from Butia catarinensis. • ABc-600 removed up to 99.0 % of synthetic pharmaceutical-industry wastewaters. • The maximum sorption capacity of ABc-600 was 717.2 mg g−1. • The mechanism of adsorption was explored. A high surface area activated carbon was produced from the seed of Butia catarinensis (Bc), which was utilized for removing captopril from synthetic pharmaceutical industry wastewaters. The activated carbon was made by mixing ZnCl 2 and Bc at a proportion of 1:1 and pyrolyzed at 600° (ABc-600). The material was characterized by the Boehm titration, hydrophilic/ hydrophobic ratio, elemental analysis, TGA, FTIR, and N 2 isotherm (surface area (S BET), total pore volume (TPV), and pore size distribution (PSD)). The characterization data showed that the adsorbent displayed a hydrophilic surface due to the presence of several polar groups. The carbon material presented a TPV of 0.392 cm3 g−1, and S BET of 1267 m2 g−1. The equilibrium and kinetics data were suitably fitted to Liu isotherm and Avrami-fractional-order. The employment of the ABc-600 in the treatment of synthetic pharmaceutical industry wastewater exhibited high effectiveness in their removals (up to 99.0 %). [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]

Abstract Particle size variation plays a key role in jigging performance, and despite extensive research in the area, very little attention has been given in the case of pneumatic jigging. The aim of this study was to look into particle stratification in a pilot-scale pneumatic jig when varying the particle size and the range of the particle size distribution in ternary mixtures of aggregates. Jigging tests were especially designed to reduce contamination of jig products and a stratification index was elaborated to evaluate stratification efficiency. Experimental results provided compelling evidences that widening the particle size distribution of the system or using beds composed of particles of smaller sizes can enhance stratification by density. Similarly, smaller particles showed a remarkable tendency to concentrate in the upper zones of the stratified bed, whereas larger particles tended to concentrate more in lower zones. The obtained results suggest that particular operating features of pneumatic jigging together with differential packing effects should play a decisive role in the stratification extent of beds formed by particles of different sizes. Experimental results are of practical importance since, among other benefits, they point to the possibility to increase pneumatic jigging performance in some cases by using wider size distributions of the feed, thus reducing the need of prior stages of narrow size classification. Graphical abstract Unlabelled Image Highlights • Stratification efficiency increased with decreasing particle size class. • Stratification efficiency increased with expanding particle size distribution. • The use of wider size distribution improved recovery of larger heavier particles. • Packing effects had an important influence on stratification efficiency. [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]