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Aminophosphonates are excellent complexing agents for numerous metal ions (including uranyl). Based on this property, two sorbents have been synthesized using simple one-pot reaction: thiocarbazide (amine source), p-phthaldehyde (di-aldehyde), and trimethylphosphite (phosphorous precursor) are mixed with different molar ratios to produce bis- (2:1:2) and mono (1:1:1) α-aminophosphonate-based derivatives (B-AmPh and M-AmPh, respectively). Materials are characterized using XRD, BET, SEM, titration, elemental, FTIR, and XPS analyses to evaluate the effect of substitution rate on the physicochemical properties. FTIR and XPS are also used for elucidating binding mechanisms. Sorption properties of the materials have been tested for U(VI): the pH effect is completed by investigating uptake kinetics and sorption isotherms. At pH 4.5 (and T: 55 °C), sorption capacity increases from 0.89 to 1.22 mmol/g with the increase in the substitution degree (M-AmPh < B-AmPh). This increase is not correlated to the fraction of grafted reactive groups, meaning that steric hindrance probably contributes to limiting the accessibility and availability of aminophosphonate moieties. Pseudo-second order and Crank equation preferentially fit kinetic profiles. Langmuir equation successfully describes sorption isotherms. Sorption process is systematically endothermic and spontaneous: enthalpy and entropy changes decrease with the substitution rate. Uranium successfully desorbed using HCl (0.2 M); allows six cycles of re-use with limited loss in sorption/desorption efficiencies. The sorbents were used for U(VI) recovery from acidic leachate of uranium ore. This test shows remarkable affinity and selectivity of B-AmPh for uranium; however, after elution and precipitation the U concentrate contains about 10 % of impurities. [Display omitted] • One pot synthesis of two α-aminophosphonate derivatives (B-AmPh and M-AmPh) via different molar ratios of precursors. • Degree of substitution affects both textural and sorption features: B-AmPh is more efficient for U(VI) sorption at pH 4.5. • Limited loss in sorption and desorption performances after 6 cycles. • Both materials exhibit good durability, stability and promising potential for U(VI) removal. • High selectivity for U(VI) vs. other cations in acidic ore liquor solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Maleic anhydride polymerization with methylenebisacrylamide for sorbent synthesis. • Functionalization by thiocarbazide grafting improves Th(IV) sorption. • Functionalization for faster, higher sorption, enhanced selectivity, and stability. • Efficient removal of thorium (and uranyl) from pre-treated acidic leachate or ore. • Metal sorption through interaction with amine, carboxylic, and thiocarbonyl groups.Abstract. The copolymerization of maleic anhydride with N , N '-methylenebisacrylamide allowed synthesizing a sorbent (MaMb) that can be functionalized by amidoacidification (for grafting thiocarbazide) (synthesis of TcMaMb). The two sorbents are tested in batch systems for the removal of thorium from aqueous solutions. The characterization of the materials shows similar textural properties and the involvement of amine, carboxylic groups (for MaMb), completed with thiocarbonyl groups (for TcMaMb), in the binding of Th(IV). The maximum sorption occurs at pH close to 4 and the functionalization doubles the maximum sorption capacity (up to 1.36 mmol Th g−1). The sorption isotherm for TcMaMb is fitted by the Langmuir equation (in the case of pristine sorbent, the saturation of the sorbent is not achieved in the tested concentration range making the Freundlich equation more appropriate). The functionalization improves the uptake kinetics (equilibrium time decreased from 120-180 min to 30 min), and kinetic profiles are fitted by the pseudo-first order rate equation. The selectivity of the sorbent for Th(IV) (and to a certain extent U(VI)) is improved by thiocarbazide grafting, especially at pH above 4 (in the case of equimolar multi-component solutions). The functionalization of MaMb also enhances the selectivity of TcMaMB for thorium when applied to metal removal from pre-treated mining leachate (consistently with synthetic solutions). Bound metal can be readily desorbed (complete desorption achieved in 30 min) using 0.3 M HCl solutions for both MaMb and TcMaMb sorbents. Another advantage brought by the functionalization concerns the stability of the sorbent at recycling: after five cycles of re-use the sorption efficiency decreases by less than 2 % (meaning less than for MaMb, at about 8 %). [ABSTRACT FROM AUTHOR]

The grafting of arginine and glutamic acid on cellulose (through an intermediary step of chlorination) allows improving uranyl sorption of the biopolymer. The sorbents (Arg-Cell and Glu-Cell) were characterized by elemental analysis, FTIR spectrometry, XRD, SEM-EDX analysis and TGA. The sorption efficiency increases with pH; this can be attributed to the deprotonation of carboxylic acid and amine groups and to the formation of polynuclear hydrolyzed uranyl species. Sorption isotherms (fitted by the Langmuir equation) show sorption capacities at saturation of the monolayer of 147 and 168 mg U g for Arg-Cell and Glu-Cell, respectively (compared to 78 mg U g for raw cellulose); maximum sorption capacities at equilibrium (experimental values) reach 138, 160 and 73.4 for Arg-Cell, Glu-Cell and cellulose, respectively. Uranyl sorption is endothermic and is spontaneous for amino acid derivatives of cellulose (contrary to exothermic for cellulose). Uptake kinetics for the different sorbents are fitted by the pseudo-second-order rate equation. Uranium can be desorbed using sulfuric acid solutions, and the sorbents can be recycled for a minimum of five cycles of sorption/desorption: the decrease in sorption capacities at the fifth cycle does not exceed 13%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of Cs(I) sorbent by CH 2 O-condensation of aminomethane sulfonic acid. • Sorption isotherm fitted by Langmuir equation (g m : 1.99 mmol Cs g−1). • Fast uptake kinetics modeled by pseudo-first order rate equation (t eq : 60 min). • Easy desorption (0.3 M HNO 3) and remarkable stability (5 cycles). • Antimicrobial effect, poor cytotoxicity for natural cells (≠to cancerous cells). A new sorbent (ACES-F micro-particles) is readily synthesized by the one-pot reaction of N-(2-acetamido)-2-aminoethanesulfonic acid with formaldehyde (poly-condensation reaction). The mesoporous sorbent is characterized by BET analysis (S BET : ≈6 m2 g−1), SEM-EDX (N: ≈7–8 % and S: 5 %), FTIR spectroscopy (identification of amine, sulfonic groups and their interactions with metal ions), TGA, elemental analysis, and titration (pH PZC : ≈5.7). The study of pH effect on Cs(I) shows an optimum close to 8 (with intermediary optimum at pH 4, associated with different reactive groups). The micron-size sorbent shows fast sorption (equilibrium in 60 min) and the pseudo-first order rate equation fits the kinetic profile. The sorption isotherm reaches up to 1.99 mmol Cs g−1; the Langmuir equation models isotherm profiles. The sorption decreases with increasing temperature; sorption is exothermic. Cesium uptake is affected by the presence of NaCl; however, even in large excess of salt (i.e., 4 M) sorption remains relatively high (loss <60 %). Selectivity is confirmed by the remarkable preference of the sorbent for Cs against alkali and other competitor metal ions, especially at pH eq ≈7. Metal desorption is highly effective using 0.3 M HNO 3 solutions: complete desorption occurs in 30 min. The sorbent can be recycled for at least five cycles (losses <3 %). The interest of ACES-F for cesium recovery from seawater is confirmed by the study of Cs(I) sorption (and other major elements) from Vietnam and Egypt samples. The safety of the sorbent for aqueous bodies is evaluated by the cytotoxicity of the sorbent (limited against normal cells but highly reactive for cancerous cells); while the sorbent shows interesting antimicrobial properties for Gram+, Gram- and pathogenic yeast. [ABSTRACT FROM AUTHOR]

Fe(III) is efficiently extracted from concentrated HCl solutions using Amberlite XAD-7 impregnated with tetraalkyl phosphonium chloride ionic liquid (IL) (synthesis of extractant-impregnated resin, EIR). The sorption efficiency is controlled by metal speciation and IL loading in the EIR. Sorption isotherms in mono-component solutions are described by the Langmuir equation, while the extended Langmuir equation perfectly fits sorption isotherms from binary Fe(III)/Zn(II) solutions. The thermodynamic study confirms the endothermic nature of the sorption. Uptake kinetics are fitted by the pseudo-second order rate equation. While temperature and metal concentration have a relatively limited effect on kinetics, the IL content more significantly affects the mass transfer of Fe(III). Water, sodium sulphate, nitric acid, and sulphuric acid almost completely desorb Fe(III) from loaded EIRs. Resin recycling was tested for eight cycles without significant decrease of the sorption and desorption efficiencies. [ABSTRACT FROM AUTHOR]

A sorbent was produced by chemical modification (tannic acid grafting) of polyethylenimine (PEI) and encapsulation in alginate gel beads. The sorbent was characterized by SEM-EDX and FTIR analyses before being used for the sorption of Cu(II), Zn(II) and Ni(II). The influence of pH was tested and sorption isotherms have been determined: the Langmuir equation fits well experimental data; for Cu(II), the bi-site Langmuir equation was preferred. Metal sorption capacity exceeds 1 mmol metal g−1and amine groups (with hydroxyl groups of tannic acid or carboxylic groups of alginate) contribute to metal binding. The pseudo second-order rate equation fits kinetic profiles well. [ABSTRACT FROM PUBLISHER]

Cysteine-functionalized chitosan magnetic nano-based particles were synthesized for the sorption of light and heavy rare earth (RE) metal ions (La(III), Nd(III) and Yb(III)). The structural, surface, and magnetic properties of nano-sized sorbent were investigated by elemental analysis, FTIR, XRD, TEM and VSM (vibrating sample magnetometry). Experimental data show that the pseudo second-order rate equation fits the kinetic profiles well, while sorption isotherms are described by the Langmuir model. Thermodynamic constants (G°, H°) demonstrate the spontaneous and endothermic nature of sorption. Yb(III) (heavy RE) was selectively sorbed while light RE metal ions La(III) and Nd(III) were concentrated/enriched in the solution. Cationic species RE(III) in aqueous solution can be adsorbed by the combination of chelating and anion-exchange mechanisms. The sorbent can be efficiently regenerated using acidified thiourea. [ABSTRACT FROM AUTHOR]

Chitosan functionalized with 2-mercaptobenzimidazole (2-MBI) (i.e. 2-MBI@Chit) shows high sorption capacity (i.e., 1.28 mmol MB g−1) for methylene blue (MB) (at pH close to 9.3). Sorption is weakly decreased (by less than 25%) by high NaCl concentration (up to 45 g L−1). The sorption (slightly endothermic) is fitted by the Langmuir equation. The kinetic profile is fitted by the pseudo-first order rate equation (PFORE): equilibrium reached within 90 min of contact. The resistance to film diffusion is minimized when setting agitation speed at 200 rpm. Dye desorption is successfully achieved (up to 94.5%) using 0.8 M HCl; desorption kinetics is little slower than the sorption step. The loss in sorption capacity at the fifth sorption/desorption cycle does not exceed 5%. Yoon–Nelson, Bohart–Adams, and bed-depth service time equations are used for analyzing the breakthrough in fixed-bed columns. At the exhaustion of the column, the sorption capacity approaches the maximum sorption capacity in batch: all the reactive groups remain accessible in dynamic sorption mode. The dye is efficiently recovered from spiked seawater and the sorption performance is depreciated by less than 16% while comparing tap water and seawater under selected experimental conditions. [Display omitted] • Methyl benzimidazole/chitosan for efficient sorption of methylene blue. • Maximum sorption capacity close to 1.28 mmol g−1, fitted by Langmuir equation. • Fast kinetics (equilibrium ~ 90 min), fitted by pseudo-first order rate equation. • Dye elution by 0.8 M HCl solution; sorption stability over 5 cycles (loss < 5%). • Efficient modeling of breakthrough curves in columns by the Yoon–Nelson equation. [ABSTRACT FROM AUTHOR]

• Alginate beads produced from upcycled resources (algal biomass, bi-valve shells). • Functionalizing the beads with urea and methylene blue improves Cr(VI) sorption. • Maximum sorption capacity reaches 8.53 mmol Cr g−1 (Langmuir fit of isotherm). • Fast sorption (30−60 min) fitted by the pseudo-second order rate equation. • Readily desorption using 2 M NaCl/0.5 M NaOH solution, high stability for 5 cycles. The valorization of algal biomass and bi-valve shells allows synthesizing, in the presence of urea, a sorbent highly efficient for methylene blue (MB) sorption (sorption capacity: 1.5 mmol MB g−1 at pH 5.8). The dye-functionalized sorbent shows enhanced sorption properties for Cr(VI) recovery at pH 3. The sorption isotherm is fitted by the Langmuir equation: maximum sorption capacity reaches 8.53 mmol Cr g−1 (for MB-loading: 1.5 mmol g−1). Different mechanisms may be involved such as the electrostatic attraction of anionic species, chelation on reactive groups, reduction of Cr(VI) into Cr(III). Under selected experimental conditions, the sorption is achieved within less than 60 m. The kinetic profiles are controlled by the pseudo-second order rate equation. Alkaline NaCl solutions effciently desorb chromate while maintaining a good stability of the dye (negligible release). Therefore, the sorption and desorption performances are maintained remarkably stable for at least 5 sorption/desorption cycles. The sorbent is successfully applied for chromate recovery from Cr(VI)–spiked solutions (tap water and wastewater from petrochemical unit) with limited loss in sorption performances. The sorbent is characterized by BET, TGA, FTIR, SEM, EDX and zetametry to help in the understanding of binding mechanisms and sorption performances. [ABSTRACT FROM AUTHOR]

The development of new materials is needed to address the environmental challenges of wastewater treatment. The phosphorylation of guar gum combined with its association to chitosan allows preparing an efficient sorbent for the removal of U(VI) from slightly acidic solutions. The incorporation of magnetite nanoparticles enhances solid/liquid. Functional groups are characterized by FTIR spectroscopy while textural properties are qualified by N2 adsorption. The optimum pH is close to 4 (deprotonation of amine and phosphonate groups). Uptake kinetics are fast (60 min of contact), fitted by a pseudo-first order rate equation. Maximum sorption capacities are close to 1.28 and 1.16 mmol U g−1 (non-magnetic and magnetic, respectively), while the sorption isotherms are fitted by Langmuir equation. Uranyl desorption (using 0.2 M HCl solutions) is achieved within 20–30 min; the sorbents can be recycled for at least five cycles (5–6% loss in sorption performance, complete desorption). In multi-component solutions, the sorbents show marked preference for U(VI) and Nd(III) over alkali-earth metals and Si(IV). The zone of exclusion method shows that magnetic sorbent has antibacterial effects against both Gram+ and Gram- bacteria, contrary to non-magnetic material (only Gram+ bacteria). The magnetic composite is highly promising as antimicrobial support and for recovery of valuable metals. [ABSTRACT FROM AUTHOR]

With the target of recovering rare earth elements (REEs) from acidic leachates, a new functionalized hydrogel was designed, based on the phosphorylation of algal/polyethyleneimine beads. The functionalization strongly increased the sorption efficiency of the raw material for Pr(III) and Tm(III). Diverse techniques were used for characterizing this new material and correlating the sorption performances and mechanisms to the physicochemical structure of the sorbent. First, the work characterized the sorption properties from synthetic solutions with the usual procedures (study of pH effect, uptake kinetics, sorption isotherms, metal desorption and sorbent recycling, and selectivity from multi-element solutions). Optimum pH was found close to 5; sorption isotherms were fitted by the Langmuir equation (maximum sorption capacities close to 2.14 mmol Pr g−1 and 1.57 mmol Tm g−1). Fast uptake kinetics were modeled by the pseudo-second order rate equation. The sorbent was highly selective for REEs against alkali-earth and base metals. The sorbent was remarkably stable for sorption and desorption operation (using 0.2 M HCl/0.5 M CaCl2 solutions). The sorbent was successfully applied to the leachates of Egyptian ore (pug leaching) after a series of pre-treatments (precipitation steps), sorption, and elution. The selective precipitation of REEs using oxalic acid allows for the recovery of a pure REE precipitate. [ABSTRACT FROM AUTHOR]

There is a need for developing new sorbents that incorporate renewable resources for the treatment of metal-containing solutions. Algal-polyethyleneimine beads (APEI) (reinforced with alginate) are functionalized by grafting amidoxime groups (AO-APEI). Physicochemical characteristics of the new material are characterized using FTIR, XPS, TGA, SEM, SEM-EDX, and BET. AO-APEI beads are tested for the recovery of Sr(II) from synthetic solutions after pH optimization (≈ pH 6). Uptake kinetics is fast (equilibrium ≈ 60–90 min). Sorption isotherm (fitted by the Langmuir equation) shows remarkable sorption capacity (≈ 189 mg Sr g−1). Sr(II) is desorbed using 0.2 M HCl/0.5 M CaCl2 solution; sorbent recycling over five cycles shows high stability in terms of sorption/desorption performances. The presence of competitor cations is studied in relation to the pH; the selectivity for Sr(II) is correlated to the softness parameter. Finally, the recovery of Sr(II) is carried out in complex solutions (seawater samples): AO-APEI is remarkably selective over highly concentrated metal cations such as Na(I), K(I), Mg(II), and Ca(II), with weaker selectivity over B(I) and As(V). AO-APEI appears to be a promising material for selective recovery of strontium from complex solutions (including seawater). [ABSTRACT FROM AUTHOR]

• Synthesis of magnetic and non-magnetic mercaptobenzimidazole chitosan derivatives. • Silver sorption is enhanced by sonication in terms of kinetics and thermodynamics. • Selectivity for precious metals vs. base metals, especially in presence of EDTA. • High desorption efficiency and stability of the sorbent at recycling. • Highly efficient recovery of precious metals from acidic leachates of E-waste. The recycling of precious and strategic metals from secondary resources (including E-wastes) is of critical importance for the recovery of scarce metals widely used in High-Tech devices. Therefore, the development of efficient and selective sorbents is of great importance. The grafting of 2-mercaptobenzimidazole onto chitosan microparticles allows developing highly selective sorbents. The incorporation of magnetite particles is also a strategic aspect for facilitating the use and recovery of microparticles. Sonication (at two different frequencies: 37 kHz and 80 kHz) shows high potential for improving both kinetic and thermodynamic aspects associated with silver uptake on 2-MBI-chitosan materials. Sorption capacities as high as 3 mmol Ag g−1 can be obtained with contact times as low as 20–30 min. The sorption isotherms are successfully fitted by the Langmuir and the Sips equations, while the kinetic profiles are modeled using the pseudo-second order rate equation and the resistance to intraparticle diffusion. The sorption process is exothermic: the sonication (and the frequency of sonic generator) strongly changes the thermodynamic parameters. The sonication also speeds up metal desorption, which is highly efficient using acidic thiourea solutions: the sonication allows also reducing the concentration of thiourea in the eluent required for complete silver elution. The sorbent shows remarkable stability is terms or sorption and desorption for five successive recycling runs. The acid leachates of printed circuit board are efficiently treated with the 2-MBI-chitosan sorbent for the recovery, enrichment and separation of precious metals (Ag, Au and Pd) from base metals (major elements: iron copper, aluminum, tin). [ABSTRACT FROM AUTHOR]

• Highly percolating alginate/polyethylenimine membranes obtained by air-drying. • Membranes show strong affinity for selenate anions in acidic solution. • FTIR and XPS spectra reveal the electrostatic attraction and reduction mechanism. • Great desorption efficiency and reusability of membranes are demonstrated. • Strong stability of membranes at re-use. New high percolating alginate membranes are designed without using sophisticated drying methods: negatively charged alginate reacts with positively charged polyethylenimine (PEI), prior to be crosslinked with glutaraldehyde and air-dried. This is sufficient to obtain a highly macroporous structured membrane. Highly percolating properties of these new A-PEI membranes make the material applicable in natural drainage systems. The high density of amine groups in composite membranes explain their high affinity for anions in acidic solutions. FTIR, SEM-EDX and XPS analysis are used to explore the sorption mechanism. Se(VI) is sorbed through electrostatic attraction between positive amine groups and negative selenium anions; in a second step, bound Se(VI) is reduced by amine and hydroxyl groups in acidic conditions. A-PEI membranes are successfully used for recovering Se(VI) anions at pH 2. The maximum sorption capacity is close to 83 mg Se g−1; the sorption isotherm is described by the Sips and Langmuir equations. The membranes are poorly sensitive to flow rate in the range 15–50 mL min−1. The kinetic profiles are fitted by the pseudo-first order rate equation. Solute desorption is operated using NaOH solutions; the sorbent shows a remarkable stability in sorption and desorption properties for a minimum of 4 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • CuO-based nanocomposites (CuO-MAP and CuO-BAP) are successfully elaborated by in-situ precipitation after the impregnation of the aminophosphonate matrices with copper sulfate solution. • Nano-composites show improved textural properties and sorption characteristics with substantially higher selectivity for uranyl ions. • After 6 cycles, nanocomposites displayed high durability and recyclability with limited loss in sorption and desorption performances. • Outstanding selectivity and affinity for U(VI) vs. other cations from complex acid ore leachate. Two aminophosphonate matrices (mono-aminophopshonate, MAP, and bi-aminophosphonate, BAP) are synthesized, varying the molar proportions of three precursors (thiocarbazide, p-phthalaldehyde, and triphenylphosphite). Nano-composites (CuO-MAP and CuO-BAP) are successfully elaborated by impregnation of the matrices with copper sulfate solution before processing to in situ precipitation of copper in alkaline solution (simultaneous partial Cu reduction). The sorbents are characterized using: TEM, XRD, elemental analysis, SEM-EDX, BET, titration (pH PZC), XPS and FTIR analyses. Uranium sorption properties are compared for the different sorbents through the study of pH effect (optimum close to 4.5), the uptake kinetics (equilibrium reached in 60 min) and sorption isotherms. Uptake kinetics are finely fitted by the pseudo-second order rate equation (and the resistance to intraparticle diffusion). The sorption isotherms are modeled by the Langmuir equation with maximum sorption capacity (mmol U g−1) decreasing according to CuO-BAP(1.15) ≫ CuO-MAP(0.80) > BAP(0.74) ≫ MAP(0.50). The enhanced textural properties and the increase in the density of sorption sites (probably completed by a better steric arrangement for improved reactivity) may explain this ranking. The sorption is endothermic: sorption capacity and affinity coefficient increase with temperature. Uranium is readily desorbed from loaded-sorbents (efficiency > 98 %) using either HCl (0.2 M) solution or acidified urea (0.25 M) solution (pH 2.5) for aminophosphonate matrices and nano-composites, respectively. The type of sorbent does not affect the stability at recycling: at the sixth cycle, the loss in sorption and desorption performances varies by 6.2–7 % and 4.2–4.9 %, respectively. CuO-BAP sorbent shows high potential for uranium recovery from complex acid ore leachate. The broad spectrum of bound metals does not allow producing a pure yellow cake after ammonia precipitation of eluate (containing up to 15–22 % impurities). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Successful amidoximation of SiO 2 /polyacrylonitrile composite (SiO 2 /PAO). • PAO/SiO 2 highly efficient for Ga(III) recovery from slightly acidic solution. • Ga(III) desorption using 0.5 M HCl solutions for sorbent recycling. • PAO/SiO 2 sorbent is selective for Ga(III) recovery from multi-metal solutions. • Ga(III) efficiently and selectively recovered from Bayer liquor using SiO 2 /PAO. Abstract The copolymerization of styrene with divinylbenzene (DVB) in the presence of silica particles produces a commercial silica-supported polymer (SiO 2 -P) that was chemically reacted with acrylonitrile to synthesize silica-supported polyacrylonitrile (PAN/SiO 2). PAN/SiO 2 was functionalized by grafting amidoxime moieties to produce PAO/SiO 2 sorbent (silica-supported polyacrylamidoxime). The sorbent (PAO/SiO 2) was characterized by XPS, TGA, FTIR, pH pzc , elemental and SEM-EDX analyses and tested for Ga(III) recovery from aqueous solutions. The sorption performance was investigated through the study of pH effect, sorption isotherms at different temperatures, and uptake kinetics under slightly acidic conditions (around pH 4) and at pH close to 13.7 (similar to Bayer liquor). The equilibrium was reached within 60 min; the kinetic profiles can be fitted by the pseudo-second order rate equation (PSORE) and the resistance to intraparticle diffusion equation (RIDE). The maximum sorption capacity reaches 1.34 mmol Ga g−1 at 25 °C (1.76 mmol Ga g−1 at 55 °C): the sorption process is endothermic for solutions prepared by alkaline dissolving of Ga 2 O 3. The sorption capacities are higher for solutions prepared with Ga(NO 3) 3 salt: the maximum sorption capacity increased up to 2.1–2.6 mmol Ga g−1 (from 25 to 55 °C). Langmuir and Sips equations were used for fitting sorption isotherms. Metal desorption and sorbent recycling were performed using 1.5 M HCl solution. Forty-five minutes were sufficient for achieving complete desorption of Ga(III). Sorption and desorption performances remain stable for a minimum of 5 cycles. Sorbent selectivity for gallium recovery was demonstrated in the presence of an excess of competitor cations. The sorbent was successfully applied for Ga(III) recovery from Bayer liquor at high pH values (around 13): combining relatively high efficiency and selectivity compared with LSC-600 amidoxime resin. [ABSTRACT FROM AUTHOR]

Polyglycidyl methacrylate (PGMA, obtained by dispersion polymerization method) can be successfully functionalized to improve the sorption of Nd(III). Pristine PGMA is first modified by amination (N-PGMA), before grafting amino-alkylcarboxylate and amino-alkylphosphonic ligands to produce A-PGMA and P-PGMA, respectively. These materials are characterized by CHNP, FTIR-spectrometry, XRD, TG-TDA and pH zpc. Following that, the Nd(III) sorption properties are compared. At optimum pH: 4.5–5.0, the sorbents can be ranked according the series: P-PGMA (0.645 mmol Nd g−1) < A-PGMA (0.736 mmol Nd g−1) (vs. 0.304 mmol Nd g−1 for N-PGMA). Sorption capacities increase with temperature. Sorption isotherms are modeled using the Langmuir equation. Equilibrium is reached within 180 min. Uptake kinetics are controlled by the resistance to intraparticle diffusion (fitted by the Crank equation). The sorption is endothermic, spontaneous and followed by an increase of the entropy of the system. Elution and regeneration are carried out using HNO 3 solutions achieving >91%. Theoretical DFT calculation (molecular modeling) and FTIR spectroscopy, the interactions of Nd(III) with reactive functional groups (carboxyl, hydroxyl, amine and phosphonate groups) are characterized. Finally, the sorbents are tested on pre-treated leachate of Egyptian monazite: REEs' sorption performances are correlated with their intrinsic properties and compared for the two sorbents. [Display omitted] • Carboxylation and phosphonation of aminated-PGMA for enhanced Nd(III) removal. • Endothermic sorption with capacities reaching up to 0.74–0.84 mmol Nd(III) g−1. • Pseudo-first order reaction rate and crank equation for fitting kinetic profiles. • FTIR analysis and DFT calculation for interpreting the sorption mechanisms. • Sorbent affinity correlates with cation polarizing power for REEs (ore leachate). [ABSTRACT FROM AUTHOR]

[Display omitted] • Easy synthesis of two α-aminophosphonate derivatives through one-pot reaction. • Ethylenediamine aminophosphonate sorbent efficient for Pb(II) sorption at pH 5. • The number of amine groups influences both textural and sorption properties. • Limited loss in sorption and desorption performances after 5 cycles. • High selectivity for Pb(II) vs. divalent cations in multi-component solutions. A one-pot synthesis procedure is designed for preparing two α-aminophosphonate-based-sorbents (DA and TA sorbents). The reaction takes place between amine precursors (two different aliphatic amines with different chain lengths and amino group content; i.e., ethylenediamine (DA) or diethylenetriamine (TA), respectively) and both salicylaldehyde and diphenyl phosphite. Ionic liquid may be used under controlled conditions as an alternative to TiCl 4 catalyst. These materials are first characterized by SEM-EDX, AFM, BET, XRD, FTIR, 1H-, 13C-, and 31P NMR, XPS, TGA, elemental analysis (CHNP), and titration (PZC). Combined with the study of pH effect on Pb(II) sorption, FTIR and XPS analyses are used for exploring the mechanisms involved in metal binding. In a second step, the sorption properties are compared for Pb(II) recovery at pH ≈5. Maximum sorption is influenced by the length of the chain: DA (0.694 mmol Pb g−1) > TA (0.494 mmol Pb g−1). The sorption isotherms are modelled by the Sips equation for DA (and the Langmuir Dual Site equation) and by the Langmuir equation for TA. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) indicate the spontaneous, endothermic nature and randomness increases during the sorption process. The uptake kinetics (equilibrium reached ≈120 min) is almost equally fitted by the pseudo-first-order rate equation and the pseudo-second-order rate equation. The sorbents show selective Pb(II) sorption against heavy base metals in multi-component solutions. QSAR tools (quantitative activity structure–activity relationships) are used for evaluating the correlation between their intrinsic metal characteristics and their affinities for sorbents. The sorbents are efficiently recycled for at least 5 cycles using 0.2 M HCl as the eluent (loss in sorption and desorption performances ≈10-14% at the fifth cycle, compared with the first cycle). [ABSTRACT FROM AUTHOR]

[Display omitted] • Synergistic quaternization/phosphonation of algal/PEI beads favors W(VI) binding. • Langmuir dual site and Sips models for fitting isotherm for bi-functional sorbent. • Fast kinetics (≈60–90 min) fitted by pseudo-second order rate equation. • High stability in sorption and desorption performance (at 5th recycling). • Selectivity for W against base and alkali-earth metals (in real effluent). Algal/polyethyleneimine composite beads (A L PEI) have been successfully functionalized by grafting phosphonate (A L PEI-P), quaternary ammonium groups (A L PEI-Q), and by dual moieties (A L PEI-PQ). The materials are characterized by a wide diversity of analytical methods: SEM and SEM-EDX, TGA, BET, FTIR and XPS, elemental analysis and titration (detailed discussion in Supplementary Information). FTIR and XPS analyses show contributions of quaternary ammonium, hydroxyl, and phosphonate groups in tungstate binding (which may involve polynuclear species, depending on the pH). The synergistic effects of phosphonate and quaternary ammonium moieties contribute to strongly increase W(VI) sorption capacity up to 1.8 mmol W g−1 (i.e., 4-times compared with pristine beads), at pH 5. The strong increase of sorption properties with temperature (2.45 mmol W g−1 at T: 50 °C) demonstrates the endothermic nature of metal binding, which is spontaneous (and characterized by positive entropy change). The Langmuir Dual Site equation successfully fits sorption isotherm for functionalized sorbents (bearing phosphonate and phosphonate/quaternary ammonium groups in addition to proper reactive groups of pristine beads) contrary to the isotherms for raw beads (fitted by Langmuir equation). The pseudo-first order rate equation fits kinetics (equilibrium reached within ≈60 min). The bi-functional sorbent shows marked preference for W(VI) against base and alkali-earth metals (especially at pH close to 3.5). These properties are confirmed in the treatment of raffinate solutions (after ore leaching and solvent extraction): despite the complexity of the effluent, A L PEI-PQ reveals highly efficient for W(VI) recovery and separation. The sorbent can be used as a polishing treatment for enhancing the recovery of strategic metals. Sorbed tungstate is readily desorbed from the sorbent using 0.2 M NH 4 Cl solution. The sorbent is efficiently recycled for at least 5 cycles (complete desorption, loss in sorption performance less than 4% at the fifth cycle). [ABSTRACT FROM AUTHOR]

Highlights: [•] Alginate is used for encapsulating Prussian blue to manufacture a Tl(I) sorbent. [•] The ion-exchanger is homogenously distributed in the sorbent and accessible. [•] The sorbent is selective over monovalent cations such as Na+, K+ and Rb+. [•] Freundlich and Langmuir bi-site models fit well sorption isotherms. [•] Kinetics are controlled by pseudo-second order rate and intraparticle diffusion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Free metal ions are preferentially sorbed onto AO-APEI beads in presence of EDTA. • Preferential Dy chelation by EDTA improves selective La uptake in binary solutions. • Langmuir equation fits isotherm curve using only the concentration of free species. • Metal speciation influences both sorption isotherms and uptake kinetics. • Metal speciation influences resistance to intraparticle diffusion (kinetics). Amidoximated algal/polyethyleneimine beads are successfully applied for the sorption of two rare earths elements (REEs, Ln(III)): La (light) and Dy (heavy). The sorption properties are characterized by FTIR and SEM-EDX analyses. The pH effect on metal sorption is investigated with a double objective: optimizing metal recovery and separation. In binary solutions, Dy(III) shows slightly higher affinity for the sorbent than La(III); without significant differences in the selectivity. The difficult separation of REEs can be modulated using EDTA. Playing with the pH and the concentration of the ligand, La(III) can be separated from Dy(III). Selectivity coefficient, SC La/Dy , may reach up to 40–50. Speciation diagrams show that the preferential formation of Dy-EDTA complexes limits Dy(III) sorption while La(III) remains predominant and highly sorbed (reduced effect of Dy-competition). Optimum conditions for Ln(III) separation can be predicted by the calculation of speciation diagrams. The concept is verified for the separation of La(III) from Er(III) (heavy REE). In the presence of EDTA, sorption isotherms (mono-component solutions) present sigmoidal shapes due to the effect of metal complexation. Converting the total concentration to the concentration of sorbable species (non-complexed by EDTA) allows plotting favorable curves (Langmuir equation). The fits of experimental profiles with the modified Langmuir equation confirm the preference of the sorbent for non-complexed species. The kinetic profiles fitted by the Crank equation highlight the contribution of the resistance to intraparticle diffusion in the control of uptake kinetic; this effect is reinforced by the presence of EDTA. Metal desorption using CaCl 2 (50 mM, pH 2) or EDTA (0.5 mM, pH 6) is used for La(III) and Dy(III) desorption (yield: 80–95%), while sorption capacity progressively decreases over 3 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Successful sulfonation of chitosan/Arabic gum composite for enhanced U(VI) sorption. • Maximum sorption at pH 0 4: 1.48 mmol U g−1 (isotherm fitted by Sips equation). • Kinetics fitted by pseudo-first order rate equation (equilibrium within 20 min). • Highly efficient for treating water samples collected from Sinai wells. • Complementary antimicrobial effect and negligible cytotoxicity. A new sorbent was designed by functionalization of a bio-based composite made of chitosan and Arabic gum. The grafting of two sulfonate-bearing moieties allows reaching, at the optimum pH (i.e., pH 0 4), a sorption capacity as high as 1.48 mmol U g−1 (with strong affinity; b L being close to 356 L mmol−1). The Sips equation fits better sorption isotherms than the Langmuir equation. The maximum sorption capacity increases with temperature (while the affinity coefficient does not follow a continuous trend). The sorption kinetics are very fast; 20 min of contact are sufficient for reaching the equilibrium and the kinetic profiles are successfully fitted by the pseudo-first order rate equation. HCl solutions (0.2 M) are highly efficient for completely desorbing bound uranyl ions; the loss in sorption efficiency does not exceed 3% after 5 re-use cycles. At pH above 4, the sorbent shows high selectivity against Ca(II), Mg(II), Al(III) and Zn(II) (against Fe(III) and Cu(II), to a lesser extent). The sorbent is successfully tested for the decontamination of water samples collected from five wells located in Sinai (Egypt): uranium removal approaches 100%; metal ions like Cu(II), Fe(III), Zn(II) and Pb(II) are also remarkably recovered from samples at pH 0 5.5. Complementary tests (using agar well diffusion method) show that the sorbent brings an additional antimicrobial activity against S. aureus , B. subtilis , E. coli , P. aeruginosa, and C. albicans , with MIC values ranging between 50 and 25 µg mL−1. The sorbent is characterized by negligible toxicity, using the MTT assay method against two normal cell lines (i.e., Vero and HFB4), and a cancerous cell line (i.e., Caco-2). [ABSTRACT FROM AUTHOR]

[Display omitted] • Functionalization of magnetic-chitosan microparticles for chromate removal. • High efficiency and selectivity for imidazole carboxamide derivative. • Sorption capacities as high as 6 mmol Cr g−1, at pH 2 (including Cr(VI) reduction). • Sips and pseudo-first order rate equations for isotherm and kinetic fitting, resp. • Highly efficient Cr desorption with 0.5 M HCl and sorbent recycling (5 cycles). Textile and tannery industries are highly contaminating with discharge of high Cr concentrations. Developing bio-based sorbents with strong affinity for chromate, fast kinetics, and high recyclability is strategic for better reuse of industrial wastewater. Magnetic chitosan micro-particles (MC, for enhancing mass transfer) may constitute a solution for chromate removal from acidic solutions. The functionalization of this support with aminothiazole groups (ATA@MC) or imidazole carboxamide (AIC@MC) significantly improves chromate removal, with sorption capacities close to 6 mmol Cr g−1, at pH 2. The Langmuir and the Sips equations finely fit sorption isotherms, while the pseudo-first order rate equation fits well uptake kinetics (equilibrium within 60 min). Sorption and desorption properties are remarkably stable: sorption efficiency decreases by less than 6% at the fifth cycle (while the desorption efficiency maintains above 99%). The sorbents are highly selective for chromate removal from acidic tannery wastewater (against base metals). FTIR and XPS analyses are used for characterizing the materials and for identifying the binding mechanisms (including chromate reduction into Cr(III)). The sorbents are both showing promising performances for Cr(VI) removal in acidic solutions, including in very complex solutions such as tannery wastewater. AIC@MC is more selective for Cr(VI) removal, while ATA@MC has a broader reactivity for a wider family of metal ions. The antimicrobial properties of the functionalized sorbents are characterized by the determination of the zone of inhibition (ZOI) against Staphylococcus aureus , Bacillus subtilis , Pseudomonas aeruginosa , Escherichia coli and Candida albicans : the inhibition is slightly improved compared with magnetite chitosan microparticles. More generally, the Gram- bacteria are slightly more sensitive to the functionalized sorbents than Gram+ bacteria and Candida fungus. [ABSTRACT FROM AUTHOR]

[Display omitted] • Playing with amine precursor allows synthesizing different aminophosphonate resins. • U(VI) sorption at pH 4 is controlled by the type of precursor (best with aniline). • Sorption isotherm fitted by Langmuir equation (q m capacity up to 1.31 mmol U g−1). • Fast kinetics (equilibrium: 120 min) fitted by pseudo-first order rate equation. • Efficient desorption allows sorbent recycling for at least 5 cycles. A one-pot synthesis procedure is designed for preparing three α-aminophosphonates (R-H, R-COOH, and R-NH 2); through the reaction of amine precursors (aniline, anthranilic or o-phenylene diamine, respectively) with salicylaldehyde and triphenylphosphite, under controlled conditions. These materials are first characterized by elemental analysis, FTIR, 1H NMR, 31P NMR, BET, DLS, pH zpc , TGA and titration. In a second step, the sorption properties are compared for U(VI) recovery from mildly acidic solutions. At the optimum pH (i.e., pH 4) the sorbents can be ranked according the series: R-H (1.057 mmol U g−1) > R-NH 2 (0.746 mmol U g−1) > R-COOH (0.533 mmol U g−1). The isotherms are fitted by the Langmuir equation. Uranium uptake is relatively fast: under selected experimental conditions, the equilibrium is reached within 90 min of contact. The kinetic profiles are indistinctly fitted by the model of resistance to intraparticle diffusion and the pseudo-first order rate equation. The study of sorption thermodynamics shows substantial changes between the sorbents: uranyl uptake is endothermic with R-H and R-NH 2 sorbents, while the reaction is exothermic with R-COOH sorbent. The diversity in functional groups and the speciation of uranyl in sulfuric acid solutions induce metal-binding through a combination of chelation and anion-exchange mechanisms (in function of pH). Sodium bicarbonate solutions achieve complete desorption of uranium from loaded-sorbents; the resins can be recycled for a minimum of 4–5 cycles with limited loss in efficiencies. The successful application of these resins for uranium recovery from acidic ore leachates demonstrates their promising properties for valorization of low-grade ores. [ABSTRACT FROM AUTHOR]

[Display omitted] • Improved Mo(VI) and Nd(III)sorption properties for phosphorylated algal/PEI beads. • Uptake kinetics fitted by pseudo-first order rate equation (equilibrium time: 1 h). • Isotherms fitted by Langmuir equation (q max : 1.46 mmol Nd g−1 – 2.09 mmol Mo g−1). • Remarkable stability in sorption and desorption performances after 5 cycles. • High selectivity for Mo(VI) and REEs(III) in multi-component solutions at pH 4. Alginate-PEI beads are functionalized by phosphorylation and applied for the sorption of Nd(III) and Mo(VI). The successful grafting of phosphoryl groups (as tributyl phosphate derivative) is characterized by FTIR and XPS analysis, elemental analysis, titration (pH PZC), TGA, BET and SEM-EDX analyses. The multi-functional characteristics of the sorbent (i.e., carboxylic, hydroxyl, amine and phosphate groups) contribute in the binding of metal ions having different physicochemical behaviors. The sorption of Nd(III) is strongly increased by phosphorylation, while for Mo(VI) the enhancement is rather limited. Optimum sorption occurs at pH 3–4: maximum sorption capacity reaches up to 1.46 mmol Nd(III) g−1 and 2.09 mmol Mo(VI) g−1; sorption isotherms are fitted by the Langmuir equation. The equilibrium is reached within 30–40 min and the kinetic profiles are simulated by the pseudo-first order rate equation. The coefficients of the effective diffusivity are close to the self-diffusivity of Nd(III) and Mo(VI) in water; as a confirmation of the limited impact of resistance to intraparticle diffusion in the kinetic control. The sorbent is selective for Nd(III) over Mo(VI) and other alkali-earth or base metals (at pH close to 2.5–3). Metals can be readily desorbed using 0.2 M HCl/0.5 M CaCl 2 as the eluent. The loss in sorption does not exceed 5% at the fifth cycle, while desorption remains complete. A series of treatments (including acidic leachate, cementation, precipitation, sorption and elution) is successfully applied for the recovery of rare earths from Egyptian ore; with enrichment in the oxalate precipitate of Nd(III), Gd(III), Sm(III) and Eu(III). [ABSTRACT FROM AUTHOR]

Thiourea-formaldehyde (TF) resin is prepared by polycondensation of its two precursors; the incorporation of pre-formed magnetite particles allows synthesizing a magnetic derivative of TF (MTF). These materials are applied to the sorption of two dyes (titan yellow, TY, and rose bengal, RB). Ultrasonic treatment (UT) is tested as an alternative to mechanical agitation (MA). The two sorbents are characterized by scanning electron microscopy, vibrating-sample magnetometry, BET surface area analysis, thermogravimetric analysis, Fourier-transform infrared and NMR spectroscopy, zetametry. Sorption properties are compared for TF and MTF under both MA and UT; considering pH effect, uptake kinetics (modeled using the pseudo-second order rate equation, and resistance to intraparticle diffusion), sorption isotherms (fitted by the Langmuir and Sips equations), the effect of competitor ions, and the desorption efficiency. Optimum sorption occurs at pH 3 (balance between (a) the electrostatic interactions between protonated groups (sorbent) and anionic forms of the dyes, and (b) the competitor effects of counter anions). UT strongly decreases the contact time required for reaching equilibrium (from 240 min to 30 min). UT increases the sorption capacities: in the range 0.3–0.6 mmol dye g−1 (MA) up to 0.9–1 mmol dye g−1. The magnetic core does not change kinetics, while it increases TF sorption capacities for both TY and RB. Under UT, the maximum sorption capacities are comparable for TF and MTF; however, the affinity of MTF remains higher than TF for the two dyes. Alkaline NaCl solutions completely desorb the dyes; UT decreases both the contact time and the NaCl concentration required for achieving the complete desorption of loaded dyes. The sorbents are recycled with high stability in sorption performance for at least five cycles. [ABSTRACT FROM AUTHOR]