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Removing hazardous metals and recovering valuable strategic metals from wastewater has become an important challenge for the industry. Herein, brown algal biomass residue (AR, after bio‐stimulant extraction, currently poorly valorized) is tested for the removal of Ni(II), Cd(II), and La(III) from aqueous solutions. This valorization of industrial waste makes profit of residual amounts of alginate‐based materials, which have a strong affinity for metal cations. Fourier transform infrared (FTIR) and X‐ray photoelectron spectroscopy (XPS) techniques are used for characterizing metal/biosorbent interactions. Uptake kinetics are relatively fast (equilibrium being reached in 180–240 min). The Sips equation fits the sorption isotherms; the maximum sorption capacities at pH ≈5 reach up to 0.84 mmol La g−1, 0.92 mmol Cd g−1, and 0.78 mmol Ni g−1. In binary solutions, AR shows marked preference for La(III) over divalent cations. This selectivity may be increased by complexing base metals with EDTA, opening the route for the selective recovery of rare earth elements. HCl solution reveals more efficient (>90% for La(III), ≈82% for Cd(II) and Ni(II)) than CaCl2 solution at pH 2 for metal desorption. This waste residue from biostimulant extraction (in brown algal biomass) can be valorized for the recovery of hazardous and strategic metal ions. [ABSTRACT FROM AUTHOR]

Magnetic chitosan microparticles are functionalized by grafting a new hydrazide derivative to produce HAHZ-MG-CH, which is applied to the sorption of metal cations. The functionalization (appearance of new groups) and synthesis mechanisms are confirmed using elemental analyses, FTIR and XPS spectrometry, TGA and EDX analysis, SEM observation and titration. HAHZ-MG-CH bears high nitrogen content (≈ 10.9 mmol N g−1). Maximum sorption capacities at pH 5 reach up to 1.55 mmol U g−1, 1.82 mmol Hg g−1 and 2.67 mmol Cd g−1. Sorption isotherms are preferentially fitted by the Langmuir model. In acidic solutions, the sorbent has a marked preference for Hg(II) over U(VI) and Cd(II), while at mild pH uranyl species are preferentially bound. The sorbent has a lower affinity for Cd(II) in multicomponent solutions. Sorption occurs within 60 min of contact. The pseudo-first-order rate equation fits well kinetic profiles. HCl solutions (0.5 M) successfully desorb all the metal ions (yield exceeds 97% at the first cycle). The sorbent can be recycled for 5 cycles of sorption and desorption: the loss in efficiencies does not exceed 8%. The sorbent removes Hg(II), Cd(II) and Pb(II) from local contaminated groundwater at levels compatible with irrigation and livestock uses but not enough to reach the levels for drinking water regulations. [ABSTRACT FROM AUTHOR]

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]

A new magnetic functionalized derivative of chitosan is synthesized and characterized for the sorption of metal ions (environmental applications and metal valorization). The chemical modification of the glycine derivative of chitosan consists of: activation of the magnetic support with epichlorohydrin, followed by reaction with either glycine to produce the reference material (i.e., Gly sorbent) or glycine ester hydrochloride, followed by hydrazinolysis to synthesize the hydrazide functionalized sorbent (i.e., HGly sorbent). The materials are characterized by titration, elemental analysis, FTIR analysis (Fourrier-transform infrared spectrometry), TGA analysis (thermogravimetric analysis) and with SEM-EDX (scanning electron microscopy coupled to energy dispersive X-ray analysis). The sorption performances for U(VI), Cu(II), and Zn(II) are tested in batch systems. The sorption performances are compared for Gly and HGly taking into account the effect of pH, the uptake kinetics (fitted by the pseudo-second order rate equation), and the sorption isotherms (described by the Langmuir and the Sips equations). The sorption capacities of the modified sorbent reach up to 1.14 mmol U g-1, 1.69 mmol Cu g-1, and 0.85 mmol Zn g-1. In multi-metal solutions of equimolar concentration, the chemical modification changes the preferences for given metal ions. Metal ions are desorbed using 0.2 M HCl solutions and the sorbents are re-used for five cycles of sorption/desorption without significant loss in performances. [ABSTRACT FROM AUTHOR]

A novel composite material was prepared by the grafting of tannic acid on polyethylenimine (PEI), which allows an efficient sorption of boron (sorption capacity close to 0.89 mmol B g−1). The encapsulation of this chelating sorbent (finely crushed) facilitates its use (readily solid/liquid separation, use in fixed-bed columns) at the expense of a loss in sorption capacity (proportionally decreased by the introduction of alginate having poor efficiency for boron uptake). Sorption isotherms are modeled using the Langmuir equation, while the kinetic profiles are presented a good fit by pseudo-second order rate equation. In addition, the encapsulating matrix introduces supplementary resistance to intraparticle diffusion, especially when the resin is dried without control: freeze-drying partially limits this effect. The stability (at long-term storage) of the sorbent is improved when the sorbent is stored under nitrogen atmosphere. The presence of an excess of NaCl was investigated. The degradation of the hydrogel (by ion-exchange of Ca(II) with Na(I)) leads to a decrease in the sorption performance of composite material but the action of Ca(II) ions in the solutions re-stabilizes the hydrogel. [ABSTRACT FROM PUBLISHER]

[Display omitted] • Magnetic bi-functional (amino-sulfonate) composite efficient for U removal at pH 4. • Sorption capacity increased by 25% under UV irradiation (vs dark, visible light). • Uptake kinetics slightly improved by UV exposure. • Enhanced selectivity for U against competitor metals under UV irradiation. • Effect of the sensitivity of uranium to photoreduction (magnetite, polymer layer). The association of magnetite microparticles with bi-functional amino-sulfonate polymer (obtained by condensation of guanidine and amino hydroxynaphthalene sulfonic acid, mediated by formaldehyde) allows synthesizing a magnetic composite sorbent (M−GANS). The sorbent bearing both amine and sulfonate groups is efficient for uranyl sorption at pH 4–5. The sorption isotherms are successfully fitted by the Temkin equation, while kinetics is controlled by the pseudo-first order rate equation. The sorption properties are increased by UV irradiation in terms of both sorption capacity (by 25 %, up to 1.25 mmol U g−1) and kinetics. The sorption occurs on both amine and sulfonate groups; the improvement in sorption properties under UV irradiation is tentatively assigned to the photo-reduction of uranyl species (mediated by magnetite particles and amine groups from polymer layer). The UV irradiation improves the selectivity of M−GANS for uranium against other metal ions, tested on both synthetic and real solutions. This improvement can be correlated to the higher propensity of uranyl to be photo-reduced compared with investigated competitor ions. The recycling of the sorbent was successfully tested for five successive cycles of sorption and desorption (stably complete): the loss in sorption performances is slightly reduced (less than 1.5 % at the fifth cycle) under UV irradiation compared with experiments performed under dark conditions (loss close to 4.2 %). The uranium peroxide precipitate obtained at the end of the treatment of acid leachate of ore shows higher purity when UV irradiation was applied. [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]

A composite sorbent (MGMA) was synthesized by coating a magnetite core with glycidyl methacrylate-based polymer, further grafted with diethylenetriamine (DETA). The absence of coercivity and remanence in VSM analysis confirms that the material has super paramagnetic properties that make it readily separable from the liquid phase applying external magnetic field. The sorbent (MGMA-DETA) was tested for Hg(II) recovery from aqueous solutions (of increasing complexity). The separation of Hg(II) from multi-metal solutions was tested at different pH values. The impact of counter ions on metal sorption was also tested at different pHs. Sorption mechanisms explained the different effects of counter ions (in relation with metal speciation) and also the relative selectivity of the sorbent for Hg(II) over other base metals. Uptake kinetics and sorption isotherms were modeled with the pseudo-second order rate equation and the Langmuir equation, respectively. The thermodynamic parameters have been calculated. The sorbent was successfully tested for Hg(II) removal from two industrial effluents (from chlor-alkali industry and from mercury-oxide manufacturing). The sorbent could be recycled for at least 4 cycles of sorption/desorption. This means that the magnetic sorbent is a promising material for the efficient and selective removal of mercury from complex solutions. [ABSTRACT FROM AUTHOR]

The bioremoval efficiency of Opuntia biomass, a low-cost biosorbent and renewable resource, for cadmium ions from aqueous solutions was investigated using factorial design methodology. The functional groups involved in the sorption process were identified by FTIR spectroscopy. A factorial experimental design technique, the full factorial design 33, has been used for enhanced cadmium ions bioremoval. Three factors were considered: protonation of the sorbent, initial cadmium concentration, and sorbent dosage at three markedly different levels. An empirical model was statistically developed using response surface methodology for its optimization. The model showed that cadmium ions bioremoval in aqueous solution was affected by all the three factors analyzed. The statistical model revealed a maximum sorption capacity ( qe) of 58.4 mg/g with sorbent protonated with 0.67 M HCl, initial Cd(II) concentration of 50 mg/L, and 0.55 g/L of sorbent dosage. Bioremoval kinetic data were properly fitted by chemical sorption of pseudo-second order. The Langmuir equation fits better the sorption isotherm (equilibrium data) than other classical models. [ABSTRACT FROM AUTHOR]

Magnetic-chitosan nanoparticles, functionalized with cysteine, were synthesized and characterized by element analysis, FT-IR, XRD, TEM, and vibrating sample magnetometry. The sorbent was tested for U(VI) recovery, considering:a. pH effect,b. sorption isotherms (fitted by Langmuir equation), andc. uptake kinetics (modeled using the PSORE). Maximum sorption capacity approached 100 mg U g−1. The nanometric size of sorbent reduces the impact of resistance to intraparticle diffusion; this may explain the fast kinetics (equilibrium within 50 min). The reaction is exothermic, spontaneous. The metal could be desorbed using acidified urea solution and the sorbent could be recycled for 5 cycles. [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]

• 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]

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]

[Display omitted] • Synthesis S-bearing pyrimidine micro-particles for efficient In(III) sorption. • N- and S- reactive groups bind In(III) at pH 4 (sorption capacity: 1.87 mmol g−1). • Fast kinetics (20–30 min) fitted by pseudo-first order rate equation. • High stability in sorption and desorption performances at recycling. • Selective against trivalent cations and highly selective against base metals. A new sorbent (TcTDG, pyrimidine derivative, with high content of N-based reactive groups and S-based sites) was successfully synthesized by the polycondensation of thiocarbazide and 2-thiobarbituric acid through reaction with formaldehyde. The material is characterized by FTIR, SEM and SEM-EDX analyses, titration, elemental analysis, BET, and TGA. After interacting with In(III), the FTIR spectrum of TcTDG shows the modification of the environment of N- and S-based reactive groups. The sorption of In(III) is first studied in synthetic solutions with TcTDG micro-particles through the evaluation of pH effect (optimum at pH 4), the uptake kinetics (equilibrium achieved in 20–30 min), the sorption isotherms and the selectivity properties from equimolar solution of different metal ions. The sorption capacity significantly decreases when increasing the temperature from 15 to 50 °C: In(III) sorption onto TcTDG is exothermic. Maximum sorption capacity at room temperature and at pH 4 reaches up to 1.87 mmol In g−1; the isotherm is equally fitted by the Langmuir and the Sips equations. Indium is fully eluted from metal-loaded sorbent using 0.3 M HCl solution (equilibrium reached in 20–30 min). The pseudo-first order rate equation fits well experimental kinetic profile; although the resistance to intraparticle diffusion plays a significant role in the control of In(III) sorption. The sorbent is highly stable at recycling: the FTIR spectrum is restored after five cycles and desorption remains complete along the cycles; after five re-uses, the sorption efficiency decreases by less than 4%. The study is extended to more complex solutions: first, with multi-component synthetic equimolar solutions before investigating the application of TcTDG to metal recovery from acidic leachate of ore sample (from Eastern Central Desert, Egypt). The sorbent shows a marked preference for In(III) at pH 4 against mono-, di- and tri-valent metal ions in synthetic solutions, the preference is also appreciable but the selectivity coefficient (SC In/metal) is weaker for rare metals (between 3 and 6, vs. 10–35 for other metal ions). In the case of acidic leachate, the pH control to 4 leads to substantial precipitation of huge amounts of iron and the co-precipitation of other metal ions. The sorption capacity for In(III) (and Ga(III)) is significantly reduced by the complexity of the effluents; although the sorbent maintains a preference for these trivalent metal ions. The new sorbent shows promising sorption properties, although complementary investigation is required for optimizing the practical application of this material (conditioning, larger number of recycling steps, etc.). [ABSTRACT FROM AUTHOR]

The rare earth elements (REEs) recovery of becomes a strategic issue due to intense use in high-tech industry. One of the most important challenge in the valorization of minerals or waste resources concerns the REEs separation from heavy metals as well as their proper separation within the REEs' family. Two aminophosphates (AP) derivatives were previously prepared for uranium recovery from wastes by one-pot reaction of p -phthalaldehyde, trimethylphosphite and thiocarbazide (in different proportions, leading to Mono-AP and Bis-AP sorbents). Herein, these sorbents are successfully tested for sorption of Nd(III).). For Mono-AP and Bis-AP, the maximal sorption capacity reaches 1.3 and 1.4 mmol Nd g−1, respectively at optimum pH (i.e., 4.5). The functionalization grade weakly affects sorption property at equilibrium (equilibrium is attained in 120–180 min). Uptake kinetics is described by PFORE). Sorption isotherms are fitted by the Sips equation. Neodymium sorption is exothermic and spontaneous, the entropy change remains below 6 J mol−1 K−1 (being higher for Bis-AP). Metal desorption is successfully operated with HCl (0.2 M) solutions and at the sixth cycle, the reduction in sorption and desorption efficiencies do not exceed 7% and 4%. The materials are tested for the REEs recovery of from pre-treated acid leachate of monazite concentrate. In this work which focuses on the REEs recovery, the sorbents show first a marked (unexpected, in terms of physicochemical characteristics) preference for Nd, but also (to a lesser extent) for La>Ce>Pr (i.e., heavy REEs). The mechanisms involved in Nd(III) sorption (investigated utilizing XPS and FTIR analyses) affirm the cross contributions of phosphonate moieties, amine groups (and to a lesser extent thiocarbonyl) with differences between Mono-AP and Bis-AP in terms of relative contributions. [Display omitted] • Simple one-pot synthesis of aminophosphonate-based sorbents for Nd(III) sorption. • At pH 4.5, maximum sorption capacity reaches 1.28-1.40 mmol Nd g−1. • Sorption is exothermic and spontaneous, isotherms fitted by Sips equation while • Equilibrium reached in 60 min; kinetics fitted by pseudo-first order rate equation. • Preference for Nd and La among rare earth elements (in pre-treated ore leachate). [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] • Sulfur-functionalized SiO 2 beads for highly efficient Ag(I) sorption at pH 6. • Endothermic sorption; isotherm fitted by Temkin equation (q m ; 3 mmol Ag g−1). • Fast sorption (t eq : ≈20 min); kinetics modeled by pseudo-first order rate equation. • Strong preference for Ag(I) in multicomponent solutions and X-ray film leachate. • Remarkable metal desorption with 0.3 M HNO 3 and stable recycling. The reaction of thiocarbazide with pentaerythritol tetrakis(3-mercaptopropionate) in the presence of mesoporous silica beads allows producing a composite sorbent (PTMF-SiO 2) with high affinity for silver. The high density of both N- and S-based reactive groups (about 5 mmol g−1) explains sorption capacities as high as 3 mmol Ag g−1 at pH 6. The sorption mechanisms are correlated to the pH effect, and to FTIR and XPS spectroscopic analyses. The sorption is endothermic and spontaneous, and the sorption isotherms are successfully modeled using the Temkin equation. Uptake kinetics are fitted by the pseudo-first order rate equation: the equilibrium is reached in 20–30 min. Ultrasonic treatment allows slightly increasing both kinetics (apparent rate coefficient k 1 is almost doubled) and sorption capacities (by less than 7 %). Silver (being a soft acid) preferentially reacts with soft bases; this may explain the selective removal of Ag(I) by PTMF-SiO 2 against base metals and alkali or alkaline earth metals (in multicomponent equimolar solutions). The sorbent shows remarkable recycling stability (for at least 5 cycles): complete desorption is achieved in ≈20 min with 0.3 M HNO 3 solution and the loss in sorption does not exceed 2.5 % at the fifth recycling. Finally, the sorbent is successfully applied to silver recovery from acidic leachates of spent X-ray films (from different hospitals from Hengyang, China), as a case study. Silver is selectively recovered with high efficiency (>96 %) (together with Cu(II), to a lesser extent). [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]

[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] • Phosphonate-bearing composite highly efficient for rare earth sorption at pH 5. • Fast kinetics (fitted by pseudo-first order rate equation); contact time: 20 min. • Maximum sorption capacity: 1.43 mmol La g−1 and 1.02 mmol Tb g−1 (Langmuir model). • Readily desorption and easy sorbent recycling with high selectivity for REEs. • Complete ore processing for selective recovery of REEs using synthesized sorbent. A new process of phosphorylation of algal/polyethyleneimine composite beads allows to dramatically increase the sorption of rare earth elements (La(III) and Tb(III), as light and heavy REE elements, respectively). Sorption proceeds through interactions with several functional groups (phosphonate, but also amine, and carboxylate groups). The sorption capacity at optimum pH (pH 0 : 5, pH eq : 4–4.2) reaches 1.44 mmol La g−1 and 1.02 mmol Tb g−1 (increased by 4.5 to 6.7 compared with raw beads). Sorption isotherms are fitted by the Langmuir equation, while fast uptake kinetics (equilibrium within 20–30 min) is described by the pseudo-first order rate equation. Bound metal ions are quantitatively desorbed using a 0.2 M HCl/0.5 M CaCl 2 solution; the recycling of the sorbent for five cycles of sorption and desorption shows high stability of sorption (loss of sorption capacity < 9%) and desorption (efficiency > 99%). The sorbent exhibits a remarkable preference for REEs against Si(IV), Ca(II), and Mg(II). The sorbent is used efficiently for the recovery of REEs from acidic leachates of a sedimentary ore. A global process is designed including acidic leaching, pre-treatment of leachates by U(VI) sorption on quaternary ammonium (QA) resin (about 94% of U content). The outlet solution of QA resin is treated at different pH values: the best results are obtained at pH 0 5 (pH eq : ~4.5). The REEs are selectively recovered from the eluates by precipitation with oxalic acid: the REE-oxalate precipitate retains 70–76% of its content in the acidic leachates. After precipitation of Al(III) and Fe(III) at pH 5, residual uranium is recovered by precipitation at pH 9 (4.3% of metal leached from the ore). [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]

• Remarkable affinity of alginate/PEI membrane for Hg(II) ions over wide pH range. • Alginate/PEI membranes shows high selectivity for Hg(II) over Cu(II). • Competitive Sips model fits well Hg(II) and Cu(II) sorption isotherms. • The membrane shows high stability in strong acid or alkaline solutions. This study investigates Hg(II) and Cu(II) sorption in single and binary systems by alginate/polyethylenimine membranes. Batch experiments are conducted to assess the metal sorption performance. FTIR and SEM-EDX analyses are used to identify metal binding mechanism. The sorption kinetics are better fitted by the pseudo-second-order-equation compared to the pseudo-first-order-equation. Three isotherms are compared for fitting the sorption in mono-component solutions and the Sips model gives the best simulation of experimental data. The competitive-Sips model fits well sorption data in Hg-Cu binary solutions and finds that the Cu uptake is drastically reduced by Hg competition. Copper(II) uptake remains negligible at low pH whereas it increases with pH up to 6 because of material deprotonation. Mercury(II) sorption behaves differently, it slightly changes from pH 1 (q eq : 0.76 mmol g−1) to pH 6 (q eq : 0.84 mmol g−1) due to chloro-anion formation. Therefore, playing with the pH allows separating Hg(II) from Cu(II). [ABSTRACT FROM AUTHOR]

• Bi-functionalization of silica particles increases Sr(II) sorption properties. • Methacrylic (80%)/amidoxime (20%) substitution ratio is optimum. • Maximum sorption capacity reaches 1.57 mmol Sr g−1 at pH 8. • Total Sr(II) desorption and weak loss in sorption properties at the fifth recycling. • The sorbent is remarkably selective to Sr(II) in seawater. Silica microspheres are functionalized through the grafting of either polymethacrylic acid or amidoxime groups (mono-functional composite, PMAA/SiO 2 and PAO/SiO 2 , respectively) or in combination (bi-functional composite, PAO x MAA 100-x /SiO 2). The materials are characterized by textural analysis, TGA, SEM-EDX, elemental analysis, FTIR, XPS, pH PZC in order to confirm the synthesis route, identify the reactive groups and support the interpretation of sorption mechanisms toward Sr(II). The sorption of Sr(II), at optimum pH 8, involves amine groups and hydroxyl/carboxyl groups in the bi-functional composite sorbent. The comparison of sorption properties shows that maximum sorption requires a majority of carboxylic groups from polyacrylic compared with amidoxime functions; optimum formulation: PAO 20 MAA 80 /SiO 2 sorbent. Sorption isotherms are efficiently fitted by the Langmuir and Sips equations: the maximum sorption capacity reaches around 1.38 mmol Sr g−1. Kinetic profiles for sorption are modeled using the pseudo-first order rate equation; equilibrium is achieved within 40–60 min. Complete desorption of Sr(II) using 1 M HCl solutions is even faster; equilibrium time being 15–20 min. The sorbent can be recycled for 5 cycles with a limited decrease in the sorption performance, and full desorption. In fixed-bed column, the breakthrough curves are fitted by the Thomas equation. In multi-component solutions, the sorbent shows a preferred selectivity according the sequence: K(I) > Ba(II) > Na(I) > Ca(II). Tested on seawater, the sorbent shows high distribution ratio for Sr(II), B(III) and Mo(VI) [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]

• Macroporous membrane obtained by controlled alginate/polyethyleneimine interaction. • Dual crosslinking alginate/calcium and PEI/glutaraldehyde for structured foam. • Highly percolating, stable foam with outstanding properties for chromate binding. • Sips equation for modeling chromate sorption. • Uptake kinetics controlled by pseudo-second order rate equation. Highly percolating membranes are prepared by the interaction of polyethylenimine and alginate (with glutaraldehyde crosslinking). SEM illustrates the macroporous structure of the material. The material is characterized by FTIR before and after chromate anions sorption. Batch-simulated continuous sorption experiments revealed that the maximum sorption occurred at pH 2 and the flow rate has limited effect on sorption efficiency. Uptake kinetics and sorption isotherms are well fitted by the pseudo-second-order rate and Sips equations, respectively. Maximum sorption is found close to 314 mg g−1. Competition effects from Ca(II), Cu(II), Cl−, NO 3 −, and SO 4 2− are investigated to evaluate sorbent selectivity. The membranes are applied to remediate a simulate of Cr(VI) contaminated electroplating wastewater. Successive cycles of sorption and desorption show that the membranes maintain sorption capacity higher than 200 mg Cr g−1 for both Cr(VI) and total chromium for the first two cycles. These new highly percolating membranes have promising performances for Cr(VI) removal. [ABSTRACT FROM AUTHOR]

• PGMA was functionalized with aminophosphonic groups to sorb rare earth elements. • XPS, FTIR and molecular modeling were applied for characterizing metal binding. • Sorption isotherms and uptake kinetics are modeled for La(III) and Y(III) recovery. • Metal desorption and sorbent recycling are highly efficients. • The treatment of monazite leachate is discussed in terms of affinity for REEs. After synthesis of parent PGMA micro-particles by dispersion polymerization method, diethylenetriamine (DETA) is grafted on the polymer (DETA-PGMA). In the last step, methylene phosphonic groups are grafted on DETA-PGMA by reaction of phosphonic acid groups onto amine functions in the presence of formaldehyde to produce polyaminophosphonic acid sorbent (PPA-PGMA). The sorbent is characterized by elemental analysis, FTIR spectrometry, XPS, XRD, TG-TDA and SEM-EDX analyses. The sorption properties of the material are tested for the sorption of La(III) and Y(III): the effect of pH on sorption performance is investigated before studying uptake kinetics, sorption isotherms (and thermodynamics), metal desorption and sorbent recycling. Maximum sorption capacities reach up to 0.79 mmol La g−1 and 0.73 mmol Y g−1 at pH 5 (optimum initial pH value). Sorption isotherms are characterized by a saturation plateau: the Langmuir equation fits well data. The sorption on micron-sized particles is fast and equilibrium is reached within 3–4 h: the kinetic profiles are modelled by the Crank equation (resistance to intraparticle diffusion) though the pseudo-first order rate equation fits well experimental data. Nitric acid (0.5 M) solutions can be used for metal recovery and the sorbent is re-used for at least 6 cycles of sorption and desorption with limited decrease in performance (less than 7%). The sorbent has a preference at pH 5 for La(III) vs. Y(III) but the selectivity coefficient is not high enough for potentiating the selective separation of the two metals. [ABSTRACT FROM AUTHOR]