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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]

Graphical abstract Highlights • Efficient grafting of hydrazinyl amine on chitosan-coated magnetite. • High sorption capacity for divalent metals at near neutral pH. • Sorption isotherms are fitted by Sips equation. • Sorbent can be reused for at least 5 cycles using 0.5 M HCl as eluent. • Selectivity for Pb(II) for decontaminating multi-metal stormwater. Abstract The sorption properties of a functionalized magnetic chitosan sorbent have been investigated for the recovery of Ni(II) and Pb(II) from aqueous solutions. This material was prepared by one-pot co-precipitation of chitosan with formation of magnetic core, followed by a series of grafting steps to immobilize hydrazinyl amine derivative at the surface of chitosan layer. The physico-chemical characteristics of this composite material were investigated using FTIR, XRD, XPS, thermogravimetric, titration, elemental analyses. In a second step, the sorbent was tested for heavy metal sorption on synthetic solutions through the study of pH effect, sorption isotherms and uptake kinetics, selective sorption (in function of pH), metal desorption and sorbent recycling. Sorption isotherms were modeled using the Sips equation while the uptake kinetics was fitted by the pseudo-second order rate equation. The sorption capacity reached 4.3 mmol Ni g−1 and 2.5 mmol Pb g−1 but the sorbent was more selective to Pb(II) over Ni(II), especially in acidic conditions. The decrease in sorption capacity at the fifth cycle does not exceed 8%. In the final step of the study, the sorbents were successfully applied for metal recovery from multi-metal synthetic solution and from a contaminated stormwater collected in a local mining area. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Methyl aminophosphonate-grafted chitosan very efficient for uranyl sorption. • Full physico-chemical characterization of aminophosphonate derivatives of chitosan. • Successful desorption of uranyl using sodium bicarbonate solutions. • Stability of sorption and desorption performances for 4 successive cycles. • Efficient removal of uranium from acidic leachates of local uranium tailing ores. Abstract A one-pot synthesis procedure was used for preparing two derivatives of chitosan bearing α-aminophosphonate moieties. Chitosan functionalization was performed by reacting chitosan with glutaraldehyde and triphenylphosphite or trimethylphosphite under selected experimental conditions. The materials (CS-Ph and CS-Me, respectively) were characterized using different analytical procedures for confirming their suggested structures: scanning electron microscopy (coupled to energy dispersive X-ray analysis), Fourier-transform infra-red spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy analyses, thermogravimetric analysis and elemental analysis. The sorption properties of these materials were compared for U(VI) recovery through the study of pH effect, sorption isotherms, thermodynamics, uptake kinetics and sorbent recycling (metal desorption and sorbent re-use). The sorption isotherms were modeled using the Langmuir and the Sips equations while the kinetic profiles were preferentially fitted by the pseudo-second order rate equation. The comparison of sorption properties shows that the methyl α-aminophosphonate derivative is much more effective in uranium recovery than the phenyl derivative: maximum sorption capacities reached at pH 5 around 245 mg U g−1 and 114 mg U g−1, respectively. Tentative explanations are suggested associated to the acid-base properties, the steric hindrance and the donor/acceptor behavior of reactive groups. Experimental data show that uranyl sorption process proceeds via an exothermic and spontaneous reaction for the two sorbents. Metal desorption was successfully tested using sodium bicarbonate solutions and the sorbent was recycled four times: the sorption and desorption efficiencies progressively decreased but remained relatively high at the fourth cycle (sorption: 88–90% of initial sorption and desorption decreasing by 5% between the first and the fourth cycles). Finally, the sorbents were efficiently tested on acidic ore leachate. [ABSTRACT FROM AUTHOR]

Magnetic chitosan particles were successfully modified by amidoxime-grafting (as evidenced by FTIR analysis, SEM-EDX analysis, elemental analysis, X-ray diffraction (XRD), thermogravimetric analysis and titration). The effect of pH was investigated showing optimum sorption at pH 4 for U(VI) and pH 5 for Eu(III). Uptake kinetics are relatively fast: the equilibrium was reached within 60–90 min; and the kinetic profiles were preferentially fitted by the pseudo-second order rate equation. Sorption isotherms are equally fitted by the Langmuir and the Sips equations; under optimal conditions maximum sorption capacity reaches 1.5 mmol U g −1 and 2.47 mmol Eu g −1 . In bi-component solution, at pH close to 4.9, uranyl is enriched on the sorbent (higher selectivity coefficient) while maintaining high sorption capacities. The selectivity for Eu(III) sorption is higher at pH 2.3 but at the expense of a decrease in sorption capacities. Metal ions can be readily and fast desorbed using 0.5 M HCl solutions: 30–90 min are sufficient for achieving the complete desorption of U(VI) and about 95% of Eu(III) desorption. Sorption and desorption performances are maintained almost constant over 5 cycles of sorption/desorption: the sorbent can be efficiently recycled. Uranium was successfully recovered from alkaline leachate of a sedimentary dolostone ore material. [ABSTRACT FROM AUTHOR]

A composite material (PAN-Na-Y-zeolite) was prepared by polymerization of acrylonitrile in the presence of Na-Y zeolite. The composite was functionalized by amidoximation through the reaction of hydroxylamine on nitrile groups of the composite. The sorbent (APNa-Y-zeolite) was fully characterized by FTIR spectrometry, XRD diffraction, thermogravimetric analysis, scanning electron microscopy, zetametry and BET analysis. The sorption properties of APNa-Y-zeolite were investigated for the recovery of Cu(II), Cd(II) and Pb(II) from synthetic solutions before being tested for the purification of local tap water. Sorption properties were characterized through the study of pH effect, uptake kinetics, sorption isotherms. The pseudo-second order rate equation fitted well kinetic profiles. Sorption isotherms were modeled using the Langmuir, the Freundlich and the Sips equations. Thermodynamic parameters were evaluated through variation of temperature. While the sorption of Cu(II) and Cd(II) was endothermic, Pb(II) recovery was exothermic. Metal ions were successfully desorbed using 5 M HCl solutions. High concentrations of NaCl hardly alter sorption performance, contrary to humic acid that slightly reduces metal binding. [ABSTRACT FROM AUTHOR]

The grafting of urea and biuret on alginate backbone (confirmed by FTIR spectrometry analysis) increases by 53–84% the sorption efficiency of the biopolymer for Cd(II), Cu(II) and Pb(II) recovery from mild acidic solutions (i.e., pH in the range 4.5–5.5). Sorption isotherms are successfully described by the Langmuir and the Sips equations: maximum sorption capacities reach up to 3.7 mmol Cd g −1 , 4.7 mmol Cu g −1 and 4.8 mmol Pb g −1 for alginate-urea beads. The affinity of the sorbent for metal ions is correlated to the electronic properties (softness) and configuration of hydrated ions and to the HSAB properties (Hard and Soft Acid-Bases rules) of the ligands present on the sorbent. The diffusion properties are playing a significant role in the control of the uptake kinetic profiles; however, the pseudo-second order rate equation also allows a good fit of experimental sorption kinetics. In multi-component solutions the sorbents maintain a higher affinity for Pb(II) over the other two divalent cations. [ABSTRACT FROM AUTHOR]

The incorporation of glutaraldehyde-crosslinked polyethyleneimine (GLA-PEI) in algal biomass beads (AB/PEI) substantially increases the sorption capacity for Pd(II) and Pt(IV) compared to pure algal beads ( Laminaria digitata ) prepared by an original one-pot synthesis procedure (using a homogeneous ionotropic Ca-gelation, without addition of supplementary alginate). The sorption properties are compared to a reference material (alginate beads). Sorption efficiency increases with pH in relation with deprotonation of carboxylate and amine groups, limitation of the competition effect of counter anions and effect of metal speciation. Sorption isotherms (fitted by the Langmuir equation) show maximum sorption capacities close to 1.28 mmol Pd g −1 and 0.59 mmol Pt g −1 for the composite sorbent at pH 2.5, with a marked preference for Pd(II) against Pt(IV) (sorption isotherms in bi-component solutions), especially for alginate and algal beads that are more selective than AB/PEI (an excess of chloride ions limits this selectivity). The uptake kinetics are controlled by the resistance to intraparticle diffusion though the kinetic profiles are well fitted by the pseudo-second order rate equation. The drying conditions have critical impact on the diffusion properties: freeze-drying limits the irreversible collapse of the porous structure (which happens with air-drying): the presence of cellulose-like fibers (and/or agglomerates of GLA-PEI) in AB and AB/PEI limits this impact. [ABSTRACT FROM AUTHOR]

A new hybrid material was prepared using chitosan, glycidyl methacrylate and magnetite microparticles. The concentration of amine groups on the sorbent was increased by grafting diethylenetriamine. These materials were tested for the sorption of Hg(II) metal ions. These materials showed high affinity and selectivity for Hg(II) uptake from aqueous solutions: maximum sorption capacity reached 2.6 mmol g −1 at pH 4.0. The influence of pH was tested on the selective separation of Hg(II) from a mixture of Hg(II), Co(II), Cu(II), Fe(II), Ni(II), Zn(II) and Mg(II). The effect of counter anions was also studied at different pH values. Sorption may occur by chelation of cationic mercury species on amino groups or by ion exchange of chloroanionic mercury species on protonated amino groups. Uptake kinetics and sorption isotherms were modeled using the pseudo-second order rate equation and the Langmuir equation, respectively. The distribution coefficient was obtained at different temperatures and the thermodynamic parameters have been calculated: the sorption is endothermic, spontaneous and contributes to increase the entropy of the system. Potassium iodide was used for Hg(II) desorption from loaded sorbents: desorption yields 99%, and the sorbent could be efficiently recycled for a minimum of three sorption/desorption cycles. [ABSTRACT FROM AUTHOR]

Highlights: [•] Highly porous composites are prepared for immobilizing nickel potassium ferrocyanide. [•] The composite material is very efficient for removing Cs(I) in the range pH 2–8. [•] The process is selective for Cs(I) even in presence of large excess of Na(I), K(I). [•] Kinetics are controlled by the pseudo-second order rate equation. [•] The discs can be used for dynamic and reactive filtration of radionuclide solutions. [Copyright &y& Elsevier]

Abstract: Acid Black 1 (AB1) is a diazo dye containing both NN and CC chromophores groups that has considerable health effects being irritating for skin, eye and respiratory system. It is essential to remove this dye from wastewater. In this study, the removal of AB1 with brown macroalgae Sargassum glaucescens and Stoechospermum marginatum was studied using a batch system. The effects of parameters such as initial pH (in the range 2–10), contact time (within 90min), biomass dosage (in the range 1–9g L−1), initial dye concentration (in the range 10–50mgL−1), particle size of biosorbent (0.53–500μm) and agitation speed (from 70 to 180rpm) on the adsorption capacity of AB1 were investigated. The equilibrium data indicated that the Freundlich model provided the best correlation of the experimental data for both biosorbents at least in the concentration range investigated in this study. The biosorption kinetic data were successfully described with pseudo-second order model (PSORE) for two biosorbents. Thermodynamic parameters showed adsorption of dye was feasible and endothermic at all temperatures (283–313K) for both biosorbents. A decrease in particle size of biosorbents increased acidic dye removal capacity. The agitation speed influences AB1 sorption capacity and optimum agitation speed observed at 130rpm among different agitation speed (i.e. 70–180rpm). FT-IR analysis demonstrated the involvement of different functional groups, mainly hydroxyl, carboxyl and amine groups. These results confirm that these algae have a good potential for removal of AB1 from aqueous solution at low dye concentration. [Copyright &y& Elsevier]

Abstract: Cyphos IL-101 ionic liquid (IL; tetradecyl(trihexyl)phosphonium chloride) was immobilized in Amberlite XAD-7 for the preparation of an extractant impregnated resin (EIR) that was used for Pd(II) sorption from HCl solutions. Chloro-palladate anionic species are bound to the EIR by electrostatic/anion exchange mechanism between anionic species and phosphonium cation (IL). Maximum sorption capacity increases with extractant loading and depends on HCl concentration reaching values up to 71mg Pdg−1 EIR for an EIR with 401mg ILg−1 EIR, in 0.5M HCl solutions. Uptake kinetics are controlled by the resistance to intraparticle diffusion (effective diffusivity varying in the range 1×10−11 to 20×10−11 m2 min−1) as confirmed by the limited impact of agitation speed (negligible resistance to film diffusion). IL loading is a key parameter since it controls the filling of resin porous network and consequently the mass transfer properties: diffusivity in the extractant phase is reduced compared to diffusivity in water. Increasing IL loading increases sorption capacity but induces supplementary limitations to intraparticle diffusion. Increasing temperature decreases IL viscosity, which, in turn, enhances diffusion in this extractant phase. Nitric acid and thiourea in hydrochloric acid solutions allows complete desorption of Pd(II) from loaded EIR. The resin can be recycled for at least five cycles maintaining high sorption and desorption efficiencies. [Copyright &y& Elsevier]

Abstract: Posidonia oceanica leaves have been pre-treated with HCl solutions to elaborate a biosorbent that was carried out for Pb(II) sorption at pH 4 and pH 5. The sorption of Pb(II) was characterized using SEM-EDAX, XPS spectrometry and FT-IR spectroscopy. Maximum sorption capacity reached up to 140mgPbg−1 at pH 5. The uptake kinetics were controlled by chemisorption reaction rate. This was correlated to the lamellar structure observed using SEM analysis. The influence of sorbent dosage, particle size and metal concentration on uptake kinetics was also investigated. Sorption performances are compared to other biosorbents and to previous studies on P. oceanica for binding of mineral and organic compounds. [Copyright &y& Elsevier]

[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]

• Magnetic chitosan micro-particles efficiently grafted with amine and dithizone. • Uranyl sorption increases by functionalization (i.e., diethylenetriamine amine). • Ultrasonic treatment (frequency: 80 kHz) drastically increases mass transfer. • Microwave speeds up sorption but drastically reduces sorption capacity. • Metal desorption is greatly enhanced by short microwave exposure. Magnetic chitosan nanoparticles, activated by glycidyl methacrylate, can be functionalized by grafting diethylenetriamine (DETA) and dithizone for improving U(VI) sorption at pH around 5. The physicochemical properties of the materials have been characterized by a wide variety of analytical techniques. Uranyl sorption increases with the pH (progressive deprotonation of amine and sulfur groups). Uptake kinetics are controlled by the agitation mode: the equilibrium time is reduced while using ultrasonic treatment (especially at highest frequency: 80 kHz): the cavitation effect improves the accessibility to internal reactive groups (sorption capacity is increased). The diffusivity coefficient is increased by 4–5 times. In the case of microwave, the sorption capacity is significantly reduced (especially for R-Dithizone, down to 0.8 mmol U g−1) because of temperature increase, which limits the sorption (exothermic mechanism). Mass transfer is tremendously enhanced: equilibrium time is less than 60 s (30 min for ultrasonic treatment and 120 min with mechanical agitation). Sorption capacity at monolayer saturation (Langmuir) decreases with increasing the temperature from 2.20 to 1.74 mmol U g−1 for R-Amine (from 1.77 to 1.22 mmol U g−1 for R-Dithizone). The sorption enthalpy is close to −19.7 kJ mol−1 for R-Amine (with positive entropy change, ΔS°) and −34.2 kJ mol−1 for R-Dithizone (negative ΔS°). Metal desorption is highly efficient using 0.3 M Na 2 CO 3 /0.1 M H 2 O 2 solution. Metal desorption is instantaneous (less than 1 min) and complete when using microwave treatment. The ultrasonic treatment allows improving desorption efficiency and decreasing the concentration of the eluent compared with mechanical agitation. The process is successfully applied for uranyl separation from the leachates of marine sediments, especially in the presence of Complexon III (masking agent). [ABSTRACT FROM AUTHOR]

• The sulfonation of algal/PEI composite beads produce very efficient sorbent for Sc. • The sorption process is fast (30–40 min equilibrium time). • At pH eq ~ 4, the maximum sorption capacity reaches 2.68 mmol Sc g−1. • Rare earth elements totally desorbed using HCl/CaCl 2 , with good sorbent recycling. • REEs strongly enriched onto S-A L PEI after the treatment of a red mud solution. The one-pot synthesis of algal biomass/polyethyleneimine beads, A L PEI (electrostatic interaction followed by calcium ionotropic gelation), produces a stable sorbent whose sorption properties for rare earth elements (REEs) are significantly improved by functionalization. The grafting of sulfonic groups (S-A L PEI), which have high affinity for REEs, increases sorption capacities as high as 2.68 mmol Sc g−1, 0.61 mmol Ce g−1 and 0.53 mmol Ho g−1, at pH close to 4 (equilibrium pH). Sorption isotherms are fitted by the Langmuir equation for scandium and cerium; for holmium, the Freundlich and the Sips equations show better fits. Sorption occurs within 30–40 min; kinetic profiles are fitted by the pseudo-first order rate equation and the Crank equation (resistance to intraparticle diffusion). The sorbent has a marked preference for Sc(III) against Ce(III) and Ho(III) (confirmed by selectivity tests). The sorbent is also selective for REEs against alkali-earth elements. The three metals are readily desorbed (within 20–30 min) using HCl/CaCl 2 solution. Desorption remains higher than 99% for 5 cycles while sorption performance is decreased by less than 6% at the fifth cycle. The sorbent is tested for the recovery of valuable metals from red mud solution at different pH values. Despite the large excess of heavy metals in the industrial solution, S-A L PEI shows a good affinity for REEs at pH close to 3.46 with important enrichment factors (in the range 19–118 depending on the metal). The material is fully characterized by BET, TGA, FTIR, XPS, elemental analysis, titration and SEM-EDX analysis. The sorption involves different mechanisms (on amine and sulfonic groups) including electrostatic attraction and chelation depending on pH and metal speciation. [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]

• 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]