The association of alginate (from brown algal biomass) and branched polyethyleneimine (PEI) (through dual crosslinking involving glutaraldehyde with amine groups of PEI, and calcium for ionotropic gelation of the biopolymer) allowed preparing stable support (APEI) that can bind Re(VII) in mild acidic conditions. However, the quaternization of APEI (as Q-APEI, through the grafting of (3-chloro-2-hydroxypropyl)trimethylammonium groups) strongly enhanced perrhenate sorption (from 0.544 to 1.51 mmol Re g(-1)) at pH 4. The combination of FTIR and XPS spectrometric methods demonstrated that most of the sorption proceeds by ion-exchange/ electrostatic attraction of perrhenate anions onto protonated amine groups and quaternary ammonium groups and/or chelation with primary and secondary amine groups (though carboxyl/carbonyl may also contribute to a lesser extent). Equilibrium time was also improved by quaternization: under selected experimental conditions, equilibrium is reduced from 90 to 30 min; the pseudo-first order rate equation fits the kinetics. The Temkin equation simulates sorption isotherms better than the Langmuir equation. The beneficial effect of quaternization was confirmed by the selectivity (and distribution ratio) in equimolar multi-metal solutions and in the presence of increasing amounts of NaCl. Sorbents show remarkable stability in sorption performances for ten successive sorption/desorption cycles; using 0.5 M HNO3 solution as the eluent: the loss in performance did not exceed 5% for Q-APEI at the last cycle (14% for APEI). Perrhenate being a realistic surrogate of pertechnetate, optimized experimental conditions were successfully applied for the removal of 99Tc from a series of synthetic solutions (prepared with variable levels of radioactivity and compositions; increasing the salinity of the solutions). These complementary tests confirm the significant enhancement in sorption performance with quaternized material (in terms of both kinetics and isotherms).

Herein, an efficient functionalized cellulose-based sorbent (F-Cel) was synthesized via chlorination followed by 1-amino-2-naphthol-4-sulfonic acid grafting. Comprehensive characterization (via CHN analysis, XRD, XPS, pH(PZC), SEM-EDX) validated successful functionalization and revealed critical structure-property relationships. The sorption efficiency exhibited strong pH-dependence, peaking at pH 3.5 for Th(IV) and 4.5 for U(VI). Kinetic equilibria occurred at 90 min (Th(IV)) and 120 min (U(VI)), adhering to pseudo-first-order (Cel) and pseudo-second-order (F-Cel) kinetics, reflecting their distinct surface functionalities. The F-Cel achieved superior sorption capacities (0.716 mmol/g for Th(IV) and 0.655 mmol/g for U(VI) at 298 K) compared to Cel (0.341 mmol/g for U(VI) and 0.309 mmol/g for Th(IV) at 298 K). This represents a similar to 2.1-fold and similar to 2.3-fold increase in capacity for Th(IV) and U(VI), respectively. This leap stems from synergistic -SO3H (ion-exchange) and-OH/-NH2 (chelation) groups, contrasting Cel's physisorption, as conclusively validated through multispectral mechanistic analysis. Thermodynamically, F-Cel exhibits spontaneous endothermic sorption for both metals, contrasting Cel's exothermic behavior. U(VI) shows > 86 % desorption efficiency in NaHCO3/HCl with stable recyclability over 7 cycles (<14 % capacity loss), demonstrating robust regeneration potential. Moreover, functionalization boosts Th(IV) affinity, evidenced by a higher distribution coefficient (D-Th = 3.064 L/g vs. D-U = 0.293 L/g), and an exceptional selectivity separation coefficient (SCTh/U= 10.7), representing about 5.4 & times; fold improvement over Cel.

Ruthenium removal from complex solutions (highly saline effluents, seawater) is a critical challenge. Herein, the sorption capacity of chitosan/SiO2 composite beads (Ch-Si) for ruthenium nitrosyl is increased three-fold after phosphoramidate grafting (DPA-Ch-Si, 1.6 mmol Ru g(-1)) at pH 5. Uptake kinetics and sorption isotherms are compared at pH(0): 3, 5 and 10; playing with the mode of agitation (mechanical, MA, vs. ultrasonic treatment, UT). The sorbent maintains good sorption capacities at pH 3 and 10. Uptake kinetics modeled by pseudo-first order rate equation is boosted by functionalization. For Ch-Si, sorption isotherms are modeled by the Langmuir or Sips equations (depending on the pH), while for DPA-Ch-Si the best fits depend on pH, temperature and mode of agitation. Ruthenium sorption is spontaneous and endothermic for the two sorbents. For DPA-Ch-Si, the sorption capacity increases from 1.62 to 1.70 mmol Ru g(-1) to 2.23-2.32 mmol Ru g(-1) (T increasing from 21 to 50 degrees C). Nitric acid solution (0.3 M) reveals highly efficient for back extraction; ruthenium is completely released in <15 min. The functionalized sorbent can be reused for a minimum of 10 cycles, with limited loss in performance. Phosphoramidation improves sorption selectivity for the treatment of equimolar multicomponent solutions (Na, Ca, Mg, Fe, Al, U, and Nd). The effect of pH on sorption selectivity is evaluated in simple multi-metal solutions and complex environment. In seawater, the selective recovery of ruthenium is favored at pH close to 10. These tests confirm the promising perspectives offered for ruthenium removal from complex environments. Physicochemical characterizations of the sorbent (and their modes of interaction with ruthenium nitrosyl) included SEM, BET, TGA, FTIR, XPS, and elemental analyses.

Gallium being classified as a critical metal, its recovery from secondary sources became a strategic issue. Therefore, the sorbents design for high affinity toward gallium recovering is thus a challenge. A new sorbent was designed with high sorption affinity based on pyridine and hydrazinyl groups (HZP-GA). This offers a remarkable sorption performance at mild acid pH (approximate to pH 4) with maximum sorption up to 265 mg Ga g-1. The isotherms fitted by the Sips equation, while the sorption is endothermic and spontaneous. Fast sorption kinetics was detected (25 min is sufficient for complete sorption) and fitted with PFORE. Gallium sorption is easily and fast reversed; 0.3 M HCl solution, with full desorption in 20 min. A very limited loss in sorption performance after five cycles, revealed to high chemical stability. The HZP-GA shows a marked preference of Ga (III) than most other competitor ions in the solution, while the preference of trivalent metal ions was noticed over mono-and di-valent cations after investigated in equimolar multicomponent solutions. In the processing of pre-treated acid leachates of U-bearing ores; gallium has the priority for recovering at pH 4-5, which indicates that the HZP-GA reveals a promising tool for recovering of precise metals from complex natural solutions.

This study thoroughly explores the synthesis, characterization, and antimicrobial efficacy of three α-aminophosphonate-chitosan (α-AP-Cs) compounds and their nano‑silver functionalized organic hybrids. α-AP-Cs derivatives (CU, CT and CSC) were synthesized via an in-situ, one-pot reaction using chitosan and triphenyl-phosphite, with different carbamide-glutaraldehyde crosslinkers; urea-glutaraldehyde, thiourea-glutaraldehyde and semicarbazide-glutaraldehyde, respectively. Subsequently, their corresponding α-AP-Cs‑silver nanocomposites (CU-Ag0NPs, CT-Ag0NPs and CSC-Ag0NPs) were synthesized via solid-state approach. Their physicochemical and morphological profiles were fully characterized and compared against chitosan-Ag0NPs (Cs-Ag0NPs) and their bare organic-cores via CHNS/P/O, FT-IR, XRD, TEM, EDX, XPS and UV-visible analysis. The synthesis procedure, including phosphonation and carbamide-glutaraldehyde crosslinking, was confirmed through spectroscopic and elemental analyses. XPS and XRD affirmed the metallic silver with FCC structure. The UV-visible absorption peak was ⁓399 nm with averaging TEM size of the semi-spherical Ag0NPs around 30.4 nm. Thereafter, antimicrobial properties were systematically explored and optimized by evaluating minimum inhibition concentration, dose-killing, growth kinetics curves, protein leakage, and antibiofilm activity against bacterial strains (Streptococcus mutans and Pseudomonas aeruginosa) and fungal strains (Candida albicans and Rhizopus oryzae). Notably, incorporating α-aminophosphonate and Ag0NPs into chitosan-backbone markedly enhanced its antimicrobial efficacy against bacterial and fungal biofilms. Finally, a detailed structure-activity relationship study was conducted to elucidate the antimicrobial mechanisms.

The highly efficient Sr-90 removal from contaminated effluents became a critical challenge for the development of nuclear activities. Herein, chitosan is associated with bentonite for manufacturing spherical composite beads (Ch-BEN). This material having weak affinity for strontium (hard acid according Pearson's principles), it was necessary functionalizing the support with hard base groups for enhancing metal removal. Ch-BEN was functionalized as S-Ch-BEN, by grafting 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). The coexistence of N-bearing groups and sulfonic acid moieties (associated with tautomerization effects) was characterized by Fourier-Transform infrared and X-ray photoelectron spectroscopy for confirming chemical functionalization and for correlating sorption mechanisms. The sorption capacity (at the optimum pH; i.e., 7) was increased by 2.5 to 2.7-fold after AMPS grafting (up to 2.8 mmol Sr g(-1)). Sorption isotherms were fitted by the Sips equation, while uptake kinetics was improved and followed pseudo-first order rate equation. The sorption equilibrium was achieved in 60 min for Ch-BEN compared to 30 min for S-Ch-BEN. The functionalization (with sulfonic acid groups) not only improves maximum sorption capacity and kinetics but also selective strontium recovery (from equimolar multi-component solutions and seawater). The stability at sorbent recycling was considerably improved by AMPS grafting (achieved complete desorption with 0.3 M HNO3 solution; the loss at the 10th recycling <4 %). Spherical conditioning of the composite allowed testing the capacity of the sorbent for application in fixed-bed columns. The major issue concerning strontium deals with the removal of its radionuclide forms: a series of tests using Sr-90 spiked solutions (of increasing complexity) confirmed the efficiency of S-Ch-BEN for recovering Sr-90, including for contaminated seawater. S-Ch-BEN reveals promising for environmental applications and treatment of low-level activity effluents.

Using raw and modified lignocellulosic residues as bioadsorbents in continuous adsorption is challenging but it marks significant progress in water treatment and the transition to a bio-based circular economy. This study reviews the application of bioadsorbents in fixed-bed columns for treating water contaminated with inorganic species, offering guidance for future research. It evaluates chemical modifications to enhance adsorptive properties, explores adsorption mechanisms, and analyzes bioadsorbent performance under competitive adsorption conditions. Analysis of adsorption data included evaluation of adsorption capacity in mono- and multicomponent solutions, regeneration, reuse, bed efficiency, and disposal of spent bioadsorbents. This enabled assessing their scalability to sufficiently high levels of maturity for commercialization. In multicomponent solutions, selectivity was influenced by the characteristics of the bioadsorbents and by competitive adsorption among inorganic species. This affected adsorption performance, increasing the complexity of breakthrough curve modeling and controlling the biomaterial selectivity. Models for mono- and multicomponent systems are presented, including mass transfer equations and alternatives including “bell-type” equations for overshooting phenomena and innovative approaches using artificial neural networks and machine learning. The criteria discussed will assist in improving studies conducted from cradle (synthesis of new biomaterials) to grave (end use or disposal), contributing to accurate decision making for transferring the developed technology to an industrial scale and evaluating the technical and economic feasibility of bioadsorbents.

Uranium recovery from complex effluents requires the combination of different processes including metal sorption from low-concentration solutions containing several competitor metal ions. The design of efficient sorbents (BTC/CH(s), 2-(benzo[d]thiazol-2-yl)-N-carbamoyl acetamide grafted chitosan) that combine both high sorption capacity and high selectivity was achieved by adopting a dual strategy: (a) selecting efficient functional groups (amine, amide, thioester, and hydroxyl groups, in BTC/CH sorbents), and (b) adapting the arrangement of reactive groups appropriately to fit the specific shape of the complexes (ion-imprinting IP vs. non-ion-imprinted NIP materials). This dual strategy was applied to design a chitosan-based sorbent with high sorption capacity (approximate to 1.5 mmol U g(- 1)), fast uptake (equilibrium: 15-20 min), remarkable stability (limited loss of performances after 10 reuse cycles), and strong selectivity (tested on both equimolar multi-component solutions and pretreated acid leachate), at moderately acidic pH (i.e., 4). Ion-templating strategy effectively improved selectivity by 5-10-folds. Uptake kinetics was fitted by the pseudo-first order rate equation, while the sorption isotherms were finely simulated by the Temkin equation. The sorption was exothermic, spontaneous, and the iontemplating allowed reaching more organized structure. The sorbent was highly selective against base metals, alkali and alkali-earth metals, but less efficient for the separation from thorium or rare-earth elements. The sorbent was successfully used for the recovery of residual uranyl from acidic leachates pre-treated with resins (Amberlite IRA-400 and DOWEX 50, for the recovery of U and rare-earth elements, respectively) and precipitation step (removal of Al(III)/Fe(III) at pH 4). The sorbents were characterized by elemental analysis, FTIR and XPS spectroscopy for analyzing the chemical structure of the materials and identifying their interactions with U (VI). Textural properties and pHpzc values were analyzed for supporting sorption behaviors.

The recovery of thorium from aqueous industrial effluents is a challenge not only for environmental purpose but also for the valorization of secondary resources. The complexity of these effluents not only require designing highly efficient stable sorbent with highly reactive functional groups but also with good selectivity. Phosphonic groups are efficient for the binding of thorium. Successive grafting of phosphonic groups through one-pot reaction of vinylphosphonic acid with acrylamide-based reagents (as monomer and crosslinker) for polymerizing an efficient sorbent (HVP/NIP) toward Th(IV) recovery in slightly acidic solution. On the other hand, the selectivity objective was reached by adopting an ion-imprinting strategy (HVP/IP). While the templating weakly improves sorption capacity (at 1.46 mmol g- 1 at pH close to 3), the most significant benefits concern the uptake kinetics (slightly enhanced; equilibrium being reached in 20-25 min) and more significantly the separation properties of HVP/IP, against base metals and uranium (to a certain extent). The selectivity coefficient (i.e., SCTh/ metal) increases twice (against U and Ca) and up to 16-folds against Al, at pH0 3. Fourier-transform infrared and XPS spectroscopy confirm the structural differences for both sorbents (arrangement of reactive groups) and the interactions modes involved in thorium binding mechanisms. The remarkable sorption properties of HVP/IP are also illustrated by the good stability of the sorbent at recycling (loss in sorption less than 2% at the 10th cycle): complete desorption is achieved using 0.3 M HNO3 solution. The ion-imprinted sorbent is successfully applied to the recovery of valuable metals (thorium, uranium, and gallium) from acidic ore leachate at different pH values. The materials are fully characterized using different analytical tools; i.e., FTIR, TGA, XPS, BET, titration, and elemental analysis.

Strong incentive politics have been elaborated for promoting the recovery of precious metals from secondary resources. Solid leaching generates acidic effluents that can be pre-treated using precipitation steps for partial separation before applying sorption for metal recovery from mild acidic solutions. For this purpose, a new sorbent was designed carrying numerous N- and S-bearing reactive groups with good affinity for platinum (as chloroanionic species). Thiazole precursors were first reacted before being grafted (by free radical reaction) with triallyl cyanurate (to form CTTR sorbent). The material was characterized by a series of analytical tools (SEM, BET, FTIR, XPS, TGA, elemental analysis, and titration). The effect of pH combined with FTIR and XPS spectroscopy analyses allowed identifying the mechanisms involved in metal binding: electrostatic attraction of chloroplatinate anions with protonated amine groups (especially in acidic conditions), while at moderate acidic pH, metal sorption proceeds through ligand exchange and chelation onto N-based and S-based groups. Optimum sorption was found at pH close to 4 (near pHpzcvalue). Under selected experimental conditions, the equilibrium was reached in 25-35 min. The pseudo-first order rate equation fitted well experimental profile (though the resistance to intraparticle diffusion contributed to the kinetic control). The maximum sorption capacity at room temperature reached up to 1.58 mmol Pt g- 1 (at pH 4). The sorption isotherm was successfully fitted by the Temkin equation. The sorption is spontaneous and exothermic (with reduction in maximum sorption capacity reaching up to 25 %, when temperature increases to 50 degrees C). Optimum platinum desorption was obtained with 0.3 M HCl solution (with solid/liquid ratio 1.67 g L- 1) for complete desorption and enrichment factor close to 4.6. Complete desorption was maintained over 5 cycles, while the sorption efficiency decreased by less than 3.5 % at the fifth cycle. The sorbent showed remarkable stability for PGMs (Pd(II) in addition to Pt(IV)) against alkali-earth elements or base metals (from equimolar synthetic solutions); the selectivity is driven by the preference of the reactive groups (soft base and intermediary base) for soft PGM metals against hard and borderline metal ions; this selectivity is also affected by metal speciation (formation of chloro-anionic species). The valorization of platinum from non-compliant Pt/Al2O3 catalyst was investigated after leaching with aqua regia. Platinum was precipitated from the leachate with ammonium chloride. In a second step, aluminum was removed by precipitation at pH 5. The residual solution was then treated by adsorption on CTTR: optimum separation between Pt and Al was achieved at pH approximate to 3.

A simple one-pot reaction of maleic anhydride with iminodi(methylphosphonic acid) in presence of N,N'-methylenebisacrylamide allows producing a micron-sized multifunctional sorbent (herein called MPOH-MBA, bearing both carboxylate, phosphonate groups, and tertiary amine groups). These multifunctional groups bring high reactivity for rare earth elements (REEs, hard acids) (soft bases O-bearing ligands, consistently with Pearson's principle) with modulation of positively-charged surface (amine groups for interaction with scandium sulfate species). Effectively, MPOH-MBA shows remarkable sorption capacity for Sc(III) at optimum initial pH (i.e., pH0: 4): qeq,exp reaches up to 5.34 mmol Sc g-1, at room temperature. Langmuir equation fits well experimental profiles (affinity coefficient: 0.677 L mmol-1). Scandium sorption is endothermic: sorption capacity increases up to 6.50 mmol Sc g-1 (at T: 50 °C), while the affinity coefficient increases up to 1.54 L mmol-1. Fast kinetics (equilibrium reached in 20-30 min) are favored by the micron-size of the sorbent (and its good textural properties: 51 m2 g-1 for specific surface area and pore width close to 250 Å). Kinetic profiles are fitted by the pseudo-first order rate equation. The sorbent can be easily regenerated using 0.3 M HCl solution; the loss in sorption is less than 1.5% at the fifth cycle. Main reactive groups (identified by Fourier-transform infrared spectroscopy) are carboxylate and phosphonate groups. In presence of equimolar concentrations of competitor ions: sorption is governed by preference for trivalent metal ions over divalent cations. Among trivalent metal ions rare earth elements (REEs) are preferentially bound (against Al(III) and Fe(III)); in addition, MPOH-MBA sorbs Sc(III) with higher affinity than Nd(III) and Ce(III). The sorbent shows a relative selectivity for scandium and REEs over metal ions present in huge excess (100 to 500 excess), such as Fe(III) and Al(III)), in red mud acidic leachate.

The main factors driving research into the creation and application of renewable energy sources are concerns about climate change, rising oil prices, and the depletion of fossil fuel resources. Because the transportation industry is the largest emitter of pollutants into the atmosphere, biofuel is one of the renewable energy sources used by most nations. Because it is an environmentally friendly renewable resource with the potential to lower greenhouse gas emissions, biodiesel, defined as “a substitute for or an additive to diesel fuel that is generated from the oils and fats of plants and animals”, is seen as an attractive replacement for petroleum-based diesel fuel. Because it produces biodiesel more quickly than acid catalysis, heterogeneous base catalysis is favored. High surface area improves the physicochemical characteristics of fuel and reduces the emission of dangerous pollutants. The performance of an engine is enhanced with the addition of nanoadditives. Numerous nanoadditives and the methods used to prepare them are described in this chapter. Examples of nanoadditives include metal-based (metals, metal oxides, and metal alloys), antioxidants, oxygenated additives, and cetane number enhancers. Analyses are also presented of the performance and emission characteristics. Comprehensive studies on the characteristics of emissions and the combustion behaviour of diesel engines powered by biodiesel and blends, including nanoadditives, are also included. Additionally, consideration is given to the characteristics, efficiency, and emissions of diesel engines running on biodiesel and blends, including nanoadditives.

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 1.4mmol Nd g-1, respectively at optimum pH (i.e., 4.5). The functionalization grade weakly affects sorption property at equilibrium (equilibrium is attained in 120-180min). 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 6Jmol-1 K-1 (being higher for Bis-AP). Metal desorption is successfully operated with HCl (0.2M) 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.

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 %).

Although Cs(I) and Sr(II) are not strategic and hazardous metal ions, their recovery from aqueous solutions is of great concern for the nuclear industry. The objective of this work consists of designing a new sorbent for the simultaneous recovery of these metals with selectivity against other metals. The strategy is based on the functionalization of algal/polyethyleneimine hydrogel beads by phosphonation. The materials are characterized by textural, thermo-degradation, FTIR, elemental, titration, and SEM-EDX analyses to confirm the chemical modification. To evaluate the validity of this modification, the sorption of Cs(I) and Sr(II) is compared with pristine support under different operating conditions: the pH effect, kinetics, and isotherms are investigated in mono-component and binary solutions, before investigating the selectivity (against competitor metals) and the possibility to reuse the sorbent. The functionalized sorbent shows a preference for Sr(II), enhanced sorption capacities, a higher stability at recycling, and greater selectivity against alkali, alkaline-earth, and heavy metal ions. Finally, the sorption properties are compared for Cs(I) and Sr(II) removal in a complex solution (seawater sample). The combination of these results confirms the superiority of phosphonated sorbent over pristine support with promising performances to be further evaluated with effluents containing radionuclides.

The reaction of thiocarbazide with pentaerythritol tetrakis(3-mercaptopropionate) in the presence of mesoporous silica beads allows producing a composite sorbent (PTMF-SiO2) 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-SiO2 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 approximate to 20 min with 0.3 M HNO3 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).

The association of magnetite microparticles with bi-functional amino-sulfonate polymer (obtained by conden-sation of guanidine and amino hydroxynaphthalene sulfonic acid, mediated by formaldehyde) allows synthe-sizing 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 suc-cessfully 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 ex-periments 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.

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 reac-tion 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 (SCIn/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 investi-gation is required for optimizing the practical application of this material (conditioning, larger number of recycling steps, etc.).

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), pphthaldehyde (di-aldehyde), and trimethylphosphite (phosphorous precursor) are mixed with different molar ratios to produce bis- (2:1:2) and mono (1:1:1) & alpha;-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 degrees 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.