Grafting of quaternary ammonium groups for uranium(VI) recovery: application on natural acidic leaching liquor

Photocatalytic Performance of Functionalized Biopolymer for Neodymium (III) Sorption and the Recovery from Leachate Solution

Successive grafting of new sorbent bearing amino phosphonic groups based on chitosan nano magnetite particles was performed through successive coupling with formaldehyde. The produced composite was characterized by the high sorption capacity toward rare earth elements (REEs) and consists of different types of functional groups (phosphonic, hydroxyls and amine groups) that are used for enhancing the sorption properties. The chemical modification and the sorption mechanism were investigated through different analytical tools; i.e., FTIR, SEM, SEM-EDX, TGA, BET (surface area) and pHpzc. The sorption was investigated toward Nd(III) as one of the REE(III) members under ultraviolet (UV) and visible light (VL) conditions. The optimum sorption was found at pH0 4 and the sorption capacity was recorded at 0.871 and 0.779 mmol Nd g−1 under UV and VL respectively. Sorption isotherms and uptake kinetics were fitted by Langmuir and Sips and by pseudo-first order rate equation (PFORE) for the functionalized sorbent, respectively. The sorbent showed a relatively high-speed sorption kinetic (20 min). The bounded metal ions were progressively eluted using 0.2 M HCl solution with a desorption rate 10–15 min, while the loss in the total capacity after a series of sorption recycling (sorption/desorption) (five cycles) was limited (around 3%) with 100% of the desorption efficiency, indicating the high stability of the sorbent toward an acidic medium. The sorbent was used for the recovery of REEs from leach liquor residue after pretreatment for the extraction of particular elements. From these results (high loading capacity, high selectivity and high stability against acid treatments), we can see that the sorbent is a promising tool for the selective recovery of rare earth elements in the field of metal valorization.

Modified kaolin hydrogel for Cu2+ adsorption

Removal of Cu2+ ions from contaminated water is an important but challenging task. This study reports the synthesis of a composite hydrogel from two natural polysaccharides, namely, sodium alginate and chitosan, using inexpensive kaolin as a raw material and polyacrylamide as a modifier. The hydrogel had a high adsorption capacity and selectivity for Cu2+. The composite hydrogel was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The pseudo-second-order kinetic model was the most suitable model for the kinetic results, and the Langmuir isotherm model was the most representative of the sorption system. The results revealed that the adsorption process was mainly controlled by chemisorption. The maximum adsorption capacity of the adsorbent was 106.4 mg·g−1. Therefore, this study presents a new perspective on the application of composite hydrogels as Cu2+ adsorbents.

Ecofriendly Composite as a Promising Material for Highly-Performance Uranium Recovery from Different Solutions

The development of new materials based on biopolymers (as renewable resources) is substantial for environmental challenges in the heavy metal and radionuclide ions removal contaminations. Functionalization of chitosan with sulfonic groups was achieved for improving the uranium sorption, not only from slightly acidic leachate, but also for the underground water. The prepared hydrogel based on chitosan was characterized by series of analysis tools for structure elucidation as FTIR spectroscopy, textural properties using nitrogen adsorption method, pH_PZC (by pH-drift method), thermogravimetric analysis (TGA), SEM, and SEM-EDX analyses. The sorption was performed toward uranium (VI) ions for adjustment of sorption performances. The optimum sorption was performed at pH 4 (prior to the precipitation pH). The total sorption was achieved within 25 min (relatively fast kinetics) and was fitted by pseudo-first order rate equation (PFORE) and resistance to intraparticle diffusion equation (RIDE). The maximum sorption capacity was around 1.5 mmol U g^-1. The sorption isotherms were fitted by Langmuir and Sips equations. Desorption was achieved using 0.3 M HCl solution and the complete desorption was performed in around 15 min of contact. The sorption desorption cycles are relatively stable during 5 cycles with limit decreasing in sorption and desorption properties (around 3 ± 0.2% and 99.8 ± 0.1%, respectively). The sorbent was used for removal of U from acid leachate solution in mining area. The sorbent showed a highly performance for U(VI) removal, which was considered as a tool material for radionuclides removing from aquatic medium.

Synthesis and Characterization of Functionalized Chitosan Nanoparticles with Pyrimidine Derivative for Enhancing Ion Sorption and Application for Removal of Contaminants

Modified chitosan has been widely used for heavy metals removal during the last few decades. In this research, the study was focused on the effect of modified chitosan particles after grafting with heterocyclic constituent for enhancing the sorption of Cr(VI) ions. Chitosan was functionalized by 2-thioxodihydropyrimidine-4,6(1H,5H)-dione, in which the synthesized composite considered as a nanoscale size with average 5–7 nm. This explains the fast kinetics of sorption with large surface area. The prepared sorbent was characterized by Fourier-transform infrared (FTIR), elemental analysis (EA), Brunauer–Emmett–Teller (BET surface area) theory, thermogravimetric analysis (TGA), mass spectroscopy, and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) analyses. The experimental part of this work involved the application of the synthesized sorbent for the removal of Cr(VI) ions from highly contaminated tannery effluents that are characterized by a high concentration toward chromate ions with other associated toxic elements, i.e., Pb(II) and Cd (II) ions, which underscore the importance of this treatment. Under the selected conditions (K₂Cr₂O₇ salt, C_o: 100 mg L⁻¹ and pH: 4), the sorption diagram shows high Cr(VI) sorption and fast uptake kinetics. The sorption was enhanced by functionalization to 5.7 mmol Cr g⁻¹ as well as fast uptake kinetics; 30 min is sufficient for total sorption compared with 1.97 mmol Cr g⁻¹ and 60 min for the non-grafted sorbent. The Langmuir and Sips equations were fitted for the sorption isotherms, while the pseudo-first order rate equation (PFORE) was fitted for the uptake kinetics.

High-Performance Hydrogel Based on Modified Chitosan for Removal of Heavy Metal Ions in Borehole: A Case Study from the Bahariya Oasis, Egypt

Globally, there is a rising demand for water purification. This demand is driven by numerous factors, including economic growth, increasing population, water shortage, and deterioration of water quality. The current work highlights the manufacturing of environmentally friendly and highly efficient sorbent based on chitosan nanoparticles after successive crosslinking (using glutaraldehyde) and modification through grafting of 4-aminoazobenzene-3,4′-disulfonic acid (AZDS) as a source of sulfonic groups. First, the produced sorbent was thoroughly specified using FTIR, TGA, SEM, SEM-EDX, pHpzc, BET (nitrogen sorption desorption isotherms), and elemental analyses (EA). The sorbent was tested for the sorption of Fe(III) before application to highly contaminated iron water well samples. Next, the sorption was improved as the sulfonation process was conducted under the selected experimental conditions within 25 and 20 min with a maximum capacity of 2.7 and 3.0 mmol Fe g−1 in visible light and under UV, respectively. Then, the uptake kinetics for both techniques were fitted by the pseudo-first-order rate equation (PFORE), in which the effect of the resistance to intraparticle diffusion has remained an unneglected factor, while the Langmuir equation has fitted the sorption isotherms. After that, the efficient desorption was achieved by using 0.2 M hydrochloric acid solution, and the desorption process was as fast as the sorption process; 15 min was sufficient for complete desorption. The sorbent shows high selectivity for heavy metal ions compared to the representative elements. Finally, the sorbent was used for the removal of heavy metal ions from a highly contaminated water well in the Bahariya Oasis and appeared to be highly efficient for heavy metal removal even in a diluted solution. Accordingly, it can be implemented in the task of water treatment.

U(VI) and Th(IV) recovery using silica beads functionalized with urea- or thiourea-based polymers - Application to ore leachate

Urea and thiourea have been successfully deposited at the surface of silica beads (through one-pot reaction with formaldehyde) for designing new sorbents for U(VI) and Th(IV) recovery (UR/SiO₂ and TUR/SiO₂ composites, respectively). These materials have been characterized by FTIR, titration, elemental analysis, BET, TGA, SEM-EDX for identification of structural and chemical properties, and interpretation of binding mechanisms. Based on deprotonation of reactive groups (amine, carbonyl, or thiocarbonyl) and metal speciation, the optimum pH was ~4. Uptake kinetics was fast (equilibrium within 60-90 min). Although the kinetic profiles are fitted by the pseudo-first order rate equation, the resistance to intraparticle diffusion cannot be neglected. Sorption isotherms were fitted by Langmuir equation (maximum sorption capacities: 1-1.2 mmol g^-1). Thermodynamics are also investigated showing differences between the two types of functionalized groups: exothermic for TUR/SiO₂ and endothermic for UR/SiO₂. Metal desorption is highly effective using 0.3-0.5 M HCl solutions: total desorption occurs within 30-60 min; sorption/desorption properties are remarkably stable for at least 5 cycles. The sorbents have marked preference for U(VI) and Th(IV) over alkali-earth and base metals at pH_eq ~4.8. By preliminary precipitation steps, it is possible "cleaning" ore leachates of pegmatite ore, and recovering U(VI) and Th(IV) using functionalized silica beads. After elution and selective recovery by precipitation with oxalate (Th-cake) and alkaline (U-cake), the metals can be valorized.

Photocatalytic Efficacy of Heterocyclic Base Grafted Chitosan Magnetite Nanoparticles on Sorption of Pb(II); Application on Mining Effluent

Development of bio-based sorbents (i.e., chitosan moieties) at nanoscale size for the removal of metal contaminants is the main target of this research. Grafting with thiazole heterocyclic derivative gives fast kinetics sorption, highly metal loading, and good recyclability for mining leaching solution. Different analyses tools including (thermogravimetric analysis (TGA), scanning electron microscope and energy dispersive spectroscopy (SEM-EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR), BET surface area (nitrogen sorption desorption), titration, and TEM (transmission electron microscopy)) were used to investigate the chemical and textural properties of the functionalized sorbent. The sorption was measured in normal visible light and under UV emission. The highest capacity was measured at pH 5, which reached 0.251 mmol Pb g−1 in visible light compared with 0.346 mmol Pb g−1 under UV for the pristine crosslinked chitosan (MCc). The sorption performances were improved by functionalization; (0.7814 and 1.014 mmol Pb g−1) for the functionalized sorbent (MCa-ATA) under visible light and UV, respectively. PFORE (pseudo-first-order rate equation) and RIDE (resistance to intraparticle diffusion) fit kinetics, the Sips equation is the most fit profile for the sorption isotherms for the MCc in either light and UV processes, while PFORE and RIDE for kinetics under light and UV for MCa-ATA and Sips in light and Sips and Langmuir under the UV emission. Finally, the sorbent was investigated toward a raffinate solution from ore processing and shows promising extraction tools for the most interesting elements.

Synthesis of Eco-Friendly Biopolymer, Alginate-Chitosan Composite to Adsorb the Heavy Metals, Cd(II) and Pb(II) from Contaminated Effluents

Efficient removal of Cd(II) and Pb(II) from contaminated water is considered a fundamental point of view. Synthetic hydrogel biopolymers based on chitosan and alginate (cost-effective and eco-friendly) were successfully designed and characterized by highly efficient removal contaminants. The sorbents are characterized by FTIR, SEM-EDX, TGA, XPS analyses and textural properties which are qualified by N₂ adsorption. The sorption properties are firstly investigated by the effect of pH, sorption isotherms, uptake kinetics, and selectivity from multi-metal solution with equi-molar concentration. The sorbent with 1:3 ratios (of chitosan and alginate respectively) is the most effective for metal removal (i.e., 0.81 mmol Cd g⁻¹ and 0.41 mmol Pb g⁻¹). Langmuir and Sip’s models fitted better the adsorption isotherms compared to the Freundlich model. Uptake kinetics was well fitted by pseudo-first-order rate equation, while the saturation was achieved within 40 min. The sorbent shows good reproducibility through duplicate the experiments with negligible decreasing efficiency (>2.5%). The sorbent was applied for water treatment on samples collected from the industrial area (i.e., 653 and 203 times over the MCL for Cd(II) and Pb(II) respectively according to WHO). The concentration of Cd and Pb was drastically decreased in the effluents as pH increased with removal efficiency up to 99% for both elements at pH 5.8 and SD equivalent 1 g L⁻¹ for 5 h.

Nd(III) and Gd(III) Sorption on Mesoporous Amine-Functionalized Polymer/SiO2 Composite

The strong demand for rare-earth elements (REEs) is driven by their wide use in high-tech devices. New processes have to be developed for valorizing low-grade ores or alternative metal sources (such as wastes and spent materials). The present work contributed to the development of new sorbents for the recovery of rare earth ions from aqueous solutions. Functionalized mesoporous silica composite was synthesized by grafting diethylenetriamine onto composite support. The physical and chemical properties of the new sorbent are characterized using BET, TGA, elemental analysis, titration, FTIR, and XPS spectroscopies to identify the reactive groups (amine groups: 3.25 mmol N g-1 and 3.41 by EA and titration, respectively) and their mode of interaction with Nd(III) and Gd(III). The sorption capacity at the optimum pH (i.e., 4) reaches 0.9 mmol Nd g-1 and 1 mmol Gd g-1. Uptake kinetics are modeled by the pseudo-first-order rate equation (equilibrium time: 30-40 min). At pH close to 4-5, the sorbent shows high selectivity for rare-earth elements against alkali-earth elements. This selectivity is confirmed by the efficient recovery of REEs from acidic leachates of gibbsite ore. After elution (using 0.5 M HCl solutions), selective precipitation (using oxalate solutions), and calcination, pure rare earth oxides were obtained. The sorbent shows promising perspective due to its high and fast sorption properties for REEs, good recycling, and high selectivity.

Quaternization of Composite Algal/PEI Beads for Enhanced Uranium Sorption-Application to Ore Acidic Leachate

The necessity to recover uranium from dilute solutions (for environmental/safety and resource management) is driving research towards developing new sorbents. This study focuses on the enhancement of U(VI) sorption properties of composite algal/Polyethylenimine beads through the quaternization of the support (by reaction with glycidyltrimethylammonium chloride). The sorbent is fully characterized by FTIR, XPS for confirming the contribution of protonated amine and quaternary ammonium groups on U(VI) binding (with possible contribution of hydroxyl and carboxyl groups, depending on the pH). The sorption properties are investigated in batch with reference to pH effect (optimum value: pH 4), uptake kinetics (equilibrium: 40 min) and sorption isotherms (maximum sorption capacity: 0.86 mmol U g-1). Metal desorption (with 0.5 M NaCl/0.5 M HCl) is highly efficient and the sorbent can be reused for five cycles with limited decrease in performance. The sorbent is successfully applied to the selective recovery of U(VI) from acidic leachate of uranium ore, after pre-treatment (cementation of copper, precipitation of rare earth elements with oxalate, and precipitation of iron). A pure yellow cake is obtained after precipitation of the eluate.