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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]

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. [ABSTRACT FROM AUTHOR]

The main challenge for researchers in the biomedical sectors concerns the development of new active compounds through cost-effectiveness, rapid, simple, and ecofriendly methods to overcome antibiotic resistance to pathogenic microbes. Herein, gold nanoparticles (AuNPs) were fabricated by a green approach through the reduction of chloroauric acid (HAuCl4) by harnessing the metabolites present in the aqueous extract of Zingiber officinale rhizome. UV-Vis spectroscopy, FT-IR, XRD, TEM, DLS, and zeta potential were used to characterize phytosynthesized AuNPs. In addition, the antimicrobial effect was investigated against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli), unicellular fungi (Candida albicans), and multicellular fungi (Aspergillus brasiliensis). Antioxidant and in vitro cytotoxic activities were assessed. TEM and XRD showed the successful formation of spherical and crystalline structures, with sizes in the range of 5–53 nm (average size: 15.11 ± 8.5 nm). The zeta potential value (i.e., –28.8 mV) explains the high stability of synthesized AuNPs. AuNPs exhibit promising activity against prokaryotic and eukaryotic microorganisms with variable inhibition zones and low MIC values in the range of 25–6.25 µg mL−1. Phytosynthesized AuNPs exhibit DPPH scavenging activity with percentages of 87.6 ± 0.5% at a maximum concentration (1000 µg mL−1), which can be compared with ascorbic acid (97.3 ± 0.2%). Moreover, the AuNPs displayed a target-oriented effect for cancer cell lines HepG2 and MCF7 at low IC50 concentrations of 131.9 ± 9.34 and 288.23 ± 31.39 µg mL−1 compared to the normal oral epithelial OEC cell line (487.612 ± 3.53 µg mL−1). Overall, the phytosynthesized AuNPs show wide activities that enable their use in various biomedical and biotechnological applications. [ABSTRACT FROM AUTHOR]

The recovery of strategic metals such as rare earth elements (REEs) requires the development of new sorbents with high sorption capacities and selectivity. The bi-functionality of sorbents showed a remarkable capacity for the enhancement of binding properties. This work compares the sorption properties of magnetic chitosan (MC, prepared by dispersion of hydrothermally precipitated magnetite microparticles (synthesized through Fe(II)/Fe(III) precursors) into chitosan solution and crosslinking with glutaraldehyde) with those of the urea derivative (MC-UR) and its sulfonated derivative (MC-UR/S) for cerium (as an example of REEs). The sorbents were characterized by FTIR, TGA, elemental analysis, SEM-EDX, TEM, VSM, and titration. In a second step, the effect of pH (optimum at pH 5), the uptake kinetics (fitted by the pseudo-first-order rate equation), the sorption isotherms (modeled by the Langmuir equation) are investigated. The successive modifications of magnetic chitosan increases the maximum sorption capacity from 0.28 to 0.845 and 1.25 mmol Ce g−1 (MC, MC-UR, and MC-UR/S, respectively). The bi-functionalization strongly increases the selectivity of the sorbent for Ce(III) through multi-component equimolar solutions (especially at pH 4). The functionalization notably increases the stability at recycling (for at least 5 cycles), using 0.2 M HCl for the complete desorption of cerium from the loaded sorbent. The bi-functionalized sorbent was successfully tested for the recovery of cerium from pre-treated acidic leachates, recovered from low-grade cerium-bearing Egyptian ore. [ABSTRACT FROM AUTHOR]

Sulfonic resins are highly efficient cation exchangers widely used for metal removal from aqueous solutions. Herein, a new sulfonation process is designed for the sulfonation of algal/PEI composite (A*PEI, by reaction with 2-propylene-1-sulfonic acid and hydroxylamine-O-sulfonic acid). The new sulfonated functionalized sorbent (SA*PEI) is successfully tested in batch systems for strontium recovery first in synthetic solutions before investigating with multi-component solutions and final validation with seawater samples. The chemical modification of A*PEI triples the sorption capacity for Sr(II) at pH 4 with a removal rate of up to 7% and 58% for A*PEI and SA*PEI, respectively (with SD: 0.67 g L−1). FTIR shows the strong contribution of sulfonate groups for the functionalized sorbent (in addition to amine and carboxylic groups from the support). The sorption is endothermic (increase in sorption with temperature). The sulfonation improves thermal stability and slightly enhances textural properties. This may explain the fast kinetics (which are controlled by the pseudo-first-order rate equation). The sulfonated sorbent shows a remarkable preference for Sr(II) over competitor mono-, di-, and tri-valent metal cations. Sorption properties are weakly influenced by the excess of NaCl; this can explain the outstanding sorption properties in the treatment of seawater samples. In addition, the sulfonated sorbent shows excellent stability at recycling (for at least 5 cycles), with a loss in capacity of around 2.2%. These preliminary results show the remarkable efficiency of the sorbent for Sr(II) removal from complex solutions (this could open perspectives for the treatment of contaminated seawater samples). [ABSTRACT FROM AUTHOR]

Featured Application: Metal removal from contaminated water bodies and metal recovery from industrial effluents (valorization). The necessity of decontaminating effluents for the dual purpose of environmental beneficiation and valorization of low-grade resources is driving the development of new sorbents. The functionalization of biopolymers is a promising strategy for improving sorption performance. Incorporating magnetic micro-particles offers an opportunity for the facilitated recovery of spent micron-size sorbent. Combining magnetic facilities and biopolymer functionalization represents a winning strategy. Magnetic glycine-grafted chitosan (G@MChs) was synthesized for the sorption of Ni(II), Zn(II), and Hg(II) before being applied to the removal of hazardous and strategic metals from tailing leachates. The sorbent was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy, before and after metal sorption. The acid–base properties of functionalized sorbent were also determined (pHPZC). Uptake kinetics were studied in mono- and multi-component solutions using different equations for kinetic modeling at optimized pH (i.e., pH0: 5.5). Langmuir and Sips equations were applied to model sorption isotherms in single-component solutions. In addition, sorption isotherms in multi-component solutions were used to evaluate the preference for selected metals. Maximum sorption capacities were 0.35 mmol Hg g−1, 0.47 mmol Zn g−1, and 0.50 mmol Ni g−1. Acidified urea solution (pH 2.7) successfully desorbs metal ions from G@MChs (desorption > 90%). The sorbent was tested for the recovery of hazardous and strategic metal ions from acidic leachates of tailings. This study demonstrates the promising performance of G@MChs for the treatment of complex metal-bearing solutions. [ABSTRACT FROM AUTHOR]

Featured Application: Measuring moisture in bales of paper and cardboard packaging waste is of great importance in the transaction between the waste operators and the recycling industry. The traditional method (oven drying) to measure the moisture content of bales, in addition to requiring destruction of the bales, does not allow real-time measurement, which often generates distrust or conflicts between sellers and buyers at the time of negotiations. In this work, a new method was tested with a commercial device equipped with dielectric technology. The results are quite promising, providing a more time- and cost-effective, non-destructive and reliable method in the quality control of paper and cardboard packaging waste bales, which also contributes to greater trust between negotiators. Moisture content is a quality issue raised by recycling plants in the acceptance of paper and cardboard coming from waste streams. The current way to measure this parameter is by the oven drying method, which is a slow and invasive process, costing time and resources for the recyclers to do this type of quality control. An alternative to such a measurement technique is the use of plate-form devices which indirectly measure the moisture content using the dielectric properties of water and paper. This study has tested this method and developed a representative equation for the use of devices with these properties in the Portuguese market. For that, 48 wastepaper and cardboard bales were tested with both the traditional (oven drying) method and a commercial device equipped with dielectric technology. An equation that fits the studied reality (R2 = 0.76) was achieved, and possible problems regarding the use of this device were tested. The results showed that this type of device could be used as a time- and cost-saving, non-destructive and reliable method in the quality control of wastepaper and cardboard bales. [ABSTRACT FROM AUTHOR]

The present study was undertaken in a constructed wetland (CW), setup in a tourism house, for domestic wastewater treatment. The influence of season variations on the abundance of fecal indicator organisms (total coliforms and Escherichia coli) in the wastewater and in the substrate and the roots of plants inhabiting the inlet and outlet zones of the CW was evaluated along three consecutive years. The structure and diversity of bacterial communities associated to the CW's substrate of inlet and outlet zones was also analyzed overtime. Wastewater was characterized for physicochemical and microbiological parameters and the bacterial communities colonizing the substrate surface, were analyzed by Denaturing Gradient Gel Electrophoresis (DGGE). The CW was effective in removing COD, BOD5, TSS, PO43−, NH4+, NO3−, and NO2−. It was also effective in removing fecal indicators, with a generalized decrease of total coliforms and E. coli in the substrate and in the wastewater from inlet to outlet of up to 2–3 log. The structure and composition of bacterial communities associated with the substrate was mainly influenced by the year rather than by the season or the CW zone. [ABSTRACT FROM AUTHOR]

The use of granule activated carbon (GAC) and rubber particles as the bio-fouling reducer in a membrane bioreactor (MBR) was evaluated in this study. The addition of GAC tends to temporarily reduce Transmembrane Pressure (TMP). Then, after the initial reduction, TMP gradually increased back up to 0.7 bar, indicating significant fouling on the membrane. Low TMP values were observed after adding 0.5% (V/V) rubber particles to the same MBR. The organic compound and nitrogen removal efficiencies of the MBR under intermittent aeration were over 94% and 93.3%, respectively. The results showed that Dysgonomonas, Acidobacteria, and Pantoea sp. contributed to the nitrification process while Lactobacillus, Erythrobacter, Phytobacter, and Mycobacterium contributed to the denitrification process. [ABSTRACT FROM AUTHOR]

Three commercial resins bearing sulfonic, amino phosphonic, or phosphonic/sulfonic reactive groups have been tested for the removal of iron and cadmium from phosphoric acid solutions. The sorption properties are compared for different experimental conditions such as sorbent dosage (0.5–2.5 g L−1), phosphoric acid concentration (from bi-component solutions, 0.25–2 M), and metal concentrations (i.e., in the range 0.27–2.7 mmol Cd L−1 and 0.54 mmol Fe L−1) with a special attention paid to the impact of the type of reactive groups held on the resins. The sulfonic-based resin (MTC1600H) is more selective for Cd (against Fe), especially at high phosphoric acid concentration and low sorbent dosage, while MTS9500 (aminophosphonic resin) is more selective for Fe removal (regardless of acid concentration and sorbent dosage). Equilibrium is reached within 2–4 h. The resins can be ranked in terms of cumulative sorption capacities according the series: MTC1600H > MTS9570 > MTS 9500. Sulfuric acid (0.5–1 M) can be efficiently used for the desorption of both iron and cadmium for MTC1600H, while for MTS9570 (phosphonic/sulfonic resin) sulfuric acid correctly desorbs Cd (above 96% at 1 M concentration), contrary to Fe (less than 30%). The aminophosphonic resin shows much poorer efficiency in terms of desorption. The sulfonic resin (i.e., MTC1600H) shows much higher sorption capacity, better selectivity, comparable uptake kinetics (about 2 h equilibrium time), and better metal desorption ability (higher than 98% with 1 M acid concentration, regardless of the type of acid). This conclusion is confirmed by the comparison of removal properties in the treatment of different types of industrial phosphoric acid solutions (crude, and pre-treated H3PO4 solutions). The three resins are inefficient for the treatment of crude phosphoric acid, and activated charcoal pre-treatment (MTC1600H reduced cadmium content by 77%). However, MTC1600H allows removing over 93% of Fe and Cd for H3PO4 pre-treated by TBP solvent extraction, while the others show much lower efficiencies (< 53%). [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]

Taraxacum officinale extract (TOE) has been tested for preventing the corrosion of cooling systems in desalination plants. The inhibition of corrosion effects has been characterized by chemical and electrochemical methods (Mass loss, potentiodynamic polarization and electrochemical impedance spectroscopy) and surface observations. Tests on cooling systems were carried out in seawater environment. The presence of TOE in the re-circulation loop decreases the corrosion of carbon steel by adsorption of TOE compounds on the surface of metal pipes. The optimum TOE concentration was reached at 400 mg L−1 and the inhibition efficiency was higher than 94%. TOE allowed increasing the energy barrier of the corrosion process. SEM, FT-IR and UV spectra observations confirmed that TOE prevents corrosion attacks at the surface of the pipes. HPLC analyses identified the presence of saccharides, organic acids, phenol antioxidant and caffeic acid derivatives in TOE, which may be the active promoters of corrosion inhibition. [ABSTRACT FROM AUTHOR]

The sorption of oil from crude oil-in-saline water emulsions was studied using chitosan as biosorbent. The main parameters investigated were chitosan dosage, contact time, and initial crude oil concentration at fixed initial pH. The results showed that the sorption equilibrium was reached within 120 min at oil content as low as 20 mg L−1. Sorption depends on initial oil concentration and sorbent dosage and may reach up to 95% efficiency in the most favorable conditions. The residual oil concentrations obtained after sorption were always beneath the official limit of oil discharge into environment. [ABSTRACT FROM AUTHOR]

Modified chitosan gel beads, prepared by molybdate and tungstate coagulation methods, were tested for As(V) removal from solutions in the range of 5–200 mg As L−1. The sorbent is efficient at removing As(V) from acid solutions (optimum pH close to 3), the sorption capacities for As uptake in molybdate- and tungstate-loaded beads are 75 and 44 mg As g−1 of dry mass, respectively. The mechanism of As(V) sorption is related to the ability of molybdate and tungstate ions to complex As(V) ions in acid solutions. As(V) sorption process is mainly influenced by the presence of phosphate ions, but there is no influence of co-ions as nitrate and chloride. Arsenic desorption can be performed using phosphoric acid solutions. Arsenic adsorption proceeds in acidic solutions with a partial release of molybdate and tungstate and with residual concentrations of arsenic above the regulations for drinking water. For that reason, this material is a candidate for the treatment of industrial effluents. [ABSTRACT FROM AUTHOR]

A new material, consisting of alginate–polyethyleneimine (AP) foam, with high percolating properties has been designed for palladium recovery in fixed-bed reactor. The foam, having high affinity for Pd(II), can be also used for manufacturing heterogeneous hydrogenation catalyst. SEM–EDX and TEM analyses were performed to determine the structure of the foams and the distribution of Pd nanoparticles (after metal reduction). Metal-sorbent interactions and oxidation state of Pd are characterized by XPS. Pd(0)-bearing foams are investigated for the hydrogenation of 3-nitrophenol (3-NP) using HCOOH as the hydrogen donor. The maximum sorption capacity of Pd(II) by AP foams reaches up to 224 mg g−1. The water flux (under water-depth pressure of 6 mbar) reaches 24.8 mL cm−2 min−1 (superficial flow velocity: 14.9 m h−1). The foams are remarkably stable: The mass loss under strong shaking for 2 days does not exceed 3%. For catalytic application, Pd loading conditions were optimized (flow rate, metal concentration) to reach 101 mg Pd g−1 (97% metal removal). Under these conditions, Pd overloading and nanoparticles aggregation can be minimized. The catalytic hydrogenation of 3-nitrophenol (using formic acid as the hydrogen donor) was optimum for a HCOOH/3-NP molar ratio close to 160 (pH between 3 and 4). High flow rates minimize diffusion effects; the apparent rate constant (for pseudo-first-order rate equation) reaches 9.7 × 10−3 s−1. The reuse of the foams over 30 cycles shows the long-term stability of catalytic activity. The test on continuous (one-pass) mode shows a progressive poisoning of the catalyst. However, a simple washing with water is sufficient for recovering catalytic activity. [ABSTRACT FROM AUTHOR]

BACKGROUND: The recovery of metal ions from aqueous solutions for environmental preservation or resource saving requires the development of new sorbents with enhanced separation properties. A new process has been designed for the functionalization of magnetic chitosan microparticles with grafting of either amidoxime (AO‐AHC) or hydrazinyl amine (HZ‐AHC). Their sorption properties have been tested for the recovery of uranium(VI) and zirconium(IV) from aqueous solutions. RESULTS: A wide range of analytical tools is used for characterizing not only the chemical modifications but also the interaction mode between the sorbent and target metal ions; including elemental analysis and titration, Fourier‐transform infrared (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS) characterizations, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observations, energy‐dispersive X‐ray spectroscopy (EDX) analysis and textural characterization. The optimum pH values were found in the range 4–5. The maximum sorption capacities depend on the metal and the kind of functionalization: up to 1.38 mmol U g−1 for AO‐AHC and up to 1.96 mmol Zr g−1 for HZ‐AHC. The small size of magnetic particles limits the contribution of diffusion mechanisms in the overall control of uptake kinetics and the equilibrium is reached within 40–60 min. Metal desorption is highly effective (almost quantitative over five successive cycles of sorption and desorption) using 0.3 M hydrochloric acid solutions. CONCLUSION: AO‐AHC sorbent is more selective than HZ‐AHC in terms of separation of uranium(VI) from zirconium(IV), especially at pH close to 4. The results obtained in the treatment of acidic ore leachates confirm these trends. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Two different strategies have been designed for the acid and alkaline leaching steps of hydrodesulphurization catalysts. Tests have been performed on out-of-range catalysts issued from catalyst manufacturing process. Experimental conditions have been screened for these different processes considering the effects of concentration, temperature, solid/liquid ratio, etc. The best conditions have been used for producing two leachates that were treated by precipitation for recovery of valuable metals such as cobalt and molybdenum. Post-treatments have also been designed for the selective separation of Co from Mo: X-ray diffraction analyses on selective precipitates (as sulfide) confirm the purity of produced materials. Two flow sheets are proposed that allow selectively recovering more than 95% of the valuable metals. [ABSTRACT FROM AUTHOR]

Self-acidified and granulated mesoporous alumina (SAGMA) with dendritic-like microscopic shape was prepared by a new route that involves: (a) direct dehydration of AlCl3 (in the presence of capping petroleum wax), and (b) oxidation of intermediary AlCl3-nanorods. The AlCl3 solution dispersed in petroleum wax (capping media) was firstly dehydrated at 100 °C under inert atmosphere for manufacturing anhydrous AlCl3-nanorods (length: 50-100 nm; diameter: 5-10 nm). In a second step, this support was oxidized into γ-alumina at 300 °C, under air atmosphere. In the course of the manufacturing process, released chlorine was deposited at the surface of the nanorods (more specifically during the oxidation step). The binding of chlorine (5.35%, w/w at the surface) onto γ-alumina was demonstrated by both electron dispersive X-ray analysis (SEM-EDX) and Fourier-transformed infrared spectroscopy. Specific surface area reached 230 m2 g−1; the average pore size was 7.8 nm. Material characterization was completed by measuring the surface acidity through both temperature-programmed desorption and pyridine desorption. The morphology and the phase structure were investigated using scanning electron microscopy and X-ray diffraction analysis, respectively. SAGMA (γ-alumina) can be described as a strong Lewis (1.713 mmol g−1; i.e., about 93% of total acid sites) and Brønsted acid catalyst supported on a mesoporous structure (self-granular size of 177-250 µm). Cumene conversion (through a dealkylation pathway) was tested on SAGMA: maximum catalytic activity reached 87% at 300 °C. The conversion is highly selective: the reaction produces benzene and only traces of ethylbenzene (mass fraction below 4% compared to benzene). Apart from this good catalytic efficiency, the material is characterized by its strong stability in terms of both catalytic activity (loss less than 2%, for optimum conditions) and surface acidity (loss less than 3%), even for long reaction times (i.e., 24 h) under severe conditions (i.e., T 300 °C). This new material, easily manufactured, is characterized by high efficiency and selectivity in cumene conversion into benzene, associated with high acidity and good stability. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: The nuclear power industry and other high‐tech industries require increasing quantities of uranium and rare‐earth elements (REEs). There is a need for materials that can competitively recover these metals from ore leachates (such as produced in the leaching of Egyptian ores). RESULTS: A sorbent based on the chemical grafting of glutamine moieties on a magnetic polyacrylonitrile support was synthesized: polyacrylonitrile, crosslinked with 10% divinyl benzene in the presence of magnetite, was chemically modified by a series of grafting steps to produce a magnetic polyglutamine sorbent (MGLU). The sorbent was characterized by titration, elemental analysis, X‐ray diffraction (XRD), thermogravimetric analysis, Fourier‐transform infra‐red (FTIR) spectrometry and scanning electron microscopy (SEM). The sorption properties were tested as a function of pH; the sorption isotherms were modeled using the Langmuir equation (maximum sorption capacities: 2 mmol U g‐1 and up to 3.5 mmol g‐1 for Nd(III) and Dy(III)). The equilibrium is achieved within 1 h of contact. Metal desorption and sorbent recycling are highly efficient using acidic solutions; sorption/desorption performance remains stable for a minimum of 5 cycles. MGLU was tested for metal binding in multi‐metal solutions at different pH values. CONCLUSION: This sorbent could be used for the recovery of REEs and uranium from simulated ore leachates. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

ABSTRACT A new method for preparing alginate foams with progressive release of copper in the presence of sodium lauryl sulfate (SLS, foaming agent) has been designed. Copper acts as the ionotropic gelling agent through the reaction of copper carbonate with gluconolactone. The process does not require freeze-drying contrarily to the conventional method used for preparing macroporous alginate foams. The new materials investigated in this study have remarkable thermal properties, including thermal conductivity lower than 0.041 W m−1 K−1 and low heat release (below 2 kJ g−1), which allows labeling these foams self-extinguishing materials. An experimental design methodology, based on a Box-Behnken plan with three parameters and three levels, is successfully used for evaluating the impact of the amounts of alginate, SLS, and copper carbonate on the productivity, apparent density, and shrinking at air-drying. It yielded an optimization of the process for the manufacturing of light, and stable/rigid insulating and thermally stable materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45868. [ABSTRACT FROM AUTHOR]

Two kinds of algal beads were prepared using a carrageenan-based alga (Chrondrus crispus) and an alginate-based alga (Laminara digitata) ionotropically gelled with K(I) and Ca(II), respectively: the process consists of biopolymer partial extraction followed by hydrogel formation. The beads were modified with branched polyethylenimine (bPEI) and glutaraldehyde (GA) using the impregnation method to improve their sorption capacity for Pd(II) in acid solution. SEM-EDX and FTIR techniques were used for characterizing the beads. The impacts of pH and presence of anions, cations, and Pt(IV) were studied in batch experiments. The beads were also applied for Pd(II) recovery from synthesized leaching liquors of a spent catalyst and a car catalytic converter via the sorption-desorption process. Results show that Pd is concentrated in the outer layer of L. digitata-bPEI-GA composite (LD/PEI) beads, while in the case of the C. crispus-bPEI-GA composite (CC/PEI), it is homogenously distributed in the whole mass of the sorbents. The difference is attributed to the repulsive force of the outer Ca(II)-alginate barrier of LD/PEI beads that makes it difficult for the branched polymer PEI to penetrate through the layer and be immobilized in the inner compartment. As a result, LD/PEI beads possess a lower maximum sorption capacity, but a slightly faster uptake at pH 1 than CC/PEI beads. In addition, CC/PEI beads present a better recovery performance compared to LD/PEI beads when applied for the treatment of synthesized leaching liquors. [ABSTRACT FROM AUTHOR]

Chitosan (an amino-polysaccharide obtained from deacetylation of chitin, the major constituent of crustaceous shells and insect cuticles) presents a cationic character in acidic media allowing its dissolution, its shaping and possible ion-exchange interactions with anionic compounds (a property applied in adsorption and coagulation-flocculation processes). In neutral media, non-protonated amino groups allow complexation of metal cations or organic chemicals. These different properties explain the interest taken by the scientific community in using this biopolymer. In solution it contributes to complex metals and their recovery by complexation-assisted ultrafiltration. It can also be used to coagulate-flocculate organic compounds (as anionic dyes). In the solid state, it can be used for metal ion adsorption, as well as adsorption of organic compounds (dyes, pesticides, drugs, endocrine disruptors, etc.). The adsorption and coagulation-flocculation processes will be compared and examples considered. Moreover, it is noteworthy that the thermal degradation of this type of material is also more environmentally friendly than that of conventional synthetic resins (production of hazardous by-products, etc.), a supplementary advantage of these biopolymer-based sorbents. Combined with its ability to be chemically or physically modified improving the potential and phase separation of chitosan-based materials, all these properties mean it is an excellent candidate for wastewater treatment. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Fumarated polystyrene microspheres were prepared using emulsion polymerization technique. Different instrumental techniques such as elemental analysis, SEM and FTIR were employed for full characterization of the synthetic resin. Different parameters such as pH, time and initial metal ions concentration were examined to evaluate the optimum conditions for U(VI) and Nd(III) ions sorption. For both metal ions, the sorption process fitted well with pseudo-second order kinetic model and Langmuir isotherm model. The maximum adsorption capacities were found to be 83.11 mg U g and 39.68 mg Nd g. The loaded sorbent was regenerated using 0.5 M HNO. [ABSTRACT FROM AUTHOR]

The incorporation of brown algae into biopolymer beads or foams for metal sorption has been previously reported. However, the direct use of these biomasses for preparing foams is a new approach. In this study, two kinds of porous foams were prepared by ionotropic gelation using algal biomass (AB, Laminaria digitata) or alginate (as the reference) and applied for Pb(II) sorption. These foams (manufactured as macroporous discs) were packed in filtration holders (simulating fixed-bed column) and the system was operated in either a recirculation or a one-pass mode. Sorption isotherms, uptake kinetics and sorbent reuse were studied in the recirculation mode (analogous to batch system). In the one-pass mode (continuous fixed-bed system), the influence of parameters such as flow rate, feed metal concentration and bed height were investigated on both sorption and desorption. In addition, the effect of Cu(II) on Pb(II) recovery from binary solutions was also studied in terms of both sorption and desorption. Sorption isotherms are well fitted by the Langmuir equation while the pseudo-second order rate equation described well both sorption and desorption kinetic profiles. The study of material regeneration confirms that the reuse of the foams was feasible with a small mass loss, even after 9 cycles. In the one-pass mode, for alginate foams, a slower flow rate led to a smaller saturation volume, while the effect of flow rate was less marked for AB foams. Competitive study suggests that the foams have a preference for Pb(II) over Cu(II) but cannot selectively remove Pb(II) from the binary solution. [ABSTRACT FROM AUTHOR]

Cyanex 301 and Cyanex 302 have been immobilized in alginate capsules by two methods: the matrix-type process immobilizes the extractant as homogeneous-dispersed vesicles while the mononuclear mode consists of encapsulation of the extractant drop by an alginate layer. The influence of HCl concentration on Cd(II) removal is discussed as a function of acid concentration and extractant. The sorption isotherms are fitted by the Langmuir model; maximum sorption capacities reach up to 42 mg Cd g−1in 0.1 M HCl. Uptake kinetics are controlled by resistance to intraparticle diffusion. Cadmium is desorbed using either 1 M HNO3or 1 M thiourea/1 M HCl solutions. [ABSTRACT FROM PUBLISHER]

Phosphonium-based ionic liquids have been successfully impregnated on several Amberlite XAD resins for recovering Au(III) chloro-anions. Sorption performance was evaluated through sorption isotherms (very favorable profiles) and uptake kinetics (controlled by the resistance to intraparticle diffusion). The binding mechanism consists of an ion-exchange between AuCl4− and the counter ion bound to the phosphonium cation. Increasing the IL loading proportionally increases the sorption capacity but decreases the sorption speed (by increasing the resistance to intraparticle diffusion). Changing the counter ion on the phosphonium cation (i.e., complex anion vs. chloride ion) does not improve sorption performance. Highly porous resin (high pore volume and large pore size), such as Amberlite XAD-1180, shows the best diffusion performance and highest sorption velocity (lower equilibrium time). [ABSTRACT FROM AUTHOR]

A new generation of extractant impregnated resin has been elaborated by encapsulation of extractants in biopolymer capsules. The extractant forms the core of the spherical particle, while the biopolymer entraps the extractant in a shell. The immobilization can reduce the loss of extractant. Cyanex 302 (bis(2,4,4-trimethylpentyl)monothiophosphinic acid) was efficiently immobilized into alginate capsules prepared by ionotropic gelation in CaCl2 solutions. The influence of a series of parameters on microcapsule preparation was investigated. Selected materials were tested for Pd(II) recovery from HCl solutions through the study of sorption isotherms and uptake kinetics. [ABSTRACT FROM AUTHOR]

The decontamination of dilute industrial effluents is a critical challenge for decreasing the environmental impact of mining and metallurgical activities. As an alternative to conventional processes, new extractant impregnated resins (EIRs) have been synthesized by the immobilization of Cyanex 301 and Cyanex 302 in alginate capsules using two different procedures (matrix-type immobilization vs. mononuclear encapsulation). These materials have been tested for Pb(II) sorption from acidic solutions. The Langmuir equation fitted well the sorption isotherms and the maximum sorption capacities vary between 24 and 80 mg·g−1 at pH 1, depending on the type and loading of the extractant in the EIR. Uptake kinetics were controlled by the resistance to intraparticle diffusion; though both the Crank equation (intraparticle diffusion) and pseudo-second order rate equation equally fitted uptake profiles. The amount of extractant immobilized in mononuclear capsules is lower than in matrix-type beads; this leads to lower sorption capacities but slightly better mass transfer properties. The balance between the advantages and drawbacks of the different systems makes more promising matrix-type capsules. The desorption of Pb(II) is possible using 1 M HNO3 solutions: metal ions were completely desorbed. However, the probable oxidation of the extractants (conversion to oxidized forms more sensitive to pH) reduces the sorption efficiency when they are re-used. [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]

This work focuses on the study of Hg(II) and Zn(II) sorption using pristine date pits. The effect of pH is evaluated before considering the influence of both temperature and contact time on sorption efficiency. Sorption isotherms are also determined and modelled using conventional models such as Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) equations. The best fit was obtained with the Langmuir equation and maximum sorption capacities reached 38.5 and 52.6 mg · g−1, for Hg(II) and Zn(II), respectively. An analysis of the temperature effect by the Gibbs equation showed that the sorption is exothermic and spontaneous. The mean free energy of sorption (obtained from D-R equation) confirms that metal binding occurs through a chemical ion-exchange mechanism. The kinetic profiles can be accurately fitted with the pseudo-second order rate equation. Complementary analyses (using FTIR spectrometry and SEM-EDX analysis) confirm that ion-exchange is the main binding mechanism, though a contribution of surface complexation cannot be neglected. [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]

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

BACKGROUND Modeling mass transfer steps is important for optimizing the use of sorbents such as extractant impregnated resins ( EIR). However, mathematical fit of kinetic profiles requires physical characterization for validating mechanism hypotheses. SEM-EDX is a very useful tool for achieving this objective. RESULTS In this work special attention has been focused on the simultaneous modeling of the diffusion mechanisms (using homogeneous diffusion and shrinking core models associated to resistance to film diffusion, to intraparticle diffusion and to chemical reaction rate) and the SEM-EDX analysis of the diffusion profiles for gold sorption on ionic liquid/impregnated resins (tetraalkylphosphonium IL immobilized in Amberlite XAD resins). Some discrepancies in the conclusions raised by the two approaches led to careful investigation of the effect of conditioning and storage of resins before SEM-EDX analysis. The self-diffusion of the metal ion in the EIR causes misinterpretation of diffusion profiles when inappropriate conditions are used. CONCLUSION SEM-EDX can be efficiently used for improving the understanding of diffusion mechanisms in the study of metal uptake kinetics in EIRs providing that the analysis of the samples is carried out within 24 h and the sample is freeze-dried (to limit metal-ion self-diffusion in the extractant phase). This study can obviously be extended to other sorption systems. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Alginate-based composites prepared by incorporation of bentonite into alginate or algal hydrogels show promising properties in terms of thermal degradation (mass-loss rate curves under epiradiator irradiation). They can be used as coating agent or as structured materials. Alginates characterized by high guluronic acid content are more efficient for retarding the ignition of tested materials after calcium gelation. Brown seaweed can be directly used for preparing composite blocks with clay; a pretreatment for partial extraction of alginate was introduced in the preparation of the composite material. In order to achieve a better control of drying procedures (with low apparent density, limited shrinking), another kind of composite was successfully elaborated by the incorporation of freeze-dried alginate/bentonite beads into an alginate matrix. Algal biomass (a renewable resource, which requires less processing than when using pure alginate) can be used for the green manufacturing of promising flame-retardant materials (associated to bentonite). Freeze-dried alginate/bentonite beads incorporated in alginate hydrogels show interesting thermal degradation properties allied to low-density characteristics. [ABSTRACT FROM AUTHOR]

Alginate and algal-biomass (Laminaria digitata) beads were prepared by homogeneous Ca ionotropic gelation. In addition, glutaraldehyde-crosslinked poly (ethyleneimine) (PEI) was incorporated into algal beads. The three sorbents were characterized by scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX): the sorption occurs in the whole mass of the sorbents. Sorption experiments were conducted to evaluate the impact of pH, sorption isotherms, and uptake kinetics. A special attention was paid to the effect of drying (air-drying vs. freeze-drying) on the mass transfer properties. For alginate, freeze drying is required for maintaining the porosity of the hydrogel, while for algal-based sorbents the swelling of the material minimizes the impact of the drying procedure. The maximum sorption capacities observed from experiments were 415, 296 and 218 mg Pb g-1 and 112, 77 and 67 mg Cu g-1 for alginate, algal and algal/PEI beads respectively. Though the sorption capacities of algal-beads decreased slightly (compared to alginate beads), the greener and cheaper one-pot synthesis of algal beads makes this sorbent more competitive for environmental applications. PEI in algal beads decreases the sorption properties in the case of the sorption of metal cations under selected experimental conditions. [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]

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

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]

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

Metal hexacyanoferrates are very efficient sorbents for the recovery of alkali and base metal ions (including radionuclides such as Cs). Generally produced by the direct reaction of metal salts with potassium hexacyanoferrate (the precursors), they are characterized by ion-exchange and structural properties that make then particularly selective for Cs(I), Rb(I) and Tl(I) recovery (based on their hydrated ionic radius consistent with the size of the ion-exchanger cage), though they can bind also base metals. The major drawback of these materials is associated to their nanometer or micrometer size that makes them difficult to recover in large-size continuous systems. For this reason many techniques have been designed for immobilizing these ion-exchangers in suitable matrices that can be organic (mainly polymers and biopolymers) or inorganic (mineral supports), carbon-based matrices. This immobilization may proceed by in situ synthesis or by entrapment/encapsulation. This mini-review reports some examples of hybrid materials synthesized for the immobilization of metal hexacyanoferrate, the different conditionings of these composite materials and, briefly, the parameters to take into account for their optimal design and facilitated use. [ABSTRACT FROM AUTHOR]

The recovery of three rare earth (RE) metals ions [Yb(III), Dy(III) and Nd(III), belonging to heavy, mild and light REs, respectively] was investigated using hybrid chitosan-magnetic nano-based particles functionalized by diethylenetriamine (DETA). The effect of pH on sorption performance was analyzed: the optimum initial pH value was found close to 5 (equilibrium pH value close to 6.5). The nanometric size of sorbent particles (30-50 nm) minimized the contribution of resistance to intraparticle diffusion on the control of uptake kinetics, which is efficiently modeled using the pseudo-second order rate equation: under selected experimental conditions the contact time required for reaching equilibrium was less than 1 h. Sorption isotherms were efficiently modeled using the Langmuir equation: maximum sorption capacities reached about 50 mg metal g, regardless of the RE. The temperature had a very limited effect on sorption capacity (in the range 300-320 K). The thermodynamic parameters were determined: the sorption was endothermic (positive values of Δ H°), spontaneous (negative values of Δ G°) and contributed to increasing the disorder of the system (positive values of Δ S°). The three REs have similar sorption properties on DETA-functionalized chitosan magnetic nano-based particles: the selective separation of these elements seems to be difficult. The sorbed metal ions can be removed from loaded sorbents using thiourea, and the sorbent can be recycled for at least five sorption/desorption cycles with a limited loss in sorption performance (by less than 6 %). The saturation magnetization was close to 20 emu g; this means that nano-based superparamagnetic particles can be readily recovered by an external magnetic field, making the processing of these materials easy. [ABSTRACT FROM AUTHOR]

Magnetic-chitosan nano-based particles were successfully prepared by a simple one-pot co-precipitation method before being functionalized with three different amino acid groups (i.e., alanine, serine, and cysteine) using epichlorohydrin as the linking agent. The structural and functional characteristics of the nanosorbents were investigated by elemental analysis, Fourier transform infrared spectrometer, X-ray diffraction, TEM, and vibrating sample magnetometry. The sorption properties of these materials were tested for Dy(III) recovery from aqueous solution: pH effect, uptake kinetics, and sorption isotherms were investigated. Sorbent particles are super-paramagnetic and their size is in the range of 15-40 nm. Kinetic profiles are successfully modeled with the pseudo second-order rate equation. The Langmuir and the Dubinin-Radushkevich equations fit well-sorption isotherms. The maximum sorption capacities at pH 5 (optimum pH, and at T: 27 ± 1 °C) are close to 14.8, 8.9, and 17.6 mg Dy g for alanine, serine, and cysteine type, respectively. Cationic species RE(III) in aqueous solution appear to be sorbed by combined chelation and anion-exchange mechanisms. The sorption process begins at low-metal concentration by a physical monolayer sorption at low ion concentration before metal ions can be sorbed at higher metal concentration by coordination. The values of the thermodynamic parameters Δ G° and Δ H° indicate the spontaneous and endothermic nature of the mechanism, while the positive values of Δ S° show that during the sorption process the randomness increases. Finally, the sorbent can be efficiently regenerated using acidified thiourea: the amount of Dy(III) sorbed is hardly reduced, at least during the first four sorption/desorption cycles. [ABSTRACT FROM AUTHOR]

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

Chitosan, an abundant biopolymer extracted from crustacean shells, can be used as a structuring agent by the insertion of calcium oxide and used as a catalyst in transesterification reactions. These calcium-incorporated chitosan spheres were calcined in order to obtain a porous calcium catalyst without organic material. The materials were characterized using X-ray diffraction, thermogravimetric analysis, Fourier transform infrared and X-ray photoelectron spectroscopies, temperature-programmed desorption of CO2, scanning electron microscopy and specific surface area analysis. Afterwards the calcined calcium/chitosan spheres were used in the transesterification reaction of sunflower oil with methanol. The conversion of sunflower oil to methyl esters ( YFAME), under optimized reaction conditions, which were determined by factorial experimental design ( XMR, 1:9; XCAT, 3 wt%; time, 4 h; temperature, 60 °C; magnetic stirring, 1000 rpm), was 56.12 ± 0.32 wt%. These results show that chitosan can be used as a precursor for the formation of calcium/chitosan spheres, yielding a porous calcium oxide (with higher surface area) that can be used as an alkaline catalyst for biodiesel production. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

ABSTRACT Extractant impregnated resins (EIRs) were prepared by impregnation of Amberlite XAD-7 with tetraalkylphosphonium chloride ionic liquid (IL). The EIRs were tested for the sorption of Hg(II) in HCl solutions. Mercury is bound on the EIR through an ion exchange mechanism involving chloroanionic species and the IL. The effect of HCl concentration and IL content is studied and the sorption isotherms are obtained in 1 M HCl solutions: the sorption capacity linearly increases with IL loading up to 100 mg Hg L−1. A little fraction of the IL immobilized on the resin (about 40 mg IL g−1) is tightly bound to the polymer limiting its reactivity with metal ions. The uptake kinetics are mainly controlled by intraparticle diffusion. At high IL loading the kinetics are slowed down, while the temperature has a limited impact. Nitric acid can be used for desorbing mercury and recycling the EIR for at least five cycles. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41086. [ABSTRACT FROM AUTHOR]

Chitosan is an aminopolysaccharide that binds metal ions through different mechanisms such as ion exchange, chelation or formation of ternary complex. The sorption performance depends on the characteristics of the solution (pH, presence of ligands, metal speciation) and the properties of the biopolymer (crystallinity, degree of deacetylation, molecular weight). Sorption performance is also controlled by the accessibility and availability of reactive groups (diffusion properties). These interactions chitosan/metal ions can be used for environmental applications (recovery of toxic or valuable metals) but also for the synthesis of new materials. Hybrid materials (chitosan/metal ion composites) can thus be used for manufacturing new sorbents with improved functionalities, supported catalysts, antimicrobial supports and sensors. The physical versatility of the biopolymer is an important criterion for designing these new materials: The conditioning of the material under the form of hydrogel beads, membranes, fibers and hollow fibers, foams and sponges enhances sorption performance and allows developing new applications. [ABSTRACT FROM AUTHOR]

Original ruthenium supported ionic liquid phase (SILP) catalysts based on alginates as supports were developed for olefin metathesis reactions. The marine biopolymer, which fulfills most of the requisite properties for a support such as widespread abundance, insolubility in the majority of organic solvents, a high affinity for ionic liquids, high chemical stability, biodegradability, low cost, and easy processing, was impregnated by [bmim][PF6] containing an ionically tagged ruthenium catalyst. These biosourced catalysts show promising performances in ring-closing metathesis (RCM) and cross-metathesis (CM) reactions, with a high level of recyclability and reusability combined with a good reactivity. [ABSTRACT FROM AUTHOR]

Chitosan was used to immobilize phosphonium-based ionic liquids, combined with silica particles, to prepare catalytic materials in the form of highly porous monoliths. These catalytic materials were studied for the hydrogenation of 4-nitroaniline into p-phenylenediamine in the presence of formic acid as hydrogen donor in a column reactor. Experimental conditions for the elaboration of the materials were evaluated by their impact on palladium sorption, on the structure of the materials, and on their catalytic efficiency. The concentration of chitosan in the initial solution and the size and concentration of silica particles had to be carefully chosen to elaborate homogeneous materials, with good mechanical resistance and stability in water. The chitosan characteristics and the type of ionic liquid immobilized in the material did not significantly affect the structure of the materials but proved to be crucial for their catalytic efficiency. Higher catalytic performances were obtained using materials prepared from chitosan of high-deacetylation degree and with Cyphos IL-101. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]