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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]

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]

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]

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 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]

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]

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]

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]

Lessonia nigrescens and Lessonia trabeculata kelps have been tested for the sorption of mercury from aqueous solutions. A pretreatment (using CaCl2) allowed stabilizing the biomass that was very efficient for removing Hg(II) at pH 6–7. Sorption isotherms were described by the Langmuir equation with sorption capacities close to 240–270 mg Hg g−1 at pH 6. The temperature had a negligible effect on the distribution of the metal at equilibrium. The presence of chloride anions had a more marked limiting impact than sulfate and nitrate anions. The uptake kinetics were modeled using the pseudo-second-order equation that fitted better experimental data than the pseudo-first-order equation. The particle size hardly influenced sorption isotherms and uptake kinetics, indicating that sorption occurs in the whole mass of the biosorbent and that intraparticle mass transfer resistance was not the limiting rate. Varying the sorbent dosage and the initial metal concentration influenced the equilibrium, but the kinetic parameters were not drastically modified. Metal can be eluted with hydrochloric acid, citric acid, or acidic KI solutions. [ABSTRACT FROM AUTHOR]

Two chitosan hydrogels (prepared by NaOH neutralization and by polyphosphate ionotropic gelation) have been tested in the dry state for Pd(II) and Pt(IV) sorption at pH 2. Similar sorption isotherms with maximum sorption capacities close to 190 mg Pd g−1 and 235 mg Pt g−1 were achieved. The sorption mechanism involves electrostatic attraction of the chloro-anionic species onto protonated amine groups; the drastic decrease of sorption capacity with the addition of chloride ions supports this hypothesis. SEM-EDAX analysis suggests that sorption proceeds, in kinetic terms, through a shrinking core mechanism. Metal ions can diffuse throughout all the sorbent volume. The main differences between the sorbents are revealed by kinetics. The hydrogels prepared by ionotropic gelation in polyphosphate (C-PPh) allows reaching equilibrium much faster than the hydrogels prepared by the neutralization process (C-NaOH). While for C-PPh sorbent the chemical reaction rate seems to control sorption profiles, in the case of C-NaOH a combination of mechanisms including intraparticle diffusion resistance controls uptake kinetics. Metal desorption from loaded sorbents is possible using thiourea alone or in association with HCl solutions. The recycling of the sorbents is possible but for a limited number of cycles. [ABSTRACT FROM AUTHOR]

A magnetic glycine-grafted chitosan sorbent (Gly) was functionalized to produce a hydrazide derivative (HGly). The two sorbents were tested in batch mode for the sorption of a series of 10 metal ions present in the groundwater collected in three wells in the Wadi (valley) Nasib mining area (SW Sinai, Egypt). HGly is much more efficient for metal recovery than Gly. Under selected experimental conditions (sorbent dosage 1.5 g L−1), the sorption efficiency is not sufficient for achieving the standard levels for drinking water: the most problematic metal ions in terms of drinkability remain aluminum (too high metal concentration in the groundwater), cadmium, and chromium for the three wells (and nickel in the case of only one well). Increasing the sorbent dosage improves the treatment efficiency. The sorbent (HGly) was tested in fixed-bed columns. The breakthrough curves were compared for the different metals for the groundwater collected in the most contaminated of the three wells. The levels of metal concentration in the treated groundwater are too high for direct use in irrigation. However, they are consistent with the standards for livestock drinking water (based on FAO recommendations, Food and Agriculture Organization of the United Nations). The metals can be readily desorbed using 0.5 M HCl solutions with a relatively high concentrating effect (i.e., 50 times). The re-use of the sorbent for three successive cycles of sorption/desorption cycles shows a progressive but weak decrease in sorption and desorption performances. [ABSTRACT FROM AUTHOR]