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Indium is an extremely important element for industry that is distributed in the Earth's crust at very low concentrations. The recovery of indium by silica SBA-15 and titanosilicate ETS-10 was investigated at different pH levels, temperatures, times of contact and indium concentrations. A maximum removal of indium by ETS-10 was achieved at pH 3.0, while by SBA-15 it was within the pH range of 5.0–6.0. By studying kinetics, the applicability of the Elovich model for the description of indium adsorption on silica SBA-15 was shown, while its sorption on titanosilicate ETS-10 fitted well with the pseudo-first-order model. Langmuir and Freundlich adsorption isotherms were used to explain the equanimity of the sorption process. The Langmuir model showed its applicability for the explanation of the equilibrium data obtained for both sorbents, the maximum sorption capacity obtained using the model constituted 366 mg/g for titanosilicate ETS-10 at pH 3.0, temperature 22 °C and contact time 60 min, and 2036 mg/g for silica SBA-15 at pH 6.0, temperature 22 °C and contact time 60 min. Indium recovery was not dependent on the temperature and the sorption process was spontaneous in nature. The interactions between the indium sulfate structure and surfaces of adsorbents were investigated theoretically using the ORCA quantum chemistry program package. The spent SBA-15 and ETS-10 could be easily regenerated by using 0.01 M HCl and reused with up to 6 cycles of adsorption/desorption with a decrease in the removal efficiency between 4% and 10% for SBA-15 and 5% and 10% for ETS-10, respectively. [ABSTRACT FROM AUTHOR]

The efficiency of Cu(II) removal from aqueous solution by two adsorbents, silica SBA-15 and titanosilicate ETS-10, was investigated. Effects of various experimental parameters such as: contact time, pH, initial copper concentration, adsorbent dosage, temperature were investigated in order to determine the maximum adsorption capacity of the adsorbents. The maximum adsorption capacity of silica SBA-15 was achieved at pH 5.0, and of titanosilicate ETS-10 at pH 6.0. The Freundlich, Langmuir, and Temkin isotherm models were applied in order to describe the equilibrium adsorption of Cu(II) by the studied adsorbents. Equilibrium data fitted well to the Langmuir model with a higher adsorption capacity of ETS-10 (172.53 mg·g−1) towards Cu(II) than SBA-15 (52.71 mg·g−1). Pseudo-first- and pseudo-second-order, Elovich, and Weber–Morris intraparticle diffusion models were used for description of the experimental kinetic data. It was found that the pseudo-first-order and pseudo-second-order kinetic models were the best applicable models to describe the adsorption kinetic data. Thermodynamic parameters that characterize the process indicated that the adsorption of Cu(II) onto the two adsorbents is spontaneous and endothermic. [ABSTRACT FROM AUTHOR]

Adsorption behavior of uranyl and thorium ions from synthetic radioactive solutions onto functionalized silica as sorbent has been investigated. The effect of contact time, initial concentration of radioactive solutions, sorbent mass, pH value and temperature on the adsorption capacity of the sorbent was investigated. Negative values of Gibbs free energy of adsorption suggested the spontaneity of the adsorption process on both functionalized silica with -NH groups and with -SH groups. Positive values obtained for ΔH° indicates that the adsorption is an endothermic process. The adsorption isotherms were better fitted by Freundlich model and the adsorption kinetic was well described by the pseudo-second order equation. Desorption studies indicated that the most favorable desorptive reagents for UO is HNO 1 M and for Th is EDTA 1 M solutions. [ABSTRACT FROM AUTHOR]

The adsorption capacity of two sorbents, silica SBA-15 and titanosilicate ETS-10, toward Ce(III) was tested. The obtained sorbents were characterized using X-ray diffraction, nitrogen adsorption-desorption, Scanning electron microscopy, and Fourier-transform infrared spectroscopy. The effects of solution acidity, cerium concentration, time of contact, and temperature on Ce(III) sorption were investigated. The maximum Ce(III) removal by silica SBA-15 was achieved at pH 3.0 and by titanosilicate ETS-10 at a pH range of 4.0–5.0. The Freundlich, Langmuir, and Temkin isotherm models were applied for the description of equilibrium sorption of Ce(III) by the studied absorbents. Langmuir model obeys the experimentally obtained data for both sorbents with a maximum sorption capacity of 68 and 162 mg/g for silica SBA-15 and titanosilicate ETS-10, respectively. The kinetics of the sorption were described using pseudo-first- and pseudo-second-order kinetics, Elovich, and Weber–Morris intraparticle diffusion models. The adsorption data fit accurately to pseudo-first- and pseudo-second-order kinetic models. Thermodynamic data revealed that the adsorption process was spontaneous and exothermic. [ABSTRACT FROM AUTHOR]

Erratum: Dragan, E.S., et al., Contribution of Cross-Linker and Silica Morphology on Cr(VI) Sorption Performances of Organic Anion Exchangers Embedded into Silica Pores. The correct words are "Brunauer-Emmet-Teller (BET)". Reference 1 Dragan E.S., Humelnicu D. Contribution of Cross-Linker and Silica Morphology on Cr(VI) Sorption Performances of Organic Anion Exchangers Embedded into Silica Pores. [Extracted from the article]

Removal of Cr(VI) from the environment represents a stringent issue because of its tremendous effects on living organisms. In this context, design of sorbents with high sorption capacity for Cr(VI) is getting a strong need. For this purpose, poly(vinylbenzyl chloride), impregnated into porous silica (PSi), was cross-linked with either N,N,N',N'-tetramethyl-1,2-ethylenediamine (TEMED) or N,N,N',N'-tetramethyl-1,3-propanediamine, followed by the reaction of the free -CH2Cl groups with N,N-diethyl-2-hydroxyethylamine to generate strong base anion exchangers (ANEX) inside the pores. The PSi/ANEX composite sorbents were deeply characterized by FTIR spectroscopy, SEM-energy dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), and water uptake. The sorption performances of composites against Cr(VI) were investigated as a function of pH, contact time, initial concentration of Cr(VI), and temperature. It was found that the cross-linker structure and the silica morphology are the key factors controlling the sorption capacity. The adsorption process was spontaneous and endothermic and well described by pseudo-second-order kinetic and Sips isotherm models. The maximum sorption capacity of 311.2 mg Cr(VI)/g sorbent was found for the composite prepared with mesoporous silica using TEMED as cross-linker. The PSi/ANEX composite sorbents represent an excellent alternative for the removal of Cr(VI) oxyanions, being endowed with fast kinetics, equilibrium in about 60 min, and a high level of reusability in successive sorption/desorption cycles. [ABSTRACT FROM AUTHOR]