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Silica-gel supported ester-terminated polyamidoamine (PAMAM) dendrimers (SG-G0.5, SG-G1.5, and SG-G2.5) were utilized as adsorbents for the removal of Fe(III) from fuel ethanol. The adsorption property was systematically investigated by determining the effects of dendrimer generation, contact time, temperature, initial Fe(III) concentration, and adsorbent dosage on the adsorption. Static saturated adsorption indicates the adsorption capacity increases with the increasing of dendrimer generation by following the sequence of SG-G2.5 > SG-G1.5 > SG-G0.5. Adsorption kinetic shows that the adsorption equilibrium can reach within 200 min for all the adsorbents. The adsorption kinetic can be well fitted by pseudo-second-order model and is controlled by film diffusion process. Adsorption isotherm demonstrates the adsorption favors high temperature and initial Fe(III) concentration. The adsorption isotherm follows Langmuir model and carries out by monolayer chemical ion-exchange mechanism. Thermodynamic parameters imply the adsorption process of Fe(III) by SG-G0.5, SG-G1.5 and SG-G2.5 is a spontaneous, endothermic and entropy increased process. The regeneration property shows the adsorbents exhibit good reusability and maintain excellent adsorption capacity after three adsorption-desorption cycles. Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculation indicate the interaction of carbonyl oxygen and amine nitrogen groups with Fe(III) mainly dominate the adsorption process. [ABSTRACT FROM AUTHOR]

An environmental acidic ionic liquid was prepared with 1-allyl-1H-imidazole, 1,3-propyl sulfonic acid lactone and H 2 SO 4 and was immobilized on silica-gel to synthesize the catalyst used to prepare biodiesel from waste cooking oil by a one-step method. The structure of the catalyst was characterized by BET, FTIR, DSC/TGA and SEM. The effect of methanol oil mole ratio, catalyst dosage, reaction temperature, and reaction time on the conversion of waste cooking oil to biodiesel was investigated, and the optimum reaction conditions were determined by an orthogonal test. The optimum reaction conditions were shown as follows: methanol oil mole ratio of 25:1, catalyst dosage of 5 wt% of oil, reaction temperature of 60 °C, reaction time of 20 h, and the yield of 87.58%. The yield could reach 70.02% after reusing the catalyst 5 times. [ABSTRACT FROM AUTHOR]

Silica-gel-based adsorbents (SG-DETA and SG-DETA2) grafting of dendrimer-like highly branched polymer were prepared by an improved methods of a combination of homogeneous and heterogeneous. FTIR analysis, SEM analysis, pore structure analysis and thermodynamic analysis manifested that dendrimer-like highly branched polymer was successfully grafted onto the silica surface. The results of the adsorption thermodynamics and kinetics of the as-synthesized SG-DETA and SG-DETA2 showed the adsorbents had good adsorption capacity for Au(III), and the best interpretation for the experimental data was given by the Langmuir isotherm equation. The maximum adsorption capacity for Au(III) were 2.09 and 2.12 mmol g −1 of SG-DETA and SG-DETA2 at 35 °C, respectively. Moreover, the study indicated the adsorption kinetics of SG-DETA and SG-DETA2 could be modeled by the pseudo-second-order rate equation wonderfully. The SG-DETA and SG-DETA2 adsorbents had excellent adsorption selectivity for Au(III) in binary metal solution systems. Therefore, the high adsorption capacity make these adsorbents have significant potential for Au(III) uptake from aqueous solutions using adsorption method. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption properties of silica-gel supported hyperbranched polyamidoamine dendrimers (SiO2-G0–SiO2-G4.0) have been investigated by batch method. The effect of pH of the solution, contact time, initial Pb(II) ion concentration, temperature and coexisting metal ions have been demonstrated. The results indicated that the optimum pH value was 5. Adsorption kinetics was found to follow the pseudo-second-order model and controlled by film diffusion. The adsorption isotherms were fitted by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models. Langmuir isotherm model was found to be more suitable to describe the equilibrium data, suggesting the uptake of Pb(II) ions by monolayer adsorption. From D–R isotherm model, the calculated mean free energy E demonstrated the adsorption processes occurred by chemical ion-exchange mechanism. FTIR analysis revealed that amine groups were mainly responsible for the adsorption of Pb(II) by amino-terminated adsorbents, while Cr groups also participated in the adsorption process of ester-terminated ones. The adsorbents can selectively adsorb Pb(II) from binary ion systems in the presence of Mn(II), Cu(II), Co(II), and Ni(II). Based on the results, it is concluded that SiO2-G0–SiO2-G4.0 had great potential for the removal of Pb(II) from aqueous solution. [Copyright &y& Elsevier]

In the present work, adsorption of anionic azo dye, new coccine (NCC) on silica and silica-gel in an aquatic environment was discovered. Effective conditions such as adsorption time, pH, the influence of dosage on NCC adsorption using strong polycation, poly-diallyl-dimethylammonium chloride (PDADMAC) modified silica (PMS) and PDADMAC modified silica-gel (PMSG) were systematically studied. The removal of NCC using PMS and PMSG were much higher than that using raw silica and silica-gel without PDADMAC in all pH ranges from 3 to 10. The adsorption of NCC onto PMS and PMSG was achieved maxima at the same conditions of contact time 30 min, pH 6. The optimum adsorbent dosages of PMS and PMSG for NCC removal were 10 and 20 mg·mL−1, respectively. Experimental results of NCC adsorption isotherms onto PMS and PMSG at different ionic strength were fitted by Langmuir and Freundlich models. The NCC removal efficiencies using PMS and PMSG were higher than 87%, indicating that PMS and PMSG are novel and reusable adsorbents for removal of anionic dye. Based on adsorption isotherms, and surface group changes after PDADMAC modification and NCC adsorption examined by Fourier transform infrared spectroscopy (FTIR), we demonstrate that electrostatic interaction between positively charged adsorbents' surfaces and negative sulfonic groups of NCC are the main driving force for anionic azo dye adsorption onto PMS and PMGS adsorbents. [ABSTRACT FROM AUTHOR]