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Adsorption of fluoride by PES/LDH (layered double hydroxide) blend flat-sheet membrane was investigated. The SEM, AFM, and fluoride adsorption capacity of the membrane were evaluated. The addition of LDH led to a significant enhancement in the adsorption capacity of the membrane. The batch adsorption experiments demonstrated that the membrane effectively removed fluoride in a wide pH ranging from 2–10. The adsorption equilibrium could be established in 30 min, and the maximum adsorption capacity was 2.63 mg/g. The pseudo-second-order kinetics was observed for the adsorption process which followed the Langmuir-type adsorption isotherm. The membrane can be regenerated with 0.1 M NaOH. This work provides a new method to the adsorptive removal of hazardous substance in aqueous solutions. [ABSTRACT FROM AUTHOR]

Mesoporous magnesium silicate gel was successfully synthesized and characterized by N2adsorption/desorption technique and FT-IR. The adsorption experiments of anionic dye (weak acid red 2R) onto prepared magnesium silicate gel were studied by varying mass of adsorbent, dye concentration, pH, temperature, and contact time. The results showed magnesium silicate gel had high surface area, 277.37 m2 g−1. The adsorption capacity increases with increasing initial dye concentration, adsorption temperature, and contact time. The experimental data were applied to three adsorption kinetic models and the results indicated that the adsorption behavior was described very well by the second-order kinetics model with the high correlation coefficients (R2 > 0.99). Intra-particle diffusion was performed in three different stages. The activated energy obtained was 127.6 kJ mol−1and the enthalpy, entropy, and standard free energy were calculated and given that ΔHоwas 80.1 kJ mol−1, ΔSоwas 300.1 J mol−1, and ΔGоwere negative values at the different temperatures. The adsorption process is rapid and physisorption in nature. Therefore, magnesium silicate gel would be used in the industrial wastewater treatment as a potential adsorbent. [ABSTRACT FROM PUBLISHER]

Present study deals with the fluoride removal from aqueous solution by using hybrid adsorbent fabricated with Mg/Fe composite oxide and alginate via simple blending method. The fluoride adsorption capacity of the resulting hybrid adsorbent was systematically evaluated with batch adsorption experiments in various operation parameters including initial pH, adsorbent dose, co-existing anions, contact time and temperature. The results indicated the hybrid adsorbent kept good adsorption performance for fluoride over a broad pH range and even in the presence of co-existing anions. With adsorbent dose of 10 g/L, 96.6% of fluoride ion can be reduced from aqueous solution of 10 mg/L at natural pH. The adsorption of fluoride onto the adsorbent is found to be a multi-step rate-limiting reaction with exothermic nature and follows pseudo-second order kinetics. Thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) coupled with energy dispersive spectrum (EDS) and Fourier transform-infrared spectroscopy (FT-IR) were employed to characterize the hybrid material and explore the possible adsorption mechanism. It is suggested that ligand exchange and electrostatic interaction played an important role in the process of fluoride adsorption. Regeneration of adsorbent was also conducted, and 83.3% of the original fluoride removal rate was maintained after three regeneration cycles. [ABSTRACT FROM AUTHOR]