[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to investigate the removal efficiency of polyvinyl alcohol (PVA) from aqueous solutions by adding Fe2+ externally in combination with electro-generated hydrogen peroxide at polyacrylnitrile (PAN)based activated carbon fiber (ACF) cathode. The comparison of ACF cathode and graphite cathode suggested hydrogen peroxide might efficaciously be electro-generated from oxygen reduction on the large surface area-ACF cathode, this was more favorable for electro-Fenton process. Various operating parameters that could potentially affect the PVA removal efficiency were investigated, including solution pH, Fe2+ concentration, applied current density, and solution temperature. The effects of the current density and solution temperature on the electrical energy consumption (EEC) and PVA removal efficiency were also evaluated. The findings indicated that complete PVA removal from aqueous solutions could be achieved within a reasonable electrolysis time, and with relatively low EEC. The optimum solution pH, Fe 2+ concentration, applied current density, and solution temperature were found to be 3, 0.5 mM, 3 mA cm-2, and 298 K, respectively.
[Show abstract][Hide abstract] ABSTRACT: This study used batch adsorption techniques to evaluate the potential suitability of tea waste as an environmentally friendly adsorbent for the removal of indium ions from aqueous solution. In addition, we also investigated the effects of process parameters, such as the solution pH, initial concentration of indium ions, adsorbent dose and temperature on adsorption performance. The experimental data were fitted with several adsorption isotherm models to describe the adsorption process of indium ions onto the tea waste. The predictions of the Freundlich isotherm model satisfactorily matched the experimental observations. In addition, the kinetic data obtained at different initial concentrations were analyzed using pseudo-first-order and pseudo-second-order kinetic models. A pseudo-second-order model provided a good fit to the experimental results with correlation coefficients greater than 0.99. Thermodynamic parameters, including the Gibbs free energy, enthalpy, and entropy, indicated that the indium adsorption of aqueous solutions onto tea waste was feasible, spontaneous and endothermic in the temperature range of 288 K to 318K. This study indicated that tea waste could be used as an effective and environmentally friendly adsorbent for the treatment of indium-containing aqueous solutions.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to explore the feasibility of removing silica particles and reducing turbidity from oxide chemical mechanical polishing (oxide-CMP) wastewater. Based on the dynamic characteristics of batch electrocoagulation, three operating stages (lag, reactive, and stabilizing) are proposed to identify the relationships among the zeta potential of the silica particles, solution turbidity, and the corresponding mean particle size of the silica. Experimental results show that the silica particles were destabilized and settled at the critical mean particle size, which was estimated to be above 520nm after 10min, and the corresponding turbidity removal mostly occurred during the reactive stage. Furthermore, the corresponding mean particle size varied from 520 to 1900nm as the treatment time progressed from 10 to 20min, which also occurred during the reactive stage. Several parameters, including different electrode pairs, electrolyte concentration, applied voltage, and the optimum condition of power input were investigated. Experimental results indicate that a Fe/Al electrode pair is the most efficient choice of the four electrode pair combinations in terms of energy consumption. The optimum electrolyte concentration and applied voltage were found to be 200ppm NaCl and 30V, respectively.