Removal Of Trace Cd And As From Drinking Water With The Electrosorption Technology

The quality of drinking water directly affects the human’s health, because drinking water effect directly on the human body and is indispensable for human every day. Drinking water pollution has been reported in many cities and countries in China. The drinking water pollution with heavy metal in rural and mine areas are very serious, especially. Due to economic backwardness, it is necessary for China to develop the drinking water treatment technology with low-cost. The methods of remove heavy metals from water include chemical precipitation, ion exchange, membrane separation, electrolysis, adsorption method. Each method has some advantages and disadvantages. Capacitive adsorption technology (CAT) was found on the end of the20th century for water treatment. Comparing to other technology, CAT has many advantages, such as simple equipment, low energy consumption, without secondary pollution, recycling and fast processing speed. Consequently, CAT is especially available for the rural and mine areas in China.The electrode material is the important issue of CAT for removal of heavy metals from drinking water. Since the20th century, nano-materials as a noval material have been developed quickly. Compared with conventional materials, the nano-materials have been attracted more and more attentions because they are with small particle size, large surface area, high chemical activity etc. Nano-materials have high surface energy, and then it is easy to combine with other matters, inducing the high adsorptive capacity for heavy metals. It is very important to develop the novel electrode based on nano-material with high adsorption capacity of heavy metal.In this paper, the Manganese oxide/active carbon fiber (MO/ACF) was prepared and its electrosorptive properties of Cd(Ⅱ) in aqueous solution were investigated. The structure of MO/ACF was characterized with transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Furthermore, the Cd(Ⅱ) electrosorptive properties of MO/ACF electrodes with different bias potentials, ionic strengths and loaded amount of manganese oxides were measured and the electrosorption isotherm and kinetics were investigated. The Cd(Ⅱ) electrosorptive capacity of MO/ACF was6times higher than that of pure ACF. The optimal adsorptive bias voltage was1.50V and the optimal electrolyte concentration of NaCl was O.lmol/L. The adsorption isotherm was agreed well with the Freundlich adsorption model and its maximum electrosorption capacitie was14.88mg/g by Langmuir model. The higher adsorptive capacity of MO/ACF than that of pure ACF is attributed to higher capacitance and more adsorptive sites of MO/ACF.For the removal arsenic form drink-water, the novel TiO2/ACF was investigated in detail in this paper. The TiO2powder (size about25nm) was loaded on the ACF, as TiO2/ACF electrodes. The structure of TiO2/ACF was characterized with transmission electron microscopy (TEM) and X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Furthermore, the arsenic electrosorptive properties of TiO2/ACF electrodes with calcination temperature, ionic species and loaded amount of TiO2were measured and the electrosorption isotherm and kinetics were investigated. The optimal load quality of TiO2was0.80g per ACF electrode(0.30g), and optimum calcination temperature was450℃. The maximum electrosorption capacitie of TiO2/ACF was8.09mg/g, about200%higher than that of ACF. Moreover, the electrode performance was stable than other materials such as pure ACF, Manganese oxide/ACF, and iron oxides/ACF. It can process100ppb arsenic of drinking water to6ppb (lower than lOppb of national drinking water standards), demonstrating our novel electrode is with potential practical application.