Photoelectrocatalysis Oxidation Of Arsenic（Ⅲ） In Drinking Water By Hydrothermal Synthesized TiO₂Loaded On Activated Carbon Fiber

In this paper, butyl titanate and conductive activated carbon fiber (ACF) pre-treated by nitric acid was used as the starting material and carrier substrate, respectively. The photocatalyst (TiO2/ACF) was successfully synthesized by hydrothermal method and the catalytic oxidation properties of Arsenic (As(Ⅲ)) was investigated.The surface of ACF was pre-treated by hydrogen peroxide, nitric acid, sodium chlorate, and anodizing, respectively, and then the TiO2/ACF was prepared. Taking loading rate, firmness and the morphology of the ACF surface into consideration, the optimum method was that the ACF was pre-treated by nitric acid with a volume fraction of50%for90min at40℃. At this time, the quality of loaded TiO2is0.00942g·g1.The TiO2nanoparticles prepared by hydrothermal method at the temperature of180℃for3h has a strong absorption in the ultraviolet region. The nanoparticles were fairly well dispersed on the ACF surface belongs to the type of anatase with an average particle size was about9nm. In addition, the nanoparticles were firmly bonded to the ACF surface and exhibit strong quantum size effect and high catalytic activity.The As(Ⅲ) and As(V) were absorbed by TiO2/ACF. The kinetics of adsorption process can be better described by the pseudo-first order kinetics. The rate constants of adsorption of As(Ⅲ) and As(Ⅴ) is1.258×10-2min-1and1.283×10-2min-1, and the adsorption capacity of As(Ⅲ) and As(Ⅴ) is81.0μg·g-1and160.0μg·g-1, respectively. The results received from the analysis of the rate controlling step of absorption show that the As(Ⅲ) was mainly absorbed by TiO2/ACF through two processes involving film diffusion and adsorption reaction when the concentration of As(Ⅲ) was less than200μg/L.The results of As(Ⅲ) photoelectrocatalytic oxidation of TiO2/ACF showed that the photocatalytic and photoelectrocatalytic oxidation of As(Ⅲ) process obeyed to the pseudo-first order kinetics. The efficiency of catalytic oxidation was significantly affected by the value of pH. The reaction rate in alkaline conditions is much higher than the acidic conditions. The catalytic efficiency is not significantly decreased for As(Ⅲ) photoelectrocatalytic oxidation when recycled for many times. The nano-TiO2particles were bonded to the ACF surface so firmly that they would not easily fall off even stirred for a long time. The catalytic efficiency decreased seriously when added PO43-and SiO32-to the reaction system. However, the SO42-, Cland NO3-has little influence on the catalytic efficiency. In the process of As(Ⅲ) photoelectrocatalytic oxidation, the bias cannot oxidize As(Ⅲ) itself, but enrich As(Ⅲ) and promote the separation of photo-generated holes and electrons. Therefore, the photocatalytic efficiency can be improved significantly. The results showed that the optimum bias voltage is0.5V, and the type of gas bubbling into the system of photoelectrocatalysis oxidation As(Ⅲ) has little difference on the conversion rate. The conversion rate was up to86.7%after UV irradiation for60min in the condition of the pH value is7, the initial concentration of As(Ⅲ) is2.0mg/Land the solid/solution ratio is1.0g/L, respectively.