Electrochemical Oxidation of Arsenites by an Anode of Reticulated Vitreous Carbon as Previous Step for Removal

摘要

The main factor that affects the performance of the arsenic removal from water is its oxidation state. It is known that As(III) is harder to be removed than As(V) due to the fact that H{sub}3ASO{sub}3 is a nonionic compound with a pK{sub}1=9.22 while H{sub}3ASO{sub}4 (As(V)) dissociates ready with a pK{sub}1=2.25. In the oxygen-poor environment like in groundwater, arsenic exists mainly as As(III). For the purpose of obtaining a higher degree of removal of arsenic from contaminated groundwater, it is necessary to oxidize the As(III) to As(V) prior to the other treatment processes. In this work an electrochemical reactor, having an anode made from reticulated vitreous carbon of 100pores per inch (100ppi), was used to oxidize As(III) to As(V), this eliminates the need of adding more chemical substances to the treatment system. The performance of this special designed electrochemical reactor was evaluated at various applied cell voltages, reaction time, the concentration of the supporting electrolyte (NaCl), flow rate of the arsenic (As(III)) contaminated water through the electrochemical reactor and the pH of the aqueous media. Our experimental results indicated that for an aqueous solution containing 1.0ppm in As(III) and at 3.0volts applied cell potential with a flow rate at 10mL/min and 0.10M in NaCl, the percentage of oxidation of As(III) to As(V) was closer to 100%.