Study On The Electrochemical Behavior And Pretreatment Process Of Seawater Electrolysis

Serious problems of water shortage have stimulated the investigation and application on the seawater desalination. With the development of membrane technology, reverse osmosis (RO), as a major desalination technology, has been applicated commercially for many years. However, RO menbranes are sensitive to the types of pollutants, such as suspended solids, colloidal species and organic matters, etc. As a result, pretreatment is the absolutely necessary process for RO system.Electrochemical treatment techniques have been used prior to a RO system for seawater desalination. In fact, these new and environmental techniques use the electron as the main reagent, which is a "clean reagent".In this study, Dimentionally Stable Anode (DSA) electrodes were placed in a self-made diaphragm electrolyzer. The sludge of magenesium hydroxide was produced in cathode, which adsorbed suspended solids, colloidal species and organic matters. It was similar to the process of conventional adsorption. The anodic reaction related to the formation of chlorine (Cl2 and HOCl) subsequently used for neutralizing alkaline water from cathode chamber and disinfection for desalination. Therefore, a new form of pretreatment consisting of seawater electrolysis without addition of any coagulants may be adequate.The electrochemical behaviors of anode was investigated by polarization curves and cyclic voltammetry method, which consisted of chlorine and oxygen evolution potential, current efficiency, electric catalytic activity, the electrode strengthen life and the rate determining step, etc. In order to evaluate the ptimum operating conditions, the effect of current dencity and water velocity on product water quality was performed. The results show that the RT anode has high electric catalytic activity and the oxygen evolution potential is 244 mV higher than chlorine evolution potential.Meanwhile, the current efficiency is as high as 91%, and electrode strengthen life is about 55 h. Optimum operating conditions at the current of 8 A and water velocity of 14 L/h, bring down the turbidity below 1.00 NTU, SDI15 below 3 and CODMn removal more than 80%. The results qualify the influent standard of RO. Moreover, the rate of chlorine evolution is 1.75 mL/s, and the diaphragm can be reused after pickling.