Zero-emission of desulfurization wastewater is one of the main demands for coal-fired power plants. As typical high salinity wastewater, it is hard to purify the desulfurization wastewater from coal-fired power plants through traditional physicochemical treatment or biochemical treatment, e.g. COD and Cl-. A high concentration of Cl- ion in desulfurization wastewater restricts wastewater reuse and zero-emission. Electrochemical technology is an attractive method for high salinity wastewater zero-emission, which provide a versatile, efficient, cost-effective, easily automatable, and clean industrial process. For advanced treatment of effluent after triple box process treatment in power plants, this paper reports an electrochemical method to remove COD and Cl- from the desulfurization wastewater, which combines electrolysis with electrocoagulation. Aluminum plate and stainless steel plate are applied as the anode and the cathode for electrocoagulation. Homemade β-PbO2 coated Ti anode and stainless steel cathode are used for electrolysis. Homemade β-PbO2 coated Ti anode is prepared with a two-step galvanostatic electrodeposition. The electrodeposition solution is 1 mol∙L-1 Pb(CH3SO3)2 solution with pH=1~2. The temperature is set as 50 oC. Firstly, an 80 ~ 100 m dense and smooth β-PbO2 coating is electrodeposited onto the titanium mesh at 5 mA∙cm-2, which is used to protect the titanium substrate. Secondly, the electrodeposition current density is increased to 20 mA∙cm-2. About 0.5 mm more electroactive β-PbO2 coating is deposited on the top layer. The electrooxidation mechanisms and dynamic parameters of SO32-, HSO3-, and Cl- on the homemade β-PbO2/Ti are investigated particularly by linear scan voltammetry. It is testified that the homemade β-PbO2/Ti is an excellent anode material for sulfite and chloride electrooxidations. A continuous plug flow electrolyser is homemade to test the feasibility and economy of the electrochemical method, which consists of an electrocoagulation section and an electrolysis section. The electrocoagulation section can remove almost all suspended solids and a part of COD. To meet the industry-standard 《Discharge standard of wastewater from limestone-gypsum flue gas desulfurization system in fossil fuel power plant》(COD-1), the energy consumptions of the electrolyser are 10.78 kWh∙m-3 and 15.17 kWh∙m-3 at 3.5 V and 4.0 V, respectively. For zero-emission, 91.43% of COD and 92.98% of Cl- can be removed within 300 min at 4.0 V.
desulfurization wastewater, lead dioxide, electrocatalysis, COD, sulfite, dechlorination
Ju-Cai Wei, Juan Yi, Xu Wu. Electrochemical Advanced Treatment of Desulfurization Wastewater from Coal-Fired Power Plants[J]. Journal of Electrochemistry, doi: 10.13208/j.electrochem.2205041.