Advanced Decomposition of Coking Wastewater in Relation to Total Organic Carbon Using an Electrochemical System

Abstract

IntroductionAs a new type of electrochemical processing, electrochemical technology has recently been paid more and more attention in the wastewater treatment field due to its advantages of larger specific surface area, better transfer effect, higher current efficiency, and space-time yield [1][2][3]. Electrochemical treatment of wastewater is a relatively new type of wastewater treatment technology that is gradually developing into a promising technology [4][5]. Meanwhile, it has been successfully applied in the purification of wastewater from dye production [6] and from textile wastewater containing cyanides [7], phenols [8][9], and domestic sewage [10].Coking wastewater is generated from coal coking, coal gas purification, and by-product recovery processes of coking [11][12][13][14]. It contains complex inorganic and organic pollutants such as ammonium, sulfate, cyanide, thiocyanate, phenolic compounds, polynuclear aromatic hydrocarbons, and polycyclic nitrogen-containing acyclic compounds, Pol. J. Environ. Stud. Vol. 26, No. 2 (2017) AbstractThis research included experiments on the advanced treatment of coking wastewater by electrochemical reactor. The results showed that a favorable operating condition could be obtained through the electrochemical course, when electrolysis time was 60 min, current density was 8 A, and electrode span was 1 cm. Under this condition, total organic carbon (TOC) removal efficiency could reach 73%, and the removal mechanism had also been analyzed. In addition, the electrodes' morphology characteristics and components were analyzed through a scanning electron microscope, and the results showed that on the surface of anode and cathode electrodes there were quite a few cracks, the amount of which increased after use. Meanwhile, the content of chemical elements on the electrodes' surface changed obviously after use -especially Ti content (from 39.66% to 92.69%) on the anode and Fe content (from 72.57% to 53.66%) on the cathode. The result was probably caused by the redox reaction, namely the shedding of the coating on the anode electrode's surface, and reactions around the cathode electrode's surface.