Study On Malachite Green Dye Treatment By Three Dimensional Electrolyte In Wastewater

Triphenylmethane dyes are widely used on the market at present. These kinds of dyes with complex structures are toxic. A large amount of waste and wastewater are produced in production, transportation and the use process of dyes. Triphenylmethane dye wastewater with large chromaticity and high COD is degradation-resistant and harmful to the environment and human health.In view of this situation, Malachite green, as a kind of typical triphenylmethane dyes is degraded by a three-dimensional electrode reactor with DAS electrode as anode, graphite plate as cathode and activated carbon as particle electrode. Because of the adsorption of activated carbon, before each experiment, activated carbon should be saturated with wastewater, to reduce its influence to the experimental results. Several influence factors are studied on the degradation experiments, including the pH value of the system, the voltage, the type and concentration of electrolyte, the aeration and the electrolysis time. The optimum reaction conditions and parameters are seeked by orthogonal test. The influence of various parameters on the test order from big to small as follows, electrolytic time> electrode voltage> system pH> value of electrolyte concentration> aeration. The final electrolysis conditions are determined to 8V for electrode voltage,6 for initial pH value,0 for aeration quantity,0.1 mol/L for electrolyte (Na2SO4) concentration and 120 min for electrolysis time. In the reaction condition, the final degradation rate is 92% and 86% for malachite green and COD.The the distribution of electric field and oxidation-reduction potential of electrolysis reactor are also studied in electrolytic process. The results show that the oxidation-reduction potential close to positive pole will increase while the oxidation-reduction potential close to negative pole will decrease. By reducing the sampling interval, increasing the number of sampling, measuring MG concentration and COD concentration of the sample, and then being scanned by means of UV-Vis, initially explore the mechanism and kinetics of degradation reactions of formulas.Particle electrode is the key point and difficult problem in three-dimensional electrode method. Activated carbon because of its good conductivity and adsorption is favored by many researchers, but also because of its conductivity resulting in short-circuit current and bypass current is very large during the experiment, and the effective current is very small relative to the total current, lead to low current efficiency and a waste of power resources. In order to improve the current efficiency, researcher will incorporate quartz sand into the activated carbon, such particles are non-conductive, to reduce the short-circuit current. Because the two kinds of particles are different at size and density, stratification phenomenon of the two kinds of materials appears in the process of electrolysis frequently. In this study, other substances were loaded on activated carbon, including metal oxide, conductive polymer and nonconductive polymer materials, in order to investigate the effect of electrolysis. The results showed that current decreases and current efficiency improves obviously with adding nonconductive particles at the same electrolytic conditions, and the degradation rate of both malachite green and COD reaches above 70%, the best current efficiency is activated carbon loading with PTFE.