Electrochemical And Photoelectrochemical Treatment Of Dye Waste Water

The highly coloured waste water of texitile industy contains many complex componds and is harmful to environment. So the discoloration of dye waste water is paid great concern by both governments and reaserchers. Photochemical and photoelectrochemical treatments are two advanced oxidation processes which are widely used because of characters such as high efficiency, simple operation and being benign to environment.In this work, Photochemical and photoelectrochemical treatments are investigated to treat the dye waste water. In the photoelectrochemical experiment, The effect of Cl^- and SO₄^2- ions on the photoelectrocatalytic degradation of the reactive brilliant K-2BP using TiO₂/Ti as anode is investigated, since Cl^- and SO₄^2- are the most common inorganic ions in dye polluted water. It is found that the concentration of the electrolyte, the acidity of the solution and the use of mixed electrolytes alter the degradation process. When NaCl is used as the electrolyte, active chlorine is formed during the process, and is found to be responsible in combination with photo- and electro-effects for the degradation of dye; while Na₂SO₄ is used as electrolyte, two categories of reactions will occur. SO₄^2- may trap HO·and h+, thus the efficiency of degradation is reduced. Under the conditions investigated, SO₄^2- ion may also catalyze the formation of hydrogen peroxide, which is active for the degradation, and then the degradation is favored.In the electrochemical degradation, the mechanism of Methyl Orange degradation with electrochemical method has been studied in 0.1M NaCl solution with RuOx-PdO/Ti as anode. Chemical oxygen demand (COD), ion chromatography(IC), FTIR and GC-MS analyses were employed to obtain the details of electrochemical degradation. During the reaction, inorganic ions (SO₄^2-, NO₃^–), low molecular weight compounds, chlorinated compound, benzene derives and long chain alkenes could be formed. The formation of chlorinated compound provided strong evidence that during electrochemical process with NaCl as electrolyte, Cl^– was involved in the degradation reaction to form chlorine-substituted byproduct. Formation of long-chain alkenes radicals demonstrated that CH₃·radicals could be formed in the process. The thorough mechanism of the Methyl Orange is proposed in this study.