| As the fast development of printing and dyeing industry, dyeing wastewater hasaugment significantly both in variety and quantity, and has threatened waterenvironment security. Electrocatalytic oxidation technology is a new water treatmenttechnology for refractory organics，which has been developed in recent years. It hasdrawn wide attention for its good features such as simple operation and lessside-products.In order to seek effective and stable electric catalytic anode, four kinds of titanium substrate PbO2electrode were prepared by electrodeposition in this paper, the effectof different substrate and coating on the catalytic degradation of methyl orange was compared. The research results showed that the best electrode was prepared successfully, whose substrate was titanium mesh, interlayer and active layer was α-PbO2and β-PbO2,respectively. The stability and catalytic activity of this electrode was both good, theenergy consumption was also low. The electrodes were characterized by SEM, it showed that the crystal surface active layer was uniform distribution and the particles was small, thus the matrix can be covered finely, which improved the stability and service life of the electrode.Further study to the preparation of electrode electric catalytic performance,Withself-made new-type lead dioxide electrode as the anode and stainless steel plate as thecathode, this research studied the degradation processes of single and complex dyestuffunder different technological conditions. The results are as following:In the experiment of the methyl orange degradation.With methyl orange initialconcentration equals30mg/L, charging current density equals21mA/cm2, and pHequals5, after120minutes of reaction, the removal ratio of methyl orange can be ashigh as94.45%.The addition of chloride ion can improve indirect oxidation ability,with the concentration of Cl as60mmol/L, after20min of electrolyzation under bestconditions, the removal ratio of methyl orange can reach91.77%. The methyl orangedecolorizing mechanism showed:In the process of electrical catalytic degradation, azostructure of methyl orange was damaged, benzene ring was attacked by hydroxyl free radical constantly, thus methyl orange was degraded into small molecular compoundand the goal of decolorization was achieved.Study the influences of current density, pH, Cl concentration on electrocatalyticoxidation effectiveness of complex dyestuff wastewater (mixture of methyl orange andmethylene blue as simulant). The results are as following:Current density has a great impact on complex dyestuff decolourization. Thedecolourization rate increases rapidly with the increase of current density. In thedegradation of complex dyestuff, the decolourization ratio of methyl orange issignificantly higher than that of methylene blue. In addition, the comparison of methylorange degradation in single and complex dyestuff shows that methyl orange degradesfaster in complex dyestuff than in single dyestuff.In the process of complex dyestuff degradation, the lower the pH, the better thedecolourization effect. The decolourization ratio decreases significantly with theincrease of pH. In single component, pH has a greater impact on electrocatalysis effectof methyl orange than that of methylene blue. The decolourization ratio of methyleneblue varies little from pH6to pH10. Generally speaking, decolourization is better inthe area of pH3~6, considering that we need considerable amount of acid to get a lowpH, this method is more suitable for treating acidic dye wastewater without dilution orneutralization.The increase of Cl concentration has a great impact on decolourization effect.After the addition of chloride ion, the decolourization ratio of methyl orange andmethylene blue in complex dyestuff increase rapidly. The decolourization ratioincreases with the increase of Cl concentration. In complex dyestuff, methyl orangehas a priority of degradation, and the degradation of methylene blue is inhibitedbecause of the competitive effect of methyl orange. |
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