.uv / Naclo <sub> 2 </ Sub> System Degradation Of Dyeing Wastewater

Dyeing wastewater, which contain strong color, high pH, temperature and COD, are difficult to be degraded. Adsorption ,biodegradation and advanced oxidation process (AOP)methods in relation to dye removal and its degradation have been proposed. UV/NaClO₂ could solved the problems of homogeneous chlorine-dioxide alone such as pH had to be adjusted to a limited range,the oxide degradation is selective.On the contrary, very little literature is available in terms of UV/NaClO₂ for decoloration of Disperse dyes, acid dyes, direct dyes, reactive dyes and basic dyes. Chlorine-dioxide (ClO₂) is a novel neutral oxy-chlorine species which is effective for the oxidation of dyeing wastewater. In recent years, a chlorine dioxide generation system of high efficiency is provided, and a further object is the provision of the apparatus which can be constructed at low price. UV/NaClO₂ is the technology use electrolitic processes to generate chlorine dioxide form an aqueous solution of sodium chlorite or sodium chloride.Oxidants was selected as the representative to study the reaction mechanism with UV/NaClO₂. This process involves irradiation of an aqueous solution of sodium chlorite with ultraviolet light. The chlorine dioxide(ClO₂) that is formed can be recovered in liquid phase,.depending upon the purpose of the operation. The experimental conditions were T=15 min, NaClO₂100 mg/L , the result is ClO₂ 48mg/L,ClO₂- 14.8mg/L and Cl- 11.8 mg/L.The effects of UV/NaClO₂ on the degradation of five typical daye of the disperse dyes, acid dyes, direct dyes, reactive dyes and basic dyes in aqueous solution were investigated systematically and the results showed that UV/NaClO₂ has different removal ratio to these dyes under identical conditions, with the best value above 90%for acid dyes and basic dyes,and 70%to 90% for reactive dyes,and the70%to 90% and 30%to 70% for direct dyes and disperse dyes.In lab chlorine dioxide treatment of dyeing wastewater studies showed that chlorine dioxide was suitable for the removal of reactive dyes. The effects of initial pH, dosage of oxidant, temperature and equilibrium time on the reactive dyes of Reactive Blue KN-R, Reactive Red X-3B, Reactive Red KE-3B and Reactive Blue X-BR by chlorine dioxide were studied in detail. Efficacy the color removal rate depend on the structures of various classes of dyes as well as the intermediates formed. The presence of a azo-bis group of reactive red KE-3B and less oxidation of chlorine dioxide of high concentrations was probably the reason why color removal of reactive red KE-3B was less affected than other dyes.Kinetics about Acid Red GR, Reactive Red KE-3B, basic fuchsin, and Disperse Red 4BS Direct Red 9 in simulated aqueous solution with UV/NaClO₂ were studied and the results showed that the reaction was pseudo-first.