[Degradation of azo dye acid orange 7(AO7) by heat, ZVI and heat/ZVI activated persulfate].

Effects of temperatures, PS concentrations and ZVI dosages on AO7 decomposition were investigated in sole heat and ZVI activating systems. The degradation results of two systems were compared for selecting a better activating way for AO7 degradation and finally the two activating ways were combined for getting the optimal AO7 degradation efficiency. The degradation of AO7 by Heat/PS systems followed pseudo first-order kinetics. The reaction rates increased with increasing reaction temperatures (elevated from room temperature to 90 degrees C) and also increased when initial PS concentrations varied from 1 to 12 mmol x L(-1). For ZVI activating systems (ZVI/PS systems), the degradation rate of AO7 was the highest when ZVI dose was 0.2 g, and it reached to 95.6% within 90 min. Comparing ZVI/PS systems with Heat/PS systems, the results showed that the ZVI activation was a more effective way to activate PS than the heat activation for AO7 degradation. AO7 degradation processes by ZVI/heat/PS systems were two-stage pseudo first-order kinetic processes, and the combining of two activating ways significantly increased the reaction rates. By the addition of ZVI to the Heat/PS system, the apparent activation energy E(a) of AO7 degradation reduced from the original 130.26 kJ x mol(-1) to 27.70 kJ x mol(-1).