Study On Dyeing Wastewater Treatment With Catalytic Wet Peroxide Oxidation And O₃/H₂O₂ Advanced Oxidation Processes

Dyeing wastewater treatment is attracting increasing attention. In this study, processes of catalytic wet peroxide oxidation and ozone/hydrogen peroxide coupled oxidation were employed to treat two synthetic dyeing wastewaters consisting of cationic dye Crystal Violet (CV) and anionic dye Acid Red-B (AR-B) respectively. The aim of this work was to remove color and to improve the biodegradability of dyeing wastewaters.In the study on the treatment of CV synthetic dyeing wastewater, a series of Zn-Fe layered double hydroxides (LDHs) were prepared and were calcined to obtain layered double oxides (LDOs). Under room temperature and atmosphere pressure, decolorization of CV wastewater by catalytic wet H2O2 oxidation was investigated, and the decolorization kinetics was developed. The results show that the color removal efficiency of 100% was achieved in 30 min when 0.20 g of Zn-Fe LDOs and 5 ml of 3% H2O2 were added into 100 ml of 50 mg/L CV wastewater. The decolorization capacity of the prepared Zn-Fe catalyst was highly selective. Under the same condition, the decolorization efficiency could be> 93% for CV whereas almost no decolorization effect was observed for some anionic dyes. Scaning electronic microscopy and BET surface area analyses suggest that the particle size of the newly prepared catalyst was significantly smaller than those of the used ones. However, there was no marked variation in the surface area of the Zn-Fe catalyst during the decolorization experiments.In the study on the treatment of AR-B synthetic dyeing wastewater, O3/H2O2 coupled oxidation was investigated in order to improve its biodegradability. The experimental results show TOC/UV254 was exponentially related to BOD5/COD, and could be an easy way to reflect the biodegradability of wastewaters. Color removal efficiency of 97% was achieved when the dosage of ozone was 503 mg/h, the H2O2/O3 molar ratio was 3, and the initial concentration of AR-B was 500 mg/L. The corresponding COD removal efficiency was 80% and the TOC/UV254 was increased from 9.7 to 71.4. By UV-Vis and GC-MS analyses, it is believed that AR-B was oxided and docomposed to smaller organic compounds.