Catalytic ozonation for the degradation of polyvinyl alcohol in aqueous solution using catalyst based on copper and manganese

摘要

Polyvinyl alcohol (PVA) is widely used in industries and exists in corresponding effluents. As a refractory water-soluble polymer, PVA is hard to be biologically degraded and may cause membrane blockage problem in reclaiming the wastewater. Therefore, it is necessary for PVA-containing wastewater to be pretreated. In this study, the heterogeneous catalytic ozonation to degrade PVA was investigated. The composition of catalysts was screened, the catalyst preparation and the reaction conditions were optimized, and the degradation mechanism was discussed. According to the results, gamma-alumina was selected as support, copper and manganese were selected as active components, and subsequently the complex catalyst, copper-oxygen-manganese/gamma-alumina (CMA), was formed. The optimal preparation conditions of CMA were as follows: molar ratio of copper to manganese was 1:2 while loading rate was 4 wt%; copper and manganese loaded on g-alumina successively by ultrasonic impregnation at 25 degrees C for 2.5 h, then dried at 100 degrees C for 4 h, and calcined at 500 degrees C for 4 h. When the initial concentration of PVA solution was 20 mg/L, the optimal dosage of the catalyst for catalytic ozonation was 100 mg/L. The removal rate of PVA reached 97.8% in 15 min at pH = 7, and 99.3% in 10 min at pH = 10. The leaching of the metals in CMA could be neglected, and the catalyst still had a satisfactory result after five cycles of reuse. The catalytic ozonation followed the mechanism of hydroxyl radical reaction. Although only a small fraction of PVA was mineralized after reaction, the long chains of PVA molecules were broken into smaller pieces. Therefore, it is an effective pretreatment method for reclaiming PVA-containing wastewater. (C) 2020 Elsevier Ltd. All rights reserved.