Oxidative degradation of formaldehyde in wastewater by MgO/O3/H2O2 in a rotating packed bed

Abstract

The magnesium oxide (MgO) / ozone (O3) / hydrogen peroxide (H2O2) system was proposed in this study for oxidative degradation of formaldehyde in wastewater in a rotating packed bed (RPB), and the effects of initial pH, high gravity factor β, MgO dosage, O3 concentration and H2O2 concentration on the formaldehyde removal rate were investigated. The results showed that at an initial pH of 9, a high gravity factor of 40, a MgO powder dosage of 4 g/L, a H2O2 concentration of 5 g/L, a O3 dosage of 65 mg/L, a liquid flow of 90 L/h and a gas flow rate of 100 L/h, a 99.93 % and 93.98 % removal rate could be achieved for formaldehyde (2200 mg/L) and chemical oxygen demand (COD) after 60 min, respectively, and the final formaldehyde concentration was 1.45 mg/L, which met the Grade 2 standard set in the Chinese National Standards for Integrated Wastewater (GB 8978-1996). The degradation rates of formaldehyde and COD by RPB-MgO/O3/H2O2, bubbling reactor (BR)-MgO/O3/H2O2, RPB-O3/H2O2 and RPB-MgO/O3 were also compared in the study. The results showed that RPB-MgO/O3/H2O2 allowed for more efficient degradation of formaldehyde in wastewater. Possible degradation mechanisms of formaldehyde in wastewater were proposed based on ion chromatography.