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

The magnesium oxide (MgO) / ozone (O-3) / 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 beta, MgO dosage, O-3 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 O-3 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/O-3/H2O2, bubbling reactor (BR)MgO/O-3/H2O2, RPB-O-3/H2O2 and RPB-MgO/O-3 were also compared in the study. The results showed that RPB-MgO/O-3/H2O2 allowed for more efficient degradation of formaldehyde in wastewater. Possible degradation mechanisms of formaldehyde in wastewater were proposed based on ion chromatography.