Degradation of formaldehyde by UV/Hydrogen peroxide process

Abstract

Degradation of the synthetic formaldehyde wastewater using advance oxidation process, UV/hydrogen peroxide, was investigated in order to apply this system as a pre-treatment method for formalin solution used in the hospitals. The effects of solution pH, molar ratio of formaldehyde to hydrogen peroxide, and initial concentration of formaldehyde on process performance were systemically studied. It was revealed that UV photolysis had a little effect on degradation of formaldehyde. The highest efficiency of formaldehyde degradation was achieved with the molar ratio of formaldehyde to hydrogen peroxide at 1:2 at pH 7 within 240 min. At the molar ratio lower than the optimum condition, an inadequate amount of hydrogen peroxide was presented. On the contrary, the highest ratio than that causing the decomposition of hydrogen peroxide itself. Regarding the study of the pH effect, it was found that formaldehyde degradation in acidic solution gave a favorable oxidation rate than that in basic solution. However, the highest formaldehyde removal efficiency was observed at neutral pH. The toxicity and total organic carbon reductions were determined. The toxicity reduction below EC50 was attained when the initial concentration less than 5,000 mg/l. The formaldehyde degradation by UV/hydrogen peroxide did not accomplish the total mineralization since the by product of formaldehyde, formic acid, was identified in GC Chromatogram during the reaction period. Findings from this study can be potentially applied for formalin wastewater with the formaldehyde concentration less than 5,000 mg/l.