Advanced oxidation of high concentrations of formaldehyde in aqueous solution under fluorescent and UV light

Abstract

Background: Formaldehyde (FA) is a carcinogen compound, which is soluble in water. FA can be removed from aqueous solution using advanced oxidation methods. Methods: In this study, the oxidation of FA was studied under fluorescent and UV light. Hydrogen peroxide (H2O2) was used as an oxidant. The pH value and H2O2 amount of samples were optimized. The chemical oxygen demand (COD), FA concentration, and H2O2 consumption were followed. Results: It was observed that the pH value of the sample was more significant under fluorescent light than UV light at oxidation of FA. The highest COD removal and H2O2 reduction were 18.57 and 30.90%, respectively, at pH 12.00, with a 1:1 ratio of FA:H2O2 under fluorescent light. 86.41% FA and 62.12% COD removal were achieved at pH 7.00, with a 1:2 ratio of FA:H2O2, under UV light. It was observed that H2O2 was consumed at all pH values under UV light. On the other hand, under fluorescent light, the concentration of H2O2 decreased only at pH 12. In control samples containing only H2O2, the H2O2 reduction was 92.09% at pH 11.91, while it was 2-6% at other pH levels under fluorescent light. The H2O2 reduction changed between 33 and 44% at different pH values under UV light. The oxidation of FA was found to be suitable for the pseudo-first-order kinetic model and Langmuir isotherm model. Conclusion: The most effective oxidation was obtained at the original pH value (7.00) and 1:2 ratio of FA:H2O2 under UV light.

Keywords

• water treatment
• formaldehyde
• uv light
• hydrogen peroxide