Advanced oxidation of formaldehyde in the aqueous solutions using UVC/S2O82- process: Degradation and mineralization

Abstract

Background: As a human carcinogen, formaldehyde is a toxic chemical imposing adverse effects on \npublic health and environment. Due to its high reactivity, colorless nature, sustainability, purity in \ncommercial forms, and low prices, the production and consumption of this compound has expanded \nvastly in industries. \nMethods: In this study, a UVC photoreactor with a total volume of 120 mL was used and operated \nin a rotary mode. To determine the residual concentration, high-performance liquid chromatography \n(HPLC) device was applied whose detector was set at a wavelength of 355 nm and equipped with C18 \ncolumn (with dimensions of 25 × 4.6 mm i.d, and particle size of 5 μm). Total organic carbon (TOC) \nwas determined using a TOC analyzer. \nResults: The optimal condition in this study was obtained at pH=3 and formaldehyde concentration \nof 350 mg, so that the removal of formaldehyde and TOC was 98.2% and 95.1%, respectively, after 35 \nminutes reaction time. The formaldehyde removal efficiency was assessed in the presence of methanol \n(MeOH), tert-butyl alcohol (TBA), and salicylic acid (SA) scavengers, and it was indicated that SO4 \n•- \nradicals were the most effective factors in formaldehyde destruction. By increasing the concentrations \nof MeOH, TBA, and SA to 2.5 g/L, the degradation efficiency of formaldehyde dropped from 98.02% \nto 69.78%, 64.68%, and 45.14%, respectively, at 35 minutes reaction time. The removal of formaldehyde \nin the presence of nitrate was significantly reduced and it had a significant effect on the removal of \nformaldehyde. \nConclusion: In this study, the removal of formaldehyde was investigated in the presence of various \nanions including bicarbonate, carbonate, chloride, sulfate, and nitrate. According to the results, the \nUVC/S2O8 \n2- process is a convenient and cost-effective method for the removal of formaldehyde. \nKeywords: Formaldehyde, Advanced oxidation, Bicarbonates, Carbonates, Sulfates, Nitrates