Advanced oxidation of formaldehyde in aqueous solution using the chemical-less UVC/VUV process: Kinetics and mechanism evaluation

Abstract This study was conducted to evaluate the degradation of high concentrations of formaldehyde in the chemical-less UVC/VUV photo-reactor. 99.5% degradation and 94% chemical oxygen demand (COD) removal of 200 mg/L formaldehyde was achieved in the UVC/VUV photo-reactor at reaction time of 60 min and solution pH of 7. The effect of water anions such as carbonate, bicarbonate, nitrate, chloride, sulfate and phosphate was examined on degradation and COD removal of formaldehyde; nitrate and carbonate exhibited the highest inhibitory effects on the process. Besides, treatment of formaldehyde-contaminated tap water was also investigated and formaldehyde removal was decreased from 99.5% is aqueous solution to 86.2% in tap water. The findings of radical scavenging tests revealed that hydroxyl radical was the most predominant oxidizing agent contributed in degradation of formaldehyde. It is concluded therefore that the UVC/VUV process as a unique chemical-less process efficient for advanced degradation of high concentrations of formaldehyde.