Sulfite excitation by photolysis to produce reducing species for 4-chloro-2- methylphenoxyacetic acid photo-reduction

Abstract

Abstract The photo-reduction of MCPA by UV/Sulfite reduction process is the subject of this study. The optimal pH was (MCPA: Sulfite molar ratio of 3:1 and pH 11) after 20 min reaction time. The Impact of In UV/Sulfite process, the pseudo-first-order reaction constant decreases as concentration rises from 50 to 200. mg L− 1, Kobs and robs decreased and reached from 0.299 to 0.029 min− 1 and 14.95 to 5.80 mg L− 1 respectively. Also, the analysis of energy consumption using the kinetic model and IUPAC shows that with the increase in the concentration of MCPA from 50 to 200 mg L− 1, the amount of EEO from 0.821 to 6.54 kwh.m− 3 in the kinetic model and from 0.91 increases to 6.29 kwh.m−3 in the IUPAC model. in the decomposition of MCPA such as 2-prop-1-en-1-yloxyacetic acid (C5H8O3) and 1-ethoxyprop-1-ene (C5H10O) and hexa-1,3,5 -triene (C6H8), converted. These simple compounds have a high potential to become water and carbon dioxide. The improvement of biodegradability was investigated at 30 min reaction time and the amount of photo-reduction of MCPA, COD and TOC were 100%, 35% and 24%, respectively. In order to evaluate the toxicity of UV/Sulfite process effluent, the acute toxicity test by Kirby-Bauer disc was used, results showed that the zone of inhibition surrounding the disk reduced from 31 mm (without treatment) to 5 mm after treatment. As a Conclusion Sulfite/UV process had a good performance in converting toxic materials into degradable organic materials and the effluent toxicity to the environment was very low.