Efficient decomposition of pentachlorophenol by a high photon flux UV/sodium hydrosulfite: Kinetics, intermediates and associated transformation pathway

This study was conducted to investigate the performance of sodium hydrosulfite-mediated photoreduction (SMP) process for the reduction of the pentachlorophenol (PCP). The influence of various parameters, quenchers and anions in water, were investigated on the performance of the SMP. The PCP degradation rates by SMP, UV alone and sodium hydrosulfite alone were achieved 100 %, 65 % and 16 %, respectively (under optimum conditions: sodium hydrosulfite dosage, 100 mg L −1 ; pH, 7.0 and reaction time, 80 min). Also, the kinetic studies confirmed the superiority of SMP than the other process (r obs values for SMP were 69 and 9.8 times of the sodium hydrosulfite alone and UV alone, respectively).Under the selected conditions 56 % of total organic carbon (TOC) was mineralized. The amounts of energy consumed for SMP, UV alone and sodium hydrosulfite alone were estimated 16, 35 and 19 and kWh m -3 , respectively. The results indicated adding quenchers in the solution, significantly was declined degradation performance . Therefore, it was found the SMP process due to smaller total cost and energy consumption and also the higher r obs , might be an efficient method for the removal of pentachlorophenol form aqueous solution.