Degradation of 4-Chlorophenol in Aqueous Solution by Sono- Electro-Fenton Process

摘要

Electro-Fenton (EF) and ultrasound radiation (US) have been of interest for the removal of chlorinatedcompounds from water. This study evaluates the effects of different parameters on sono-electro-Fenton(SEF) for degradation of 4-chlorophenol (4-CP) in an aqueous solution. This study uses pulsing USwaves along with Pd-catalyzed EF to degrade contaminants in water while maintaining temperature.The usage of pulsing US waves along with Pd catalyzed EF to remove contaminants while maintainingtemperature has not been reported previously. SEF ability to degrade 4-CP was compared with theperformance of each process (EF and sonolysis) alone. Initial pH, current density, backgroundelectrolyte, Fe2+ concentration, Pd/Al2O3 catalyst concentration, US waves, and sonifier amplitudewere optimized in a two electrode (Ti/mixed metal oxide or Ti/MMO) batch system. The degradationof 4-CP increased from 1.85% by US to 83% by EF to nearly >99.9% by coupled SEF. With USradiation under 70% amplitude and 1:10 ON/OFF ratio, the removal rate of 4-CP increased to 98%compared to 62% under EF alone within the first 120 min in the presence of 80 mg L-1 Fe2+, 16.94 mAcm─2 of current density, 1 g L-1 Pd/Al2O3 catalyst (10 mg Pd), and initial pH of 3. However, thedegradation rate decreased after 120 min of treatment, and complete 4-CP removal was observed after300 minutes. The sonolysis impacted the 4-CP removal under coupled SEF, mostly due to thecontribution of mass transfer (micromixing), while radical formation was found to be absent under theconditions tested (20kHz). The pulsed US was found to increase the temperature by only 8.7oC, whichwas found not to impact the 4-CP volatilization or degradation. These results imply that low-level USfrequency through pulses is a practical and efficient approach to support electro-Fenton reaction,improving reaction rates without the need for electrolyte cooling.