Efficient degradation of phenol in aqueous solution by Fe2+/H2O2/CaO2 system

Abstract

The traditional Fenton treatment of phenol wastewater can achieve a good degradation efficiency. However, this technology requires pH adjustment before and after the treatment, which will corrode the reactor and increase economic loss. In this study, to overcome the disadvantages of traditional Fenton, a synergistic degradation method of phenol in water by adding calcium peroxide (CaO 2 ) in Fenton oxidation was proposed. Under the optimal dosage (Fe 2＋ : H 2 O 2 : CaO 2 = 1 : 2: 1), the COD removal rate (phenol 100 mg/L) reached 95.59% within 15 min. Results showed that the Fe 2 + / H 2 O 2 /CaO 2 system exerted a good degradation efficiency on phenol in a wide pH range (3–11). In addition, studies have showed that adding CaO 2 in Fe 2 + / H 2 O 2 system was more effective to increase the utilization rate of iron ions and H 2 O 2 , and the amount of reactive oxygen species (ROS) in the system was more than when the same amount of H 2 O 2 was added, free radical detection showed that ⋅ OH and system. The effects of anions (Cl − , NO 3 − , SO 4 2 − , and HCO 3 − ) on the performance of Fe 2 + / H 2 O 2 /CaO 2 were studied. Certain amounts of Cl − , SO 4 2 − , and HCO 3 − affected the COD removal rate more than NO 3 − . Finally, the degradation pathway of phenol was proposed based on mass spectra. This study provided a valuable method for the efficient degradation of industrial wastewater. • The addition of CaO 2 significantly improved organics degradation in the Fe 2 + / H 2 O 2 system. • The Fe 2 + / H 2 O 2 /CaO 2 system exerted a good degradation efficiency in a wide pH range (3–11). • Adding CaO 2 to the Fe 2 + /H 2 O 2 system effectively promoted the reduction of Fe 3＋ to Fe 2＋ and improved the utilization rate of iron ions and H 2 O 2 . • ⋅ OH and ⋅ O 2 − were identified as the main active substances in the Fe 2 + / H 2 O 2 /CaO 2 system.