Catalytic ozonation of high saline petrochemical wastewater using PAC@Fe II Fe 2 III O 4 : Optimization, mechanisms and biodegradability studies

Abstract

Abstract This work specially focused on preparation of a magnetic catalyst, carbon impregnated by iron oxide (PAC@Fe3O4), and consider its catalytic ability for the first time in ozonation of high saline petrochemical wastewater (PCW) from PVC and VCM manufacturing industries. The structural and surface properties of the catalyst, the effect of operational factors, biodegradability and mechanisms were also studied in details. Results revealed that the influence of pH on COD removal rate was negligible, whereas process performance was significantly affected by various concentrations of catalyst and ozone. Under the optimum operational conditions, COD and TOC removal reached to 75.3 and 50.3% after 120 min catalytic ozonation, respectively. Organic compounds were also degraded through transformation of ozone into OH both over catalyst surface and in the solution as identified by tert-butanol. A probable comprehensive mechanism include adsorption, homogeneous and heterogeneous catalytic ozonation was also proposed. The biodegradability of PCW was noticeably improved based on the BOD5/COD ratio, AOS and COS indices after 120 min reaction by PAC@Fe3O4/O3 system. The catalyst indicated a weak iron leaching and high catalytic activity upon five recycling cycles, which confirms that it can be reused many times. Therefore, the PAC@Fe3O4/O3 process was an effective and promising technique for successful PCW treatment, due to the efficient reduction of COD, achieve discharge standards and enhance biodegradability.