Application of a Zero-Valente Iron-Per Sulfate System to Treat Petrochemical Wastewater With High-Total Dissolved Solids Containing Para-Chlorophenol

Background: Zero-valent iron (ZVI) can effectively activate persulfate (PS) generating free sulfate radicals (SO4•–), thereby presenting a promising technology to degrade recalcitrant organic contaminants such as para-chlorophenol (PCP) in wastewater. Objectives: The current study aimed to examine the feasibility and application of ZVI/PS system through batch experiments to degrade PCP of petrochemical effluent, which its treatment is included in The United States environmental protection agency (USEPA) priority pollutant list. Materials and Methods: Effects of dosages of ZVI (0.056 - 2.8 g/L), ZVI to PS molar ratio (0.1 - 5.0), PS concentration (2.5 - 25.0 mM/L), pH = (3.0 - 11.0), contact time (5 - 240 minutes), and ZVI reusability (three cycles) on PCP degradation were examined. Results: The results showed that the PCP degradation increased with an increase in ZVI dosage from 0.056 to 1.4 g/L, an increase in persulfate concentration from 2.5 to 15.0 mM/L, and an increase in ZVI to PS molar ratio from 0.1 to 2.5. The optimal initial pH for PCP removal was 5.0 and the maximum removal efficiency of 70% was achieved within 120 minutes. Moreover, the ZVI catalyst was reused until the third cycle to activate the persulfate and degrade PCP. However, the degradation efficiency of PCP gradually decreased to 51.7% when the ZVI reuse time increased. Conclusions: The results indicate that using ZVI/PS system is not an efficient enough method to treat petrochemical effluent, due to the complexity of petrochemical wastewater matrix and high- total dissolved solids (TDS) content, as well.