Ferrous Iron Combined with Different Oxidants for Thermal Desorption Wastewater Treatment from Petroleum Hydrocarbon Contaminated Sites

Abstract:

Ferrous iron （Fe²⁺） combined with three oxidants， sodium hypochlorite （NaClO）， sodium persulfate （Na?S?O₈） and hydrogen peroxide （H₂O₂） were used to treat thermal desorption wastewater from the crude oil-contaminated soil. The influences of pH， Fe²⁺ dosage， oxidant dosage and reaction time on the treatment efficiency were investigated. The results show that PHCs （typical pollutants in thermal desorption wastewater） can be effectively removed by Fe²⁺/H₂O₂ and Fe²⁺/Na?S?O₈， with a removal efficiency of 100.0% and 97.8%， respectively. However， the chemical oxygen demand （COD） removal efficiency of Fe²⁺/H₂O₂ system is significantly higher than that of Fe²⁺/Na?S?O₈. Fe²⁺/H₂O₂ can oxidize and decompose organic matters completely， while Fe²⁺/NaClO and Fe²⁺/Na?S?O₈ can only convert organic matters into intermediate substances. The multivariate analysis results indicate that pH and oxidant dosage are the main factors affecting the removal efficiency. The cost of Fe²⁺/H₂O₂ in the treatment of thermal desorption wastewater is higher， but it has the best removal efficiency. The cost of Fe²⁺/Na?S?O₈ is lower than that of Fe²⁺/H₂O₂. However， COD cannot be degraded completely. Fe²⁺/NaClO has the lowest cost but the worst removal efficiency. Hence， considering the removal effect and economic factors， the Fe²⁺/H₂O₂ system is more suitable for the treatment of thermal desorption wastewater.