Reuse of Ferric Sludge by Ferrous Sulfide in the Fenton Process for Nonylphenol Ethoxylates Wastewater Treatment

Abstract

In this paper, Fenton process was determined to be an effective technique to treat the refractory nonylphenol ethoxylates (NPEOs) wastewater. The chemical oxygen demand (COD) removal efficiencies above 89% were obtained when the initial COD concentration was 12,000 mg/L. However, a large amount of ferric sludge (SS = 8.724 g/L) would be produced after the Fenton oxidation of the wastewater and must be disposed appropriately. A novel process for Fenton sludge reused by low-cost ferrous sulfide (FeS) was also investigated. Experimental results show that the Fenton sludge could be reduced to produce a certain amount of Fe2+ in the acidic mixed liquor by FeS. This mixed liquor from Fenton sludge could be used as the new catalyst in the Fenton process and was also highly effective for the NPEOs wastewater treatment. The residual FeS from the mixed liquor could be used for the next batch of the reaction.