Coagulation enhancement of nonionic surfactant nonylphenol polyethoxylate with 9 mol of ethoxylate (NP9EO), was conducted by partial oxidation using zero-valent iron (ZVI)/hydrogen peroxide (H2O2) since coagulation is a typical process in many small-scale wastewater treatment plants but it is difficult to remove NP9EO due to micelle formation, and partial oxidation as pretreatment using the proposed process might be adequate and economically feasible. In this study, effects of pH, ZVI dosage, and H2O2 concentration were all investigated. The results show, highest NP9EO removal was observed at pH 2 instead of pH 1.5, since the presence of extra ferrous ion in the lower pH consumed the hydroxyl radicals, resulting in low removal efficiency. In addition, ferrous ion was converted to ferric ion for pH higher than 2 which reduced the efficiency of Fenton reaction. NP9EO removal efficiency by coagulation with ZVI/H2O2 pretreatment was as high as 99%, which is 40% higher than that without ZVI/H2O2 pre-treatment. The optimum dosages for ZVI/H2O2 oxidation were about 125 mg/L of H2O2 and 3 g/L of ZVI with NP9EO removal higher than 85%. But considering the following coagulation, the optimum dosages were about 125 mg/L of H2O2 and 2.5 g/L of ZVI with NP9EO removal efficiency of 95%. Besides, the dissolution of ferric ion from ZVI/H2O2 was able to reduce/replace the requirement of the traditional ferric chloride.
Desalination and Water Treatment 51(7-9), pp.1590-1595