Reduction of Fulvic Acid in Drinking Water by Ferrate

Acting as a powerful oxidant, efficient coagulant, and effective disinfectant, ferrate is a good multifunctional agent for water and wastewater purification. In this study, some of these key aspects were studied for treating water containing fulvic acid, including the reduction efficiency of fulvic acid (FA) in drinking water and the optimum conditions for reducing FA using ferrate prepared in the laboratory. Jar tests and pilot tests were employed in the studies and the results of FA reduction were analyzed spectrophotometrically. Ferrate in these tests exhibited good oxidation capacity on FA. The ultraviolet absorption (UVA) of 2 mg/L FA in water can be reduced about 90% when the weight ratio of ferrate to FA was 12:1. Adsorption to and coprecipitation with Fe(OH)3 precipitate produced by ferrate decomposition can also result in additional FA reduction. In the presence of turbidity, ferrate can oxidize and adsorb simultaneously and over 95% of UVA was reduced with the same weight ratio of 12:1. Combining the application of ferrate and polyaluminum chloride (PAC) or iron chloride (FeCl3) was more effective for FA reduction. The UVA of 2 mg/L FA was reduced 100% in synthetic drinking water by a joint treatment with 8 mg/L ferrate (FeO42? by weight) and 0.8 mg/L PAC (Al by weight) or 6 mg/L ferrate (FeO42? by weight) and 0.8 mg/L Fe3+ (Fe by weight). The pilot test performed more effectively for FA reduction than did the jar test.