Possible applications of ferrate(VI) in the treatment of industrial wastewater effluent in the laboratory

Abstract

This paper shows the effects of ferrate(VI) application in the treatment of industrial wastewater effluent in laboratory conditions. Samples used are a mixture of wastewater effluent from various industrial plants whose composition was determined by analyzing samples before the ferrate(VI) treatment. Determining physical-chemical characteristics of the samples showed very high chemical oxygen demand (COD) and the concentrations of individual pollutants are higher than the maximum allowed. In the tested samples, the COD was from 18 (sample 1) to 580 times (sample 2) greater than allowed (allowed 45 - 150 mg/l), while the concentrations of certain metals were several times higher than allowed (Cu allowed 0,1 mg/l, Zn allowed 0,2 mg/l). Also, a high concentration of total phosphorus content (allowed 2 mg/l) and fluoride was found (allowed 20 mg/l), 2-3 times higher than permissible. The applied Na2FeO4 was synthesized by electrochemical method and applied in situ. Physical-chemical testing of samples, after treatment with different amounts (2, 5, 8, and 10 ml) of Na2FeO4, concentration of 8 g/l showed that ferrate(VI) can be used as a multifunctional agent in the purification of industrial wastewater, where in the amount of contaminating matter is reduced below the maximum permitted level. It was demonstrated the high efficiency of ferrate(VI) as a strong oxidant in the removal of total P and suspended materials. Also pointed out was the high sorption power of the generated ferric(III)hydroxide, which with its developed surface absorbs 95,5% of the F- and removes it from the solution in the form of sludge. Showed a high efficiency of ferrate(VI) in the total removal of P (70 to 99,5%), and F- (89 to 95,5%), but depending on the presence of the total COD value or the presence of the total organic substances. At high values of the COD major part of ferrate(VI) is consumed in the oxidation of organic material and the formation of Fe(OH)3, which accelerate the process of decomposition of ferrate(VI), which contributes to lower the efficiency of the removal of P and F-.