Multiple functions of liquid ferrate in the pretreatment of flue-gas desulfuri zation wastewater.

The pretreatment of flue-gas desulfurization (FGD) wastewater directly affects the subsequent treatment effect of water. Liquid ferrate(VI) was used for the first time in the pretreatment of FGD wastewater. Influential factors including ferrate(VI) dosage and dosing method were investigated by batch tests. The results show that when the dosage of Na₂FeO₄ is 1.0 g/L, the removal rate of Mg²⁺, Ca²⁺, SO₄^2-, NH₄⁺ and chemical oxygen demand were 99.80%, 83.09%, 7.24%, 28.72% and 26.46%, respectively. The strong oxidizing property of the liquid ferrate, the alkali therein, and the co-precipitation of the product promote the removal of these substances. Morphologic and element analysis confirmed that the composition of precipitates were Fe₁₆O₁₆(SO₄)₂(OH)₁₂·nH₂O, FeO(OH), CaSO₄ and Mg(OH)₂. This paper provides a demonstration and theoretical guidance for the application of ferrate(VI) in FGD wastewater pretreatment. [ABSTRACT FROM AUTHOR]