Potassium ferrate enhances ozone treatment of pharmaceutical wastewaters: Oxidation and catalysis

This work verified the ability of potassium ferrate to catalyse ozone-driven oxidation of refractory organic matter in a secondary effluent of a wastewater treatment plant at a local pharmaceutical factory. The effect of potassium ferrate reduction products on ozone decomposition was investigated by evaluating the variation in ozone concentration in water. The mechanisms were revealed by separating residual potassium ferrate reduction products from solutions and analysing the dissolved organic carbon (DOC), ultraviolet absorption (UV254), and fluorescent organics. The results showed that (1) the decomposition rate of aqueous ozone was higher with the potassium ferrate reduction products than without them, implying the catalytic ability on ozone decomposition. (2) The reduction products of potassium ferrate during ozone treatment resulted in an increase of 14.9 % in the DOC removal rate and 29.03 % in the UV254 removal rate compared with the results of treatment with potassium ferrate alone. These results show that the reduction products of potassium ferrate can promote ozone oxidation of refractory organic compounds in secondary effluents, and a multistage oxidation system in which potassium ferrate combined with ozone is technically feasible. To the best of our knowledge, this is the first study to verify that the synergistic effect of ferrate (VI)-ozone is due to the catalytic effect of reduction products on ozone oxidation.