Degradation of triethanolamine and chemical oxygen demand reduction in wastewater by photoactivated periodate

Abstract

The rapid reduction of chemical oxygen demand (COD) of industrial wastewater is achieved using a novel oxidant, periodate (IO_4^−), coupled with ultraviolet (UV) irradiation. The wastewater is characterized by a high COD, low total suspended solids, variable triethanolamine (TEA) concentrations, and low concentrations of iron and zinc. The use of periodate and UV irradiation with either aqueous TEA solutions or real wastewater is shown to be effective in reducing the COD to acceptable levels. The optimal pH for COD degradation is determined to be 7.6 because of the combined effects of pH on the speciation of TEA and IO_4^− Increasing the ratio of the initial concentrations of period ate to TEA, [IO_4^−]_0/[TEA]_0, increased the degradation rate up to an apparent saturation value. Irradiation with a 1 000-W mercury-xenon lamp increased the COD pseudo-first-order degradation rate constant by a factor of 5.5 for synthetic TEA solutions and 2.3 for industrial wastewater, compared to irradiation with a 1 000-W xenon lamp.