Feasibility, mechanisms, and optimisation of organic pollutant degradation by thermally activated persulphate

Abstract

The thermally activated persulphate (TAPS) degradation process, although recognised as an effective means for pollutant degradation, is challenged by the high cost of energy and a sub-optimal operation due to the limited elucidation of its mechanisms. In this laboratory study, it is shown that waste heat from industries such as textile dyeing is adequate for the rapid degradation and mineralisation of orange G, a typical azo dye used as the main organic probe compound, in the absence or presence of a high concentration of inorganic salts relevant to the textile industry. Other probe compounds investigated are humic acid, salicylic acid, and caffeine. The study, for the first time, highlights the important role of radical kinetic energy in determining the rate and effectiveness of TAPS mineralisation of pollutants. One effect of the kinetic energy of radicals is the existence of an optimal mineralisation temperature. For an uncatalysed persulphate activation, the optimal temperature, independent of the target pollutant, was identified as 90°C. Overall, the study provides important new insights for the design and operation of TAPS degradation processes.