Effect of organic molecular weight on mineralization and energy consumption of humic acid by H2O2/UV oxidation

In this study, the effect of molecular weights (MWs) on mineralization, energy consumption, kinetic reaction, and trihalomethane formation potential (THMFP) of humic acid was evaluated by the process of H2O2/UV oxidation. Three ranges of MWs of 100 k-10 kDa (sample A), 10 k-1 kDa (sample B), and less than 1 kDa (sample C) were investigated. The results showed that the reaction constant k increased with either increased UV intensity or increased H2O2 dose; the order of k was k(A) > k(B) > k(C), for all UV intensities from 16 to 64 W and H2O2 dose from 25 to 100 mg L-1. In terms of E-EO and E-EM, the energy consumption decreased as the H2O2 dose increased with the descending order of sample C > sample B > sample A. The three samples had an initial dissolved organic carbon (DOC) of 20 mg L-1 with the related values of THMFP of 325, 359, and 468 mu g L-1 for samples A, B, and C, respectively. After H2O2/UV oxidation, the combination of a higher UV power with a shorter time was a better treatment condition for samples A and B as residual DOC and THMFP were smaller.