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

ABSTRACT

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 μg 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.

KEYWORDS:

• Energy consumption
• H₂O₂/UV
• humic acid
• THMFP
• molecular weight