Study on the Removal of Humic Acid from Road Tunnel Drainage Systems Based on Electric Field-Enhanced Co(II)-Mediated...

The issue of clogging in highway tunnel drainage systems primarily stems from the long-term accumulation of floc-like sediments formed by the chelation of natural organic matter with metal ions. This study employed an electric field-enhanced Co-(II)-mediated peroxymonosulfate system (E/Co-(II)/PMS) for the efficient treatment of humic acid. Compared with the E/Co-(II), Co-(II)/PMS, or E/PMS systems alone, the E/Co-(II)/PMS system exhibited superior humic acid removal performance, with a degradation rate of 92.3% in 30 min, which significantly improved the oxidation efficiency. The study reveals the mechanism of Co-(II) activation of PMS to generate sulfate radicals (SO₄ ^•-) and hydroxyl radicals (HO^•), and maintains the reaction in a sustained and efficient manner by cathode-driven Co-(III)/Co-(II) cycling. The experimental results showed that pH = 7, 0.2 mM Co-(II), and 17 mA/cm² current density were the optimal parameter combinations, and the degradation was inhibited by the inorganic anion CO₃ ^2-, PO₄ ^3-, and Cl^-, which increased with its concentration, with the strongest inhibitory effect being observed for Cl^-. The present study not only provides an efficient technical solution to address the issue of organic clogging in tunnel drainage systems, but also provides a theoretical and applied basis for the electrochemical oxidative degradation of organic pollutants in complex water quality through the analysis of the mechanism and optimization of the parameters.