Evaluation of the potentials of humic acid removal in water by gas phase surface discharge plasma

Degradation of humic acid (HA), a predominant type of natural organic matter in ground water and surface waters, was conducted using a gas phase surface discharge plasma system. HA standard and two surface waters (Wetland, and Weihe River) were selected as the targets. The experimental results showed that about 90.9% of standard HA was smoothly removed within 40 min's discharge plasma treatment at discharge voltage 23.0 kV, and the removal process fitted the first-order kinetic model. Roles of some active species in HA removal were studied by evaluating the effects of solution pH and OH radical scavenger; and the results presented that O 3 and OH radical played significant roles in HA removal. Scanning electron microscope (SEM) and FTIR analysis showed that HA surface topography and molecular structure were changed during discharge plasma process . The mineralization of HA was analyzed by UV–Vis spectrum, dissolved organic carbon (DOC), specific UV absorbance (SUVA), UV absorption ratios, and excitation-emission matrix (EEM) fluorescence. The formation of disinfection by-products during HA sample chlorination was also identified, and CHCl 3 was detected as the main disinfection by-product, but discharge plasma treatment could suppress its formation to a certain extent. In addition, approximately 82.3% and 67.9% of UV 254 were removed for the Weihe River water and the Wetland water after 40 min of discharge plasma treatment.