Effects of nitrate and chloride ions on the photocatalytic degradation of humic acid

Abstract

The removal of natural occurring organic compounds in drinking water has gainedattention, recently. The reason for this is their ability of being the major precursor ofDisinfection by-Products like Trihalomethanes. Therefore, new methods based onphotocatalytic and photochemical degradation processes are investigated. The object ofadvanced oxidation processes is to mineralize organic contaminants with the help of strongoxidizing agent such as hydroxyl radical from hydrogen peroxide and ozone in the presenceof a catalyst or UV light.In this study the influence of nitrate and chloride ions on the photocatalyticdegradation of humic acid in aqueous medium was investigated. Bench scale experimentswere carried out using titanium dioxide as the photocatalyst and the Black Light Fluorescentlamp as the irradiation source. The effects of various concentrations of nitrate and chlorideions on the photocatalytic degradation of humic acid was followed by TOC, UV280, Color400and Co10r436.The presence of nitrate ions in the reaction medium caused an approximately30-50 % adsorption as observed by dark reactions. Following adsorption, photocatalyticdegradation took place in 30 min. Further irradiation up to 60 min. did not cause anysignificant degradation.The presence of chloride ions in the reaction medium reflected a 40-50 % removal. of humic acids by adsorption. Upon irradiation approximately 30 % removal took placedepending on the concentration of chloride.