Photocatalytic Degradation Of Humic Acid By Nano-composite TiO₂/Se Catalysts

Humic acid(HA) is a conventional chlorination disinfection by-products(DBPs) of trihalomethanes category carcinogens(THMs) in the main precursor, so it is a serious problem that how to remove HA in the raw water effectively. There are some adventages about the degradation of HA with Photocatalytic Oxidation, such as mild reaction conditions, ervironment-friendly, and so on. In this paper, TiO₂ was modified with selenium and selenium compounds, then two catalysts were prepared, and their photocatalytic oxidation degradation of HA was investigated. The main studies are as follows:(1)The Cu₂Se-TiO₂/Se catalysts were prepared with Cu₂Se as the selenium source, tetrabutyl titanate as precursor, and ethanol as solvent. Cu₂Se-TiO₂/Se was characterized by XRD and SEM-EDAX. The dependence of photo-catalysts'crystal styles, phase composition and their photocatalytic degration of HA on the inhibitor(diethanolamine, glacial acetic acid, acetyl acetone), calcination temperature, dosage of Cu₂Se was investigated. Results showed that, the Cu₂Se-TiO₂ /Se catalysts prepared with Cu₂Se: Ti(OC4H9)4 = 0.05: 1(wt:wt), acetic acid as the inhitor, and calcined at 450℃for 2h perform excellently on the degradation of HA. The influences on the removal rate of HA was studied further, and results showed that, the removal rate of humic acid(10mg/L, pH=6.5) is about 78.8% with 1.5g/L dosage of the catalyst at room temperature for 3h.the removal rate of HA can up to 78.8%.(2) The Se-TiO₂/Se catalysts were prepared with Se as the selenium source and characterized by XRD and SEM-EDAX. The influences on the removal rate of HA such as calcination temperature of catalysts, feed ratio, initial concentration of HA, reaction time and dosage of catalysts was investigated, and results showed that, the removal rate of humic acid(10mg/L, pH=7.0) is about 94.9% with 4g/L dosage of the catalyst at room temperature for 3h.(3)The UV lamp(UV 253.7nm), black light(UV 365nm), incandescent (L450 700nm) were used to study the influence of light source to the removal rate of HA. Combined with characterization such as DRS, SEM, the influence of selenium source on the photocatalytic degradation of HA was investigated. Results showed that, HA removal rates for Se-TiO₂/Se/UV(253.7nm), Se-TiO₂/Se/UV(365nm) and Se-TiO₂/Se/ L(450⁷00nm) were up to 92.4%, 91.6% and 70.8%, better than Cu₂Se-TiO₂/Se (83.3%, 10.2% and 5.9%). It meaned that the photocatalytic activity would be significant differences when Se present in the catalysts with different forms.