Study On Treatment Of Wastewater Containing Chelated Copper By TiO₂ Photocatalysis

In most cases, copper wastewater contained plenty of chelating agent in the electroplating industry, copper and chelating agent could often form a stable chelate. The copper in wastewater can not be effectively removed with traditional chemical precipitation method, becoming typical processing difficulties in the electroplating wastewater. TiO2 photocatalytic technology as recently developed a new type of water treatment technology was usually adopted for its high efficiency, complete degradation products, non-selective, oxidation and reduction, little secondary pollution, etc.Based on suspended TiO2, photocatalysis of wastewater containing complex copper was studied under ultraviolet in the paper, obtaining the variation of reactant during the reaction process by atomic absorption, COD tester, XRD diffraction. The different variables affecting the removal efficiency of copper such as dosage of TiO2, reaction time, initial pH value, reaction atmosphere and mechanism were investigated.The result showed that the removal rate of EDTA-Cu was increased with the increasing of TiO2 dosing quantity, the removal rates of copper and COD in wastewater were the highest,96.56% and 59.17%, respectively. However, when the dosage of TiO2 to a certain extent, degradation effects of EDTA-Cu with TiO2 dosing quantity change had already not obvious. After 40 min reaction, the removal rate of copper was not increased, but the removal rate of COD was gradually increased instead. The degradation of EDTA-Cu was little influenced by temperature, but greatly influenced by pH, the removal rates of copper and COD in wastewater were the highest, when the pH values were 4 and 2 respectively. Different gases could significantly impact on photocatalytic reaction efficiency, the treatment of air was better than nitrogen, oxygen. The photocatalytic of copper was obviously promoted by EDTA, and the degradation of EDTA-Cu was influenced by chelating agent with different complexation constants. Finally, the photocatalytic reaction mechanism of EDTA-Cu was analyzed. The degradation process was as follows:coordinate bond of EDTA-Cu was first ruptured, the releasing copper ion was removed in the form of precipitation, and the freed EDTA was directly oxidized to small molecules acid and long chains of esters, ether by hydroxyl groups, eventually became NO3-, CO2 and H2O, etc.Therefore, photocatalysis of wastewater containing complex copper with nano-TiO2 was feasible, getting good effect.