Degradation Of 2, 4-Dichlorophenol With TiO₂/Ti And Fe Double Anodes Photoelectrocatalytic Oxidation

The danger of environmental hormone organisms that can distory incretory,neural and genital systems is terrible, and it is difficult to degrade them because of longer stay time and higher toxicity. Photocatalysis of TiO₂ is applied in the treatment of water or wastewater, particularly in toxic wastewater treatment. With the aggravation of environmental pollution and enhancement of environmental consciousness, it is time to develop a high effective process for water or wastewater treatment. Based on the above problems, TiO₂/Ti and Fe double anodes photoelectrocatalytic oxdition process (PECO) is designed and its application in environmental hormone treatment is studied in this research. Under current and UV-A irradiation, TiO₂ PECO and E-Fenton reaction occur in TiO₂/Ti and Fe double anodes PECO integrated process, and their cooperation effect enhances the degradation to pollutants.TiO₂/Ti photoelectrode was firstly prepared by a low-voltage anodization process and its characteristics were tested. TiO₂/Ti and Fe double anodes PECO reactor was designed and degradation of 2,4-DCP was investigated, when TiO₂/Ti and Fe were used as anodes; GF was used as cathode and SCE was used as reference electrode. The cooperation effect of TiO₂ PECO and E-Fenton reaction was studied. Furthermore, degradation kinetics and HO·generation were researched. Under the optimal conditions, degradation of DMP was studied using this double anodes PECO process, which proved that this integrated process had high degradation and mineralization ability to hormone chemicals.In the stage of preparation, TiO₂/Ti photoelectrode was prepared by a low-voltage anodization process which was conducted in HF/HNO3 electrolyte, and the factors of preparation process were studied and optimized. The koken of XRD, SEM, FTIR, XPS and characteristics of TiO₂/Ti electrode were tested. Experimental results showed that nano-size TiO₂ thin film symmetrically growed on Ti surface using 30V anodization voltage after 60min. The best calcination temperature and rate for crystal transfer was 500℃and 5℃/min, and crystal phase mainly composed of anatase. The even size of TiO₂/Ti thin film prepared by the low-voltage andization process was controlled in 60nm showed by SEM. Titanium oxide formed on Ti surface was mainly titanium dioxide, which was proved by XPS and FTIR. Oxidation potential of TiO₂/Ti thin film tested by cyclic voltammetry was 0.7V and adhesive attraction tests showed that TiO₂/Ti thin film had long using time.In the stage of 2,4-DCP degradation with TiO₂/Ti and Fe double anodes PECO integrated process, TiO₂ PECO process was firstly studied. Factors and pH change were investigated in TiO₂ PECO process. In TiO₂/Ti and Fe double anodes PECO integrated process, a variable rheostat was connected with stainless steel to control current distribution to TiO₂/Ti and Fe anodes. This design had three advantages. The first was that all oxids were produced by itself, because Fe²⁺ was released from Fe anode and H₂O₂ was generated nearby cathode; the second was that degradation of 2,4-DCP increased by the cooperation of photoelectro-effect; and the last was that pH range was greatly widened. Moreover, The factors of current and its distribution to two anodes, bubbling O₂ and its flow speed, irradiation intensity, 2,4-DCP initial concentration, TiO₂/Ti electrode effective area, pH and anions of solution were investigated. Furthermore, the generation and accumulation of H₂O₂, application of pH, removal of chlorine ion and mineralization of 2,4-DCP were studied in this integrated process. Experimental results showed that the degradation and mineralization of 2,4-DCP could get to 95.3% and 80%, and removal efficiency of chlorine ion reached 81%, under 15mg/L 2,4-DCP concentration, 3.2mA current and 0.2:3.0 distribution to TiO₂/Ti and Fe anodes, 40ml/min O₂, 158μW/cm2 UV-A irradiation intensity, 5cm2 TiO₂/Ti electrode effective area and 3.0 pH value. The high generation efficiency of H₂O₂ proved that this integrated process had high generation efficiency. Furthermore, the effect of pH on 2,4-DCP degradation showed that this double anodes integrated process could work well in a wide pH range. Under the optimal conditions, the degradation of DMP was studied in this integrated process. Experimental showed that this integrated process had the high degradation and mineralization performance to treat environmental hormone organisms.Degradation model and kinetics of TiO₂ PECO and TiO₂/Ti and Fe double anodes PECO integrated process were studied and built based on the above experiments. The effect of 2,4-DCP concentration, applied voltage, irradiation intensity, bubbling speed and TiO₂/Ti area on kinetics constant was studied. Degradation kinetics of TiO₂/Ti and Fe double anodes PECO integrated process was gotten. The experimental results of HO·generation showed that a perfect linearity relationship between generated HO·quantity and 2,4-DCP degradation appeared, which proved that main oxid in integrated process was HO·and degradation of 2,4-DCP was mainly caused by HO·. The experiment of HO·generation also proved that there was an obvious cooperation between TiO₂ PECO and E-Fenton reactions.