Study On A Composite Electrode Based On Hydrous Zirconium Oxide For Deflouridation

Excessive fluoride in groundwater is a problem found in many parts of China, which has become drinking water safeness trouble. Although, several technologies have been widely developed and evaluated for defluoridation, almost all of the existing technologies have problems and limits. It is necessary to develop and implement an effective and economic technology for deflouridation.A novel material with high fluoride adsorption performance and electrosorption capacity was successfully developed in this study, which was applied in three-dimensional electrode reactor.Co-precipitation was applied to preparation the zirconium hydroxide as a type drinking-water defluoridation adsorbent and its preparation condition was studied. Fluoride adsorbent removal performance was systemic evaluated. And fluoride adsorption mechanism was discussed based on the analysis of the surface properties before and after fluoride adsorption by using SEM,XRD,BET and spectroscopic technique. The following results were obtained through the research:The optimal preparation condition are conclude that alkali adding speed is 2ml·min-1, pH value is 7.0, drying time is 72h, calcinations temperature is below 100℃. The optimum pH range for fluoride adsorption was 4, and the maximum adsorption capacity calculated from the Freundlich isotherm equation at pH 4.0 was 160 mg/g and at pH 7.0 was 70 mg·g-1.The normal coexisting anions in groundwater, such as sulfate, nitrate and chlorine, did not affect fluoride adsorption performance. Phosphate, arsenate and humic acid, on the other hand, influenced fluoride adsorption through competitive adsorption. The amorphous structure, big BET surface area (138m2g-1) and a narrow pore size distribution in the mesopore region of the hydrous zirconium oxide adsorbent might be the main reason for the high fluoride adsorption capacity. Based on the FTIR and XPS results, it is found that all the surface active sites for fluoride adsorption, whose hydroxide group could be replaced by fluoride. The molding method was combined zirconium hydroxide with graphite materials, adding a binder to make electrodes and the conditions of the method was studied. The composite particle removal performance and experiments in three-dimensional reactor were evaluated, The main achievements including the best optimal molding process, the maximum adsorption capacity which was less than zirconium hydroxide powder, but higher than conventional adsorbents. The BET surface and pore size distribution were not change after molding.Electrochemical method was applied to evaluate different molding particle electrode, including Ac impedance, cyclic voltammetry, and constant current charge-discharge. Molding method was futher determined. Composite electrode has specific capacitance of 0.00401F·g-1, lower internal resistance and multiple times charge-discharge.