Removal Of Bisphenol A And Phosphate By Ferrate

The development of science and technology caused advent of increasing amout of new industries, resulting in increase of industrial wastewater and sewage discharged into the water environment. Thus, water quality of the water resources are deteriorated, and aquatic ecosystems were damaged to various extents. The protection and management of water resources gradually become an important work. Ferrate, as a new multifunctional water treatment material are recognized gradually by people, and it has high strenghth for removing endocrines,phosphate from water. Hence, ferrate, bisphenol A and phosphate as the main research reagent was selected to evalute the effectiveness of Fe(â…¥) to remove BPA and phosphate together from water, and to investigate the effectiveness of phosphate removal by Fe(â…¥) enhanced by the addition of Fe(â…¡), and to study the performance of ferrate on the removal of pollutants.Firstly, the removal efficiency of Bisphenol A(BPA) and phosphate by Fe(â…¥)was inverstigated. The results showed that increasing ferrate dose effectively improved the removal of BPA. The removal efficiency increased as the increase of ferrate dose and the water temperature, and at pH 6-7, ferrate oxidation achieved high removal efficiency of Bisphenol A. During the process of ferrate decom- position, it could be seen that the Fe(â…¡I) are formed in ferrate catalytic reaction, but it was not just simply to generate Fe(â…¡I), the intermediate valence iron Fe(V) or Fe(IV) may be generated. The removal efficiency of BPA was increased by ferrate in the way that ferrate was added in the same total dose at different times, and the addition of t- butanol could reduce the efficiency of BPA removal. It demonstrated that not only ferrate but also the intermediate valence oxidizing substances participate in the process of oxiding BPA. In the experiment of removing BPA and phosphate together by Fe(â…¥), the phosphate removal by ferrate was superior to the case of Fe³⁺, the newly hydrated ferric oxide which was generated by ferrate reduction could remove phosphate very well.Increasing the mount of newly formed hydrous ferric oxide could enhance the effectiveness of removal for phosphate, thus the removal efficiency of phosphate by Fe (â…¥)/Fe (â…¡) is evaluated. The research results indicated that Fe(â…¥)/Fe (â…¡) system could remove more phosphate than Fe³⁺. FTIR analysis showed that the floc particles structure formed in situ in Fe(â…¥)/Fe(â…¡) system involved in the formation of FeOOH, which could be a good adsorbent for phosphate, it is not only a simply adsorbent, but a nner complexes with phosphate by adsorption, also hence the complexation reaction took place. The variation of turbidity and pH solution during this process also supported this expectation.Between Fe(â…¥)/Fe(â…¡) system and Fe³⁺, the optimal molar ratio of Fe/P was 1.32 in the Fe(â…¥)/Fe(â…¡) system, the optimal molar ratio of Fe/P was 1.72 in the case of Fe³⁺. The presence of chloride ions and nitrate ion had little impact on the removal of phosphate, but the presence of sulfate and ammonia had some inhibition effect on the removal of phosphate. At lower pH range, the presence of silicate improved the removal of phosphate by Fe(â…¥)/Fe(â…¡) system, but at higher pH range it also reduce the removal efficiency of phosphate. Under alkaline conditions, the existence of calcium ions promoted phosphate removal. The surface topography characteristics of flocculants could be improved by the presence of these cations from the results of SEM analysis. The organic matter in the water background inhibited the removal of phosphate. In the coagulation process when pH is 5-7, Fe(â…¥)/Fe(â…¡)achieved very good treatment effectiveness, but the effluent turbidity somewhat was elevated.In order to enhence the turbidity removal in Fe(â…¥)/Fe (â…¡) system, Fe(more valences) system was added to remove oganic matter and phosphate together. It was found that the optimal molar ratio of Fe(â…¥):Fe(â…¡) was 0.5 in Fe(â…¥)/Fe(â…¡) system, and the optimal molar ratio of Fe(â…¥):Fe(â…¡):Fe(â…¡I) was 1:2:4 in the Fe(more valences) system. The increase of ferrate addition is for further oxidation of the organic matter which could be degraded by ferrate. The residual ferrate can react with organic and ammonia, the presence of ferric would also promote the process of organic oxidation by ferrate.Conclusively, this research provided results for both oganic matter and phosphate removal together by Fe(â…¥), and the addition of different valence iron could enhance the pollutant removal. The results may provide theoretical and technical basis for practical engineering application.