电吸附技术去除水中磷酸盐离子的研究

水体富营养化是世界各国面临的重大环境污染问题.水中的磷酸盐作为水体富营养化的关键因素,如何有效去除日益引起研究者的关注.本研究利用电吸附技术处理水中PO_4~(3-)、HPO_4~(2-)和H_2PO_4~- 3种常见磷酸盐离子,并分析电吸附和脱附的特性及机理.实验得到电吸附处理K_3PO_4时,离子去除率最大,但脱附率最差,这严重影响电吸附电极的再生性.K_3PO_4溶液中存在大量的OH~-,炭电极对KOH产生物理吸附,该吸附类型比电吸附的双电层吸附难脱附.添加少量HCl调节磷酸盐的pH,减少OH~-,将溶液中PO_4~(3-)转化为HPO_4~(2-)和H_2PO_4~-,可以提高电极的脱附率,增加电极的循环使用效率,同时可增加溶液中磷含量的去除率.炭电极电吸附K_3PO_4+HCl溶液时,电极的再生性良好,连续循环四次,离子去除率由28.7%降为26.6%.

Research on removal of phosphate from water by electroadsorption technology

Eutrophication of water body is a major environmental pollution problem for all the countries in the world. The technology of effectively removing phosphate as a key factor of eutrophication has attracted increasing attention. In this study, three common phosphate ions including PO₄^3-, HPO₄^2- and H₂PO₄^- were treated by using electroadsorption technology, and the characteristics and mechanism of electroadsorption and desorption were analyzed. When the K₃PO₄ is electroadsorbed, the ion removal rate is the highest and the desorption rate is the worst,which seriously affects the regeneration of the electroadsorption electrode. There are a large number of OH^- in the solution of K₃PO₄, which can be physically adsorbed by using carbon. Compared with the double layer adsorption, physical absorption due to capacitive carbon is very difficult to desorb. Adding a small amount of HCl can adjust the pH of K₃PO₄, reduce the OH^-, and convert PO₄^3- to HPO₄^2- and H₂PO₄^- in solution, which increases the desorption rate of electroadsorption process and the recycling efficiency of electrodes. Concurrently, adding the HCl can increase the removal rate of phosphorus content in solution. When K₃PO₄+HCl solution is electroadsorbed by using carbon electrode, the regeneration of the electrode has good performance. The ion removal rate decreased from 28.7% to 26.6% after four consecutive cycles.