电化学除磷过程的条件优化与机理研究

Condition Optimization and Mechanism of Electrochemical Phosphorus Removal Process

为优化电化学除磷过程的条件并探究反应机理,通过模拟实际污水研究了初始pH值、初始磷浓度C0及曝气强度j对电化学除磷过程的影响,同时对不同条件下电化学除磷过程进行了动力学分析。结果表明:随着初始pH值的增加,TP去除率先增加后减小;随着电解时间的增加,溶液pH值增大。当C0为5 mg/L、电解时间为60 min、初始p H值为6~8时,TP去除率达到84.5%以上;且当初始pH值为7时,TP去除率达到最高值,为87.69%。C0越高,TP去除率越低,但除磷的能耗也越低。当C0为9 mg/L时,电解60 min后,TP去除率为72.79%,去除单位质量磷的能耗仅为0.059 kW·h/g,比C0为5 mg/L时节约能耗0.025 kW·h/g。当j为0.14~0.28 L/min时,电解60 min后,TP去除率达到86.0%以上,比j为零时至少提高了43.6%。动力学拟合结果表明,电化学除磷过程中存在着化学配位反应和吸附反应。当pH值为3~5时,除磷过程以化学配位反应为主,当pH值为7~11时,除磷过程则以吸附反应为主;且pH值增加不会减弱除磷过程中的吸附反应。当C0为8~9 mg/L时,化学配位作用的除磷效果达到极限水平。曝气一方面有利于Fe2+氧化为Fe3+,促进化学配位反应,另一方面可以缓解电极钝化,提高除磷效率。

In order to optimize the conditions of electrochemical phosphorus removal and explore the reaction mechanism,the effects of initial pH,initial concentration of phosphorus (C0) and aeration intensity (j) on the electrochemical phosphorus removal process were studied through simulating the actual sewage,and the kinetics of electrochemical phosphorus removal process under different conditions were analyzed. The TP removal rate increased firstly and then decreased with the increase of initial pH,and the solution pH increased with the increase of electrolysis time. TP removal rate reached more than 84. 5% when C0 was 5 mg/L,electrolysis time was 60 min and initial pH was between 6 and 8. The TP removal rate reached the maximum value of 87. 69% when the initial p H was 7. The higher the C0,the lower the TP removal rate and the energy consumption per unit phosphorus removal were. When C0 was 9 mg/L,the TP removal rate was 72. 79% after electrolysis for 60 min,and the energy consumption per unit phosphorus removal was only 0. 059 k W·h/g,saving 0. 025 kW·h/g compared with C0 of 5 mg/L. When j was between 0. 14 L/min and 0. 28 L/min,the TP removal rate was more than 86. 0% after electrolysis for 60 min,which was at least 43. 6% higher compared with j of zero. The kinetics fitting results showed that chemical coordination reaction and adsorption reaction took place during the process of electrochemical phosphorus removal. The removal of phosphorus was mainly ascribed to chemical coordination when pH was between 3 and 5. However,the adsorption was the main process of phosphorus removal when p H was between 7 and 11. The increase of pH did not weaken the adsorption reaction during phosphorus removal. When C0 was between 8 mg/L and 9 mg/L,the phosphorus removal effect of chemical coordination reached the limit level. On the one hand,aeration was advantageous to the oxidation of Fe2+ into Fe3+,promoting chemical coordination reaction. On the other hand,it could alleviate electrode passivation and improve the phosphorus removal efficiency.