pH对预氧化沸石滤柱启动过程中除锰效率的影响

Effect of pH on manganese removal efficiency during the start-up process of pre-oxidation zeolite filter column

针对当前接触氧化除锰法启动期较长的问题,采用改性沸石滤料耦合次氯酸钠预氧化辅助滤柱启动,采用扫描电子显微镜(SEM)、能量色散X射线光谱(EDS)、X射线衍射(XRD)、X射线光电子能谱(XPS)对滤料进行分析,探究了原水pH对滤柱启动中锰去除效率的影响,并对持续运行过程中次氯酸钠的投加量进行了优化,对改性沸石滤料进行静态吸附实验,并在进水pH分别为6.5、7.0、7.5时进行滤柱启动实验。结果表明,改性沸石滤料对Mn^(2+)的吸附符合Langmuir模型与准二级动力学方程,当pH为5.5~8.0时,随pH升高改性沸石滤料对Mn^(2+)的去除率上升。在3种pH条件下,滤柱的锰穿透期分别为5、8和9 d,并分别在第20、16和14天启动成功;次氯酸钠预氧化启动的3种滤柱次氯酸钠最低投加量分别为0.8、0.3与0.2 mg·L^(-1)。SEM与XRD表征结果证实了水钠锰矿在滤料表面的出现;而EDS与XPS结果分别表明,更高的pH会同时带来滤料表面锰元素含量和锰价态的升高。以上研究结果可为地表水水厂中对除锰有利的pH范围及沸石在启动过程中对锰的吸附作用提供参考。

In view of the long start-up period of the current contact oxidation manganese removal method,modified zeolite filter media coupled with sodium hypochlorite preoxidation was used to assist the start-up of the filter column.Scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS)were used to analyze the filter materials,the effect of raw water pH on the start-up of the filter column was investigated,and the dosage of sodium hypochlorite for continuous operation was optimized.Static adsorption experiments were conducted on modified zeolite filter media,and column start-up experiments were conducted at feed water pH of 6.5,7.0 and 7.5,respectively.The results showed that the adsorption of Mn^(2+)by the modified zeolite filter media was in accordance with the Langmuir model and quasi-secondary kinetic equation,and the removal rate of Mn^(2+)by the modified zeolite filter media increased with increasing pH when the pH was 5.5~8.0.The manganese penetration periods of the filter columns at the three different pHs were 5,8 and 9 days,respectively,and were successfully activated on day 20th,16th and 14th;and the minimum doses of sodium hypochlorite were 0.8,0.3 and 0.2 mg·L^(−1)for the three filter columns with sodium hypochlorite preoxidation,respectively.SEM and XRD results confirmed the appearance of Birnessite on the surface of the filter media,while the EDS and XPS results showed that higher pH resulted in both higher manganese content and higher average valence on the surface of the filter media,respectively.The results of this study can provide a reference for the pH range favorable for Mn removal in surface water plants and the adsorption of Mn by zeolites during start-up process.