【作者】 张斌；

【导师】 黄丽；

【作者基本信息】 华中农业大学 ， 土壤学， 2016， 硕士

【摘要】 为探究皂角苷和柠檬酸对重金属的去除过程和效果,本文以武汉市几家污水处理厂的污泥样品和吸附Cu/Zn的高岭石为研究对象,利用皂角苷和柠檬酸溶液对其进行提取,探讨两种提取剂的浓度(0-7%/0-2 mol/L)、pH(2-6)、振荡时间(0-48 h)、振荡温度(10、25、40℃)、提取次数(1-4次)对重金属去除率的影响,分析去除前后重金属的形态,结合去除过程中浸出液的pH以及红外光谱(FTIR)分析手段探究去除机理。主要研究结果如下:皂角苷溶液能够有效的去除污泥中的重金属,浓度增加,重金属去除率增加。pH的变化对Cu、Ni、Pb去除率的影响较小,而在pH减小到2时Zn的去除率明显增加;Zn需要经过48 h的振荡才能有较好的去除,而Cu、Ni、Pb在6-12 h便达到最大去除;增加温度,Cu的去除率下降而Zn的相反,温度变化对Ni和Pb的去除影响不大;经过4次提取,Cu、Ni、Pb、Zn的累积去除率最大能达到33%、76%、21%和39%。单次提取,柠檬酸对污泥中重金属的去除率大于皂角苷的,随着柠檬酸浓度的增加,重金属的去除率迅速增加到最大后开始下降;pH增加,Cu和Zn的去除率增加而Ni和Pb的相反;振荡在1-6 h便达到最大去除;温度增加,Cu的去除率增加而Ni、Pb和Zn的保持不变;4次提取后,Cu、Ni、Pb、Zn最大的累积去除率分别为64%、40%、79%和81%。皂角苷溶液去除高岭石上的重金属时,Cu和Zn的去除率随浓度的增加而增加,Cu和Zn的去除率最大能达到50%和49%;Cu和Zn的去除率均在低pH下较高;经过2 h的振荡,Cu和Zn即达到最大去除;Cu的去除效果在低温下较好,而温度变化对Zn的去除率影响不大。柠檬酸溶液去除高岭石上的Cu和Zn时,去除率随浓度、pH和时间的变化规律与污泥中Cu和Zn的一样,Cu和Zn的去除率最大能达到56%和49%;但随温度的变化,Cu的去除率保持不变而Zn去除效果在高温下较好。柠檬酸去除污泥和高岭石以及皂角苷去除高岭石中重金属后浸出液pH保持稳定,但皂角苷去除污泥中重金属后浸出液pH受去除条件影响较大,增加振荡时间、提高振荡温度、增加提取次数以及降低皂角苷溶液pH均能降低浸出液的pH。原始污泥样品中Cu以可氧化态和残渣态为主,Ni和Pb以残渣态为主,Zn以残渣态和酸溶态为主。皂角苷和柠檬酸去除污泥中重金属后,Cu和Ni以残渣态和可氧化态为主,Pb的酸溶态和可还原态的比例增加,皂角苷溶液处理后污泥中Zn的残渣态减少而柠檬酸溶液处理后Zn的残渣态增加。皂角苷与柠檬酸去除污泥中重金属时,相同位置特征峰强度发生变化但两种淋洗剂处理后特征峰强度变化程度不同,皂角苷与柠檬酸对高岭石层间结构以及与化学键结合的重金属均有去除。更多还原

【Abstract】 To explore the removal process and result of heavy metals by saponin and citric acid, sewage sludge collected from municipal wastewater treatment plants in wuhan and kaolinite adsorbed with Cu/Zn were conducted to investigate the removal of heavy metals by saponin and citric acid. Various factors such as the concentration of desorbents(0-7%/0-2 mol/L), pH(2-6), contact time(0-48 h), temperature(10, 25, 40 ℃), extract times(1-4) and the change of distributions of heavy metals before and after removal were studied. To explore the removal mechanism by means of the pH change of eluent during the removal and infrared spectrum analysis(FTIR). Results showed that:Heavy metals in sewage sludge could be effective removed by saponin, the removal rate of heavy metals increased with the increase of saponin concentration. The pH change had no significant effect on removal of Cu, Ni, Pb, but higher removal rate of Zn obtained when the pH decreased to 2. Cu, Ni, Pb were able to achieve the maximum removal rate when the reaction time was during 6-12 h, however, a better removal of Zn need to go through to 48 h. With the increase of temperature, the removal efficiency of Cu decreased but that of Zn increased, while Ni and Pb remained relatively constant. Cu, Ni, Pb and Zn obtained the highest cumulative removal rate of 33%、76%、21% and 39% after extracted 4 times.By single removal, the removal efficiency of heavy metals in sewage sludge by citric acid was better than saponin. The removal rate of heavy metals increased rapidly to the maximum followed by a decline with the increase of saponin concentration. With the increase of pH, the removal efficiency of Cu and Zn increased while that of Ni and Pb decreased. The maximum removal achieved only when the reaction time was during 1-6 h. With the increase of temperature, the removal efficiency of Cu increased, while Ni, Pb and Zn remained relatively constant. Cu, Ni, Pb and Zn obtained the highest cumulative removal rate of 64%、40%、79% and 81% after extracted 4 times.The removal of heavy metals on kaolinite by saponin indicated that, the removal rate of Cu and Zn increased with the increase of saponin concentration, the maximum removal rate of Cu and Zn were 50% and 49%. Higher removal rate of Cu and Zn obtained when the pH was lower. The maximum removal achieved only after 2 h. The removal efficiency of Cu was better at low temperature, while Zn remained relatively constant when the temperature changed.The removal of Cu and Zn on kaolinite by citric acid indicated that, the variation of removal rate with concentration, pH and reaction time were same as that of sewage sludge, the maximum removal rate of Cu and Zn were 56% and 49%. But when temperature changed, the removal efficiency of Cu remained relatively constant while Zn was better at high temperature.After the removal of sewage sludge and kaolinite by citric acid and the removal of kaolinite by saponin, the pH of eluent remained relatively stable. But the pH of eluent had significant effect with removal conditions when the removal of sewage sludge by saponin, with the increase of contact time, temperature, extract times and the decrease of pH value of saponin solution, the pH of eluent decreased.In the original sewage sludge samples, Cu was mainly in the presence of oxidizable and residual, Ni and Pb were mainly in the presence of residual, while that of Zn was in the presence of acid-soluble and residual. After the removal by saponin and citric acid, Cu and Ni were mainly in the presence of residual and oxidizable, the proportion of acid-soluble and reducible of Pb were increased, the proportion of residual of Zn was decreased by saponin extract while that of Zn was increased by citric acid extract.FTIR results showed that the intensity of the peak changed at the same position but changed in different level after the removal by saponin and citric acid. The heavy metals in interlayer structure and ttat combined with chemical bond could all be removed by saponin and citric acid.更多还原