皂角苷对几种生活污泥中Cu和Zn的去除

Removal of Cu and Zn from sewage sludge by saponin

为探讨皂角苷对污泥中Cu和Zn去除的机制,采用化学淋洗的方法研究皂角苷浓度（0~7%）、p H（2~6）、振荡时间（0~48h）、温度（10、25、40℃）和提取次数（1~4次）对四种生活污泥中Cu和Zn去除率的影响,分析去除前后重金属的形态,并监测去除过程中浸出液p H的变化。结果表明,单次淋洗条件下,皂角苷对Cu的去除率大于Zn;皂角苷溶液的p H对Cu的去除没有显著影响,而Zn的去除率在p H下降到2时明显增加;Cu经过6~12 h的振荡就能达到最大去除,Zn则需要经过较长时间的振荡（48 h）才能达到较好去除;提高振荡温度,Cu的去除率降低而Zn的增加;随着提取次数的增加,Cu和Zn的去除率均增加,Cu的去除以第1次提取为主,Zn的4次提取均有较好效果,用3%的皂角苷溶液连续4次提取后,Cu和Zn的累积去除率最大分别达到32.61%和39.32%;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p H均能降低浸出液的p H。经过3%的皂角苷溶液的提取,污泥中各形态Cu的含量均减少,其中66%以上的酸溶态被去除;而Zn的酸溶态含量减少不明显,可还原态、可氧化态和残渣态均有所降低,但以残渣态的减少为主。

A chemical washing experiment was conducted to investigate the performance and mechanism of Cu and Zn removal from four types of sewage sludge by saponin. The effects of various factors such as saponin concentration（0~7%）, p H（2~6）, contact time（0~48 h）,temperature（10, 25, 40 ℃）, and washing number（1~4）on Cu and Zn removal and the changes of heavy metal distribution before and after washing were examined. The p H changes of effluent during the removal of Cu and Zn from sewage sludge was also monitored. In single washing, the removal efficiency of Cu was better than that of Zn. The p H of saponin solution had no significant effect on the removal of Cu,whereas higher removal efficiency of Zn was obtained when p H was decreased to 2. The maximum Cu removal was achieved when the reac-tion time was 6~12 h. However, a better removal of Zn needed a longer reaction time（48 h）. With increasing temperature, the removal efficiency of Cu was decreased but that of Zn was increased. The cumulative efficiencies of Cu and Zn removal were increased with increasing number of washing. The removal of Cu mainly happened at the first washing, while the Zn removal remained good during all 4 washing. Four washing with 3% saponin at natural p H removed Cu and Zn by 32.61% and 39.32%, respectively. The effluent p H decreased with increases in contact time, temperature, and number of washing but with decreases in p H values of saponin solution. After washing with 3% saponin, allfractions of Cu were reduced, with acid soluble fraction being removed more than 66%, while Zn fractions（reducible, oxidizable, and residual）except acid soluble fraction showed decreases, with the most reduction found in residual fraction.