利用淋洗剂组合去除土壤中重金属及淋洗液回收技术研究

发布时间：2018-10-13 14:12

【摘要】：本文以湖南郴州受多种重金属污染土壤为研究对象,通过实验室实验,开展了一系列振荡淋洗实验,确定最佳淋洗剂、最佳淋洗条件、最佳淋洗组合。同时开展淋洗剂回收的研究工作,并且对淋洗后的土壤进行发芽实验,以验证其生态毒性。从而为在更大范围内修复重金属污染土壤储备技术和经验。主要结论如下：(1)通过对采集土壤样品的分析,该土壤中Cu、Zn、Pb、Cd、As的含量分别为46 mg·kg~(-1)243 mg·kg~(-1),322 mg·kg~(-1),1.32 mg·kg~(-1)、32 mg ·kg~(-1)。其中Cd污染最为严重,超过国家限定标准4.4倍,其次还伴随有一定程度的Zn、Pb、As污染。(2)通过比较三种不同的EDTA盐(Na-EDTA、NH4-EDTA、Ca-EDTA)对土壤的淋洗效果,结果表明,三种EDTA盐对土壤中Cu、Zn、Pb、Cd都具有一定的淋洗效果,对As几乎没有去除效果,对不同重金属的去除率表现为：CdPbCuZnAs,对同一重金属,三种盐在淋洗能力上表现为NH4-EDTA Na-EDTA Ca-EDTA.(3)对Na-EDTA、NH4-EDTA、Ca-EDTA的淋洗液浊度进行测定,其浊度分别为35NTU、33NTU、2.5NTU,Ca-EDTA淋洗液具有沉降性更好的优势,考虑到后续处理的方便程度,采用Ca-EDTA为所选淋洗剂。(4)Ca-EDTA的最佳淋洗条件为：浓度25 mmol·L~(-1),固液比1：5,淋洗时间2h,连续淋洗3次,在该条件下累计可以去除土壤中26.30%的Cu、12.37%的Zn、45.18%的Pb、73.28%的Cd。(5)考虑到Ca-EDTA对As几乎没有去除效果,我们引入Ca-EDTA+草酸、Ca-EDTA+磷酸氢二钾的淋洗剂组合实验,结果表明,磷酸氢二钾对As去除效果较差,草酸对As去除效果较好,同时对Cu、Zn、Pb、Cd还有一定去除能力,经过Ca-EDTA连续淋洗3次,草酸连续淋洗2次,可以累积去除土壤中42.49%的Cu、21.98%的Zn、44.21%的Pb、83.46%的Cd、17.74%的As,淋洗后土壤中各重金属指标均低于国家土壤环境质量标准中的重金属限定值的二级标准。考虑到EDTA的难降解性,建议先用EDTA再用草酸的淋洗顺序。(6)利用Na_2S溶液对EDTA淋洗液进行处理,结果表明：Na_2S的投加量为3mmol时,Cu、Zn、Pb、 Cd的去除率均达到100%。EDTA淋洗液在经过Na_2S处理后,其回收的EDTA溶液对土壤重金属仍有一定的去除能力,但其效能下降了约30%。(7)氯型阴离子交换树脂对淋洗液中的重金属具有较好的吸附效果,在固液比为1：20的条件下,对淋洗液中Cu、Zn、Pb、Cd的去除率分别为：100%、74%、96%、95%。树脂可以再生,再生后的树脂对淋洗液中Cu、Zn、Pb、Cd的去除率分别为95.65%、74.56%、99.69%、100%。(8)通过对淋洗后的土壤进行紫云英的发芽实验,结果表明,经过淋洗后,土壤对紫云英的发芽状况有一定的抑制作用,因为土壤中的营养元素在淋洗过程中也发生了流失,通过添加有机肥、复合肥,能使肥力得到一定程度的恢复,有利于增加紫云英发芽率。
[Abstract]:In this paper, a series of oscillatory elution experiments were carried out in Chenzhou, Hunan Province, by means of laboratory experiments. The best eluent, the best leaching conditions and the best elution combination were determined. At the same time, the study on the recovery of eluent was carried out, and the germinating experiment was carried out on the eluted soil to verify its ecological toxicity. So as to remediate the heavy metal contaminated soil storage technology and experience in a wider range. The main conclusions are as follows: (1) the contents of Cu,Zn,Pb,Cd,As in the soil were 46 mg kg~ (-1) 243 mg kg~ (-1), 322 mg kg~ (-1), 1.32 mg kg~ (-1), 32 mg kg~ (-1), respectively. Cd pollution was the most serious, 4.4 times higher than the national standard, followed by a certain degree of Zn,Pb,As pollution. (2) the leaching effect of three different EDTA salts (Na-EDTA,NH4-EDTA,Ca-EDTA) on soil was compared. The three kinds of EDTA salts had a certain leaching effect on Cu,Zn,Pb,Cd in soil, but had little effect on As removal. The removal rates of different heavy metals were as follows: CdPbCuZnAs, for the same heavy metal. The elution ability of the three salts was as follows: NH4-EDTA Na-EDTA Ca-EDTA. (3) was used to determine the turbidity of the eluent of Na-EDTA,NH4-EDTA,Ca-EDTA. The turbidity of the eluent was 35NTUU33NTU2.5NTU2.5NTU2.5NTUU2.5NTa-EDTA, which had the advantage of better sedimentation, taking into account the convenience of subsequent treatment. Ca-EDTA was used as the eluent. (4) the optimum elution conditions of Ca-EDTA were as follows: concentration 25 mmol L ~ (-1), solid / liquid ratio 1: 5, elution time 2 h, continuous elution 3 times. Under this condition, the Cd. (5) of Pb,73.28% of Zn,45.18% of 26.30% of Cu,12.37% in soil could be removed. Considering that Ca-EDTA had little effect on As removal, we introduced Ca-EDTA oxalic acid and Ca-EDTA dipotassium hydrogen phosphate into the eluent combination experiment, the results showed that, The effect of potassium hydrogen phosphate on As removal was poor, oxalic acid on As removal was better, and there was a certain removal ability on Cu,Zn,Pb,Cd. After 3 consecutive Ca-EDTA elution, oxalic acid was eluted twice. 42.49% of Cu,21.98% can be removed from soil by the As, elution of Pb,83.46% Cd,17.74% of Zn,44.21%. The indexes of heavy metals in the soil are lower than the second grade standard of the limited value of heavy metals in the national soil environmental quality standard. Considering the difficult degradability of EDTA, it is suggested that the elution sequence of EDTA and oxalic acid should be used first. (6) the eluent of EDTA is treated with Na_2S solution. The results show that when the dosage of Na_2S is 3mmol, the removal rate of Cu,Zn,Pb, Cd can reach that of 100%.EDTA eluent after Na_2S treatment. The recovered EDTA solution still has some removal ability to heavy metals in soil, but its efficiency has decreased by about 30%. (7) chlorine anion exchange resin has a better adsorption effect on heavy metals in eluent, and the ratio of solid to liquid is 1:20. The removal rates of Cu,Zn,Pb,Cd in the eluate were as follows: 100%, 96% and 95%, respectively. The resin can be regenerated. The removal rate of Cu,Zn,Pb,Cd in the eluate by the regenerated resin is 95.65 ~ 74.56 and 99.6969 / 100 respectively. (8) through the experiment on the germination of purple cloud in the eluted soil, the results show that, after leaching, The soil has a certain inhibitory effect on the germination of Astragalus sinensis, because the nutrient elements in the soil have also been lost during the leaching process. By adding organic fertilizer and compound fertilizer, the fertility can be restored to a certain extent. It is beneficial to increase the germination rate of Ziyunxin.
【学位授予单位】：湖南农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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