利用提取剂去除土壤中铬的研究

发布时间：2018-08-30 15:37

【摘要】：土壤是所有生物体赖以生存的场所,然而目前土壤铬污染已经开始对粮食安全、生态平衡、人体健康带来一定的影响,因此有必要去除土壤中的铬。化学提取法是一种有效去除土壤重金属的方法,选择有效的提取剂是该方法的关键。本文选用生物表面活性剂无患子皂苷和鼠李糖脂以及螯合剂GLDA(谷氨酸N,N-乙酰乙酸四钠)为提取剂,单一人工污染的土壤为供试材料,通过振荡提取实验,从提取剂的浓度、pH、提取时间、提取次数、提取剂组合方式等方面入手,考察对土壤中铬去除的影响,最后分析经提取后土壤中铬形态的变化情况。所得结果如下:(1)无患子皂苷和GLDA两种提取剂可以有效地去除土壤中铬。适当增加提取剂浓度、延长提取时间、增加提取次数均能够提高土壤中铬的去除率。当无患子皂苷浓度为21 g.L-1,提取时间为24 h时去除效果最佳,为32.05%;当GLDA浓度为0.70%,提取时间为24 h时去除率达67.59%。但是,两种提取剂提取的最佳酸碱条件并不相同。无患子皂苷在酸性条件下提取效果最好,而GLDA则在碱性条件下提取效果最佳,酸性次之,中性最差。这与两种提取剂本身性质有关。(2)利用BCR法测定提取前后铬的形态变化情况发现:无患子皂苷可以部分去除弱酸提取态和可还原态铬,去除率分别为59.25%和40.09%,而对于可氧化态以及残渣态,几乎没有去除。GLDA可以有效去除弱酸提取态和可还原态铬,部分去除可氧化态铬,去除率分别为100%、87.59%和33.13%,而对于残渣态,去除效果同样不明显。弱酸提取态和可还原态是土壤中比较活跃的两种形态,经过两种提取剂提取都可以明显降低两种形态的铬,因此降低了环境风险。(3)选用生物表面活性剂与螯合剂混合,组成两种复合提取剂研究其对土壤中铬的去除效果发现:无患子皂苷与GLDA复合后提取效果得到明显提高,在GLDA浓度低于0.50%时与无患子皂苷复合对土壤中铬的去除表现为协同作用,高于0.50%后则表现为拮抗作用;鼠李糖脂与GLDA复合后提取效果也有明显提高。适当延长提取时间、减少土水比也可有效提高土壤中铬的去除率。不同的组合方式提取效果不同,将两种提取剂混合后的提取效果要高于单独使用两者的效果。两种复合提取剂提取的最佳酸碱条件相反,无患子皂苷与GLDA复合适合在酸性条件下提取,而鼠李糖脂与GLDA复合则适合在碱性条加下提取,最佳的酸碱范围由复合提取剂中适应范围较窄的一方决定。
[Abstract]:Soil is the place where all living organisms live. However, soil chromium pollution has begun to affect food security, ecological balance and human health, so it is necessary to remove chromium from soil. Biosurfactant saponin, rhamnolipid and chelating agent GLDA (glutamic acid N, N-acetoacetate tetrasodium) were selected as extractant, and single contaminated soil was selected as test material. The concentration, pH value, extraction time, extraction times, extractant combinations of chromium in soil were investigated by oscillating extraction experiment. The results are as follows: (1) Saponin and GLDA can effectively remove chromium from soil. Increasing the concentration of extractant, prolonging the extraction time and increasing the extraction times can improve the removal rate of chromium from soil. 21 g.L-1, extraction time for 24 hours, the best removal effect was 32.05%; when the concentration of GLDA was 0.70%, extraction time for 24 hours, the removal rate reached 67.59%. However, the two extractants extraction of the best acid-base conditions are not the same. The results showed that saponin could partly remove weak acid and reducible chromium, and the removal rates were 59.25% and 40.09% respectively. However, for oxidizable and residual state, GLDA could effectively remove weak chromium. The removal rates of acid extractable and reducible chromium were 100%, 87.59% and 33.13% respectively, while the removal efficiency of residual chromium was also not obvious. Environmental risk. (3) Selecting biosurfactant and chelating agent to compose two kinds of compound extractant to study the effect of removing chromium from soil. The results showed that the effect of extracting chromium from soil was obviously improved after compounding saponin and GLDA. When the concentration of GLDA was lower than 0.50%, the combination of saponin and saponin showed synergistic effect on removing chromium from soil. The extraction efficiency of Rhamnolipid and GLDA was also significantly improved after 0.50%. Appropriate prolongation of extraction time and reduction of soil-water ratio could also effectively improve the removal efficiency of chromium in soil. The optimum acid-base conditions of the two compound extractants were contrary. The combination of saponin and GLDA was suitable for extraction under acidic conditions, while rhamnolipid and GLDA was suitable for extraction under alkaline conditions. The optimum acid-base range was determined by the narrow adaptability of the compound extractant.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X53

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