【摘要】：土壤是所有生物體賴以生存的場(chǎng)所,然而目前土壤鉻污染已經(jīng)開(kāi)始對(duì)糧食安全、生態(tài)平衡、人體健康帶來(lái)一定的影響,因此有必要去除土壤中的鉻�；瘜W(xué)提取法是一種有效去除土壤重金屬的方法,選擇有效的提取劑是該方法的關(guān)鍵。本文選用生物表面活性劑無(wú)患子皂苷和鼠李糖脂以及螯合劑GLDA(谷氨酸N,N-乙酰乙酸四鈉)為提取劑,單一人工污染的土壤為供試材料,通過(guò)振蕩提取實(shí)驗(yàn),從提取劑的濃度、pH、提取時(shí)間、提取次數(shù)、提取劑組合方式等方面入手,考察對(duì)土壤中鉻去除的影響,最后分析經(jīng)提取后土壤中鉻形態(tài)的變化情況。所得結(jié)果如下:(1)無(wú)患子皂苷和GLDA兩種提取劑可以有效地去除土壤中鉻。適當(dāng)增加提取劑濃度、延長(zhǎng)提取時(shí)間、增加提取次數(shù)均能夠提高土壤中鉻的去除率。當(dāng)無(wú)患子皂苷濃度為21 g.L-1,提取時(shí)間為24 h時(shí)去除效果最佳,為32.05%;當(dāng)GLDA濃度為0.70%,提取時(shí)間為24 h時(shí)去除率達(dá)67.59%。但是,兩種提取劑提取的最佳酸堿條件并不相同。無(wú)患子皂苷在酸性條件下提取效果最好,而GLDA則在堿性條件下提取效果最佳,酸性次之,中性最差。這與兩種提取劑本身性質(zhì)有關(guān)。(2)利用BCR法測(cè)定提取前后鉻的形態(tài)變化情況發(fā)現(xiàn):無(wú)患子皂苷可以部分去除弱酸提取態(tài)和可還原態(tài)鉻,去除率分別為59.25%和40.09%,而對(duì)于可氧化態(tài)以及殘?jiān)鼞B(tài),幾乎沒(méi)有去除。GLDA可以有效去除弱酸提取態(tài)和可還原態(tài)鉻,部分去除可氧化態(tài)鉻,去除率分別為100%、87.59%和33.13%,而對(duì)于殘?jiān)鼞B(tài),去除效果同樣不明顯。弱酸提取態(tài)和可還原態(tài)是土壤中比較活躍的兩種形態(tài),經(jīng)過(guò)兩種提取劑提取都可以明顯降低兩種形態(tài)的鉻,因此降低了環(huán)境風(fēng)險(xiǎn)。(3)選用生物表面活性劑與螯合劑混合,組成兩種復(fù)合提取劑研究其對(duì)土壤中鉻的去除效果發(fā)現(xiàn):無(wú)患子皂苷與GLDA復(fù)合后提取效果得到明顯提高,在GLDA濃度低于0.50%時(shí)與無(wú)患子皂苷復(fù)合對(duì)土壤中鉻的去除表現(xiàn)為協(xié)同作用,高于0.50%后則表現(xiàn)為拮抗作用;鼠李糖脂與GLDA復(fù)合后提取效果也有明顯提高。適當(dāng)延長(zhǎng)提取時(shí)間、減少土水比也可有效提高土壤中鉻的去除率。不同的組合方式提取效果不同,將兩種提取劑混合后的提取效果要高于單獨(dú)使用兩者的效果。兩種復(fù)合提取劑提取的最佳酸堿條件相反,無(wú)患子皂苷與GLDA復(fù)合適合在酸性條件下提取,而鼠李糖脂與GLDA復(fù)合則適合在堿性條加下提取,最佳的酸堿范圍由復(fù)合提取劑中適應(yīng)范圍較窄的一方?jīng)Q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.
【學(xué)位授予單位】：廣西大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：X53

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