發(fā)布時間：2019-06-07 12:22

【摘要】：重金屬主要來源于污灌、化肥農(nóng)藥的大量使用、礦山和工業(yè)生產(chǎn)產(chǎn)生的“三廢”、城市垃圾和大氣沉降物等。重金屬進入土壤后,不能被微生物降解,只能發(fā)生遷移和轉(zhuǎn)化等,其污染具有隱蔽性、長期性和不可逆性的特點。它們會污染水體和空氣,影響作物和生物的生長,并通過食物鏈危害人體健康和生命。土壤重金屬污染受到人們的日益關(guān)注。如何修復(fù)重金屬污染土壤,降低重金屬污染帶來的危害,已成為環(huán)保領(lǐng)域的重要研究內(nèi)容。眾多修復(fù)技術(shù)中土壤淋洗修復(fù)技術(shù)作為一種快速有效的污染土壤治理技術(shù)越來越受到重視。本研究以浙江富陽某煉銅廠附近受Cd、Cu、Pb和Zn復(fù)合污染土壤為研究對象,采用振蕩、靜置和超聲三種不同浸提方式,以檸檬酸和EDTA為浸提劑,通過研究兩種浸提劑分別在不同浸提方式下對重金屬的去除效果,篩選出最佳濃度、處理時間以及超聲功率,并采用Tessier連續(xù)提取法分析檸檬酸浸提前后土壤中四種重金屬形態(tài)的變化。以期為復(fù)合重金屬污染土壤淋洗修復(fù)提供科學(xué)理論依據(jù)。主要研究結(jié)果如下:1.檸檬酸處理對四種重金屬均具有良好的去除效果。無論哪種浸提方式,均是以Zn去除效果最好,Cd效果最差而Cu和Pb效果相當(dāng),但是在低濃度時,Pb去除率低于Cd。無論哪種浸提方式,Pb和Zn去除率均隨著檸檬酸濃度的增加而增加,但增幅隨之減少,Cu的去除率則先增加后基本保持不變,而Cd變化不明顯。2.通過比較檸檬酸浸提前后土壤中重金屬形態(tài)分布的變化,檸檬酸能夠很大程度上改變土壤中重金屬的形態(tài)分布,主要去除以可交換態(tài)和碳酸鹽結(jié)合態(tài)形式存在的Cd以及以碳酸鹽結(jié)合態(tài)和鐵錳氧化物結(jié)合態(tài)形式存在的Cu、Pb和Zn。3.EDTA處理對四種重金屬也具有較好的去除效果。三種浸提方式中Cu和Pb的去除率均高于Cd和Zn。其中以Pb的去除效果最好,去除率高達99%。除了Cd去除率在振蕩浸提中基本保持不變,四種重金屬的去除率變化規(guī)律一致,均是隨著EDTA濃度的增加而呈現(xiàn)出先升高后下降的趨勢。4.從檸檬酸和EDTA處理對Cd、Cu、Pb和Zn四種重金屬的去除率分析得出,檸檬酸和EDTA浸提實驗中最佳振蕩時間均為4 h,最佳靜置時間均為24 h,最佳超聲功率均為500 W和超聲時間均為30 min。綜合考慮成本和去除率后,三種浸提方式中選用0.2 mol·L-1檸檬酸連續(xù)浸提兩次為最優(yōu)條件。而EDTA振蕩浸提和超聲浸提時最佳濃度均為0.03 mol·L-1,靜置浸提時為0.07 mol·L-1。由此可見,在同等去除效果的條件下,應(yīng)用超聲波后,相對于振蕩浸提和靜置浸提,浸提時間大大減少。因此,超聲波輔助浸提土壤中重金屬效果較好,具有一定的應(yīng)用前景。
[Abstract]:Heavy metals mainly come from sewage irrigation, the extensive use of chemical fertilizers and pesticides, the "three wastes" produced by mining and industrial production, municipal solid waste and atmospheric sedimentation, and so on. After heavy metals enter the soil, they can not be degraded by microorganisms, but can only be migrated and transformed. The pollution has the characteristics of concealment, long-term and irreversibility. They pollute water and air, affect the growth of crops and organisms, and endanger human health and life through the food chain. People pay more and more attention to heavy metal pollution in soil. How to repair heavy metal contaminated soil and reduce the harm caused by heavy metal pollution has become an important research content in the field of environmental protection. Among many remediation technologies, soil leaching remediation technology has been paid more and more attention as a rapid and effective remediation technology of contaminated soil. In this study, the soil polluted by Cd,Cu,Pb and Zn near a copper smelting plant in Fuyang, Zhejiang Province was taken as the research object. Three different extraction methods, oscillatory, static and ultrasonic, were used and citric acid and EDTA were used as extractants. The removal efficiency of heavy metals by two kinds of extractants under different extraction methods was studied, and the optimum concentration, treatment time and ultrasonic power were selected. The changes of four heavy metals in soil before and after citric acid extraction were analyzed by Tessier continuous extraction. In order to provide scientific theoretical basis for leaching and remediation of soil polluted by compound heavy metals. The main results are as follows: 1. Citric acid treatment has a good effect on the removal of four kinds of heavy metals. No matter which extraction method, the removal effect of Zn is the best, the effect of Cd is the worst, but the effect of Cu and Pb is the same, but at low concentration, the removal rate of Pb is lower than that of Cd.. No matter which extraction method, the removal rates of Pb and Zn increased with the increase of citric acid concentration, but the increase decreased, the removal rate of Cu increased at first and then remained basically unchanged, but the change of Cd was not obvious. 2. By comparing the morphological distribution of heavy metals in soil before and after citric acid extraction, citric acid can change the speciation and distribution of heavy metals in soil to a great extent. The removal of Cd in the form of exchangeable and carbonate bound states and the treatment of Cu,Pb and Zn.3.EDTA in the form of carbonate bound state and iron manganese oxide bound state also have good removal effect on four kinds of heavy metals. The removal rates of Cu and Pb in the three extraction methods were higher than those of Cd and Zn.. Among them, the removal effect of Pb is the best, and the removal rate is as high as 99%. Except that the removal rate of Cd remained basically unchanged in oscillatory extraction, the removal rate of four kinds of heavy metals changed the same, and all of them increased at first and then decreased with the increase of EDTA concentration. 4. The removal rates of Cd,Cu,Pb and Cd,Cu,Pb by citric acid and EDTA treatment were analyzed. the results showed that the optimum shaking time and static time of citric acid and EDTA extraction were 4 h and 24 h, respectively. The optimum ultrasonic power is 500W and the ultrasonic time is 30 min.. After considering the cost and removal rate, 0.2 mol 路L ~ (- 1) citric acid was selected as the optimal condition for the three extraction methods. The optimum concentration of EDTA oscillatory extraction and ultrasonic extraction was 0.03 mol 路L ~ (- 1), and that of static extraction was 0.07 mol 路L ~ (- 1). It can be seen that under the condition of the same removal effect, the extraction time is greatly reduced compared with the oscillatory extraction and the static extraction after the application of ultrasonic wave. Therefore, ultrasonic assisted extraction of heavy metals in soil has a good effect and has a certain application prospect.
【學(xué)位授予單位】：浙江農(nóng)林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：X53

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