摘要
尾矿含有大量的重金属离子,大多数尾矿没有采取处理措施,只是暂时堆存,已经成为矿区重要的污染源,尾砂中重金属元素的释放、迁移,会对附近土壤环境产生重金属污染,进而导致土壤质量下降,生态系统退化,水污染,农作物减产,对当地的环境构成严重的威胁。人们开始重视尾砂矿区的生态修复问题。在国内外研究的基础,本文研究了湖南省铜山岭铅锌矿尾砂重金属在电动技术处理情况下的去除情况,并采用优化的BCR(European Community Burean of Reference)连续提取方法对重金属Pb、Zn、Cu进行形态分析,研究在电动力技术条件下重金属及其各种形态的去除效果。
电动修复技术是国际环境科学和工程领域的前沿课题之一。它的基本机理是:土壤中的水在电场力的作用下发生电解反应,阴极产生氢气和氢氧根离子,阳极产生氧气和氢离子,阳极产生的氢离子在电场和浓度梯度的作用下,向土壤内部迁移和扩散,氢离子在迁移和扩散的过程中,置换和溶解土壤中的重金属污染物,被溶解后的重金属污染物在电场和浓度梯度的作用下,以离子迁移和电渗的方式朝阴极方向定向迁移,从而达到去除土壤污染物的目的。
本文首先进行了电动力技术对尾砂的适应性研究。经过7天的电动实验,结果表明:重金属Pb、Zn和Cu的总去除率分别为26.5%、24.4%和30.7%,其中酸溶态去除效果显著,分别达到47.8%、73.4%和71.3%。Pb和Cu的铁-锰氧化物结合态去除率为30.1%和35.1%,其他形态去除率较低,在8%左右。电动力修复技术适用于铅锌尾砂修复,但由于尾砂pH值影响尾砂中重金属的存在形态,还影响尾砂的电导率,最终影响尾砂重金属的修复效率,因此,必须对修复技术进行改进才能更有效的进行尾砂修复。
在前面研究的基础上,实验II和实验III研究了改进电动技术对尾砂重金属的处理情况,分别采用了中间循环冲洗技术和阴极循环冲洗技术。经过7天的电动实验,实验II结果表明:重金属Pb、Zn、Cu的总去除率分别为40.8%,36.9%和45.1%,此次改进电动技术,重金属的去除率有了明显的提高,与未采用改进电动技术相比,重金属Pb、Zn、Cu的去除率分别提高了14.3%,12.5%和14.4%,其中酸溶态去除效果显著,分别达到62.4%,84.8%和80.8%,与未采用改进电动技术相比,去除率分别提高了14.6%,11.1%和9.5%。其他形态的重金属去除率液略有提高。实验III结果表明:重金属Pb、Zn、Cu的总去除率分别为39.3%,37.3%和50%,重金属的去除率也有了明显的提高,与未采取改进技术相比,去除率分别提高了12.8%,12.9%和19.3%。其中,酸溶态去除效果显著,Pb、Zn和Cu的去除率分别为69.8%,85.8%和83.5%,与未采用改进电动技术相比,去除率分别提高了22%,12.4%和12.2%。其他形态的重金属去除率液也略有提高。
There are many heavy metals in the mine tailings. Most of the tailings have been left without any management. It has become the main source of heavy metal contamination in the mining areas, which including soil substrates contaminated, soil texture destroyed, short of nutrient, ecological landscape destroyed, water pollution and biological diversity decrease。Work should do to restore the ecology on mined areas. Basing on the research ago, The elecrokinetic technique for removing heavy metals in a Lead-Zinc mine tailing was examined. The redistributions of Pb, Zn and Cu were determined using the sequential extraction procedure of the optimized European Community Burean of Reference (BCR) before and after the examination.
Electroremediation technique is an advancing task of global environment science and technology. Its principle is that: application of direct electric current via electrodes immersed in a saturated soil results in oxidation at the anode, generating an acid front that cause desorption and dissolution of heavy metals. The desorped and soluted heavy metals are migrated toward cathode reservoir by electric field and ions concentration grads by the means of electromigration, electroosmosis and diffusing.
Firstly, a series of elecrokinetic technique tests about mine tailings are conducted. The results showed that total removal efficiencies of Pb, Zn and Cu were 26.5%, 24.4% and 30.7% respectively after electroremediation for seven days. The removal efficiencies of acid extraction fraction of Pb, Zn and Cu were 47.8%, 73.4% and 71.3%.The removal efficiencies of Fe and Mn oxides fraction of Pb and Cu were 30.1% and 35.1%. The removal efficiencies of other fractions were only about 8%. The electroremediation technology is efficient to remedy the Lead-Zinc mine tailing. pH value of the soil decreased electro-conductivity of soil, and then reduce remediation efficiency by precipitating of heavy metals. Hence, electroremediation techniques should be enhanced so as to efficiently remove Pb from contaminated red soil.
Secondly, a series of experiments used enhancement elecrokinetic technique are conducted. Experiment II is conducted by the middle recycle washing technology. The results showed that total removal efficiencies of Pb, Zn and Cu was 40.8%,36.9%and45.1% respectively after electroremediation for seven days. Contrasted to experiment I, the removal efficiencies was increased by 14.3 %,12.5%and 14.4%respectively. The removal efficiencies of acid extraction fraction of Pb, Zn and Cu were 62.4% ,84.8 % and 80.8 % . Contrasted to experiment I, the removal efficiencies was increased by 14.6%,11.1%and 9.5%. The removal efficiencies of other fractions of the heavy metals are also increased.Experiment III is conducted by controlling pH value of the cathode reservoir with HAc. The results showed that total removal efficiencies of Pb, Zn and Cu was 39.3%,37.3%and 50% respectively after electroremediation for seven days. Contrasted to experiment I, the removal efficiencies was increased by 12.8%,12.9%and 19.3%respectively. The removal efficiencies of acid extraction fraction of Pb, Zn and Cu were69.8%,85.8%and 83.5%. Contrasted to experiment I, the removal efficiencies was increased by 22%,12.4%and 12.2%. The removal efficiencies of other fractions of the heavy metals are also increased.
引文
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