沸石强化热处理对土壤中铜和锌的固定作用

为研究热处理对土壤中重金属的固定作用,从甘肃白银采集铜和锌污染土壤,研究了好氧和厌氧热处理法及沸石强化热处理法对土壤中铜和锌形态变化的影响。结果表明,与好氧热处理相比,厌氧热处理对土壤中的铜和锌有更好的固定效果,且温度越高固定效果越好。在500℃时,厌氧热处理可使土壤中铜和锌的可氧化态和残渣态之和分别由原土样的31.7%和31.3%提高到93.3%和89.4%。在好氧条件下,在200~450℃范围内,是否添加沸石对土壤中铜和锌的固定效果并无明显影响;而在500℃时,添加沸石处理对重金属铜、锌的固定效果明显提高。在500℃时,与好氧热处理相比,添加沸石强化好氧热处理下铜和锌的弱酸可提取态质量比下降了12.7%和12.1%,而残渣态质量比增加了8.6%和12%。

Immobilization of copper and zinc in the soil through zeolite-enhanced thermos treatment

This article is intended to make an exploration to identify and determine the evolutionary change of the copper and zinc speciation in the course of the heat treatment so as to work out the actual effect of the changes of heat treatment conditions,including those of the enhanced aerobic,anaerobic and zeolite content concentration on the distribution of copper and zinc speciation in the soil. Particularly speaking,what we want to do is to find if the thermal treatment can be used as a promising way to decontaminate and initialize the heavy metal content in the soil,for which purpose we have collected soil samples contaminated by copper and zinc from Baiyin City,Gansu Province. As a result, we have found that the thermal changes in the soil in the form of copper and zinc can be expected to follow the trends over the temperature range under study in a sequential extraction procedure developed by the European Communities Bureau of Reference. As can be found,there exists a fixed stronger effect on the copper and zinc content in the soil under the anaerobic heat treatment condition than under the aerobic heat treating one. Furthermore, it has been found that,the higher the temperature,the better the fixed effect would be under the temperature range of 200-500 ℃. For example,at the high temperature of 500 ℃,it is possible for the anaerobic heat treatment to reach the respective effects of oxidization of copper and zinc residues in the soil by a percentage at about 93. 3％ and 89. 4％ respectively from the 31. 7％ and 31. 3％ of the original soil samples. And,in comparison,under the aerobic conditions,no significant difference can be found with the effect of zeolite fortification on the fixation of copper and zinc in the soil in a temperature range between 200-450 ℃,whereas it is possible to find the fixing effect of heavy metal copper and zinc can be obviously promoted at the temperature of 500 ℃. But,in contrast,in the condition of zeolite enhanced heat aerobic treatment, copper and zinc weak acid extractable content can only be reduced by 12. 7％ and 12. 1％,whereas it would be possible to increase the residual content by 8. 6％ and 12％. On the other hand,with the increase of the thermos treatment temperature,it would be possible to reduce continuously the content of the organic substance in the soil. Therefore,as compared with the anaerobic treatment,greater changes can be found in the organic substances in the aerobic soil with the changes of temperature.