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T-MAC3808(金币+40):第三段的,呵呵。不错,我再改改专业词就ok 2010-11-14 15:36:25
Recently, with the development of industry and agriculture, more and more wastewaters containing heavy metals was discharge into water bodies, such as rivers and lakes, polluting the bottom slit of water. Heavy metals is one sort of the most common pollutants in environment and a threat to human health and the environment due to the toxicity, non degradability and food chain enrichment. The secondary pollution could be introduced by the heavy metals depositing in the sediments and then releasing into the water bodies owning to the interference of external factors. In this study, the physi-chemical properties, content, existed forms of zinc and lead heavy metals in Xiawan silt was deternined and the corresponding dynamic release process was studied. In addition, the influence of pH value and organic acids on the release of two metals was investigated for the purpose of understanding the release mechanism and developing the related control measures.
In the paper, the dynamic process of zinc and lead heavy metals in silts and the influence of pH value, organic acids on release of two metals were investigated by the static flask experiment. It was shown that the sediment zinc, lead release kinetics could be well described with the exponential equation, Elovich equation and the second order kinetic equation. The capbility of different salts to leach heavy metal decreases as follows, KCl> KH2PO4 ≈ NaNO3. In addition, pH value of zinc and lead exhibited important influence on the release of two metals. The decrease of pH value is advantageous to the release process. Namely, such process could be speeded under acidic conditions and is dependent on the types of heavy metals and sediments. Three organic acids with low molecular weight were utlized to leach the Zn and Pb of two silts. The ability of three acids for leaching zinc was as follows, citric acid> malic acid> tartaric acid, while the ability to leach Pb, decrease in the order, citric acid> tartaric acid> malic acid. Furthermore, with the increase of organic acid concentration, the release amount of Zn and Pb increases and the release of Zn was superior to that of Pb. In addition, with the same organic acids, the Zn and Pb metals of the 1 #silt are easier leached than those of 2 # silt. |
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