The influence of heavy metal combined forms of sludge on the heavy metal removing efficiency by chemical extraction

• Main Authors: Hao-Ting Chien, 簡豪挺
• Other Authors: Ming-Muh Kao
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/97378370903373503646

碩士 === 國立成功大學 === 環境工程學系碩博士班 === 90 === The production of hazardous heavy metals sludge in Taiwan has reached 320,000 tons per year. Sludge disposal methods of solidification and landfill is irrelevantly, the future trend presented showing recycle and reuse. This research try to use acid or chelating agent to remove heavy metals from sludge and evaluate the influence of form of heavy metal by sequential continuous extraction on the extract efficiency. The biological toxicity test before and after acid or chelating agent of sludge were evaluated, too. Sludge sampled from electroplating、leather、iron-steel and materials manufacturing industry, the results of sequential continuous extraction indicated that heavy metals fractions were significantly different. Heavy metals in sludge existed as the forms of carbonate fraction, Fe-Mn fraction and residue fraction mostly. The mobile of heavy metals is not high because pH of sludge is above 7. For the extraction experiments, the results indicated that 0.1N HCl was more effective extract to carbonate fraction,61%~90% carbonate fraction of electroplating and leather sludge was extracted, but only 1.6%~13.8% carbonate fraction of iron- steel and materials sludge was extracted because of solution pH was neutralized. When HCl concentration was increase to 1N, carbonate fraction, Fe-Mn fraction and residue fraction was extracted to 100%, 56%~91% and 0%~20%, respectively. EDTA and DTPA was more effective extract to carbonate fractions independent of pH but could not extract completely because of reagent strength was not enough. Sludge toxicity evaluation results show that root elongation was more sensitive than seed germination, the raw sludge cause inhibition on the root length growth because EC was higher. After HCl treatment, although total metal concentrations in sludge were decreased but lower pH and residual niclel、copper content cause root length growth is worse. After EDTA and DTPA treatment, seed germination and root growth conditions were better than HCl treatment form because of chelators pH value were near 7.0 .