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磷酸盐预处理后热解对生物质中吸附Pb(Ⅱ)的固定化作用
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摘要
植物修复技术在治理土壤和水体重金属污染方面具有运行成本低、可原位修复、操作安全、环境友好等优势。但是,如何处理富集重金属后的植物修复材料,控制二次污染的发生,已成为制约植物修复技术能否推广应用的瓶颈。本文提出将磷酸盐预处理与热解技术结合,用于处置吸附Pb(II)的生物质,试图将生物质转化为稳定的生物炭同时固定其中所含的重金属。以对Pb吸附能力较强的芹菜生物质为例,经磷酸二氢钙(Ca P)预处理后在350oC热解,可将生物质中的Pb完全转移到炭(Char350)中,DTPA可提取Pb含量由生物质中的68.1%下降到不足5.0%,连续提取分析结果(见Fig.1)表明稳定态(F4、F5)含量显著提高,XRD和SEM/EDX分析表明,炭中的Pb主要以稳定的磷酸盐形式存在。
Remediation of heavy metal contaminated soil and water using plant biomass(namely phytoremediation) is considered to be a green technology,but the harmless disposal of biomass accumulated with heavy metals is a challenge.A potential solution for this problem was proposed by combining phosphate pretreatment with pyrolysis in this work.Pb(II) ions were accumulated in celery biomass with superior sorption capacity.Then the Pb(II)-contaminated biomass was pretreated with monocalcium phosphate(Ca P),and pyrolyzed at 350 oC.In this way,Pb from biomass was almost totally recovered in chars,and the percentage of DTPA-extractable Pb was reduced to less than 5% of total Pb in chars through Ca P pretreatment.Pb(II) immobilization was further confirmed by speciation with a sequential extraction procedure,which indicated that more than 95% of Pb(II) was converted into stable species that composed mainly of lead phosphates according to the XRD and SEM/EDX analyses.
引文

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