生物炭灰分在Cr(VI)还原中的作用机制研究

Biochars, featured with abundant surface functional groups and high adsorptive capacity, play important roles in reducing and detoxifying Cr(VI) in polluted soils. Currently, studies on the mechanisms of biochar-involved Cr(VI) reduction mainly focuses on the roles of organic functional groups. Whilst the roles of the ashes of biochars in Cr(VI) reduction reactions were still unclear. To answer the scientific question how the ashes of biochars contribute to Cr(VI) reduction, an experimental study is proposed. The roles of ashes as electron donors, electron shuttles and/or catalysts for Cr(VI) reduction will be explored, aiming to elucidate the mechanisms involved in the promotion of Cr(VI) reduction by biochar ashes. It would also be investigated the characteristics of biochar oxidation process and the changes in Cr(VI) reduction reactions under the influences of ashes, aiming to illustrate the mechanisms involved in the sustaining stability of biochar by ashes. The research results would identify main features and key factors in the participation of biochar ashes in Cr(VI) reduction, and reveal the mechanisms involved in the synergic transformation of biochar and Cr(VI). It would be of importance in improving the theoretical understanding of the concerned issue, and also provide with fundamental supports to soil remediation techniques.

生物炭是一种表面基团丰富、吸附能力强的碳质材料，在土壤Cr(VI)还原脱毒中起着重要作用。目前对生物炭在Cr(VI)还原中的作用机制集中关注于其有机基团，而针对无机灰分的作用过程特征及影响因素的认识尚不明晰。本项目拟针对生物炭灰分在Cr(VI)还原中的作用机制这一重要科学问题开展系统研究。通过考察生物炭灰分在Cr(VI)还原中的电子供体作用、电子介体作用和其它促进作用，揭示灰分促进Cr(VI)还原的作用机制；通过考察灰分影响下生物炭氧化的过程特征，阐明生物炭灰分对生物炭抗氧化的作用及机制。预期研究成果将明确生物炭灰分参与Cr(VI)还原的重要过程特征和主控因子，揭示生物炭和Cr(VI)协同转化过程规律及机制，有望对生物炭和Cr(VI)这两类物质转化相互影响的动态过程规律获得新认识，为土壤Cr污染修复治理提供理论指导，具有重要的理论研究价值和实际指导意义。

生物炭是一种表面基团丰富、吸附能力强的碳质材料，在土壤六价铬（Cr(VI)）还原脱毒中起着重要作用，但目前对生物炭中灰分对Cr(VI)的作用过程特征及机制的认识尚不明晰。针对这一重要科学问题，本研究重点聚焦以污泥生物炭为代表的高灰分生物炭作用下的Cr(VI)还原过程，揭示了其自身碱性导致溶液pH上升是制约吸附-还原-固定过程的主控因子，探明了生物炭可介导有机酸与Cr(VI)间的电子传递进而促进对Cr(VI)的还原去除，论证了生物炭-铁间的交互作用均可显著提高对Cr(VI)的还原去除和固定作用，明确了氧化对生物炭还原Cr(VI)的提升作用，高灰分生物炭则有助于抵抗氧化变化，在氧化后其对Cr(VI)的去除能力变化相对较小。基于以上结论，制备了富铁生物炭材料，利用其炭-铁交互作用协同高效去除废水中的Cr(VI)。本研究成果明确了生物炭灰分参与Cr(VI)还原的重要过程特征和主控因子，揭示了生物炭和Cr(VI)协同转化过程规律及机制，有望对生物炭和Cr(VI)这两类物质转化相互影响的动态过程规律获得新认识，为土壤Cr污染修复治理提供理论指导。