生物炭中溶解性炭黑对重金属迁移的影响

Biochars have attracted a great deal of research attention because of their wide applications. Dissolved carbon black (DB) from biochars has significant mobility after the application of biochars in the environment. The expected strong interactions between DB and heavy metals may enable DB as an effective carrier for heavy metal transport. Thus, the interactions between DB and heavy metals are the key for understanding the environmental functions of biochars. The characteristics of DB are determined by the raw materials of biochars as well as the geochemical processes during their release, for example, the biotic and abiotic degradation process. However, DB characteristics as affected by their source and geochemical processes were not extensively studies, let alone the persistent release kinetics of DB from biochars. The potential impact of DB on heavy metal behavior, with the emphasis on biochar immobilization of heavy metals, could not be properly evaluated. The interaction mechanisms between DB and heavy metals remains largely unexplored. In this study, biochars will be prepared from different materials, including different sources of agricultural solid waste and biomass model compositions (cellulose and lignin). The pyrolysis temperature varies in the range of 200-600 oC. DB will be extracted from these biochars and characterized using Raman spectroscopy, elemental analysis, and Fourier Transform Infrared Spectrometer. The relationship between DB and the parent material properties will be discussed. Chemical degradation experiments will be conducted for various biochars. DB release kinetics as well as the their property change will be analyzed. A kinetics release model will be established for DB release during biochar degradation. Meanwhile, the interactions between DB and heavy metals will be systematically studied. DB-heavy metal interactions controlled by DB properties will be highlighted. Combining DB characterization work, the role of DB in heavy metal immobilization by biochars could be evaluated. A full evaluation of biochar functions in heavy metal sequestration as affected by DB is thus possible. This work will provide important information to speculate biochar persistence as well as their environmental implications after their application.

生物炭的广阔应用前景吸引了研究者的广泛关注，其中的溶解性炭黑（DB）具有显著的流动性，DB作为一种高效的吸附载体对污染物迁移的影响显著，是了解生物炭环境效应的关键。DB不仅受生物炭母质影响，亦会在生物和非生物过程中发生不同程度降解，性质发生变化。遗憾的是，DB的溶出及其持续性产生对生物炭-重金属相互作用的影响尚未深入研究。本研究拟用不同源的生物质制备生物炭，研究其中DB的性质与生物炭性质的关联性，并用化学氧化模拟生物炭的老化，结合全样化学分析描述DB的性质及其在降解过程中的动态变化，尝试定量描述DB的持续溶解释放。在此基础上，研究DB与重金属的相互作用机制，以及DB的释放对重金属行为的影响，这一过程可能降低生物炭对重金属的固定/钝化。本研究将为系统认识生物炭的环境效应提供重要的基础信息，有助于全面评估DB影响下生物炭在环境修复中的功能。

生物炭中的溶解性炭黑（DB）作为一种高效的吸附载体对污染物迁移的影响显著，是了解生物炭环境效应的关键。本研究以玉米秸秆和松木为原料制备生物炭，研究其老化过程中DB的释放及其与重金属的相互作用机制。研究结果表明：.（1）DB芳香性较低，主要由类腐殖酸构成。玉米秸秆含有相对较高的纤维素，其DB产率高于松木生物炭。随热解温度升高，DB产率不断降低，芳香性降低而极性增强。老化生物炭所释放DB（ADB）主要由类腐殖酸及类富里酸组成。老化玉米秸秆生物炭DB（ACD）产率高于松木生物炭DB（AWD），这与玉米秸秆含有相对较多的纤维素有关。ACD较AWD的芳香性和极性更强。随着热解温度升高，ACD和AWD的亲水性和芳香性均有所增强。.（2）玉米秸秆生物炭对铜离子的吸附量高于松木生物炭。热解温度≤400 °C生物炭中的羧基、羟基官能团与铜的络合有效促进了其对铜离子的吸附。DB释放导致生物炭表面含氧官能团含量减少从而使其对铜的吸附量降低。老化玉米秸秆生物炭对铜离子的吸附量高于老化松木生物炭。老化生物炭中的羧基、羟基官能团与铜的络合有效促进了其对铜的吸附。老化过程中DB释放，使老化生物炭表面吸附位点增加以及孔隙结构更为丰富使其对增大铜离子的吸附量增加。.（3）DB富含脂肪族官能团，芳香族和烷氧基官能团很少，酚羟基官能团与铜离子能够很好发生络合作用。玉米秸秆生物炭中DB（CDB）较松木生物炭中DB（WDB）含有更多类富里酸和类腐殖酸为其与Cu(II)的络合提供了结合位点，从而使其络合稳定常数高于WDB。随着热解温度的升高，ADB所含类腐殖酸组分会逐渐分解成分子量较小的类富里酸，提供更多的结合位点，增强DB与铜离子的络合能力。ACD由于具有较强的极性和较丰富有机质组分，其与铜离子的络合稳定常数及结合容量均大于AWD。.本研究将为系统认识生物炭的环境效应提供重要的基础信息，有助于全面评估DB影响下生物炭在环境修复中的功能。