典型重金属修复植物亚临界水热液化反应过程中的重金属释放机制与催化效应

Nowadays, more and more heavy metal phytoremediating plants need to be environment-friendly disposed, due to increasing heavy metal pollution of soil and wide attention on phytoremediation technology for its unique advantages. However, as far as we know, little information is available about hydrothermal liquefaction of heavy metal phytoremediating plants in sub-critical water. In this study, the typical heavy metal phytoremediating plants (sedum plumbizincicola) will be disposed by hydrothermal liquefaction in sub-critical water. The main objectives of the research are to investigate the release mechanism and catalytic effect of heavy metal (Zn/Cd/Cu/Pb). To obtain the controlling factor and release mechanism for heavy metal releasing from plants, the effect of conditions of hydrothermal liquefaction on the removal efficiency of heavy metal will be first studied. Accordingly, changes of fraction distribution, valence and crystal composition of residual heavy metal in solid products will be simultaneously explored. The characterization of liquefaction products (such as the yields of reducing sugar and bio-oil, the concentrations of high value-added chemicals, the properties of solid product and compositions of gas), derived from the sedum plumbizincicola with different pollution loads will be determined. Meanwhile, the effect of released heavy metal (Zn/Cd/Cu/Pb) on the hydrolysis, degradation and polymerization reaction of plant compositions will be explained. Thus, the catalytic effect of released heavy metal on the hydrothermal liquefaction of plant will be received. This study is of great scientific significance to extend the resource utilization of heavy metal phytoremediating plants.

我国重金属污染土壤日趋严重，植物修复以其独特的优势受到关注，进而越来越多的重金属修复植物需要环境友好地处置。然而，重金属修复植物的亚临界水热液化利用研究甚少。本申请拟采用亚临界水热液化反应转化典型重金属修复植物（伴矿景天），阐明植物体内携带污染重金属（Zn/Cd/Cu/Pb）的释放机制及溶出金属的催化效应。通过分析水热液化反应条件对植物体内携带污染重金属的释放效率及固相产物中残余重金属形态、价态及晶体组分变化的影响，揭示植物体内携带污染重金属的释放控制因子及释放机制。项目还将基于不同污染水平及单个金属污染的伴矿景天的液化反应产物特征（还原糖产率、生物油产率、高附加值化学品浓度、固相产物属性及气体产物组分），揭示溶出金属（Zn/Cd/Cu/Pb）对植物组分的水解、分解与再聚合反应的影响，阐明溶出金属对植物水热液化反应的催化效应。该项目对于拓展废弃重金属修复植物的资源化利用具有重要的科学意义。

重金属污染土壤修复的日趋重视，促使了重金属修复植物的环境友好型资源化利用处置技术的更快发展。项目以重金属Zn修复场地的伴矿景天修复植物和盆栽培养不同浓度重金属Pb富集的盐肤木修复植物为研究对象，研究修复植物体内重金属在亚临界水热条件下的释放机制、形态转换与风险评价，以及对植物成分的催化效应。（1）在低温水热条件下（220 °C），伴矿景天植物体内90%的锌能够释放至溶液，且体内残留的锌转化至残渣态，降低了环境风险；固相易活化至多孔炭材料，活化材料孔隙率显著与水热温度相关；溶出的Zn2+催化纤维素水解，高分辨质谱结果指示Zn2+促进液化产物裂解，并促进呋喃类物质转化为乙酸，乙酸浓度的增加有利于修复植物体内重金属的溶出。（2）培养了不同重金属Pb的盐肤木，探究了植物体内重金属对其释放和液相产物的影响；释放至溶液中Pb催化盐肤木产甲酸、乙酰丙酸和乙酸，酸浓度显著相关于Pb浓度；释放至溶液中的Pb催化纤维素水解为葡萄糖，葡萄糖进一步脱水产生5-HMF，5-HMF可以氧化产生乙酸，或通过脱水产生乙酰丙酸和甲酸。