生物质水热炭可变组分的脱除、硫掺杂改性与土壤重金属（Pb2+）修复研究

Hydrophobic organic compounds, enriched in the surface of biomass based hydrochar, are variable components, which have high environmental risk. In this study, the removal mechanism for variable components of hydrochar will be firstly studied on the basis of hydrochar components characteristic. Accordingly, the environmental benefits promotion of variable components removed-hydrochar (VCRH), and the improvement remediation mechanism of Pb polluted soil by sulfur (S) doped VCRH will be further confirmed in our research. (1) To discern the demethanation trend of hydrochar by solvents desorption, the changes of C, H and O contents of hydrochar in the VK diagram will be carefully illustrated. (2) To expound the mechanism of environmental benefits promotion, the correlations between the DOM toxicity, carbon sequestration potential and Pb adsorption ability of VCRH with the materials characteristics will be determined, respectively. (3) The functional groups in the VCRH for the interaction with S doping will be studied to explain the adsorption mechanism of solution Pb by S doped VCRH. (4) The effects of soil conditions (pH, contents of organic matter and ions), VCRH properties, S doping content on the soil Pb immobilization will be studied. Accordingly, the remediation mechanisms of Pb polluted soil by S doped VCRH could be determined. (5) Lastly, we will assess the plant risks of soil remediated by S doped VCRH. Simultaneously, a technology for the remediation of heavy metal polluted soil by VCRH will be established in this study. A step by step approach to guide research content will be considered. This study is of great scientific significance to extend the sustainable application of hydrochar and technological development for the polluted soil remediation of heavy metal.

生物质水热炭富集的疏水性有机物是可变组分，具有高环境风险。本申请基于水热炭特点，研究水热炭可变组分的脱除机制、脱除可变组分后水热炭的环境效益提升、硫掺杂改性脱除可变组分后水热炭提高Pb污染土壤修复机制。分析溶剂脱除可变组分后水热炭的元素组成在VK图中的变化路径，阐明水热炭的脱甲烷机制；分析脱除可变组分后水热炭的释放DOM环境毒性、固碳能力和Pb吸附性能与材料属性关联，阐明水热炭环境效益提升机制；分析脱除可变组分后水热炭上与硫掺杂成键的官能团，解释硫掺杂水热炭与溶液Pb沉淀的提升固定机制；分析土壤条件（pH、有机质与离子含量），水热炭属性，硫掺杂量对固定Pb的影响，揭示硫掺杂水热炭修复Pb污染土壤的机制；评估硫掺杂水热炭修复Pb污染土壤的生物安全性，建立重金属污染土壤的改性水热炭修复技术。该项目研究内容层层递进，对于拓展生物质水热炭可持续性应用与土壤重金属污染修复技术发展具有重要科学意义。

生物质水热炭富集的疏水性有机物是一种高环境风险的组分，对其可变组分进行脱除不仅有利于减少水热炭的环境风险，也有利于水热炭的活化改性，以提高其对土壤中重金属的去除能力。项目研究发现，生物质水热炭富集的疏水性有机物可以通过溶剂进行脱除以减少DOM的释放。而脱除可变组分后的水热炭则可以通过NaHS对进行硫掺杂改性，以增加其表面的酸性官能团，进而提高材料对Pb污染土壤修复的能力（Pb > 250 mg/g）。在亚临界水热反应体系中，水热液组分是具有宽泛的分子量分布的聚合物。所得的高温水热液不仅在光照条件下能增强对Ag+的还原效果，也能直接消杀环境中的禽流感病毒（H1N1、H5N1和H7N9）和难消杀的芽孢杆菌，具有广谱性。此外，不同重金属污染生物质的水热反应体系中展示出不同的反应路径。生物质的水热产物能促进了As(V)向As(III)的转化，导致液相产物的毒性显著增加；而Cu则会富集在水热炭中（Cu0为主），并获得高附加值化学品（例如乙酰丙酸和乙酸）。项目进一步探究了含氮生物质在活化改性过程中其内源碱金属（如K,Na）与有机氮之间的关系，发现了内源金属易于与有机氮发生络合和碳热还原产生剧毒氰化物（如KCN），增加材料的合成风险。在此基础上，利用含杂原子的塑料废弃物与含氮生物质共热解，可以实现控制生物炭中的MCN生成，减少对生物的毒性效应。此外，通过引入了“一石三鸟”活化剂 KSCN，以实现氧置换反应而产生具有高表面积（1906 m2/g，微孔率≥ 82%）和 N/S 含量的N/S 共掺杂微孔碳材料，展示出优异的甲烷储存性能(0.15 g/g)和水净化能力。本项目研究成果为我国的生物质及其衍生水热炭的改性设计和可持续性应用与重金属污染修复技术的发展提供强有力的技术支撑。