畜禽粪便/秸秆基复合活性炭对土壤重金属钝化机理的研究

Animal manures-derived biochars which can be applied to remediation of the heavy metals-polluted soil are one means of high value application of manures. In this project, to solve the low BET of biochar based livestock, the highly adsorption, cheap, stable manure-straw based activated carbons will be designed and constructed through activated carbonization of animal manures and straw co-pyrolysis. Furthermore, their interfacial coupling and stabilities could be improved via various adding percent of straw materials. The composition-morphology-performance intrinsic relationship and synergistic effect between manure straw-based activated carbon and heavy metal in soil will be carefully investigated. The transfer and adsorption of heavy metal within manure-straw based activated carbons will also be investigated. The design principal of composition and structure of manure-straw based activated carbons will be developed and proposed by this project. The relationship of composition-structure-heavy metal adsorption and control methods of the composite remediation materials will be revealed during investigating this project. The intrinsic mechanism of the adsorption enhancements in heavy metal will be explained. This is of great significance in promoting the development of adsorption theory and increasing new knowledge of remediation materials production. This investigation will provide new insight into the fabrication of advanced remediation materials and enhance the application of manure straw-based activated carbon in adsorption of heavy metal of soil.

以畜禽粪便、秸秆等为原料的生物质炭因具有吸附重金属离子的特性，已应用于土壤重金属修复领域。项目组前期工作表明，畜禽粪便炭灰分大、表面有氧官能团多，利于对重金属进行化学吸附，秸秆炭比表面积高、孔隙结构发达，利于进行物理吸附。本项目以提高生物质炭对土壤重金属的综合吸附效率为目标，拟采用畜禽粪便与秸秆进行复合，制备高效吸附重金属离子的畜禽粪便/秸秆基复合活性炭，通过研究其组成、形貌、孔隙结构和表面有氧官能团与土壤重金属离子赋存形态的内在关系、协同效应和离子迁移机理，揭示畜禽粪便/秸秆基复合活性炭对土壤重金属离子的钝化机理，掌握组成-结构-重金属离子钝化的构效关系与调控方法，进而阐明抑制重金属生物有效性的机制。本项目的开展将为制备低成本、高吸附性、高稳定性的环境友好型土壤重金属离子钝化剂提供科学依据，并对拓展生物质能源转化与利用途径具有重要意义。

寻找可长期固定重金属的土壤改良剂受到人们的关注。本项目研究了（1）热解温度引起的畜禽粪便/秸秆基的单一/复合生物质炭的官能团演变与重金属吸附性能的构效关系。（2）复合比例引起的畜禽粪便/秸秆基复合活性炭的官能团变化、比表面积与重金属吸附性能的构效关系；（3）畜禽粪便/秸秆基复合活性炭的孔径变化与土壤重金属吸附的构效关系。研究结果包括：（1）鸡粪炭和鸡粪/玉米秸秆复合炭的Cu2+液相吸附性能与热解温度呈正向关系，鸡粪炭在800℃达到Cu2+吸附最高值66.48 mg/g，在200℃为最低值34.74 mg/g；玉米秸秆炭的Cu2+最高吸附值在500℃(28.52 mg/g)；鸡粪炭的Cu2+吸附性能优于玉米秸秆炭，鸡粪/玉米秸秆复合炭的Cu2+吸附性能介中间；鸡粪炭的表面官能团的峰强与热解温度成正向关系，而高温对玉米秸秆与复合物料炭影响较小。（2）按照一定质量比例复合制得鸡粪/玉米秸秆复合活性炭，Cu2+吸附效率与鸡粪（CM）比例含量呈现正向关系，而碘吸附、亚甲基蓝吸附和比表面积与玉米秸秆（CS）比例含量呈现正向关系，对于Cu2+吸附，吸附剂的表面官能团的影响大于比表面积的影响。（3）鸡粪颗粒活性炭、鸡粪/玉米秸秆复合颗粒活性炭、玉米秸秆颗粒活性炭，及对照组微孔、中孔、大孔活性炭作为不同孔径的代表，玉米秸秆活性炭对溶液中Cd2+的吸附效果最好，其次是微孔活性炭，优于鸡粪活性炭、复合活性炭及其它孔径活性炭，表明比表面积和孔径分布对Cd2+的吸附影响大于表面官能团的影响。在土壤淋溶实验中，玉米秸秆活性炭的Cd2+淋出量最低，说明其对土壤中Cd2+的吸附效果最好；其次是微孔活性炭。本项目的研究将为重金属污染土壤的原位修复提供理论和技术依据。