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Formation and Physicochemical Characteristics of Nano Biochar: Insight into Chemical and Colloidal Stability

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journal contribution
posted on 24.08.2018, 00:00 by Guocheng Liu, Hao Zheng, Zhixiang Jiang, Jian Zhao, Zhenyu Wang, Bo Pan, Baoshan Xing
Nano biochar (N-BC) attracts increasing interest due to its unique environmental behavior. However, understanding of its formation, physicochemical characteristics, and stability of N-BC is limited. We therefore examined N-BC formation from bulk biochars (B-BCs) produced from peanut shell, cotton straw, Chinese medicine residues, and furfural residues at 300–600 °C. Carbon stability and colloidal processes of nano peanut shell biochars (N-PBCs) were further investigated. N-BCs formed from pore collapse and skeleton fracture during biomass charring, breakup due to grinding, and sonication. Amorphous fraction in B-BCs was more readily degraded into N-BCs than graphitic component. The sonication-formed N-PBCs contained 19.2–31.8% higher oxygen and fewer aromatic structures than the bulk ones, leading to lower carbon stability, but better dispersibility in water. Heteroaggregation of N-PBCs with goethite/hematite destabilized initially and then restabilized with increasing concentrations of N-PBCs. Compared with stacked complexes of N-PBCs-hematite, the association of goethite with N-PBCs could form interlaced heterostructures, thus shielding positive charges on goethite and causing greater heteroaggregation. These findings are useful for better understanding the formation of N-BCs and their environmental fate and behavior in soil and water.