Preparation of high porosity biochar materials by template method: a review

Biochar plays an important role in soil improvement, pollutant removal, and nitrogen reduction. The excellent adsorption performance of biochar is closely related to its pore structure. Therefore, this paper combines a large amount of literatures to investigate the principle and method of preparing carbon materials by using the template method, and the idea of preparing high porosity biochar by template method was proposed. The results show that: (1) The specific surface area of the carbon materials prepared by the template method is more than 400 m² g^-1, and the total pore volume is more than 0.3 cm³ g^-1, which is much higher than the biochar materials prepared under the traditional high temperature anoxic pyrolysis. (2) Compared with the hard template method, a soft template method with simple operation, low toxicity of the compound, and low cost is selected. (3) The lignin, which is also a hydrophilic carbon source similar to phenolic resin, can be used as an ideal carbon precursor. (4) In the selection of templating agents, the specific surface area and total pore volume of carbon materials prepared by using F127 as a template are relatively large, showing more excellent pore size performance. (5) Finally, the idea of using template method to prepare high porosity biochar is proposed: lignin extracted from straw material is used as precursor, block polymer F127 is used as template, an appropriate amount of a cross-linking agent and a solvent is added, and finally the target biochar material is prepared by pyrolysis carbonization.