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.

Magnetic zeolite imidazole framework material-8 as an effective and recyclable adsorbent for removal of ceftazidime from aqueous solution

Zeolitic imidazolate framework-8 (ZIF-8) was synthesized by solvothermal method and the adsorption pore size was adjusted by changing the amount of template agent. The ZIF-8@SiO₂@Fe₃O₄ derived from self-assembly of ZIF-8 and SiO₂@Fe₃O₄ were then synthesized and used for ceftazidime (CAZ) removal. ZIF-8 was a regular dodecahedral particle with uniform particle size. The pore diameter was 6.47 nm and the specific surface area was 1182.5 m²·g^-1 in ZIF-8@SiO₂@Fe₃O₄. The adsorption of CAZ on ZIF-8@SiO₂@Fe₃O₄ as a function of adsorption temperature, contact time, ionic strength solution pH, and humic acid concentration were investigated. The error of equilibrium adsorption capacity between model fitting and actual experiments is only 1.19%. Kinetics for CAZ removal on ZIF-8@SiO₂@Fe₃O₄ was found to follow pseudo-second-order kinetics. Langmuir, Freundlich and Sips isotherm fitted the adsorption data well and gave similar correlation coefficients, suggesting a single layer adsorption of CAZ on ZIF-8@SiO₂@Fe₃O₄. The ZIF-8@SiO₂@Fe₃O₄ showed no apparent loss in CAZ adsorption after five cycles. These features indicate that the ZIF-8@SiO₂@Fe₃O₄ may be a promising adsorbent for CAZ removal from aqueous solution.