Skic Kamil, Adamczuk Agnieszka, Gryta Angelika, Boguta Patrycja, Tóth Tibor, Jozefaciuk Grzegorz
Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4 str, Lublin, 20-290, Poland.
Research Institute for Soil Sciences, Centre for Agricultural Research, HUN-REN, Fehérvári út 132-144, Budapest, Hungary.
Sci Rep. 2024 Dec 5;14(1):30362. doi: 10.1038/s41598-024-81030-9.
Nitrogen adsorption isotherms, along with the BET model for interpretation, are recommended for estimating biochar surface area. The frequently measured small surface areas of biochars contrast with their high sorption and cation exchange capacities. We hypothesised that water adsorption provides a better tool for estimating the surface area of biochars. Although adsorption energy also appears to be a valuable surface characteristic, there is a lack of studies on this subject. We studied the surface areas and adsorption energies of three waste deposits - peat, willow dust and biochar prepared from these materials at different temperatures - using nitrogen and water vapour adsorption isotherms. The BET model accurately described all water vapour adsorption isotherms but failed for some nitrogen isotherms. Alternative methods for estimating surface areas and adsorption energies were proposed in cases where the BET model did not apply. Nitrogen adsorption was typically much lower than water vapour adsorption, and the estimated surface areas reflected this. However, nitrogen adsorption energies were significantly higher. Nitrogen surface areas increased with pyrolysis temperature, while water vapour surface areas decreased. The surface area estimated from nitrogen adsorption was generally much lower than needed to accommodate the surface-charged groups responsible for the cation exchange capacity of biochars.
推荐使用氮吸附等温线以及用于解释的BET模型来估算生物炭的表面积。生物炭经常测得的小表面积与其高吸附和阳离子交换容量形成对比。我们假设水吸附为估算生物炭的表面积提供了更好的工具。尽管吸附能似乎也是一种有价值的表面特性，但关于这一主题的研究较少。我们使用氮和水蒸气吸附等温线研究了三种废弃物——泥炭、柳树屑以及由这些材料在不同温度下制备的生物炭——的表面积和吸附能。BET模型准确地描述了所有水蒸气吸附等温线，但对一些氮等温线不适用。在BET模型不适用的情况下，提出了估算表面积和吸附能的替代方法。氮吸附通常远低于水蒸气吸附，且估算的表面积也反映了这一点。然而，氮吸附能显著更高。氮表面积随热解温度升高而增加，而水蒸气表面积则减小。由氮吸附估算出的表面积通常远低于容纳负责生物炭阳离子交换容量的表面带电基团所需的表面积。
