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| Effects of NaHCO3 pretreatment on the properties and phosphorus adsorption capacity of biochar |
| Received:August 01, 2023 |
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| KeyWord:adsorption of phosphorus on biochar;NaHCO3 pretreatment;surface characteristic;pore structure;polar functional group |
| Author Name | Affiliation | E-mail | | MENG Xiangzhi | College of Ecology and Environment, Southwest Forestry University, Kunming 650224, China | | | YUAN Jie | College of Ecology and Environment, Southwest Forestry University, Kunming 650224, China | | | WANG Keqin | College of Ecology and Environment, Southwest Forestry University, Kunming 650224, China | | | HOU Lei | College of Ecology and Environment, Southwest Forestry University, Kunming 650224, China | houlei_1985@126.com |
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| Abstract: |
| In order to explore the effect of NaHCO3 pretreatment on the properties of different types of biochar and its phosphorus（P） adsorption capacity, the differences in the surface characteristics and pore structures of three types of biochar including straw, shell or kernel, and other types before and after NaHCO3 pretreatment were compared by using elemental analysis, photoelectron spectroscopy, pore size analysis, and scanning electron microscopy. The mechanisms of biochar properties affecting P adsorption were discussed based on the adsorption isotherms and related fitting results of Freundlich and Dubinin-Radushkevich models. The results showed that：After NaHCO3 pretreatment, the specific surface area and pore volume of all types of biochar were increased by 2.70%-110.84% and 1.42%-123.80%, respectively. The aromaticity（C=C）of biochar was increased with H / C increased by 5.56% - 29.41%, whereas the contents of polar functional groups（C—O and C=O）were decreased with polar index（O+N）/C decreased by 13.18%-46.34%. The release amount of P from pristine biochar ranged from 78.33 mg·kg-1 to 568.33 mg·kg-1. NaHCO3 pretreatment significantly increased the adsorption capacity of P to all types of biochar, which showed similar affinities with adsorption coefficient of Freundlich, which ranged from 119 mg1-n·Ln·kg-1 to 254 mg1-n·Ln·kg-1. Furthermore, physical adsorption was the dominant effect based on the fact that all the adsorption-free energy ranged from 5.85 kJ·mol-1 to 7.29 kJ·mol-1. The contribution of biochar surface characteristics to P adsorption capacity outweighed that of pore structure, in which the content of C O group was the key factor. This study indicated that NaHCO3 pretreatment could significantly increase P adsorption capacity of biochar through moderately changing its properties and is an alternative pretreatment approach for the environmental application of biochar. |
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