Adsorption mechanism of low-temperature air oxidation biochar for benzene pollutants
Biochar is an efficient adsorption carrier for benzene pollutants,but the adsorption capacity of directly carbonized biochar for benzene pollutants is limited.Low-temperature air oxidation is effective in modifying the structure of biochar and enhancing its adsorption capacity of benzene pollutants.However,the adsorption behavior and mechanism of low-temperature air oxidation biochar for benzene pollutants still needs to be further clarified.Herein,low-temperature air oxidation biochar was prepared by a two-step acti-vation method using bamboo chips as raw material and CaCl2 as activator.The adsorption processes and be-haviors of low-temperature air oxidation biochar for four benzene pollutants including phenol,aniline,hy-droquinone,and p-nitrophenol were deeply analyzed with comprehensive adsorption experiments,biochar structure characterization,and density flooding theory(DFT)calculations.The adsorption properties and mechanisms of oxygen-modified biochar for benzene pollutants were studied.The results showed that the adsorption performance of low-temperature air oxidation biochar for benzene pollutants was influenced by the synergistic effect of the pore structure and surface functional groups of biochar.Biochar regulated the ad-sorption and storage process of benzene pollutants at a spatial geometric scale through the pore filling effect of microporous structure.Oxygen atoms were assigned to the surface of the carbon skeleton of biochar in the form of hydroxyl,aldehyde and carboxyl groups after the oxidation of biochar by low temperature air.The electronic structure of the carbon skeleton was influenced by the electronic scale,modifying the adsorp-tion position and type of interaction between the carbon skeleton and benzene pollutants.The adsorption ca-pacities of biochar for benzene pollutants were significantly enhanced through mechanisms such as electro-static attraction and hydrogen bonding.Among them,the hydrogen atoms of the hydroxyl and carboxyl groups in the carbon skeleton are easy to become donors of hydrogen bonds,while the oxygen atoms of the aldehyde group are easy to become acceptors of hydrogen bonds.
biocharlow-temperature air oxidationbenzene pollutantsquantum chemistryadsorp-tion mechanism
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