Adsorption Mechanism and Structure-Performance Relationship of Chromium Ions by Biochar
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Adsorption Mechanism and Structure-Performance Relationship of Chromium Ions by Biochar Menghong Li & Xiaoli Guo & Ying Wei & Aiju Liu & Jie Lu & Xiaoyin Niu & Yanfei Ma & Shuang Li & Zhenxiao Shang & Xinpeng Liu
Received: 16 April 2020 / Accepted: 22 September 2020 # Springer Nature Switzerland AG 2020
Abstract In order to further explore the adsorption mechanism of chromium ion by biochar, organic components (OCs) and inorganic components (ICs) of biochar (RC) were prepared, and adsorption experiments of chromium ions by these types of carbon (RC, OC, IC) were performed. The three types of carbon were characterized before and after adsorption of chromium ions, using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Boehm titration, and zero charge (pHpzc). Results showed that the adsorption efficiency of IC on trivalent chromium (Cr3+) was the strongest, ion exchange of Cr3+ with metal cations present on IC being the main adsorption mechanism, accounting for 61% of the total adsorption capacity. Among the metal ions, K+ accounted for about 51%. The REDOX between Cr3+ and carboxyl accounted for 20% of the total adsorption capacity. Other adsorption mechanisms, such as chelation between Cr3+ and carboxyl, and co-precipitation between Cr3+ and carbonate, occupied a small proportion. OC showed the largest adsorption capacity to hexavalent chromium (Cr6+). The adsorption mechanism of OC to Cr6+ was the result of combined actions, such as electrostatic attraction, and REDOX between Cr6+ with the aromatic π-conjugated system and reductive functional groups like hydroxyl. Among them, the REDOX accounted for 53% of the total adsorption of Cr6+ by OC. M. Li (*) : X. Guo : Y. Wei : A. Liu : J. Lu : X. Niu : Y. Ma : S. Li : Z. Shang : X. Liu College of Resources and Environmental Engineering, Shandong University of Technology, Zibo 255000 Shandong, China e-mail: [email protected]
Keywords Biochar . Chromium . Adsorption mechanism . Structure-performance relationship
1 Introduction Biochar, a carbon-rich, solid by-product of biomass pyrolysis under oxygen-limited conditions is an environmentally functional material that has received special attention in recent years (Huang et al. 2019; Qiu et al. 2019). Because of its special structures and properties, biochar has shown great application potential in soil amelioration, carbon sequestration, and environmental pollution remediation (Khorram et al. 2018; Mandal et al. 2016). Biochar has been proven to be an effective adsorbent for organic pollutants and heavy metal removal, due to the abundant pore structures and large number of surface functional groups, such as carboxyl and hydroxyl (Niazi et al. 2018; Inyang et al. 2016; Zhang et al. 2016; Yan et al. 2017). Biochar is a highly heterogeneous material, composed of inorganic minerals (ash) and organic carbon, both of which may play important roles in the adsorption process. For example, inorganic minerals showed a very big contribution towards the binding of metal cations, and organi
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