Fabrication of composites with ultra-low chitosan loadings and the adsorption mechanism for lead ions
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RESEARCH ARTICLE
Fabrication of composites with ultra-low chitosan loadings and the adsorption mechanism for lead ions Shuo Ai 1,2
&
Yongchun Huang 1,2 & Tenghui Xie 1,2 & Xiangyu Zhang 1,2 & Chengdu Huang 1,2
Received: 16 April 2020 / Accepted: 26 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Through a facile impregnation–precipitation strategy, chitosan was dispersed on bentonite to prepare an organic/inorganic hybrid composite for Pb2+ adsorption. The strong promotion effect of a small amount of highly dispersed chitosan on the Pb2+ adsorption capacity of clay minerals was unveiled. With a chitosan loading of 0.4 wt%, the experimental adsorption capacity reached 261.3 mg/ g. The good dispersion of chitosan played a crucial role in the high capacity. The large proportion of mesopores in the adsorbent facilitated mass transfer, and thereby adsorption equilibrium states could be achieved within 15 s. The adsorption isotherms were consistent with the Freundlich expression. The Pb2+ adsorption capacity was suppressed with the addition of 150 ppm Ca2+ and almost eliminated in the presence of 150 ppm Mg2+. The adsorption enthalpy change was measured to be − 28.6 kJ/mol and Gibbs free energy change was in the range of − 18.4 to − 16.7 kJ/mol, indicating that this adsorption process was exothermic and spontaneous. The FTIR and XPS results demonstrated that the amino groups on chitosan could bond with Pb2+, and contributed to the high adsorption capacity. DFT calculation results showed that the amino and hydroxyl groups in adjacent chitosan units could be tri-coordinated with Pb2+, and the energy of system was greatly decreased due to the coordination interaction. Keywords Lead . Adsorption . Chitosan . Bentonite . Coordination
Introduction Heavy metal lead causes DNA damage (Kelainy et al. 2019), kidney disease, cancers (Wani et al. 2019), and blood disease (Eguchi et al. 2018). Moreover, lead element is prone to migrate into animals (Korbecki et al. 2019) and crops (Ma et al. 2019). Mines, smelters, lead-acid battery recycling factories, and fuels are dominant lead pollution sources (Brenda et al. 2015; Gottesfeld and Cherry 2011). For instance, an excess of lead was detected around battery factories in China (Liu et al. 2017), the USA (Pichtel et al. 2000), Eastern Europe (Rieuwerts et al. 1999), South America (Paoliello and Capitani 2005), and so forth. Therefore, it is urgent to develop Responsible editor: Tito Roberto Cadaval Jr * Shuo Ai [email protected] 1
Department of Biological and Chemical Engineering, Guangxi University of Science and Technology, Liuzhou City 545006, China
2
Guangxi Key Laboratory of Green Processing of Sugar Resources, Liuzhou City 545006, China
effective techniques for the abatement of Pb2+ pollution in the nature, particularly water environment. The current approaches for Pb2+ pollution elimination include ion exchange (Darwish et al. 2015), adsorption (Eda et al. 2010; Zhu et al. 2017), electrodialysis (Sadrzadeh et al. 2009), membrane filt
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