Abstract
Two novel adsorbents (LDH@GO-NH2 and LDH@GO-SH) were successfully synthesized by grafting thiol- or amino-functionalized GO onto LDH and their adsorption capacities for heavy metal ions (Cu(II) and Cd(II)) were significantly enhanced. Characterization experiments illustrated that the thiol group (-SH) or amino group (-NH2) was grafted onto LDH@GO-NH2 or LDH@GO-SH. Adsorption isotherms were satisfactorily fitted by both Langmuir and Freundlich models. The maximum adsorption capacity of Cd(II) on LDH@GO-SH at 308 K was 102.77 mg/g, which was about triple that of LDH@GO-NH2. The enhancement in adsorption capacity of LDH@GO-SH was due to the cooperative effect of LDH and GO-SH. The kinetic experimental data for LDH@GO-NH2 and LDH@GO-SH were found to be in good agreement with the pseudo-second-order model. The thermodynamic parameters calculated from the temperature-dependent adsorption isotherms indicated that the adsorption was spontaneous and an endothermic process.The possible adsorption mechanisms comprising formation of precipitation, isomorphic substitution of Mg(II), and formation of complexation with amino groups or thiol groups were proposed. Desorption experiments put into evidence that LDH@GO-NH2 and LDH@GO-SH may be promising suitable candidates for the remediation of metal ions from aqueous solutions in real work in the near future.
Highlights
Heavy metal contamination is one of the most pressing environmental concerns, affecting human health, water resources, and ecosystems
Two novel adsorbents of thiol- and amino-functionalized grapheme oxide (GO) grafted onto LDH (LDH@GO-NH2 and LDH@GO-SH) were synthesized and contrasted for adsorption properties for Cu(II) and Cd(II)
Characterization experiments illustrated that thiol group (-SH) and amino group (-NH2) were existed onto LDH@GO-NH2 and LDH@GO-SH
Summary
Heavy metal contamination is one of the most pressing environmental concerns, affecting human health, water resources, and ecosystems. Chemical modification by introducing distinct functional groups to bring new and improved physical and chemical traits is of interest Several functional groups such as amino (Ge &Ma. 2015), thiol (Yantasee et al 2007, Yari et al 2015), carboxyl and hydroxyl (Zhao et al 2017) can anchor metal ions to form stable metal complexes through a coordinate bond (Khadivi et al 2019, Tang et al.2018). 2015), thiol (Yantasee et al 2007, Yari et al 2015), carboxyl and hydroxyl (Zhao et al 2017) can anchor metal ions to form stable metal complexes through a coordinate bond (Khadivi et al 2019, Tang et al.2018) Introducing these functional groups would modify the chemical composition of the adsorbents and produce enhanced adsorption capacities (Soltanzadeh et al 2013). The regeneration performance of the prepared adsorbents was tested by 0.1 M MgCl2
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