Open Access

ARTICLE

Selective Adsorption of Ag(I) from Electronic Waste Leachate Using Modified Silk Sericin

Sijing Zhang^1*, Fengjiao Ao¹, Yongping Wang², Junxue Zhao³, Yongliang Ji¹, Shuangli Chen¹

1 School of Science, Xi’an University of Architecture and Technology, 13 Yanta Road, Xi’an, 710055, China
2 Shaanxi Provincial Academy of Environmental Science, 49 North Changan Road, Xi’an, 710061, China
3 School of Metallurgy Engineering, Xi’an University of Architecture and Technology, 13 Yanta Road, Xi’an, 710055, China

*Corresponding author:

Journal of Renewable Materials 2018, 6(1), 102-116. https://doi.org/10.7569/JRM.2017.634154

Abstract

A novel biosorbent was synthesized by grafting bisthiourea (BTU) on a silk sericin (SS) matrix. This biosorbent was denoted as BTU-SS and characterized by Fourier transform infrared spectroscopy (FTIR), zeta potential measurements, elemental analysis, and X-ray photoelectron spectroscopy (XPS). As revealed by the adsorption experiments, both BTU-SS and SS showed low affinity towards coexisting base metallic ions in Ag(I)-Cu(II)-Zn(II)-Ni(II)-Pb(II) electronic waste leachate mixtures, while their adsorption capacities towards Ag(I) reached 30.5 and 10.4 mg·g–1 at a pH of 5.0, respectively. BTU-SS showed higher selectivity towards Ag(I) than SS, as revealed by the Ag(I) partition coefficients between the biosorbents and the leachate (16634.6 and 403.3, respectively). As further demonstrated by column experiments, BTU-SS allowed the separation of Ag(I) from an electronic waste leachate. Thermodynamic studies showed that the adsorption of Ag(I) was exothermic and spontaneous, while adsorption kinetic experiments revealed that chemisorption dominated the adsorption process with activation energies of 47.67 and 53.27 kJ·mol–1 for BTU-SS and SS, respectively. FTIR and XPS analyses of fresh and Ag(I)-loaded BTU-SS further revealed an adsorption mechanism mainly involving electrostatic and coordination interactions.

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Keywords

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