Adsorptive Removal of Zn(II) from Aqueous Solution Using Fermented Sweet Sorghum Stalk Residues Grafted with Acrylic Acid by Irradiation

Jinling Wu; Jing Dong; Xuan Guo

Abstract

A novel biosorbent was prepared by grafting acrylic acid (AAc) onto fermented sweet sorghum stalk residues (FSSR) via γ-ray radiation for the adsorptive removal of Zn(II) from aqueous solution. FSSR is a typical by-product of bioethanol production, enabling low-cost and sustainable wastewater treatment. To reveal the interfacial interaction mechanism between Zn(II) and the grafted FSSR adsorbent, the Zn species, key surface functional groups, and coordination structure were systematically investigated using X-ray absorption spectroscopy techniques. Results demonstrated that γ-ray radiation effectively introduced abundant carboxyl groups onto FSSR, significantly enhancing its Zn(II) adsorption performance. Extended X-ray Absorption Fine Structure (EXAFS) analysis confirmed that Zn(II) was adsorbed as divalent cations mainly through carboxyl coordination. The coordination number N was 4.2 and a Zn-O atomic distance was approximately 1.93 Å. This work provides a promising strategy for the valorization of agricultural residues and the rational design of high-efficiency biosorbents for heavy metal contaminated water remediation.

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