Covalently linked mercaptoacetic acid on ZrO2 coupled cellulose nanofibers for solid phase extraction of Hg(ii): experimental and DFT studies

Abstract

Zirconium oxide (ZrO₂) nanoparticles were introduced onto cellulose nanofibers after being covalently functionalized with mercaptoacetic acid. We experimentally demonstrate that the nanocomposite is capable of selectively capturing Hg(II) from aqueous samples down to trace level concentrations. Density functional theory (DFT) calculations indicate that energetically favorable R–S → Hg ← O–R bidentate complex formation enhances the rapid adsorption, leading to selective extraction of Hg(II). Furthermore, the loss of ZrO₂ particles during flow-through studies is controlled and restricted after binding to CNF rather than being used directly in the column. The Hg(II) selectivity is primarily due to the Lewis soft–soft acid–base chelation of Hg(II) with the mercapto functionalities of the adsorbent. The experimental observations depict a high sorption capacity of 280.5 mg g⁻¹ for Hg(II). The limit of detection and quantification of the proposed approach were found to be 0.04 μg L⁻¹ and 0.15 μg L⁻¹, respectively. Analytical method accuracy and validity were determined by analyzing Standard Reference Materials and by the standard addition method (recovery > 95% with a 5% RSD). The findings of a Student's t-test were found to be lower than the critical Student's t value. Real water samples were successfully analyzed using the developed procedure.