Clickable Synthesis of 1,2,4-Triazole Modified Lignin-Based Adsorbent for the Selective Removal of Cd(II)

Abstract

Development of bioadsorbents for efficient removal of heavy metal ions from contaminated water is of great interest but still challenging. In this study, a 1,2,4-triazole-3-thiol modified lignin-based adsorbent (LBA) was synthesized through a UV-initiated thiol-yne click reaction chemistry for Cd(II) adsorption. The structure of LBA, prepared by thiol-yne addition reaction, was confirmed and characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and elemental analysis. Effects of pH, contact time, initial metal concentration, and temperature on the adsorption of Cd(II) on LBA were studied. Due to multiple thio-triazole units as binding sites, LBA was found to exhibit an adsorption capacity that was 8.6 times that of the raw lignin for Cd(II) adsorption. Pseudo-second-order and Langmuir models were utilized to describe the adsorption kinetics and isotherms, respectively. Furthermore, the study of adsorption selectivity suggested that LBA had high selectivity for adsorbing Cd(II) ions in the presence of other coexisting metal ions in the aqueous solution. The successful synthesis of LBA via a facile thiol-yne click reaction demonstrates a new synthesis method for preparing lignin-based functional materials with modular units and promising adsorption capacity for the removal of heavy metal ions from wastewater.