Preparation and performance of surface-modified adsorbent materials from discarded traditional chinese medicine residues

Abstract

Waste Chinese medicine residue was used as a raw material and pretreated with sodium hydroxide and hydrogen peroxide, followed by chemical modification with a silane to prepare an inexpensive and highly efficient hydrophobic biobased adsorbent material. The adsorbent was characterized with SEM, TGA and FTIR analyses. The adsorption capacities and wettabilities of the Chinese medicine residue were analyzed before and after surface modification to explore the adsorption performance and surface modification mechanism of the material. The results showed that the modified Chinese medicine residue was rough and uniformly modified with successfully grafted hydrophobic functional groups, and it had added adsorption sites exhibiting good hydrophobicities and oleophilicities. The contact angles between the modified materials and water reached 127°, and the modified Chinese medicine residue had an adsorption capacity of 51.7 mg/g for organic compounds, which was a significant improvement over the original waste Chinese medicine residue. The adsorption kinetics were best described with the pseudosecond-order kinetic model, which exhibited a higher linear correlation and was closer to the measured adsorption equilibrium value based on chemical adsorption. This study demonstrated a novel use of waste Chinese medicine residues for environmental remediation.