Chitosan and surfactant co-modified montmorillonite: A multifunctional adsorbent for contaminant removal

The demands for multifunctional adsorbents are increasing in these days because wastewater may simultaneously contain various types of contaminants. In this work, montmorillonite (Mt) was modified with both hexadecyltrimethylammonium (HDTMA) and chitosan (CTS), with the purpose of synthesizing multifunctional adsorbents that can efficiently adsorb hydrophobic organic contaminants, heavy metal cations, and dyes from water. The structural characteristics of the resulting modified samples (H/C-Mt) were first investigated using XRD, FTIR, TG, and Zeta potential measurements. According to the obtained results, both chitosan and HDTMA were intercalated into Mt interlayers, forming hydrophobic organo-phases. With increasing CTS loading amount, the basal spacing of C/T-Mt gradually increased, and the Zeta potential evolved from negative to positive. C/T-Mt could effectively uptake phenol, Cd2+, Conger red (CR), and crystal violet (CV) from water. The organo-phases created by HDTMA were responsible for the uptake of phenol on C/T-Mt, while the functional groups on CTS (e.g., -OH, -NH2) contributed to the adsorption of Cd2+. The positively charged surfaces of C/T-Mt, together with the hydrophobic interactions between C/T-Mt and contaminants, contributed to the effective uptake of CR on C/T-Mt. As for CV, the hydrophobic interactions should be the main reason for its adsorption on C/T-Mt. The obtained results suggested that C/T-Mt could be a multi-functional adsorbent for the effective uptake of different types of contaminants from water.