Individual and simultaneous adsorption of tetracycline and cadmium by dodecyl dimethyl betaine modified vermiculite

Abstract Tetracycline-cadmium combined contaminants have drawn increasing attentions due to their high environmental risk. In this study, vermiculite was modified by dodecyl dimethyl betaine (BS-12) to obtain a kind of organo-vermiculite (BS-VER). After modification, BS-12 was grafted on the surface of vermiculite successfully. Due to the negatively charged head group of BS-12 and improved hydrophobicity of BS-VER, the affinities of BS-VER towards cadmium (Cd2+) and tetracycline (TC) were enhanced. In the single system, the maximum adsorption capacities of Cd2+ and TC on BS-VER increased from 14.98 to 19.72 mg g-1 and from 16.03 to 20.95 mg g-1, respectively. In the binary system, Cd-TC complex was formed and considered to be new adsorption site for Cd2+ adsorption, resulting in slight enhanced adsorption capacity of BS-VER towards Cd2+ and TC. Ion exchange, electrostatic attraction, hydrophobic interaction and chelation reaction were the main mechanisms. BS-VER exhibited good advantages in the simultaneous removal of heavy metals and organic contaminants.