Study on adsorption performance of gemini carboxylic betaine modified clay for dyes

Abstract

To enhance the adsorption of organic pollutants by clay materials, two types of organic clay adsorbents were prepared by modifying vermiculite(Vt) and silica lamella(SL) with gemini carboxylic betaine〔1, 2-bis(N-methyl-N-carboxymethyl-tetradecylammonium)ethane, MCTA〕 surfactant as modifier. The effects of modifier addition, contact time, initial pH, dye concentration, and temperature on the adsorption performance were investigated using chrysoidine G(CG) as the adsorbent. The results showed that compared with unmodified Vt and SL(23.70 mg/g and 10.56 mg/g), the adsorption capacities of modified MCTA-Vt and MCTA-SL for CG(131.13 mg/g and 58.14 mg/g) were significantly increased. The adsorption mechanism included hydrophobic interactions of alkyl chains,electrostatic interaction of carboxyl functional groups and electron transfer between molecular orbitals. It was shown that using MCTA as modifier could not only provide hydrophobic long chains for clay to improve its hydrophobicity and increase its adsorption capacity for organic pollutants, but also endow clay with N+ cations and —COO- anion functional groups as new adsorption sites, thereby improving the adsorption capacity of clay.

Keywords

• gemini carboxylic betaine
• vermiculite
• silica lamella
• chrysoidine g
• adsorption performance