Enhanced adsorption of anionic dyes from aqueous solution by gemini cationic surfactant-modified diatomite

In this article, gemini cationic surfactant (1,4-butyl-bis (dimethyldodecylammonium bromide))-modified diatomite (GSMD) was prepared originally. Unmodified diatomite (UD) and GSMD were characterized by Fourier transform infrared (FTIR) spectroscopy, thermal analysis (TG) and specific surface area analysis. The adsorptions of anionic dyes methyl orange (MO), Suparalan Red GWN (SR) and Ramazol Blue RGB (RB) from aqueous solution onto UD and GSMD were carried out. The effects of pH, adsorption time, and initial concentration of dyes were also investigated. The results showed that GSMD had much higher adsorption capacity for anionic dye than UD in a broad pH range. The experimental maximum adsorption capacity of GSMD for MO, SR and RB was 9.4, 31.0, and 43.9 mg/g at pH 6.0 and about 13, 13 and 4.5 times of that of UD respectively. Adsorption isotherms showed that the adsorption of three dyes on GSMD followed Langmuir isotherm better than Freundlich isotherm. The effect of the amount of surfactant on adsorption capacity of GSMD and surfactant DTAB modified diatomite (DTAB-D) for MO was also compared, and the mechanism of enhanced dye adsorption capacity on GSMD was proposed.