Adsorption behaviors of modified clays prepared with structurally different surfactants for anionic dyes removal

In this study, the properties and adsorption behaviors of organoclays synthesized with two structurally different surfactants having the same carbon chain length (hexadecyltrimethylammonium bromide (HDTMAB) and benzyldimethylhexadecylammonium chloride (BDHAC)) were evaluated. The structural properties of the synthesized organoclays were examined using Fourier-transform infrared spectroscopy, zeta potential analysis, X-ray diffraction, and N₂ adsorption-desorption test. The modified clays with increased surfactant loadings (from 0.5 CEC to 3 CEC) were prepared to find the optimal surfactant loading. As a result, 1.5 cation exchange capacity (CEC) was found to be the optimal surfactant loading. The organoclay prepared using HDTMAB (H-Bt) exhibited the maximum adsorption capacity of 114.3 mg/g for anionic Orange G dye, which was 1.74 times higher than that of the organoclay prepared using BDHAC (B-Bt). Furthermore, in the presence of a mixture of cationic and anionic dye molecules in water, H-Bt tended to remove more of the cationic target compound than B-Bt (i.e., methylene blue (MB)), suggesting that H-Bt can serve as a more efficient adsorbent for the uptake of environmental contaminants in practical scenarios. Moreover, this study examined the effects of surfactant molecules on the structural properties of organoclays and their adsorption behaviors in the uptake of dye molecules.