Preparation of organobentonite by a novel semidry-method and its adsorption of 2,4–dichlorophenol from aqueous solution

• Semidry-method consumes shorter reaction time and less energy than.
• HDTMA-modified bentonite exhibited 97.0% removal efficiency to 2,4-dichlorophenol.
• There existed smaller and more separated lamella in HDTMA-modified bentonite.
• The Zeta-potential of HDTMA-modified bentonite was transformed to positive.
• The D50 of HDTMA-modified bentonite was found to decrease from 8.2 μm to 4.8 μm.

In this study, we report to prepare six modified inorganic mineral materials, including bentonite, attapulgite, montmorillonite, kaolinite and diatomite, in a novel semidry-method. Compared with traditional wet-method, this semidry-method requires fewer procedures and, thus, consumes shorter reaction time and less energy. In addition, the modified materials were found to have larger surfactant concentrations, which could result in higher removal efficiency to organic contaminants. Among these six materials, the modified bentonite (organobentonite) performed the best adsorption efficiency to 2,4-dichlorophenol (2,4-D) from aqueous solution and the removal efficiency reached 97.0%. Among four surfactants, hexadecyltrimethylammonium (HDTMA), a cationic and long hydrophobic tail surfactant, was found to be the most efficient modifier. Compared with raw bentonite, the removal efficiency of 2,4-D by HDTMA-modified bentonite (HDTMA-Bent) was enhanced up to more than 40%. The characterizations of raw bentonite and HDTMA-Bent indicated that there were smaller but more separated lamella in the HDTMA-Bent and the basal spacing could be enlarged by 128% as HDTMA inserting into the interlayers of bentonite. After being modified by HDTMA, the Zeta-potential of bentonite was transformed from negative to positive, and this variation of Zeta-potential was also consistent with the change of 2,4-D removal efficiency.