Adsorption characteristics, isotherm, kinetics, and diffusion of modified natural bentonite for removing the 2,4,5-trichlorophenol

• Treatment of the raw bentonite with sulfuric acid provides a great surface area.
• Acid-bentonite was exchanged with different alkyl chain surfactants.
• Adsorption of the TCP onto the obtained acid-organo-bentonite was studied.
• Adsorption capacity of the obtained acid-organo-bentonite is very high.
• Acid-organo bentonite is a very good and low cost material for water purification.

Adsorption of the 2,4,5 trichlorophenol (TCP) from aqueous solution onto the surface of organo-bentonites was investigated spectrophotometrically. Natural bentonite was activated with sulfuric acid at 90 °C and exchanged with a set of 4 alkyltrimethylammonium bromides (alkyl = C12, C14, C16 and C18) to evaluate the effect of carbon chain length on the TCP adsorption. X-ray diffraction was used to study the change in the structural properties of the samples. The basal spacing of the activated-bentonite (AB) increased from 13.4 to 21.5 Å by intercalation of the cationic surfactants in the interlayer space of the clays. The intercalated cationic surfactants were characterized by Fourier transform infrared spectroscopy (FTIR). The surface areas of organo-bentonites were found to be much lower than that of AB. The contact time on the adsorption process was studied and the adsorption of TCP onto organo-bentonites followed pseudo-second-order kinetics. Adsorption isotherms were established and found to correlate with the Langmuir model with correlation coefficient of 0.998. Adsorption capacity of organo-bentonite increased with increasing the alkyl chain length. Results showed that TCP strongly interacted with AB exchanged with octadecyltrimethylammonium bromide (C18).