Removal of some phenolic compounds from aqueous solutions by Na-Bentonite

ABSTRACT

The adsorption of phenol, p- nitrophenol and p- cresol from their aqueous solution onto Na-bentonite was investigated at 30[degree sign], 40[degree sign] and 50 [degree sign] C and at different pH ranging from 1.5 to 8.3. Kinetic adsorption results were obtained at 30[degree sign] C and pH 6.5. The data obtained were analyzed considering pseudo- first and pseudo-second order kinetic models. The intraparticle diffusion model was also considered to determine the diffusion process controlling the adsorption of the phenols investigated. Equilibrium adsorption isotherms were also achieved and analyzed considering both langmuir and Freundlich equations. The thermodynamic parameters were calculated and discussed. The adsorption of the investigated phenols increased with the increase of pH from 1.5 to exhibit a maximum at pH 6.5. The kinetic experiments indicated that about 95% of the adsorption was completed after 5 hr. The pseudo- second order kinetic model was more applicable to the kinetic adsorption results. The adsorption decreased with the rise of adsorption temperature. Generally, the highly soluble phenol measured the lowest adsorption capacity. The function group in the para position affected also the adsorption. The thermodynamic parameters delta G, delta h and delta S were all negative indicating the feasibility of the adsorption process