Poly (Acrylic Acid-Co-Styrene)/ HDTMA-MMT Composite for Efficient Adsorption of Phenol Wastewater: Isotherm and Kinetic Modeling

A composite, based on poly (acrylic acid-co-styrene) and organomodified montmorillonite with hexadecyltrimethyl ammonium bromide (27 wt. % in inorganics), designated as: poly(AA-co-St)/HDTMA-MMT was prepared by in situ radical polymerization. The structural and morphological properties were examined by Fourier transform infrared (FTIR) spectroscopy, X -Ray Diffraction (XRD), and scanning electron microscopy (SEM). The results show the intercalation of poly (acrylic acid-co-styrene) in the organomodified montmorillonite layers. The percent of the inorganics in the composite is 27 % as evaluated by ThermoGravimetric Analysis (TGA). The performance of the composite to remove phenol molecules from an aqueous solution was investigated by batch adsorption, under different experimental conditions. The zeta potential of poly(AA-co-St)/HDTMA-MMT composite was calculated to understand the mechanism of phenol adsorption onto poly(AA-co-St)/HDTMA-MMT. The pollutant uptake behavior was determined by UV -Vis spectrophotometry. The best results were obtained for a contact time of 180 minutes, an initial concentration of 30 mg/L, pH 6. The presence of acrylic acid and styrene can modify the surface characteristics of the composite and affect the adsorption capacity as confirmed by X -Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Interestingly, the maximum adsorption capacity was found to be 150.7 mg/g. Equilibrium modeling of the phenol removal process was carried out using the Langmuir and Freundlich adsorption isotherms. The equilibrium adsorption data were found to be well -fitted with the Freundlich adsorption isotherm. The kinetic of adsorption was best described by a pseudo -second -order expression rather than a first -order model. The interactions between phenol molecules and adsorbent were explained by electrostatic as well as hydrogen bonding interactions, as confirmed by the pseudo -second -order kinetic model. A model for the interactions between a composite and phenol molecule was proposed. Interestingly, the desorption of phenol from the adsorbent using hot water remains stable. The value of the first adsorption/desorption cycle was about 98.1 % and achieved 92.8 % after five cycles.