Activated carbon (AC) prepared from olive stone (OSAC) was modified separately by ammoniac (OSAC/AM) and sodium hydroxide (OSAC/H) aqueous solutions impregnation in order to improve their adsorption properties toward phenol. The raw and modified activated carbons were characterized. The porous structure was characterized using N 2 adsorption at 77 K. The surface functional group characteristics were examined by Fourier transform infrared (FTIR) spectroscopy, Boehm titration, the point of zero charge (pH pzc) measurement and X-ray photoelectron spectroscopy (XPS) method. The isotherms of phenol adsorption on the original and modified ACs were measured. After modification, the activated carbon showed enhanced adsorption capacity for phenol. The effect of alkaline solution concentration on adsorption process was investigated. Results showed a decrease of the microporosity of AC after alkalin treatment especially for higher solution concentration. The amounts of the surface basic groups of the modified ACs increased, in comparison with the original AC, with the increase of the alkaline concentration; however the acidic surface groups decreased. The equilibrium adsorption data were best described by Langmuir model. The maximum adsorption capacity of phenol enhanced for ammonia and sodium hydroxide, respectively, compared with the original AC. We noted that the higher alkaline concentration the higher the adsorption capacity of AC for phenol.
Nitrogen plasma treatment (NPT) of activated carbon (AC) at different conditions was carried out to introduce nitrogen-containing groups onto olive stone-activated carbon (OSAC) surfaces. Textural characteristics of raw and irradiated samples were analyzed by N and CO adsorption. Surface chemical functional groups were analyzed by X-ray photoelectron spectrometry (XPS) and Fourier Transformed Infrared spectroscopy. The results showed that after NPT, the surface textural properties of irradiated OSAC were slightly damaged, and a gradual decrease in surface area and pore volume was observed during the irradiation. XPS revealed that NPT could change the distribution of oxygen functional groups on the OSAC surface and there were more nitrogen atoms incorporated into the aromatic ring. A tentative explanation for the modification process is proposed. Phenol adsorption was enhanced from 110 mg/g for untreated AC to 635 mg/g for 30-min plasma-treated OSAC.
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