Adsorption of benzene and toluene onto KOH activated coconut shell based carbon treated with NH3

Volatile organic compounds (VOCs) have been reported to be responsible for many acute and chronic health effects and environmental degradations. In this study, coconut shell based porous carbon was produced through chemical activation with potassium hydroxide (PHAC) and chemically treated with ammonia (PHAC-AM) to improve the adsorption of benzene and toluene. The porous carbons were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and nitrogen adsorption tests. Removal efficiencies and adsorption capacities of the activated carbon samples for benzene and toluene were carried out through batch studies. Langmuir, Freundlich and Temkin adsorption isotherms were tested for the adsorption process and the experimental data were best fitted by Langmuir model. Pseudo-second-order kinetic model best described the adsorption kinetics for the two VOCs on PHAC and PHAC-AM. The removal of benzene and toluene by PHAC are; 82.5 and 85.6%, while that of PHAC-AM are; 91 and 92.3% respectively with approximately 10% increase in the uptake after the ammonia treatment. After five cycles of adsorbents regeneration test, approximately 50% of benzene and toluene was still able to be removed. The results of this study revealed that ammonia treated activate carbon (PHAC-AM) is a sustainable adsorbent for treatment of VOCs in polluted waters.