Feasibility study on the removal of toluene from the air stream by activated carbon/zeolite imidazolate framework composite material

Abstract

In the present study, a porous composite material (activated carbon (AC)@ zeolitic imidazolate framework-8 (ZIF-8)) was synthesized by in situ method to remove toluene from the gas phase. The adsorption capacity, initial removal efficiency, breakthrough time, pressure drop, desorption and regeneration of this adsorbent were compared with those of ZIF-8 and AC to determine the most suitable adsorbent. The adsorption performance of the adsorbents for toluene was also evaluated in a laboratory scale system based on BS EN ISO 10121–1:2014 and previous studies. The toluene adsorption capacities of AC, ZIF-8 and AC@ZIF-8 were 1278.7, 2828.91 and 4538.09 mg/g, respectively, at 30.5 °C, 10 mg adsorbent mass, flow rate of 300 mL/min and relative humidity of 33%. In addition, the initial removal efficiencies of AC @ZIF-8, ZIF-8 and AC were 99.51%, 88.67% and 86.01%, respectively. The 50% breakthrough time of the composite was 16045 s, which was 3.5 times that of AC and 1.6 times that of ZIF-8. Moreover, the composite retained a 99.93% capacity after six reuse cycles. The in situ synthesis of AC @ZIF-8 composite was an efficient method and the adsorbent was successfully synthesized. This composite material exhibited high adsorption capacity for the removal of toluene from the air stream. In addition, the adsorbent proved to be cost-effective, maintaining a 99.93% capacity after several reuse cycles (99.93%). Considering the high cost of MOF synthesis and the drawbacks of AC, such as low selectivity, the synthesized AC @ZIF-8 composite can be used for air purification and adsorption processes.