The effect of diverse metal oxides in graphene composites on the adsorption isotherm of gaseous benzene.

The effective removal technique is necessary for the real world treatment of a hazardous pollutant (e.g., gaseous benzene). In an effort to develop such technique, the adsorption efficiency of benzene in a nitrogen stream (5 Pa (50 ppm) at 50 mL atm min-1 flow rate and 298 K) was assessed against 10 different metal oxide/GO composite materials (i.e., 1: graphene oxide Co (GO-Co (OH)2), 2: graphene oxide Cu (GO-Cu(OH)2), 3: graphene oxide Mn (GO-MnO), 4: graphene oxide Ni (GO-Ni(OH)2), 5: graphene oxide Sn (GO-SnO2), 6: reduced graphene oxide Co (rGO-Co(OH)2), 7: reduced graphene oxide Cu (rGO-Cu(OH)2), 8: reduced graphene oxide Mn (rGO-MnO), 9: reduced graphene oxide Ni (rGO-Ni(OH)2), and 10: reduced graphene oxide Sn (rGO-SnO2)) in reference to their pristine forms of graphene oxide (GO) and reduced graphene oxide (rGO). The highest adsorption capacities (at 100% breakthrough) were observed as ~23 mg g-1 for both GO-Ni(OH)2 and rGO-SnO2, followed by GO (~19.1 mg g-1) and GO-Co(OH)2 (~18.8 mg g-1). Therefore, the GO-Ni(OH)2 and rGO-SnO2 composites exhibited considerably high capacities to treat streams containing >5 Pa of benzene. However, the lowest adsorption capacity was found for GO-MnO (0.05 mg g-1). Alternately, if expressed in terms of the 10% breakthrough volume (BTV), the five aforementioned materials showed values of 0.50, 0.46, 0.40, 0.44, and 0.39 L g-1, respectively. The experimental data of target sorbents were fitted to linearized Langmuir, Freundlich, Elovich, and Dubinin-Radushkevich isotherm models. Accordingly, the non-linear Langmuir isotherm model revealed the presence of two or more distinct sorption profiles for several of the tested sorbents. Most of the sorbents showed type-III isotherm profiles where the sorption capacity proportional to the loaded volume.