Adsorption of benzene and toluene on super activated carbon nanoparticles

Engineered nanomaterials are materials that have been purposefully manufactured and showed special properties stemming from their nanoscale dimension in the range of 1-100 nanometers. However, engineered nanomaterials produced in large quantities draw public attention because of their potential human health and environmental effects. Special concern lies on the human exposure to engineered nanomaterials that adsorb hazardous air pollutants (HAPs). Many researchers have evaluated the adsorption of HAPs on macro-sized materials, but a limited number of studies have explored HAPs adsorption on engineered nanomaterials. This study quantified and compared the adsorption capacities and dynamics of benzene and toluene on super activated carbon nanoparticles (SACNs) and granular activated carbon (GAC) with a bench-scale adsorption system. Breakthrough curves, adsorption capacities, removal efficiencies, throughput ratios and lengths of unused bed were calculated to assess the adsorption behavior of SACNs and GAC. The adsorption of mixtures of benzene and toluene on SACNs and GAC was also tested and compared to the single compound adsorption. Results showed that SACNs had superior adsorption capacities for HAPs than the GAC. SACNs had an average removal efficiency of 98.3% for benzene and toluene slightly higher than the one of GAC (96.2%). SACNs had 281% higher average adsorption capacity (1.35 g/g) for benzene and toluene than GAC (0.48 g/g). The average adsorption capacity and removal efficiency for the mixtures of benzene and toluene were 1.42 g/g and close to 100%, respectively. Adsorption kinetics was analyzed for all adsorption tests on SACNs and GAC using the time series plots. The kinetics rate constants for the adsorption of benzene and toluene on SACNs were three times larger than the ones of GAC. The adsorption rate constant values for the adsorption of benzene were slightly larger than the rate constant values for toluene on both SACNs and GAC.