Applications of inorganic–organic mesoporous materials constructed by self-assembly processes for removal of benzo[k]fluoranthene and benzo[b]fluoranthene

Abstract

The mesoporous materials MCM-41 and the functionalized inorganic–organic material p-aminobenzoic acid-MCM-41 (PABA-MCM-41) were used as adsorbents to remove the PAHs benzo[k]fluoranthene and benzo[b]fluoranthene from aqueous media. Both MCM-41 and PABA-MCM-41 exhibited the hexagonal mesostructures typical of the M41S family, as confirmed by SAXS, with type IV isotherms and type H1 hysteresis. The materials showed uniform mesopore size distributions, high surface areas, and thermal stability. Adsorption tests showed that for both mesoporous materials, the quantity adsorbed (q e) increased for higher initial PAH concentrations, and adsorption equilibrium was reached in around 90 min. The experimental kinetic data were fitted using the pseudo-second-order model, and the adsorption process could be described by the Langmuir isotherm. At higher temperatures, there were increases in the initial rates of adsorption and the kinetic constants for adsorption of the PAHs by PABA-MCM-41. The thermodynamic parameters indicated that the process was spontaneous, endothermic, and with a tendency toward disorder of the system at the adsorbent/adsorbate interface. The functionalization of MCM-41 increased the efficiency of adsorption of the PAHs by 44.5 and 32.0 % for benzo[k]fluoranthene and benzo[b]fluoranthene, respectively. Effect of contact time on adsorption of (a) B[k]F and (b) B[b]F by PABA-MCM-41. Conditions: 0.05 g of PABA-MCM-41, 5 mL of each PAH solution (concentration 200 µg L−1), temperature of 25 °C, contact time of 300 min, and agitation at 150 rpm.