Adsorption of organic compounds on mesoporous material from rice husk ash (RHA)

The MCM-41 (TEOS) and MCM-41 (RHA) were synthesized from tetraethyl orthosilicate (TEOS) and rice husk ash (RHA), respectively. The mesoporous materials were used for the removal of the naphthalene (Nap), benzo[b]fluoranthene (B[b]F), benzo[k]fluoranthene (B[k]F), and benzo[a]pyrene (B[a]P) organic compounds from aqueous media. Polycyclic aromatic hydrocarbons (PAHs) are released into the aquatic environments via petroleum spill, industrial discharge, the combustion of fossil fuels, automobile exhaust, and nonpoint sources, such as atmospheric deposition and urban runoff. These compounds can be a threat to environment and humans, since they are recalcitrant, toxic, carcinogenic, and/or mutagenic pollutants. The mesoporous silicas were characterized by FTIR, TGA, SAXS, SEM, and N-2 adsorption/desorption analyses. Removal processes were conducted to evaluate the initial PAHs concentrations and individual adsorption in comparison with the mixture of same, as well as adsorbent amount, solution pH, contact time, and temperature. The nanostructured materials exhibited the textural and structural properties typical of mesoporous materials. The q(e) values found in the kinetic equilibrium for the PAHs mixture followed the same increasing order for the two mesoporous materials: Nap < B[a]P < B[k]F < B[b]F, with removal percentages of 67.71, 94.30, 95.30, and 98.04% for MCM-41 (TEOS) and 79.94, 94.34, 95.32, and 98.25% for MCM-41 (RHA), respectively.