Performance of the MCM-41-NH2 Functionalized Mesoporous Material Synthetized from the Rice Husk Ash on the Removal of the Polycyclic Aromatic Hydrocarbons

Abstract

In this work, the authors propose of the synthesis of a new adsorbent functionalized mesoporous material (MCM-41-NH2 (RHA)) from the Brazilian rice husk for the removal of the polycyclic aromatic hydrocarbons (PAHs). The new MCM-41-NH2 (RHA) was characterized using FTIR, TGA, SAXS, and N2 adsorption-desorption analyses, on the other hand, the removal experiments were performed to determine the adsorption parameters, such as the initial concentration, MCM-41-NH2 (RHA) amount, pH, time, and temperature. The hydrothermal/post-grafting methods were sustainable for the synthesis of the MCM-41-NH2 (RHA) functionalized mesoporous material, the same presented the main characteristic absorption bands of the mesoporous arrays, hexagonal mesostructure, type IV isotherms with H1 hysteresis, high surface area, and good thermal stability. Assessment of the adsorption of the MCM-41-NH2 (RHA) showed that the amount of the PAHs mixture adsorbed increased with the increase of the initial concentration, MCM-41-NH2 (RHA) amount, and contact time, as well as, the pH = 5.6 was the best for the removal of the PAHs mixture. However, the temperature variation did not significantly alter the efficiency of the MCM-41-NH2 (RHA). The removal percentage of the PAHs were 81.20, 94.25, 94.87, and 98.14% for the naphthalene (Nap), benzo[a]pyrene (B[a]P), benzo[k]fluoranthene (B[k]F), and benzo[b]fluoranthene (B[b]F), respectively, with the equilibrium time of approximately 200 min for the all PAHs. In addition, the adsorption equilibrium followed the nonlinear pseudo-second-order and the Langmuir models, which describe satisfactory adsorption of the PAHs mixture on the MCM-41-NH2 (RHA) functionalized mesoporous material.