Adsorption of polycyclic aromatic hydrocarbons from wastewater by using silica-based organic-inorganic nanohybrid material

Polycyclic aromatic hydrocarbons (PAHs) are a group of priority pollutants, which are classified as persistent hazardous contaminants. Herein, the adsorption of three PAHs, naphthalene (NAP), acenaphthylene (ACN), and phenanthrene (PHN), from wastewater onto NH2-SBA-15 organic-inorganic nanohybrid material as a function of pH of the media (2-10), sorbent dosage (0.5-3.5 g L-1), PAH concentration (1-18 mg g(-1)), and temperature (25-45 degrees C) were elucidated. The prepared adsorbents were characterized by scanning electron microscope, transmission electron microscopy, X-ray diffractions, and thermogravimetric analysis. Among Langmuir, Freundlich, and Temkin isotherms models, it was found that the Langmuir model gave an excellent overall fit (R-2 > 0.97). The maximum adsorption capacity of 1.92, 1.41, and 0.76 mg g(-1) was obtained for NAP, ACN, and PHN, respectively. Adsorption kinetics of PAHs onto NH2-SBA-15 was in accordance with the pseudo-second-order model, providing evidence that pore mass transferring was involved. PAHs' adsorption was strongly dependent on temperature, and confirmed the spontaneous and endothermic nature of the process. The optimized sorption condition was successfully applied to the real petroleum refinery wastewater samples and the adsorption capacity of NH2-SBA-15 was satisfactory for PAHs' studies as 1.67, 1.06, and 0.24 mg g(-1) for NAP, ACN and PHN, respectively. Furthermore, reusability was successfully tested by five sequential recoveries.