A pyrolyzed oil shale by-product known as retorted shale was functionalized with HCl, HNO3, H2SO4, H3PO4, HNO3/H2SO4 (3:1), Fenton's reagent, (NH4)2S2O7, NaOH, and KMnO4 using either ultrasound (Route 1) or reflux (Route 2). The products obtained were evaluated in terms of cation exchange capacity (CEC). Structural characterization was performed using X-ray diffraction, X-ray fluorescence, and infrared spectroscopy to identify the functional groups present. The best results were achieved using Route 2 with solutions of either H3PO4 or HNO3/H2SO4 (3:1), giving CEC values of 315 and 316 mmolc kg-1, respectively. The pyrolyzed oil shale functionalized using Route 2 (reflux) with NaOH as the activating agent showed the highest sorption of methylene blue (35.6 mg g-1). The main mechanisms observed for oil shale by-product functionalization were oxidation, nitration, and CaO leaching.
Keywords:
cation exchange capacity; pyrolyzed shale; methylene blue; functional groups
