STRUCTURE AND PERFORMANCE OF SOY HULL CARBON ADSORBENTS AS AFFECTED BY PYROLYSIS TEMPERATURE

Soy hulls were evaluated as a source of adsorbent carbon for vegetable oil processing. Soy hull carbon was prepared by burning ground soy hu lls (<100 mesh) at 300, 400, 500, or 700 degrees C in a muffle furnace . The structure of the soy hull carbon was studied by scanning electro n microscope (SEM), Xray diffraction (XRD), and Fourier-transform infr ared spectroscopy (FTIR). Crude soy oil was processed with the soy hul l carbon products at 2% (w/w) in the laboratory under commercial bleac hing conditions. Free fatty acids (FFA), peroxide value, phospholipid phosphorus (PLP), and lutein content of the treated samples were deter mined. SEM of the samples revealed particle size ranging from 1 to 2 m m. Increasing the pyrolysis temperature resulted in expansion and disr uption of cellular structure. FTIR spectra of the carbon samples showe d major differences in peak intensities at 3600 to 3200, 1600, and 145 0 cm(-1) due to pyrolysis temperature. XRD revealed a predominantly am orphous structure with increasing pyrolysis temperature, which also re sulted in an increased alkaline surface. Soy hull carbon decreased the FFA content of oil samples compared to that of crude oil, with the ex ception of carbon that was prepared at 300 degrees C (P < 0.05). A sim ilar trend was observed in the adsorption of peroxides; however, no tr ends were observed in the adsorption of PLP or lutein. Higher pyrolysi s temperature decreased randomness of the carbon and imparted a certai n degree of structural order. This may be beneficial in providing phys ical access of the adsorbate molecule to the adsorbent surface.