Application of impregnated biocarbon produced from soybean hulls in dye decolorization

Waste soybean hulls (WSH) were investigated as a Fe-support in two forms: raw and carbonized (i.e. biocarbon, BC), as possible value-added materials. Fe-impregnation was implemented in order to produce heterogeneous Fenton catalysts for Reactive Blue 4 dye degradation. Materials characterization demonstrated a rise in the specific surface area due to decomposition of WSH constituents during carbonization (to obtain BC) and thermal activation (to obtain Fe-WSH and Fe-BC), thus producing catalysts with high mesoporosity and hematite as the active site for Fenton reaction. Among the investigated materials, Fe-WSH showed the greatest ability for •OH production in acidic medium. Next, the heterogeneous Fenton process was optimized by using response surface methodology, which resulted in selection of the following reaction conditions: 3 mM H2O2, 100 mg Fe-WSH, reaction time of 180 min, at a constant pH 3, RB4 concentration of 50 mg dm-3 and at room temperature. The achieved dye removal and mineralization were 85.7 and 66.8 %, respectively, while the catalyst showed high stability and the reaction intermediates formed during the oxidation process had a low inhibitory effect on Vibrio fischeri bacteria.