1186727 - Adsorption and Photocatalytic Reduction of Cr(VI) on Biochar Modified ZnO Composite (Student Poster #26)

Biochar is a carbon-rich material and is widely used to restrain greenhouse gas production. However, the low adsorption capacity of biochar derived from agricultural residuals limits its extended application. The mineral-modified biochar could exhibit high activity and selectivity upon heavy metal adsorption by its size effect and high surface area. To the best of our knowledge, few research discusses the Cr(VI) removal mechanism by the ZnO-biochar composite. So far, the research on pineapple leaves (PLB) and rice husk (RHB) modified with ZnO for Cr(VI) adsorption-photocatalytic reduction from aqueous solution has not been conducted. The as-synthesized Biochar-ZnO composite, PLB-ZnO, and RHB-ZnO have a specific surface area of 43.9 m2 g-1 and 139.7 m2 g-1, respectively, which is much higher than that of PLB (6.812 m2 g-1), RHB (127.5 m2 g-1), and ZnO (13.7 m2 g-1). The maximum Cr(VI) adsorption capacities of PLB-ZnO and RHB-ZnO were 40.8 and 33.5 mg g-1, higher than that of ZnO (20.5 mg g-1), PLB (17.2 mg g-1), and RHB (13.6 mg g-1) as determined from the Langmuir isotherm model. In the context of photocatalytic reduction, PLB-ZnO and RHB-ZnO could remove 95% and 85 % Cr(VI), respectively, under visible-light irradiation for 240 min at pH 2.0. The Langmuir- Hinshelwood (L-H) kinetic model was used to explain the effects of initial Cr(VI) concentrations on the photocatalytic process. Furthermore, XPS, SEM-EDS, and FTIR techniques were used to identify the adsorption-desorption reaction mechanisms. The Biochar-ZnO composite is a novel eco-friendly adsorbent/catalyst for effective Cr(VI) removal via adsorption coupled with photocatalytic-reduction reaction.