Synthesis of reduced graphene oxide-fungal hyphae biochar/iron oxide composite: characterization, adsorption performance, and removal mechanisms

In this study, a novel biochar, iron-impregnated reduced graphene oxide-fungal hyphae, named AOBC-rGO, was synthesized as an innovative approach for the removal of Cr(VI) ions from water. A scanning electron microscope showed the formation of large agglomerates on the surface of biochar samples while Raman analysis showed D and G bands at 1350 and 1580 cm(-1) respectively as the proof of polyaromatic hydrocarbons and graphitic material. The surface area of the AOBC-rGO was determined as 58.5650 m(2) g(-1). To evaluate the efficacy of AOBC-rGO, the effect of initial chromium concentration (25, 50, 100, 150 and 200 mg L-1), pH (2, 5, 7, 9 and 11), retention time (0, 5, 10, 20, 30, 40, 50, 60 and 90 min), and adsorbent dose (100, 300 and 500 mg L-1) was investigated in batch experiments for synthetic and real wastewater samples. Adsorption tests showed that the biochar adsorption capacity was 1116.01 mg g(-1). Furthermore, findings suggest that the chromium sorption on AOBC-rGO fits with the pseudo-second-order model and Freundlich isotherm model (R-2 > 0.93), indicating a heterogeneous surface with a dominant chemisorption mechanism. Thus, AOBC-rGO can be used as an effective adsorbent to remove heavy metals from wastewater.