Development of a novel biochar/iron oxide composite from green algae for bisphenol-A removal: Adsorption and Fenton-like reaction

In this study, algae of Aegagropila linnaei (AL) was selected as low-cost raw material to synthesize biochar/iron oxide composites for the removal of bisphenol-A (BPA). Pristine biochar (BC) with olive-shaped pores and KOH-activated acid washed biochar (ABC) with novel interconnected structure were successfully prepared and further functionalized with ferrous sulfate for effective soldering of Fe3O4 nanoparticles onto the surface of acid biochar through hydrothermal method. The iron modified acid biochar composite (FABC) was found to be with the optimal physicochemical property such as smaller crystalline size (100–150 nm), larger surface area (144.62 m2/g), larger pore volume (0.259 cm 3/g), lower capacitance decrease (2.3%), and lower resistance (0.73 Ω) as compared to other modified biochar. The removal rates of BPA by BC, ABC, and FABC were 43.2 ± 0.5%, 52.6 ± 0.3%, and 69.8 ± 2.3%, respectively, when the concentration of BPA was 10 mg/L (pH 3.0, 303k). Under acidic conditions (at pH 3.0), the reaction activity and the adsorption of hydrogen ions onto Fe3O4 nanoparticles in FABC was prompted, and further increasing the removal rate of BPA. The result suggests that adsorption played main role, while active species (⋅OH and ⋅O2−) produced by the nano-iron oxide on the surface of the composites played some effect in the removal of BPA.