Visible light photocatalytic activities of BiOBr-activated carbon (derived from waste polyurethane) composites by hydrothermal process

Hybrid materials such as activated carbon based photocatalysts are very promising advanced materials which are bifunctional with both adsorption and photocatalytic properties. In the present work, activated carbon (AC) was prepared from waste polyurethane foam materials. The photocatalytic hybrid materials were synthesized from bismuth oxide precursor (BiOBr) and activated carbon by hydrothermal process. The prepared AC-BiOBr composite was characterized by XRD, FE-SEM, surface area, porosity, zero point charge and UV-DRS. The prepared AC-BiOBr composite had lesser band gap energy (2.64 eV) when compared to pristine BiOBr (2.84 eV). The photodegradation efficiency of the prepared composite was evaluated for the degradation of malachite green dye under visible light irradiation. Preliminary photocatalytic studies were carried out by varying initial aqueous phase pH, catalyst dosage and initial malachite green dye concentration. Kinetic studies were also carried out for the degradation of malachite green dye by pristine BiOBr and AC-BiOBr composite. The rate constants of the photodegradation were evaluated by fitting the kinetic data with pseudo first-order model equation and the rate constants of AC-BiOBr composite was slightly higher than that of pristine BiOBr. The effect of adsorption on photocatalytic degradation was evaluated by adsorption experiments using AC, BiOBr and AC-BiOBr composite as dark reactions. The equilibrium adsorption data were modelled using Langmuir and Freundlich isotherms. The plausible mechanism for the photodegradation of malachite green dye was also proposed using MALDI-TOF spectral analysis. The prepared adsorbent-photocatalytic composite had good adsorption and photocatalytic degradation efficiency for the removal of malachite green dye molecules from aqueous solution.