Enhanced organic pollutant and AOX degradation of lignin-biochar/ZnAl2O4/BiPO4 with adsorption-photocatalysis synergy: Roles of lignin-biochar

In this work, lignin-biochar (LC)/ZnAl2O4/BiPO4 with adsorption and photocatalysis synergy were fabricated through hydrothermal process. The roles of lignin-biochar on the crystalline structure, shape and photoelectrochemical capacities of LC/ZnAl2O4/BiPO4 were carried out by X-ray power diffractometer pattern (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffusion reflectance spectra (UV-Vis DRS), photoluminescence spectra (PL), transmission electron microscope (TEM), scanning electron microscope (SEM), electrochemical impedance and transient photocurrent measurements. Photocatalytic experiment showed that the adsorption and photocatalytic efficiencies of ZnAl2O4/BiPO4 were greatly boosted with the introduced lignin-biochar, which is owing to its higher surface specific area, larger aromatic ring structure and superior electron transmission capacity. The highest kinetic constant of LC/ZnAl2O4/BiPO4 on the MB degradation is 2.1342 h−1 under UV illumination, increased by 5.52-fold for BiPO4 and 2.23-fold for ZnAl2O4/BiPO4, respectively. Meanwhile, the LC/ZnAl2O4/BiPO4 composites display excellent performance in the bamboo pulp bleaching wastewater treatment, and the CODCr and AOX removals of the wastewater are 65.2% and 69.2%, respectively. The lignin-biochar in the composites can not only enhance the adsorption of pollutant in the wastewater, but accept the photo-generated electrons from the semiconductor, leading to an enrichment of the pollutant and accelerated separation of electrons-holes pairs, ultimately enhancing the photocatalytic activities. The superior adsorption and photocatalytic efficiency of lignin-biochar-based composite makes it a promising candidate for the elimination of refractory pollutant in the industrial wastewater.