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

•Novel LC/ZnAl2O4/BiPO4 composites have been successfully prepared.•LC/ZnAl2O4/BiPO4 composites exhibits excellent adsorption and photocatalytic activity for MB degradation under UV lamp illumination.•LC/ZnAl2O4/BiPO4 are utilized to treat the bamboo pulp bleaching effluent, with a superior CODCr and AOX removals of 65.21 % and 69.23 %, respectively.•Roles of lignin-biochar on the enhanced photocatalytic efficiency of catalysts was proposed. 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.