Photomineralization of recalcitrant wastewaters by a novel magnetically recyclable boron doped-TiO2-SiO2 cobalt ferrite nanocomposite as a visible-driven heterogeneous photocatalyst

Abstract

In this work, different recalcitrant organic compounds including biologically treated palm oil mill effluent (POME), diazinon and paraquat dichloride and natural dye from algal growth in Solaymanshah’s dam was degraded using a novel highly efficient magnetically visible driven photocatalyst (boron doped TiO2-SiO2 cobalt ferrite) which was synthesized by a sol gel hydrothermal method. The prepared nanocomposites were characterized by UV–vis diffuse reflectance (DRS) spectroscopy, X-ray diffraction (XRD), photoluminescence (PL), Fourier transform infrared (FT-IR), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM) analyses. The results revealed that boron doped-TiO2-SiO2 cobalt ferrite nanocomposite not only expanded the response region to the visible light but also reduced recombination of the photoinduced e−/h+ pairs. The effects of various parameters, such as COD concentrations (300–800 mg/l), photocatalyst concentration (1.5–3.5 g/l) and pH (3–11) on the photocatalytic process were also evaluated. The COD contents was completely removed for the biologically treated POME, paraquat dichloride, diazinon, natural dye from algal growth in Solaymanshah dam's after 4/5, 3/5, 3 and 2/5 h, respectively at optimum conditions (initial COD concentration of 300 mg/l, catalyst loading 2/5 g/l and pH of 3). Furthermore, the magnetic nanocomposite can be easily recovered and separated with an extra magnet with a small loss of 0.01–0.05 g/l corresponding to 0.4–2 %. After being reused for three times, the reduction of COD removal efficiency of the natural dyes, diazinon, paraquat dichloride and biologically treated POME was about 1, 1, 3 and 4%, respectively that confirmed the photocatalytic stability of nanocomposite.