Fabrication Of Composite Photocatalysts From Yeasts-carbon And Their Synergistic Adsorption-photocatalysis Performance

The environmental pollution has attracted widespread attention all over the world.Wastewater often contains a variety of organic compounds and intermediates. These organicpollutants have complex componets, which make them reduce light penetration, and usuallynon-degradable. The high toxicity is the main problem in the industrial wastewater treatment.In this paper, we prepared composite photocatalysts using yeast-carbon as the host cores andTiO2nanoparticles as the guest particles. The as-obtained composite catalysts exhibitexcellent photocatalytic properties for wastewater treatment.(1)Porous carbon microspheres were fabricated using a simple pyrolysis treatment ofyeast with ZnCl2. A field emission scanning electron microscope, X-ray photoelectronspectroscopy and thermal gravimetry-differential thermal analysis was used to characterizethe physical and chemical structure of the porous carbon spheres. FE-SEM indicates that theresulting samples maintain ellipsoid shape. XRD pattern shows that the main crystal structureof porous carbon spheres is consisted of amorphous carbon. TG-DTA displays that thetransition process of yeast. Fourier transform infrared spectroscopy (FT-IR) indicates that theformation of porous carbon microspheres was related to surface chemical functional groups.The possible formation mechanisms of porous carbon microspheres can be interpreted by thecarbonization process. Polarity test shows that carbon microsphere surface exist manynon-polar groups. In alkaline and acidic dyes adsorption, porous carbon microspheres showeda higher adsorption capacity of acidic dyes.(2) In the present work, we report the preparation and photocatalytic properties ofTiO2@yeast-carbon with raspberry-like structure using a pyrolysis method. The results showthat the hybrid TiO2@yeast-carbon microspheres have ordered elliptic shapes of uniform size.XRD pattern indicates that the main crystal structure of as-synthesized composite consistedof amorphous carbon, anatase-type and rutile-type TiO2.TGA-DTA represents the transitionprocess of the composite TiO2@yeast-carbon. FT-IR indicates that the formation of hybridTiO2@yeast-carbon is related to the chemical functional groups on the surface of matrix. Thedetail formation mechanism of raspberry-like TiO2@yeast-carbon is proposed. Moreover,UV-Vis ascertains that the as-prepared microsphere possesses an obvious light response in a wide range of250-400nm. The hybrid composites exhibited excellent photocatalytic activityfor the Methylene blue due to its enhanced adsorption ability.(3) The adsorption model and the adsorption kinetics of TiO2@yeast-carbon compositemicrospheres for Methylene blue and Congo red were explored further. The results show thatthe Freundlich adsorption process is more accurate to describe the adsorption process. Theadsorption behavior of TiO2@yeast-carbon composite microspheres for Methylene blue andCongo red can be used to represent the secondary adsorption rate equation. After threerecycles, the adsorption rate of TiO2@yeast-carbon microspheres attains61.9%. Hereby, theTiO2@yeast-carbon composite microspheres possess stable photocatalytic properties.