Preparation Of Biomass Biochar/TiO₂ Composites And Their Properties

Recently,photocatalytic composites have attracted much attention due to their application potential in environmental fields.Among of various composites,biomass biochar-based composites displayed the advantages of good chemical stability,environmental friendly and reproducibility and have very broad prospects in the field of photocatalysis.In this paper,the biomass biochar/TiO2 composites were prepared,respectively,considering the dragon bamboo and Longli lignin as biomass carbon source,using impregnated activation method,microwave-hydrothermal method and calcined method.Microstructure,phase and photocatalytic activity were studied through a series of characterization methods for composite materials.In addition,the mechanism of photocatalytic degradation of MB over nanocomposites has also investigated.The conclusions were summarized as follow:(1)TiO2 nanoparticles dispersed on the surface and space of porous structure which have small size and uniform shape.Bamboo charcoal/TiO2 composites exhibited different binding force between wood fiber with different particle sizes and TiO2 particles.TiO2 nanoparticles have good crystallinity.The doping of carbon suppresses the conversion of crystal phase.This confirms that biomass plays a key role in nucleation and growth of TiO2 crystals.Simultaneously,the band gap of the TiO2 semiconductor is reduced after the complexing with bamboo charcoal,and its response to visible light is enhanced.The photocatalytic experiments showed that the degradation rate of methylene blue decreased first and then increased with the decrease of bamboo charcoal particle sizes.The photocatalytic performance of samples with 40-80 mesh was the best.The four cycles test showed that the composites have high stability,which provides a wide application potential for the industrial production of materials.(2)Biomass biochar/TiO2 composites prepared by microwave-hydrothermal method have high purity and good morphology.By changing the temperature and time of the reaction,the morphological structure of the cornposites can be changed significantly,so that the crystal of TiO2 can be transformed from rod to spherical particles and affect the growth of the crystal.The composites have a rich mesoporous structure.With the increase of temperature,the specific surface area increases gradually,with a maximum of263.8 m2/g.The photocatalytic activity of the samples increased with the increase of temperature.(3)Titanium source content and calcination temperature have different effects on the specific surface area and yield of the materials.By using CCD and RSM methed,we get the optimal reaction conditions:calcination temperature was 693 ℃,titanium source content was 0.94 g,specific surface area value can reach 246.2 m2 g-1.The material also has a large number of mesoporous structures.The photocatalytic test showed that the degradation rate of MB increased first and then decreased with the increase of the content of titanium source and temperature.