Study On Microwave-assisted Synthesis Of TiO₂ -loaded Sulfonated Coal At Low Temperature

In this paper, nano-TiO₂ was successfully loaded on sulfonated coal by the liquid phase deposition method under the help of microwave radiation with sulfonated coal chosen as the supporter, ammonia as the precipitator and Ti(SO4)2 as precursor. The components and morphology of the as-gained samples were characterized by the high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and the scanning electron microscope (SEM) with energy dispersive spectrometer (EDS). The effects of the size of sulfonated coal, the mass ratio of sulfonated coal to theoretical yield of TiO₂, the firstly microwave radiation power and its time, as well as the bathing time, and the pH value of the solution when TiO₂ deposited on the particle sizes of nano-TiO₂, its morphology, crystallinity and its photocatalytic activity, the etc. were investigated in this paper. The adsorption behavior of methyl orange by the gained samples was also discussed.It was revealed by the XRD results that nano-TiO₂ particles coated on the supporters were pure anatase with high crystallinity and a narrow distribution of sizes around 4.0 nm.The orthogonal test manifested that the firstly microwave radiation power among the three discussed factors had the strongest effect on the particle size and crystallinity of nano-TiO₂ which indicated that microwave radiation without sintering at high temperature in place of conventional heating methods not only provided the heat necessary for the synthesis, but also impelled the nucleus formation and growth of the crystal.The single factor variants experiment showed that the time of firstly microwave radiation had a very strong influence on the particle sizes while almost had no influence on the crystallinity; prolonging the bathing time or keeping the pH value of the solution when TiO₂ precipitated between 6～9 were in favor of the nucleus formation of the crystal; a positive relationship between the pH value, in the range of 6 to 9, of the solution when TiO₂ precipitated and the particle sizes of nano-TiO₂ was discovered.It was observed that the adsorption of methyl orange by the samples belonged to physical adsorption, releasing 9.229 Joule per mole.The kinetic character of the photocatalytic degradation of methyl orange in aqueous suspension by the as-gained samples under ultraviolet light was researched and it was discovered that the photocatalytic reaction obeyed the first-order kinetic reaction equation; the apparent reaction rate constant was used to judge the photocatalytic activity of the as-gained samples. It was confirmed that the sizes and crystallinity of nano-TiO₂ particles loaded on the sulfonated coal had a positive relationship with its photocatalytic activity.The study of repeatedly used samples in photocatalytic experiment showed that the as-gained samples had a quite good photocatalytic activity and performed strong stability.