| As a photocatalytic purification material,titanium dioxide has the advantages of energy saving,environmental protection,clean and non-toxic.However,due to its wide band gap,low utilization rate of sunlight and weak adsorption performance,its application in specific fields is limited.Therefore,the preparation of titanium dioxide with low energy consumption,low cost and low pollution has become a research focus in this field in recent years.The preparation of nano titanium dioxide materials by biological template method has important research and application value in the fields of environmental protection,recycling,biomimetic medicine,functional materials and so on.Wood has the advantages of natural unique hierarchical porous structure,large existing quantity,easy to obtain,renewable and so on.In this study,poplar and Chinese fir were used as the research objects respectively,and the forms of wood square,wood powder and nanocellulosic were used as biological templates,and the mixed solvents of tetrabbutyltitanate(titanium source),glacial acetic acid(inhibitor),anhydrous ethanol and deionized water were used as precursors.Through the pretreatment of wood template-precursor impregnation-high temperature calcination method with wood multilevel pore structure of titanium dioxide photocatalyst,by studying the different scales template preparation of titanium dioxide pore morphology,crystal structure and optical absorption energy absorption,discusses its adsorption performance of woodiness material template titanium dioxide and the influence of photocatalytic degradation of performance,The photocatalytic degradation mechanism of TiO2 in the graded pores was determined.The results are as follows:(1)The wood template titanium dioxide obtained by template preprocessing-precursor impregnation-high-temperature calcination process can genetically replicate the hierarchical porous structure of wood.The porous structure of template titanium dioxide has the hierarchical distribution of large pores in micron level,mesoporous pores in 2-50nm and micropores in smaller than 2nm.It is mainly inherited from wood fiber cells,asymmetric tracheids and striatal structure.The change of wood template species and size had a certain effect on the arrangement and distribution of titanium dioxide pores.(2)With wood as templates for the preparation of titanium dioxide anatase and rutile phase of mixed crystal phase,the wood template role in confined space,makes preparation of titanium dioxide wood template for smaller grain size,grain size in comparison to no template titanium dioxide decreases 5%to 46%,the nanometer titanium dioxide fiber template,the minimum is 14.63 nm.Meanwhile,under the action of wood template,the number and specific surface area of mesoporous and macroporous TiO2 were increased.The specific surface area and pore volume of TiO2 obtained from Wood template were the largest,while the adsorption pore size of TiO2 obtained from wood template was the largest.which were 19.40m2/g,0.13cm3/g and 12.47nm,respectively.Compared with template-free titanium dioxide,it increased 76%,60%and 45%.(3)There are certain differences in the adsorption performance of titanium dioxide prepared by wood templates of different species and scales to the target reaction solution.The adsorption rate of titanium dioxide prepared by wood powder template is 8%～50%higher than that prepared by wood square template.In the adsorption process of methylene blue solution,the wood powder template of Chinese fir had the fastest adsorption rate of titanium dioxide,and the adsorption capacity reached 6.50mg/g after 240 minutes static adsorption,while the wood square template of the same tree species had the lowest adsorption capacity of titanium dioxide,which was only 3.25mg/g.The adsorption process of wood template titanium dioxide is mainly physical adsorption.By fitting the diffusion model within particles,the whole adsorption process can be divided into three stages:surface adsorption with high adsorption efficiency,slow filling of micropores and equilibrium adsorption.(4)Under UV light conditions,the UV photocatalytic degradation ability of wood template titanium dioxide was improved due to the standing wave resonance consumption of UV light by its hierarchical porous structure.Among them,the nanometer titanium dioxide fiber template photocatalytic methylene blue solution and formaldehyde solution is the most outstanding performance,followed by square fir wood template titanium dioxide,the photocatalytic degradation of methylene blue solution of reaction rate constant,respectively 2.66 times and 1.89 times that of no template titanium dioxide,titanium dioxide degradation rates of formaldehyde solution compared with no template increased by 16%and 14%.(5)Preparation of titanium dioxide using wood as template can broaden the wavelength range of titanium dioxide excitation light source,enhance its absorption in the visible region,and reduce the band gap width.Five wood template titanium dioxide under the condition of visible light of formaldehyde solution and methylene blue solution showed certain catalytic degradation ability,the nanometer titanium dioxide fiber template to formaldehyde and visible light degradation ability of the methylene blue solution is highest,24.3%and 22.4%,respectively,and cypress template TiO2 visible light catalytic degradation ability to the lowest,compared with titanium dioxide without template,it only increased by 11.1%and 10.2%.Wood template titanium dioxide has a good uv degradation stability.In the uv cycle degradation test of Chinese fir wood template titanium dioxide,it was found that after five cycles of catalytic degradation.the degradation rate of methylene blue solution reached 92.1%,only 2%lower than the first catalytic degradation efficiency. |
