TiO2/核桃壳炭复合材料的制备及光催化降解苯酚研究

为提高TiO2的回收性能,促进农林废弃物的资源化利用,以核桃壳为炭源,采用溶胶 凝胶法制备TiO2/核桃壳炭复合材料。通过傅里叶红外光谱、X射线衍射、比表面积和电镜扫描等手段对复合材料的化学和晶相结构、比表面积和微观形貌进行表征,并测试其对苯酚的吸附 光催化性能。物相表征结果显示,TiO2/核桃壳炭(400℃,2 h)中TiO2以锐钛矿相颗粒分散在核桃壳炭表面,炭的固载提高了TiO2的分散性能,使其晶粒尺寸由15.7 nm降低至11.6 nm,增强了可见光吸收能力。活性分析结果表明:当TiO2含量为80%,催化剂用量为2 g/L,苯酚初始质量浓度为10 mg/L,紫外光照射240 min时,TiO2/核桃壳炭(400℃,2 h)对苯酚的降解率为97.7%,化学需氧量降解率为92.36%,优于TiO2(分别为71.55%和63.34%)和商业购买的平均粒径为25 nm的锐钛矿晶和金红石晶混合相的TiO2(降解率88.56%),且几乎完全矿化,符合一级反应动力学方程。TiO2和TiO2/核桃壳炭光催化降解苯酚的主要活性中心分别为·OH和·O-2,核桃壳炭的负载提高了TiO2吸附 光催化苯酚性能和回收效率。

Synthesis of TiO2/walnut shell carbon photocatalyst and its activity for phenol degradation

In order to improve the conversion and utilization levels of agricultural and forestry wastes,it is desired to develop a cost-effective strategy to achieve the purpose of turning waste into value-added products.The technology of directly converting walnut shell biomass into walnut shell carbon is environmental friendly.In this paper,the walnut shell carbon supported titanium dioxide(TiO2/C)composite was prepared by the sol-gel method using walnut shell as carbon source,Tetra-n-butyl titanate as precursor,and the further high temperature calcination at 400℃for 2 h.The crystal structure,the morphology structure,chemical structure,surface area and pore size and optical properties of the obtained TiO2/C composites were characterized by the X-ray diffraction,Transmission electron microscopy,Fourier transformation infrared spectroscopy,Physi-chemical adsorption instrument and UV-vis diffuse reflectance spectroscopy techniques,respectively.The adsorption-photocatalytic properties of the TiO2 supported walnut shell carbon composites were investigated by phenol removal.The influence of the TiO2 doping and calcination temperature on the phenol removal,kinetic properties and recovery performance were also investigated.The main active species and degradation mechanism of TiO2 and TiO2/C in the phenol degradation process were analyzed by means of the active species detection,COD degradation rate and liquid ultraviolet absorption spectroscopy.When the mass content of TiO2 was 80%,the amount of catalyst was 2.0 g/L and the initial concentration of phenol was 10 mg/L,the adsorption-photocatalytic properties showed that the prepared TiO2/C composite had good adsorption performance with the phenol removal rate of 16.0%under the darkness adsorption for 30 min,the phenol degradation rate was 97.7%under the ultraviolet irradiation for 240 min at room temperature,and the COD removal rate was 92.36%,which was better than that of pure TiO2 and P25-TiO2.The results showed that TiO2 existed in anatase phase in the prepared TiO2/C(400℃,2 h)catalyst.The doped TiO2 on walnut shell carbon improved the dispersion of titanium dioxide and reduced its crystalline size from 15.7 to 11.6 nm.Its surface area was 201.7 m 2/g,which was higher than TiO2(62.2 m 2/g).The TiO2 supported walnut shell carbon did not changed the pore structure and promoted its distribution of particle size,and also increased its visible light absorption properties,thus improved the photocatalytic activity.It was found that the main active centers of phenol photocatalytic degradation over TiO2 and TiO2/C were·OH and·O2^-,respectively.The photocatalytic reaction of TiO2/C was conformed to be the quasi-first order kinetics,which could be described by the equation of y=0.01730 x-0.09595.The mechanism of photocatalytic degradation was also proposed.