负载TiO2的活性炭纤维改性电极电吸附除氟

采用溶胶-凝胶法制备TiO2凝胶,将TiO2凝胶涂覆在活性炭纤维表面并进行热处理制备改性电极(TiO2/ACF),利用扫描电子显微镜(SEM)、X射线衍射光谱仪(XRD)、比表面和孔隙度分析仪对负载前后电极的表面特性进行表征,并探讨了其对NaF溶液的电吸附效果。结果表明,电极负载TiO2后表面变得粗糙,比表面积和总孔体积减小,而介孔体积和平均孔径增大。此外,表面的TiO2同时以金红石和锐钛矿的晶型存在。电吸附实验结果显示,加电可以提高吸附容量,而且电压、pH和初始氟离子浓度均对电吸附容量产生影响:电压增大,吸附容量增加,当施加电压为2 V时,电吸附容量为1.03 mg/g,比开路电位时提高40%;pH可以通过影响氟离子在溶液中的存在形态和TiO2/ACF电极表面的羟基基团对电吸附容量产生影响;初始氟离子浓度升高,电极吸附容量增大,但是去除率降低。在处理初始氟离子浓度为4 mg/L的NaF溶液时,在2 V电压、中性pH和12 h的吸附时间下,改性ACF为电极的吸附量为1.32 mg/g。

Electrosorptive defluorination on modified activated carbon fiber with TiO2-coating

A modified activated carbon fiber electrode(TiO2/ACF) was prepared by coating TiO2 gel on ACF surface.Then the surface characteristics of the new electrode were analyzed with scanning electron microscopy(SEM),X-ray diffraction spectrometer(XRD) and nitrogen adsorption-desorption isotherm method.The results showed that the modified electrode had coarse surface,decreased specific surface area(BET) and total pore volume,while both the meso-pore volume and the average pore diameter increased.The XRD patterns of the TiO2/ACF electrode indicated that both anatase structure and rutile structure were observed on its surface.Moreover,it’s obvious that the adsorption capacity of the TiO2/ACF electrode can be enhanced under external electric field when it was employed to remove fluoride ions in NaF solutions.Such adsorption capacity can also increase with the increase of the voltage and initial fluoride ion concentration,but the removal rate for fluoride ions displayed an opposite trend under the effect of initial fluoride ion concentration.The electrosorption capacity of 1.03 mg/g was achieved under applied voltage of 2 V for the TiO2/ACF electrode,being 40% higher than its adsorption capacity without external electric field.The change in pH values of NaF solution has a direct influence on the species of different fluoride ions in these solutions and hydroxyl groups on the TiO2/ACF electrode surface,and then induces a variation of electrosorption capacity of the modified electrode.In addition,as the TiO2/ACF electrode was employed to treat the NaF solutions with fluoride ions concentration of 4 mg/L,electrosorption capacity was 1.32 mg/g at the following operation parameters: voltage of 2 V,neutral pH and duration of 12 h.