微乳法制备棒状ZnO材料及其光催化性能

采用浊度法绘制十六烷基三甲基溴化铵(CTAB)/正丁醇/环己烷/硝酸锌或草酸铵水溶液体系的拟三元相图,确定微乳液稳定区域最大时CTAB与正丁醇的质量比为1∶1。在此条件下,选择m(CTAB+正丁醇)∶m(环己烷)=3∶7,以硝酸锌和草酸铵为原料,采用微乳法制备ZnO的前驱体二水合草酸锌,然后通过煅烧得到ZnO样品。考察水与CTAB的摩尔比(R)和反应物浓度对ZnO材料结构、形貌、光学性质和光催化性能的影响。实验结果表明:ZnO样品为纯的六方纤锌矿结构晶体,形貌均为棒状,且样品的尺寸随R值和反应物浓度的不同而不同。在300 W汞灯紫外光照射下,ZnO样品对亚甲基蓝溶液均具有较好的光催化性能,光催化反应过程符合准一级反应动力学。其中,在反应物浓度为0.15 mol/L,R=15条件下制备的ZnO样品在光照90 min时可使亚甲基蓝的降解率达到97.0%,且降解反应速率常数k最大,其光催化性能最好。

Preparation of rodlike ZnO materials by microemulsion method and their photocatalytic properties

Pseudo-ternary phase diagrams of microemulsion system of hexadecyltrimethylammonium bromide (CTAB)/n-butanol/cyclohexane/zinc nitrate or ammonium oxalate solution were drawn by turbidimetry, and the best mass ratio of CTAB to n-butanol was 1:1 in the maximum stable region of microemulsion. Under this condition, when m(CTAB+n-butanol):m(cyclohexane) was 3:7, zinc oxalate dihydrate, that was the precursor of ZnO, was prepared by a microemulsion method using zinc nitrate and ammonium oxalate as raw materials. ZnO materials were prepared by calcining zinc oxalate dihydrate. The effects of R (the molar ratio of water to CTAB) and reactant concentration on the structure, morphology, optical property and photocatalytic property of ZnO materials were studied. Results show that the morphologies of ZnO power are rodlike and they exhibit hexagonal wurtzite structure. The sizes of samples are affected by R and reactant concentration. All the samples have good photocatalytic effect on the catalytic degradation of methylene blue solution under the irradiation of 300 W Hg lamp, and the photocatalytic degradation process follows quasi-first-order kinetics. Among which the degradation rate of methylene blue solution achieves 97.0% for 90 min illumination and the corresponding reaction rate constant k is the largest, and with best photocatalytic property, when the reactant concentration is 0.15 mol/L, R=15.