催化学报

催化学报 ›› 2019, Vol. 40 ›› Issue (1): 70-79.DOI: 10.1016/S1872-2067(18)63160-2

• 论文 • 上一篇    下一篇

模拟太阳光照射下MIL-100(Fe)/g-C3N4异质结光催化Cr(VI)还原和双氯芬酸钠降解

杜雪冬a, 衣晓虹a, 王鹏a, 邓积光b, 王崇臣a   

  1. a 北京建筑大学建筑结构与环境修复功能材料北京市重点实验室, 北京 100044;
    b 北京工业大学环境与能源工程学院化学与化工系, 北京 100022
  • 收稿日期:2018-07-24 修回日期:2018-09-12 出版日期:2019-01-18 发布日期:2018-11-09
  • 通讯作者: 邓积光, 王崇臣
  • 基金资助:

    国家自然科学基金（51578034，51878023）；北京市属高校高水平教师队伍建设支持计划长城学者培养计划（CIT&TCD20180323）；北京市属高校高层次人才引进与培养计划和创新团队与教师职业发展计划（IDHT20170508）；北京百千万人才项目（2017A38）；北京市属高校基本科研业务费专项资金（X18075/X18076/X18124/X18125/X18276）；北京建筑大学校设基金（KYJJ2017033/KYJJ2017008）.

Enhanced photocatalytic Cr(VI) reduction and diclofenac sodium degradation under simulated sunlight irradiation over MIL-100(Fe)/g-C3N4 heterojunctions

Xuedong Dua, Xiaohong Yia, Peng Wanga, Jiguang Dengb, Chong-chen Wanga   

  1. a Beijing Key Laboratory of Functional Materials for Building Structure and Environment Remediation, Beijing University of Civil Engineering and Architecture, Beijing 100044, China;
    b Department of Chemistry and Chemical Engineering, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100022, China
  • Received:2018-07-24 Revised:2018-09-12 Online:2019-01-18 Published:2018-11-09
  • Contact: 10.1016/S1872-2067(18)63160-2
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (51578034, 51878023), the Great Wall Scholars Training Program Project of Beijing Municipality Universities (CIT&TCD20180323), the Project of Construction of Innovation Teams and Teacher Career Development for Universities and Colleges Under Beijing Municipality (IDHT20170508), the Beijing Talent Project (2017A38), the Fundamental Research Funds for Beijing Universities (X18075/X18076/X18124/X18125/X18276), and the Scientific Research Foundation of Beijing University of Civil Engineering and Architecture (KYJJ2017033/KYJJ2017008).

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摘要：

有毒重金属离子Cr（VI）广泛应用于制革、电镀、印刷、颜料和抛光等行业，因而成为地表水和地下水中常见的污染物.光催化还原Cr（VI）为Cr（Ⅲ）利用可持续能源太阳能，费用低且没有二次污染问题，已经受到广泛关注.g-C3N4是一种稳定性好且能吸收可见光的优异光催化材料，但也具有比表面积小及电子和空穴容易复合等缺点.为进一步提高g-C3N4的光催化效率，人们合成了各种新型复合材料，如g-C3N4/Bi2WO6，g-C3N4/SiW11和g-C3N4/Zn3V2O7（OH）2（H2O）2等.
本文通过非常简便的球磨-煅烧法制备了金属-有机骨架材料MIL-100（Fe）与类石墨结构氮化碳（g-C3N4）的异质结结构（MG-x，x=5%，10%，20%和30%，代表MIL-100（Fe）占复合物的质量分数），并对复合材料进行了粉末X射线衍射（PXRD）、红外光谱（FTIR）、热重（TGA）、透射电镜（TEM）、紫外-可见漫反射光谱（UV-Vis DR）和荧光光谱（PL）等表征.实验研究了MG-x在模拟太阳光照射下光催化还原Cr（VI）和降解双氯芬酸钠的性能，考察了空穴捕捉剂（乙醇、柠檬酸、草酸和双氯芬酸钠）和pH值（2-8）对光催化还原Cr（VI）效率的影响.
实验结果表明，PXRD谱图显示复合物的衍射峰位置均与MIL-100（Fe）及g-C3N4的峰位置相吻合，球磨和煅烧后无新衍射峰产生.TEM图片证明复合物中g-C3N4附着在MIL-100（Fe）表面.光照80min后，MG-x复合物的还原效率均大于92%，高于MIL-100（Fe）（75.6%）和g-C3N4（79.8%）的还原效率.其中，MG-20%的光催化活性最高，还原效率达到97.0%，且还原Cr（VI）的速率分别是MIL-100（Fe）的3.08倍和g-C3N4的2.31倍.随着MIL-100（Fe）含量的增加，复合物的光催化活性先增后减.这是因为MIL-100（Fe）含量的增加不仅有利于电荷的转移，也有利于可见光的利用，然而过多的MIL-100（Fe）可能会影响异质结的质量，不利于电荷的转移.随着溶液pH值从2提高到8，还原效率从98%降低到9%.这是因为在酸性条件下H+浓度高有利于Cr（VI）还原为Cr（Ⅲ），而当pH>6时，Cr3+与OH-形成Cr（OH）3沉淀附着在催化剂表面，影响对光的吸收，降低了光催化效率.当反应体系中加入乙醇、柠檬酸和草酸时，光催化速率提高，而加入双氯芬酸钠后光催化速率未见提高，这是由于小分子链烃有机物容易捕捉光生空穴，而双氯芬酸钠不能有效捕捉MG-20%产生的光生空穴.电化学测试证明g-C3N4的光生电子可转移到MIL-100（Fe）的导带，复合物提高了光生电子和光生空穴的分离效率，从而提高了光催化还原Cr（VI）的活性.同时，在加入H2O2的条件下，MG-20%在50min内光催化降解双氯芬酸钠的效率达到100%.MG-20%循环使用5次后，光催化效率没有明显降低，光催化剂的XRD谱没有发生明显变化，证明其具有很好的稳定性.综上，本研究提供了一种具有应用前景的高效MOF/g-C3N4复合物光催化剂.

关键词: MIL-100(Fe), g-C3N4, 异质结, 六价铬还原, 双氯芬酸钠

Abstract:

Metal-organic framework MIL-100(Fe) and g-C3N4 heterojunctions (MG-x, x=5%, 10%, 20%, and 30%, x is the mass fraction of MIL-100(Fe) in the hybrids) were facilely fabricated through ball-milling and annealing, and characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, UV-visible diffuse-reflectance spectrometry, and photoluminescence emission spectrometry. The photocatalytic activities of the series of MG-x heterojunctions toward Cr(VI) reduction and diclofenac sodium degradation were tested upon irradiation with simulated sunlight. The influence of different organic compounds (ethanol, citric acid, oxalic acid, and diclofenac sodium) as hole scavengers and the pH values (2, 3, 4, 6, and 8) on the photocatalytic activities of the series of MG-x heterojunctions was investigated. MG-20% showed superior photocatalytic Cr(VI) reduction and diclofenac sodium degradation performance than did the individual MIL-100(Fe) and g-C3N4 because of the improved separation of photoinduced electron-hole charges, which was clarified via photoluminescence emission and electrochemical data. Moreover, the MG-x exhibited good reusability and stability after several runs.

Key words: MIL-100(Fe), g-C3N4, Heterojunction, Cr(VI) reduction, Diclofenac sodium