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磺胺类抗生素因其抗菌谱广、廉价易得、对细菌性疾病的疗效好等优点被广泛用于医疗、畜牧和水产养殖. 这类抗生素在使用过程中只有少部分经过动物代谢,大量药物及其代谢产物被直接排出体外而进入水环境[1]. 另外,磺胺类抗生素较低的微生物可降解性也使得它们不易被传统的水处理工艺去除. 磺胺类抗生素在水环境中的持久性存在,严重破坏水体中菌种和群落的均衡性,给环境造成极大的影响[2].
光催化技术是一种绿色高效、能耗低的有机污染物去除方法,在水体磺胺类抗生素的去除中具有很高的应用前景. 光催化的核心是光催化剂. 因此,探寻高活性、高稳定的光催化剂具有重要意义. 二维黑磷(black phosphorus,BP)自2014年首次成功用于制备场效应晶体管以来,引起了光电领域的广泛关注[3-4]. BP具有可调的直接带隙,禁带宽度从单层BP的2.1 eV到块状BP的0.3 eV. 因此,BP作为光催化剂具有包括近红外光在内的广泛的光吸收特性[5]. 近年来,BP在光催化领域的应用越来越广泛,但其在水、氧气和光的联合作用下易降解,本征稳定性有待提高.
目前提高BP稳定性的途径主要为通过配位作用、静电作用和共价连接等方法对BP进行功能化. 例如,Zhao等[6]将磺酸钛(TiL4)配体与BP表面配位形成TiL4@BP,其在水和潮湿空气中表现出良好的稳定性,显著延长了BP的使用寿命. 另一种常用的BP稳定方法是对其加盖保护层. Luo等[7]在微尺度的BP粒子表面涂覆二氧化钛(TiO2),有效防止了BP粒子直接接触环境. 另外,将BP与在空气条件下稳定的物质进行杂化也可以提高BP的稳定性. Wang等[8]成功制备了BPTCN杂化光催化剂,在6次循环实验后,仍然保持了80%以上的催化活性,大大提高了黑磷的稳定性. 在多数研究中,BP纳米片被用于半导体复合材料中,其最佳负载可达20% wt.[4, 9]. 考虑到BP的高成本,降低BP载荷对实际应用具有重要意义. 黑磷量子点(BP quantum dots,BPQDs)相较于BP,具有量子尺寸效应、边缘效应、高比表面积和高吸收系数等优势[8]. 因此,使用BPQDs是一种有希望在不影响性能的前提下降低BP载荷的方法[5, 10].
本文以BPQDs为活性组分,TiO2为载体,采用超声辅助沉淀沉积法制备了BPQDs负载型光催化剂BP@TiO2,并对其结构进行了表征. 以磺胺甲恶唑(sulfamethoxazole,SMX)为模型污染物,考察了BP@TiO2在模拟太阳光下催化降解磺胺类抗生素的效率和稳定性.
负载型黑磷量子点光催化降解水中磺胺甲恶唑
Effective and stable photocatalytic degradation of sulfonamides antibiotics over supported black phosphorus quantum dots
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摘要: 本论文以二氧化钛(TiO2)为载体,通过超声辅助沉淀沉积法制备了黑磷量子点(BPQDs)负载型催化剂BP@TiO2,采用X射线衍射、透射电镜、紫外可见漫反射等对其进行了表征,考察了BP@TiO2催化剂在模拟太阳光下降解磺胺甲恶唑(SMX)的光催化活性. 结果表明,BPQDs的负载提高了催化剂的光电子迁移能力,降低了光生电子-空穴对的复合率,使得BP@TiO2的光催化性能相对于载体TiO2有所提高. 其中,BPQDs载荷量为0.049% wt.的催化剂活性最高,光催化降解SMX的初活性是TiO2的4倍. 循环光解实验表明,BP@TiO2在4次循环实验后仍保持较高的光催化活性,证明了它有较好的耐光腐蚀性和光催化稳定性.Abstract: BP@TiO2 photocatalysts composed of black phosphorus quantum dots (BPQDs) and titanium dioxide (TiO2) were successfully synthesized via a deposition precipitation method assisted by sonication, and were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and UV-vis diffuse reflectance spectroscopy (UV-vis DRS) techniques. The photocatalytic activity of BP@TiO2 were tested in the degradation of sulfamethoxazole (SMX) under simulated sunlight. The results showed that the loading of BPQDs improved the electron-hole separation efficiency. Compared with the pure TiO2, BP@TiO2 had a remarkably higher photodegradation efficiency for SMX. BP@TiO2 with BPQDs loading amount of 0.049% wt. exhibited the highest photocatalytic activity, which was 4 times higher than that of TiO2. The reuse experiments showed that BP@TiO2 retained 90% of its initial photocatalytic activity after 4 consecutive catalyst cycles, indicating its high stability.
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