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近年来,内分泌干扰化合物(endocrine disrupting chemicals,EDCs)对人类健康和环境安全的负面影响受到极大关注[1-3]。双酚A(bisphenol A,BPA)作为一种具有代表性的环境内分泌干扰物质,即使以痕量水平进入水体,也可通过生物积累对人体造成危害[4]。由于传统的物理吸附、生物降解等废水处理方法难以对BPA实现高效降解,因此,迫切需要寻求一种高效且无二次污染的方法去除BPA,光催化技术则具有这种潜在优势。
光催化氧化技术的关键是光催化剂。在众多催化剂中,g-C3N4因其禁带宽度窄(2.7 eV)、稳定性高、成本低廉和毒性低成为国内外研究者高度重视的材料[5]。但g-C3N4比表面积小、光生电子和空穴复合效率高,严重影响了其光催化活性,对其进行改性或与其他半导体复合构建异质结是提高光催化性能的有效方式[6]。SINGH等[7]制备了SnO2/g-C3N4复合材料,光反应1.5 h后对罗丹明B的去除率可达98.73%。WANG等[8]合成了ZnO/g-C3N4异质结,促进了光生电荷的产生和分离,在可见光下降解四氯苯酚的光催化活性增强。BI等[9]制备了g-C3N4/TNTs复合材料,在可见光下降解罗丹明B的性能得到大幅提升,这归因于构建了直接Z型异质结。磷酸银因具有较高的量子产量(高达90%),表现出优异的光催化氧化能力,但其实际应用受到光腐蚀和溶解度低的影响[10]。基于g-C3N4的高稳定性以及Ag3PO4的高量子产率,将Ag3PO4与g-C3N4复合构筑异质结,既能提高光催化效率,又可以解决Ag3PO4容易光腐蚀的问题。RAEISI-KALLIABADI等[11]研究了Ag3PO4/g-C3N4光催化降解利福平;HU等[12]研究了Ag3PO4/g-C3N4光催化降解甲基橙和四环素;WANG等[13]研究了Ag3PO4/g-C3N4光催化降解罗丹明B。这些研究结果表明,将Ag3PO4与g-C3N4 复合,可增加对可见光的吸收并可产生更多的活性位点,从而促进光生电子-空穴对的分离和传输,还可增强对可见光的吸收,使得Ag3PO4/g-C3N4的光催化活性优于单一的g-C3N4。有研究者发现,在光催化剂中加入小尺寸的石墨相氮化碳量子点(CNQDs)可以提高光催化性能[14-16]。因此,本研究利用CNQDs进一步修饰Ag3PO4/g-C3N4复合材料,采用溶剂热法和原位沉淀法制备了一系列不同质量比的CNQDs/Ag3PO4/g-C3N4复合材料;通过XRD、SEM、FT-IR、XPS、TEM、BET等分析手段表征了材料的晶型结构、微观形貌及其化学价态;此外,考察了这些复合材料降解BPA的光催化活性和稳定性、主要活性物种和关键中间产物,以期为开发新型光催化剂和建立双酚A降解方法提供参考。
CNQDs/Ag3PO4/g-C3N4复合光催化材料的制备及其对双酚A的降解性能
Preparation of CNQDs/Ag3PO4/g-C3N4 composite photocatalyst and its degradation performance of bisphenol A
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摘要: 采用溶剂热法和原位沉淀法制备了CNQDs/Ag3PO4/g-C3N4三元复合光催化剂,通过SEM、TEM、XRD、FT-IR、XPS、BET等手段对其进行了表征;以BPA为目标污染物,考察了pH、BPA初始浓度、催化剂投加量及光照强度等因素对BPA去除效果的影响;同时,对该三元复合催化剂光催化降解BPA的机制进行了探讨。结果表明,CNQDs/Ag3PO4/g-C3N4 在反应60 min时对BPA的去除率可以达到100%,分别为g-C3N4、Ag3PO4、Ag3PO4/g-C3N4的7.74、2.09和1.38倍;光催化降解BPA的最佳反应条件为:pH为11、污染物质量浓度为5 mg·L−1、催化剂投加量为1 g·L−1、光照强度为500 W;在光催化降解BPA的过程中,主要反应活性物种为·O2−和h+。基于GC-MS对反应过程中间产物的检测结果,推测出BPA可能的2种降解路径:一是BPA先转化为单环有机物,再转化为二氧化碳和水;二是BPA经活性物种直接开环形成简单烷烃,最后氧化成二氧化碳和水。
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关键词:
- CNQDs/Ag3PO4/g-C3N4 /
- 光催化 /
- 双酚A /
- 废水处理
Abstract: The CNQDs/Ag3PO4/g-C3N4 ternary composite photocatalyst was prepared by solvothermal method and in-situ precipitation method, and it was characterized by SEM, TEM, XRD, FT-IR, XPS, BET and other ways; BPA was the target pollutant, the effects of factors such as pH, BPA concentration, catalyst dosage and light intensity on BPA removal were investigated; at the same time, the mechanism of photocatalytic degradation of BPA by the ternary composite catalyst was discussed. The results showed that 100% removal rate of BPA occurred in 60 minutes after CNQDs/Ag3PO4/g-C3N4 photocatalytic degradation, which was 7.74 times of g-C3N4, 2.09 times of Ag3PO4 and 1.38 times of Ag3PO4/g-C3N4, respectively. The optimal reaction conditions for photocatalytic degradation of BPA were following: pH 11, BPA concentration of 5 mg·L−1, catalyst dosage of 1 g·L−1, and light intensity of 500 W. In the process of photocatalytic degradation of BPA, the main reactive species are ·O2− and h+. Based on the detection results of intermediate products in the reaction process by GC-MS, two possible degradation paths of BPA were inferred, one was that BPA first transformed into monocyclic organic matter, then into CO2 and H2O, the other one was BPA transformed into simple alkane through direct ring opening reaction, then were oxidized into CO2 and H2O.-
Key words:
- CNQDs/Ag3PO4/g-C3N4 /
- photocatalytsis /
- bisphenol A /
- wastewater treatment
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表 1 不同材料的比表面积、孔径、孔容
Table 1. Specific surface area, pore size and capacity of different materials
样品 比表面积/(m2·g−1) 孔径/nm 孔体积/(cm3·g−1) g-C3N4 28.301 16.694 0.042 Ag3PO4 9.641 20.852 0.036 ACN 105.190 18.637 0.211 CACN 117.759 18.446 0.247 表 2 BPA降解中间产物
Table 2. BPA degradation intermediates
编号 名称 化学式 m/z 1 4-异丙基苯酚 C9H10O 134 2 羟基-2-甲基苯酚 C8H8O2 135 3 2,3,5-三甲基己烷 C9H20 207 4 异丙苯 C9H12 120 5 十一烷 C11H24 85 6 4-羟基苯二酸 C7H7O3 206 7 5,7-二甲基十一烷 C13H28 86 -
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