Adsorption–photodegradation of humic acid in water by using ZnO coupled TiO2/bamboo charcoal under visible light irradiation

• Published in: Journal of hazardous materials 2013-11, Vol.262, p.16-24
• Main Authors: Wang, Xuejiang, Wu, Zhen, Wang, Yin, Wang, Wei, Wang, Xin, Bu, Yunjie, Zhao, Jianfu
• Format: Article
• Language: English
• Subjects: Adsorption; Bamboo charcoal; Bambusa - chemistry; Charcoal - chemistry; Humic acid; Humic Substances; Hydrogen-Ion Concentration; Kinetics; Microscopy, Electron, Scanning; Photolysis; Spectrophotometry, Ultraviolet; Titanium - chemistry; Titanium dioxide; Visible light photocatalysis; Waste Water - chemistry; Zinc Oxide - chemistry
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2013.08.037

•ZnO coupled TiO2/bamboo charcoal is prepared using a microwave-assisted sol–gel method.•HA degradation is achieved through synergistic BC adsorption and ZnO-TiO2 photocatalysis.•ZnO-TiO2/BC has high photodegradation efficiency for HA under visible-light irradiation.•ZnO-TiO2/BC is an effective photocatalyst for the removal of organic pollutants from water. ZnO coupled TiO2/bamboo charcoal (ZnO-TiO2/BC) was prepared using the sol–gel method combined with microwave irradiation. The ZnO-TiO2/BC and TiO2/BC were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N2 adsorption (BET), and UV–vis diffuse reflectance spectroscopy (UV–vis-DRS). The ZnO dopant promoted the transformation of anatase TiO2 to rutile phase, and a significant red shift of absorption edge was brought out due to the interfacial coupling effect between ZnO and TiO2 particles. The BET specific surface area and total pore volume decreased with ZnO doping, indicating that some micropores were blocked. SEM studies indicated that ZnO was almost uniformly deposited on the surface of the ZnO-TiO2/BC. The adsorption and photocatalytic degradation experiments showed that the photo-degrade efficiency for Zno-TiO2/BC was higher than that of TiO2/BC, and for both composites, the removal efficiency of HA increased as pH decreased from 10.0 to 2.0. The degradation of HA by ZnO-TiO2/BC and TiO2/BC fitted well with the Langmuir–Hinshelwood kinetics model, and HA degradation was achieved through a synergistic mechanism of adsorption and photocatalysis. ZnO-TiO2/BC could be used as an effective and alternative photocatalyst for the treatment of water contaminated by organic pollutants.