Preparation Of ZnO Composite Nanomaterials And Its Application In Sewage Treatment

With the improvement of people's living standard,the industrial waste water?From textile industry,printing industry,cosmetics industry,plastics and other industries?containing toxic metal ions and organic dyes has been paid attention to.Because most of the organic matter in water even at low temperature still with high toxicity and difficult to biodegradable,and produces a series of environmental problems,such as water resources pollution and harmful gas emissions,etc,which constitute the life and health of human beings and the environment in various biological threat.In recent years,nanoscale semiconductor materials have attracted the attention of researchers due to their great potential in environmental protection.In commonly used semiconductor materials,zinc oxide?ZnO?because of the low price,non-toxic,performance excellent,stable physical and chemical properties,etc to get an in-depth and extensive research,particularly as the directions of photocatalytic in sewage treatment.Although a lot of research has been done in this area,there are still many problems that restrict the industrial application of ZnO.The traditional ZnO particle size is larger,and the surface area is small.In the case of photocatalytic reaction,it can only degrade the molecules of organic pollutants adsorbed on the surface;ZnO has a wide bandgap,which can only be excited by UV irradiation under 387 nm.However,ultraviolet light is only 4%;Under ultraviolet irradiation,ZnO's photogenic electron-hole is extremely easy to compound,and its life span is nanosecond,which seriously affects the photocatalytic activity of ZnO.The surface energy of the ZnO particles is larger,which could reunion in the process of photocatalytic phenomenon lead to the active site to reduce,and powdered ZnO are difficult to recycle easy to cause the secondary pollution and other issues;According to the above problem,this thesis with ZnO nanofibers as the research object,by changing the calcination method and doping methods such as load on the modification,enhance its photocatalytic performance of the application of the specific work is as follows:?1?ZnO precursor compound fiber was produced through the electrostatic spinning method,with the different pretreatment and calcination method three different morphology of ZnO were obtained,which were smooth ZnO nanofibers,porous ZnO nanofibers,porous spong-shaped ZnO.Structure and component of ZnO samples were characterized by XRD,XPS,EDS and DRS,morphology was studied by SEM and TEM.The results show that the calcining condition was the important factors influencing the ZnO morphology,by controlling the heating rate,the ZnO nanoparticles can constitute porous ZnO nanofibers or porous spong-shaped ZnO.Methyl orange solution was used as simulated organic pollutants,the photocatalytic activities of the ZnO samples were evaluated by the decomposition of methyl orange under UV-light irradiation.The results show that the porous spong-shaped ZnO showed the best catalytic activity.By the photoreduction processes Ag NPS was successfully decorated on the surface of the porous spong-shaped ZnO,and the porous spong-shaped Ag/ZnO heterostructures show better photocatalytic activity.?2?A novel method for synthesizing ZnO/?-Al₂O₃ nanofibers by electrospinning and subsequent calcination is reported.The prepared nanofibers were characterized by SEM,TEM,FE-TEM,XRD,EDS,and XPS.From the SEM and TEM,the average diameter of the ZnO/?-Al₂O₃ nanofibers were 200±20nm,and the uniformity was estimated to be above 80%.The XRD peaks of the ZnO/?-Al₂O₃ nanofibers look like the combination pattern of hexagonal wurtzite ZnO and?-Al₂O₃,The ZnO/?-Al₂O₃ nanofibers exhibited an excellent capacity for adsorbing organics with a negative zeta potential such as methyl orangeand heavy metal ions such as Cr⁶⁺in aqueous solution.The mechanism of the adsorption was investigated,and the adsorption results were fitted using the Langmuir and Freundlich models.Once silver nanoparticles were decorated on the surface of the nanofibers by photoreduction,the Ag/ZnO/?-Al₂O₃ nanofibers manifested efficient photocatalytic degradation of methyl orange under UV-light illumination.?3?Hollow TiO₂ and TiO₂/ZnO nanotubes were produced using a simple and novel approach combining electrospinning with an impregnation calcination method.Using a photoreduction method,During the synthesis process,the electrospinning procedure provided sacrificial templates for the fabrication of hollow nanotubes by producing PS nanofibers,which can be immobilized on the TiO₂ surface through a soaking method.Later,the composite nanofibers of TiO₂/PS were calcined into pure TiO₂ nanotubes after complete combustion of the sacrificial templates.The morphology of the samples was characterized by SEM and TEM.The structure and components of the samples were characterized by XRD,and the ultraviolet light absorption efficiency was detected using UV-vis diffuse reflectance spectroscopy?DRS?.The band gap energy and the calculated band edge were calculated from the DRS spectrav and supplemented the photocatalytic mechanism.The synthetic mechanism of TiO₂/ZnO nanotubes and the mechanism for the enhanced photocatalytic activity have been proposed.Moreover,provide a simple and efficient method for manufacturing hollow nanotubes.