Engineering Of Mesoporous Titanium Dioxide From Titanium Glycolate Precursor And Its Application For Adsorption-photocatalytic Removal Of Antibiotics

In recent years,antibiotics used in daily life have accumulated in the natural environment because they are difficult to be naturally degraded or biodegraded.It results in prolonged contact of antibiotics with pathogenic bacteria and emergence of drug-resistant super bacteria,which is a great threat to human health.Therefore,development of effective methods to remove antibiotic pollutants in the environment have attracted widespread attention.Physical adsorption and microbial degradation were mainly used to remove antibiotic contaminants in the environment.At the same time,adsorption-photocatalysis technology has attracted attention due to its features of high efficiency,easy operation,and low energy consumption.It was found that porous titania nanomaterials not only have the same advantages of non-toxicity,chemical/thermal stability and photo-corrosion resistance with conventional titania material,but also can increase the adsorption capacity,promote the diffusion of reactants and substrate molecules,and be used as active sites to enhance photocatalytic activity.However,it is a great challenge to fabricate highly-efficient porous titanium oxide nanomaterials with optimized synthesis condition and composition.In this regard,in this thesis,titanium glycolate precursor was used to prepare porous TiO₂nanomaterials with controlled structure and composition by changing the post-treatment modes and synthesis strategies.And then the adsorption and photocatalytic performance of as-synthesized porous TiO₂ materials was studied.The harm of degradation process to the environment was also evolvated.The main research content is as follows:1.Three kinds of mesoporous TiO₂ materials synthesized from titanium glycolate precursor with three different post-treatment methods?hydrothermal,calcination,and hydrothermal-calcination,denoted as TiO₂-H,TiO₂-C,and TiO₂-H/C,respectively?were employed for the removal of ciprofloxacin?CIP?antibiotic.The variations in the composition and structure of TiO₂ nanocrystals from the precursor were studied in detail by powder X-ray diffraction,scanning electron microscopy,transmission electron microscopy,and nitrogen adsorption analysis.The impact of post-treatment approaches on the titanium glycolate precursor in terms of the adsorption capability and photocatalytic activity of TiO₂ nanoaggregates was evaluated on the removal of CIP solution.Compared to TiO₂-C and TiO₂-H/C,the TiO₂-H material exhibited superior capability towards CIP adsorption and photodegradation.Among the three kinds of post-processing methods,the hydrothermal treatment contributed larger surface areas and weaker hydrophilic properties to the TiO₂-H material,and accordingly facilitated efficient adsorption of CIP from the solution.On the other hand,the obtained TiO₂-H displayed efficient electron-hole separation and fast charge transfer capabilities,resulting in higher photocatalytic activity towards CIP degradation initiated by holes and·OH radicals than the other materials.In addition,the results of a microbiological antibacterial activity assay demonstrated that the degradation products of CIP solution were less harmful to the environment.2.The porous TiO₂ aggregates obtained by hydrothermal treatment in the first part were used to evaluate the universality of antibiotic contaminants removal by photocatalytic technology.The singal or mixed antibiotic systems were used,such as ciproflucaxin,norflucaxin,peflucaxin,tetracycline,and cefotaxime sodium.It was shown that obtained TiO₂ material has good removal and mineralization properties towards the above antibiotic systems.Among them,the single or mixed systems of contained ciprofloxacin,norfloxacin,pefloxacin and tetracycline showed the best photocatalytic mineralization performance.Through microbial experiments,it was found that the antibacterial rate of the degradation residue after photocatalytic process was significantly reduced,and the final degradation products would no longer cause drug resistance in the environment.3.Copper nanoparticles?Cu NPs?modified porous TiO₂ nano-aggregate composites?Cu@TiO₂?were prepared by a simple reduction method.The composition and structure of the composites were characterized.The involvement of Cu particles did not affect the morphology or mesoporous structure of the TiO₂ nanoaggregates,and the size of Cu particles in the hybrids was simply controlled by adjusting the added amount of Cu²⁺.The adsorption and photocatalytic performance towards Ciprofloxacin of the as-synthesized Cu@TiO₂ hybrids were determined by the mass ratio as well as the Cu particle size of Cu/TiO₂ in the hybrids.The Cu@TiO₂ hybrid with low Cu content promoted photocatalytic performance,while high Cu content improves the adsorption efficiency.Among the as-prepared Cu@TiO₂ samples,the 0.1-Cu@TiO₂ sample with Cu particle content of 0.1wt%presented the best photocatalytic efficiency,which was attributed to its having the best charge separation and transfer efficiency of photogenerated electron and holes,while10-Cu@TiO₂ with 10 wt%Cu showed the highest adsorption capability due to its having the most negative zeta potential,although its Brunauer-Emmett-Teller?BET?surface area was less than the pure TiO₂ material.A comparative study has revealed how Cu@TiO₂material composites can be optimized for adsorption and photocatalytic toxin removal.