Study On ZIF-8 Preparation By Mechanical Grinding Method And Performance Of Photocatalytic/Adsorption Removal Of Pollutants

With the rapid development of modernization,water pollution has become increasingly prominent,which contains a lot of pollutants(such as methyl orange,methylene blue,congo red,tetracycline etc.),with high biological toxicity,high chroma and difficult to biodegrade and other characteristics.Organic dye wastewater flow into the water environment will seriously affect the photosynthesis of aquatic plants,causing serious harm to water resources,the ecological environment and human health.Although adsorption method,membrane separation method,electrochemical method,etc.have achieved certain effects in the treatment of certain dye wastewater,each has its shortcomings and limitations.For example,the adsorption method is widely used because it is cheap and easy to operate,but this method only enriches the pollutants and cannot completely eliminate them.As a green and environmentally friendly treatment solution with mild conditions,photocatalytic technology can achieve high-efficiency removal of pollutants under light,and can degrade and even completely mineralize macromolecular pollutants that are difficult to biodegrade into carbon dioxide and water.However,traditional photocatalysts have various problems such as poor stability and low reaction conversion rate.Therefore,it is a challenge to find photocatalysts that are simple and scaled to synthesize,syntheses,have strong photocatalytic effects,high stability,and good cyclability to control organic dye pollution.problem.In this thesis,firstly,the was synthesized by mechanical grinding method with high throughput and rapid speed,and it was characterized by powder X-ray diffraction,FTIR,SEM,UV diffuse reflectance spectroscopy and other means.Furthermore,the performance and mechanism of its photocatalysis and adsorption removal of pollutants are discussed in detail.The main content and conclusions are as follows:Chapter 2,using ZIF-8 as the photocatalyst and methyl orange as the target to verify its photocatalytic activity.The performance of catalyst ZIF-8 under ultraviolet light is tested by adjusting solution p H,pollutant concentration,catalyst dosage,and co-existing ions.The capture experiment of the active substance is carried out,then the possible photocatalytic degradation mechanism is proposed.After three cycles of experiments,ZIF-8 was characterized by powder X-ray diffraction,FTIR to evaluate the stability and catalytic activity of the photocatalyst ZIF-8.The degradation rates of the three cycles of MO were 99.10%,98.57%,and 97%,respectively.Chapter 3,using ZIF-8 as the photocatalyst and reactive red X-3B as the target to verify its photocatalytic activity.The catalytic performance of ZIF-8 was tested under ultraviolet light by adjusting solution p H,pollutant concentration,catalyst dosage,and co-existing ions,and verify the stability of catalyst through cycle experiments.The final three cycles of X-3B degradation rate were 99.1%,99%,98%,respectively.Chapter 4,using ZIF-8 as the photocatalyst and the mixed solution of MO and X-3B as the target to test its photocatalytic activity.The catalytic performance of ZIF-8was tested by adjusting solution p H,catalyst dosage,co-existing ions and other conditions.The final degradation rates after three cycles were MO:77.05%,52.03%,25.22%;X-3B:84.01%,67.75%,51.11%.The lower cycle performance of the photocatalyst in the mixed solution was explored.By comparing the XRD,FTIR of ZIF-8 before and after the reaction,it was found that the internal structure of the photocatalyst did not collapse.It is reasonable to guess that the lower degradation rate of the photocatalyst may be caused by the concentration of the solution.The increase in the concentration of pollutants leads to a decrease in the utilization rate of light.Chapter 5,using ZIF-8 as the adsorbent and tetracycline as the pollutant to explore its adsorption removal activity.The kinetics behavior and equilibrium isotherm were well described using pseudo-second-order and Langmuir model,respectively.Thermodynamic parameters including standard Gibbs free energy(?G~o<0),endothermic(ΔH~o>0)and entropy change(ΔS~o>0),were calculated with the aid of data obtained from Langmuir adsorption isotherm indicating that the adsorption process was endothermic,spontaneous and tending to be disordered.And the adsorption process was a physical chemical adsorption.Using the photocatalytic properties of MOFs,the photoreactive degradation of tetracycline by ZIF-8 was verified under UV irradiation conditions to verify the recyclability of ZIF-8.Through three cycles of experiments,the adsorption capacities were 175.44 mg/g,165.83mg/g and 139.19 mg/g,indicating that ZIF-8 has good reusability.The effect of different p H conditions on the adsorption effect was discussed.It was concluded that when 4<p H<8,the adsorption effect was the best,and when the p H was too acidic or too alkaline,the adsorption effect would be worse.The mechanism of adsorption of tetracycline by ZIF-8 included electrostatic interactions,hydrogen bonding,andπ-πstacking,which were proved by the characterization techniques like PXRD,FTIR,and Zeta potential.ZIF-8 could be regenerated by UV irradiation,which showed excellent recycling performance.ZIF-8has great potential in the removal of tetracycline from waste water.