Preparation Of Ordered Porous Cordierite Ceramics Based On Associated Rare Earth Kaolin And Research On Its Propertie

The release of dangerous compounds has become more significant in recent years due to China’s rapid economic growth and urbanization,which have led to serious air and water pollution.The level of water pollution is far greater than the capacity of the natural environment to purify itself.Through the food chain,heavy metal ions would build up in the water and eventually cause serious harm to people.Studies have indicated that there are many locations where surface water from rivers,reservoirs,and lakes contains more lead than is permitted.In this study,a type of ordered porous cordierite ceramics with macropores and micropores was developed for the adsorption of heavy metal ions in sewage.This ceramic was prepared using the associated rare earth mineral kaolin as the main raw material and a minor amount of alumina and magnesium oxide.Four areas of scientific research and discussion are being carried out in a systematic manner:study on the mineral properties of kaolin and the crystal structure of kaolinite;study on the preparation technology and synthesis mechanism of cordierite ceramics;preparation,structure,and properties of ordered porous cordierite ceramics;and study on the lead ion adsorption properties of ordered porous cordierite ceramics.The main research contents and conclusions are as follows:（1）In order to study the raw material chemical composition,mineral composition,and microscopic morphology of associated rare earth kaolin,X-ray diffraction（XRD）,scanning electron microscopy（SEM）,infrared spectroscopy（FT-IR）,and synchronous thermal analysis（TG-DSC）were used to characterize kaolin.The results show that the mass ratio of Si O₂/Al₂O₃in the associated rare-earth kaolin is 2.13 and the content of rare-earth oxides is 0.331 wt.%.Kaolin has a lamellar structure,and its main mineral composition is kaolinite and quartz,and kaolinite has structural order.（2）In order to obtain high purity eriderite ceramic materials,a certain amount of Al₂O₃and Mg O were added to kaolin to meet the theoretical ratio of eriderite,and a series of characterization methods such as Archimedean drainage method,TG-DSC,FT-IR,XRD and SEM were used to explore the synthesis mechanism of eriderite ceramics.According to its mechanical properties,corrosion resistance,and thermal shock resistance,the ratio of raw materials required for the synthesis of cordierite is finally determined as follows:The associated rare earth elements are kaolin,80.2wt.%;alumina,7.6 wt.%;and magnesium oxide,12.2 wt.%.Combined with XRD,SEM,and EDS analysis results,the synthesis temperature range of cordierite is1200～1250°C,and the holding time is 2 h.（3）In order to study the preparation process of ordered porous cordierite ceramics,organic mesh was used as the macro template and biomass waste hemp stalk powder was used as the micro-pore-making agent,and the green blanks were superimposed by the laminated entity process to obtain the green blanks of cordierite ceramics.In the sintering process,the rubber was discharged,so as to leave the pore structure and get ordered porous cordierite ceramics.Due to the structural characteristics of the organic mesh material,the pore arrangement and fixed shape of the original organic mesh arrangement are obtained after sintering.By adjusting and controlling the mesh structure of organic matter and hemp stalk powder,porous ceramics with different porosities and structures can be prepared,and the pore structure rules are controllable.Under the optimal sintering conditions,i.e.,1260°C sintering temperature and 2 h sintering holding time,when the amount of hemp rod powder is 30 wt.%,the apparent porosity is 52.2%,water absorption is 39%,volume density is 1.19 g/cm³,and the alkali corrosion resistance rate is 99.68%.（4）In order to study the adsorption performance of ordered porous cordierite on heavy metal ions in sewage,the adsorption performance of ordered porous cordierite ceramics on heavy metal ions of lead was measured by ultraviolet visible spectrophotometer.The study says:Ordered porous cordierite ceramics have good adsorption and desorption properties for Pb（II）in water.When the initial concentration of Pb（II）solution is 80mg L-1,p H value is 6.0,the dosage of cordierite is 20g·L-1,and the adsorption reaction time is 8 h,the removal rate of Pb（II）in water can reach 97.89%.The adsorption capacity was 3.814 mg/g.The porous ceramics with 20%pore-forming agent were used as adsorbents,and with the increase in adsorption time,the adsorption effect of porous ceramics on the adsorption rate of Pb（II）became better.