Research On The Synthesis And Properties Of Isonicotinic Series MOFs Based On Ammonia Nitrogen Wastewater Treatment

Water is an important part of the natural environment and an indispensable condition for human survival and development.In recent years,due to the rapid development of human society,the problem of environment pollution has intensified.Water pollution,as a prominent issue in environmental pollution,is serious threat to human health and living environment.Therefor,the prevention and control of water pollution is very important.As a common water pollutant,ammonia nitrogen mainly exists in water in the form of nitrate,nitrous acid,ammonia and organic nitrogen.The ammonia nitrogen wastewater formed from them has a wide range of sources,resulting in ammonia nitrogen concentration,pH,and water quality in wastewater.There are differences in characteristics,so different types of ammonia nitrogen wastewater need to be treated with different methods.With the gradual deepening of people's research on ammonia nitrogen wastewater,researchers have developed treatment methods that are suitable for different conditions.As present,they are mainly divided into biological treatment methods and physical-chemical treatment methods,with obvious advantages and disadvantages,a balance must be found between cost and efficiency.As a traditional treatment method,the adsorption method is faced with the problems of improving the adsorption capacity and selectivity of the adsorbent and realizing the regeneration of the adsorbent in the treatment of the ammonia nitrogen wastewater.Although these disadvantages restrict the deeper application of the adsorption method,As for other common physical-chemical methods,its advantages of low cost,low energy consumption,simple operation and difficulty in secondary pollution make it still have a large development advantage.Metal Organic Frameworks?MOFs?have emerged as a new type of porous material that has emerged in recent years.They have a large specific surface area,a rich channel structure,and a regulated size.At the same time,some MOFs also have a flexible structure that can undergo reversible deformation and are easily regenerated.These characteristics make MOFs have a broad application prospect in the field of adsorption and separation.The selected M?INA?₂?M=Cu,Co,Ni,Zn??Ionicotinic acid series?MOFs in this paper have good water stability,large ammonia adsorption capacity,and reversible flexible structure facilitates ammonia capture and material regeneration.These characteristics make it possible for the application of ammonia nitrogen wastewater treatment.The main research contents and conclusions of this paper include:?1?We adopt an ammonia-assisted synthesis green method to prepare M?INA?₂?H₂O?₄?M=Cu,Co,Ni,Zn?series materials.This process requires fine adjustment of the amount of ammonia added to provide the crystal in a suitable environment for growth,compared with the traditional hydrothermal synthesis,this method can be quickly synthesized at room temperature.Then we transform the M?INA?₂?H₂O?₄?M=Cu,Co,Ni,Zn?series materials into M?INA?₂?M=Cu,Co,Ni,Zn?series materials through structural transformation.?2?The unsaturated metal sites in the M?INA?₂?M=Cu,Co,Ni,Zn?series of materials can adsorb water molecules and ammonia molecules.Using this property,we have explored the processing conditions in simulation of ammonia nitrogen wastewater at high concentration.Through experiments,it was found that this series of materials is suitable for treating simulated ammonia nitrogen wastewater with alkaline high concentration?1000 mg/L?,and the highest pH value that can be tolerated is 10,under which ammonia nitrogen wastewater treatment performance of the four materials is:the removal rate of Ni?INA?₂ is40.5%,the equilibrium adsorption capacity of the materials is 40.5 mg/L;the removal rate of Cu?INA?₂ is 29.9%,the equilibrium adsorption capacity of the materials is 29.9 mg/L;the removal rate of Zn?INA?₂ is 17.4%,the equilibrium adsorption capacity of the materials is 17.4 mg/L;the removal rate of Co?INA?₂is 30.4%,the equilibrium adsorption capacity of the materials is 30.4 mg/L.?3?In the process of treating ammonia nitrogen wastewater,three-dimensional materials M?INA?₂?M=Cu,Co,Ni,Zn?will convert to zero-dimensional materials M?INA?₂?H₂O?₄ and M?INA?₂?H₂O?₂?NH₃?₂?M=Cu,Co,Ni,Zn?due to the coadsorption of ammonia molecules and water molecules.We have reprocessed the material that has been subjected to the simulated ammonia nitrogen wastewater treatment experiment and placed it in an oven at 180?for 2 hours to deactivated the water molecules and ammonia molecules in the structure and regenerate the materials to M?INA?₂?M=Co,Ni,Zn?,found during the experiment that Cu?INA?₂ will be converted to Cu?OH??INA?·H₂O and lose its flexible reversible nature,making it impossible to regenerate.?4?We have conducted a recovery experiment on the NH₃ captured by the material.The ammonia nitrogen recovery rate of Ni?INA?₂ is 49.3%;the ammonia nitrogen recovery rate of Co?INA?₂ is 29.94%;the ammonia nitrogen recovery rate of Zn?INA?₂ is 26.57%;the ammonia nitrogen recovery rate of Cu?INA?₂ is 17.97%.