Synthesis And Adsorption Properties Of ZIF-8

Water is an important element which is considered as vital need and compulsory for the survival of life on earth.Nowadays,the whole world is facing severe water quality problems.Wastewaters from various industrial actions are main cause of this environmental pollution,because of carrying large amount of heavy-metal ions.Heavy metals,due to their toxic nature,have great influence of living organism.Currently,many water treatment methods for the removal of heavy-metal ions are commercially applied for example adsorption process,ion exchange,chemical precipitation,membrane filtration,electrochemical processes,and to solve the water problems.Adsorption is one of the major vital methods in wastewater treatments methodologies.It has different advantages for removal of heavy metal.The porous material is a significant segment of the economy,it is in general consideration to develop and design porous material to have versatile properties.Zeolitic imidazolate framework-8 ZIF-8 materials attained much more interest due to their feasible structures and properties with their high capability for different applications.In this research work,we have selected Zeolitic imidazolate framework-8 ZIF-8 materials which possess good crystal structure like zeolite material,which is a type of MOFs material.We focused on the synthesis of ZIF-8 material and give their adsorption properties for heavy metal ions removal.Initially,this work demonstrates the synthesis of ZIF-8 material by solvothermal method which contains zinc as metal ion and 2-methylimidazole as ligand and dimethylformamide DMF used to modifies the evolution of reaction.The various characterization techniques were used such as X-ray diffraction?XRD?,Scanning electron microscopy?SEM?and Fourier transform infrared spectroscopy?FT-IR?to explore the characteristics of synthesized ZIF-8 samples.The performance of synthesized sample of ZIF-8 was investigated in the adsorption method to eliminate of heavy metal ions from de-ionized water.The results indicate that ZIF-8 was proposed as an competent adsorbent material for heavy metal ions?HMIs?removal including Zn²⁺,Cu²⁺,Pb²⁺,Cd²⁺ and Ni²⁺ from water.The influence of some important operating parameters?i.e.,pH value of the solution,concentration of HMIs,adsorption time,and adsorbent dosage?on adsorption performance?i.e.,adsorption capacity and removal ratio?was also investigated.So,it explain when the pH of aqueos solution is high,the degree of protonation of the functional groups is strong,Competitive ion H⁺ decreases,the chemical complex interaction increased.For that reason,ZIF-8 has high capacity to adsorb the large quantity of heavy metal ions HMIs.The equilibrium adsorption time of Cu²⁺,Zn²⁺,Pb²⁺,Cd²⁺ and Ni²⁺ are 25,5,15,45 and 10 h,respectively,and the saturated adsorption capacity of HMIs are 481.9,249.6,1184.8,812.8 and 247.2 mg·g^-1,respectively.We compared this result with literature,and found that this result is better than the natural and artificial adsorbents,such as activated carbon,zeolite,rice husk,peat etc.The XRD and FT-IR characterization of ZIF-8 and ZIF-8 with ions powder reveal that before and after the adsorption process,the crystal structure has changed,and also showed that the adsorption is ion exchange chromatography and chemical complex interaction may also occur.Therefore,it is found that there is chemical adsorption except physical adsorption.In this part of the research,the preliminary adsorption mechanism is demonstrated that,correlating the experimental data with adsorption isotherm and kinetics equations and examining the ion exchange during the adsorption process.By this study,we know that the adsorption process is good correlation with the Langmuir model.The K_L order of five metal ions is Pb²⁺>2n2+>Cu²⁺>Cd²⁺>Ni²⁺.The saturated adsorption capacities are near to the results of correlation.So,that means experimental results agree with model.In this portion,the ion exchange intensity in the adsorption process was investigated by calculating the concentration of Zn²⁺ ions in the adsorption solution,then it examine that the intensity of ion exchange increase and then turn into smooth with the increase of the heavy metal ions concentration during the adsorption process.When the initial amount of metal ions HMIs is fixed value 300 mg·L^-1 then the order of ion exchange intensity is Pb²⁺>Cu²⁺>Ni²⁺>Cd²⁺.