Synthesis And Properties Of MOR Zeolites Synthesized From Natural Minerals

With the deepening of the concept of green development,the green synthesis strategy of zeolite has been explored,such as using natural minerals or industrial waste to synthesize zeolite.Natural minerals are widely found in nature.The main chemical composition of natural minerals is silicon-aluminum compounds,which is similar to the main chemical composition of zeolite.It is an environmentally friendly and cost-effective green synthesis method to synthesize zeolite by replacing pure chemical raw materials with natural minerals.In this thesis,natural stellerite（STI）and expanded perlite were used as raw materials to synthesize the pure phase of mordenite（MOR）,and the synthesis conditions affecting the crystallization of MOR zeolite were investigated.MOR zeolite has important applications in the fields of catalysis,adsorption,and ion exchange due to its unique pore structure,rich framework element composition,and excellent hydrothermal stability.CO₂ is an impurity gas of natural gas,biogas,and syngas.Selective capture of CO₂ is of great significance for the purification of the above gases.In this thesis,M-PMOR（M=Na,Sr,Mn）was prepared by ion exchange of MOR zeolite synthesized from expanded perlite.The separation performance of M-PMOR for CO₂/N₂/CH₄/C₃H₈ was investigaed.The rapid development of industrial production has produced a large amount of wastewater containing heavy metal ions.The cations in the MOR zeolite that balance the negative charge of the framework can be exchanged with the heavy metal cations in the wastewater.In this thesis,the synthesized MOR zeolite was used for the adsorption and removal of heavy metal ions Pb²⁺.The adsorption mechanism and the factors affecting the adsorption were discussed in detail.The main results of this paper are as follows:1.MOR zeolite,denoted as S-MOR,was hydrothermally synthesized without adding organic structure-directing agent using alkali-fusion activated natural stilbite as the sole aluminum source and by completing the necessary silicon source.The influence of synthesis conditions on the product was investigated.The products were characterized by XRD,SEM,TGA,MAS NMR and FT-IR.The optimum ratio was determined as follows:n（Na OH/Al₂O₃）=6.8,n（H₂O/Al₂O₃）=645,n（SiO₂/Al₂O₃）=16.4.2.MOR zeolite,denoted as P-MOR,was hydrothermally synthesized without adding organic structure-directing agent using expanded perlite as the sole aluminum source and by completing silicon source.The influence of synthesis conditions on the product was investigated.The products were characterized by XRD,SEM,TGA,MAS NMR and FT-IR.The optimum synthesis ratio was n（Na OH/Al₂O₃）=6.5,n（H₂O/Al₂O₃）=360,n（SiO₂/Al₂O₃）=17.5.M-PMOR was prepared by ion exchange of P-MOR.The separation performance of M-PMOR（M=Na,Mn,Sr）for CO₂/N₂,CO₂/CH₄,CO₂/C₃H₈ was evaluated.The results showed that the modified MOR zeolite had excellent separation performance for the separation of CO₂/CH₄,and Sr-PMOR had the highest CO₂/CH₄ separation factor.3.The removal ability of S-MOR and P-MOR zeolites for Pb²⁺in wastewater was investigated.The results showed that:（1）The removal efficiencies of S-MOR and P-MOR for Pb²⁺are all higher than 96%for the solid-liquid ratio of 1/1000,1/500,1/200,or 1/100;（2）S-MOR and P-MOR zeolites have excellent removal ability for Pb²⁺from the solutions with a p H of 3～7;（3）The adsorption process follows the Langmuir model and the maximum adsorption capacities of S-MOR and P-MOR for Pb²⁺were 384.6 mg/g and 421.9 mg/g,respectively;（4）The adsorption kinetics of both zeolites follow the pseudo-second-order kinetic model;and（5）Even the ratio of mass concentration between the competitive ions and Pb²⁺is as high as 1000:1,both S-MOR and P-MOR zeolites still have excellent selectivity for Pb²⁺,and the removal efficiency is still greater than 90%.Among the competitive ions,Na⁺and Mg²⁺have a great influence on the selectivity of S-MOR,while Mg²⁺has a great influence on the selectivity of P-MOR.