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The Preparation Of Functionalized MCM-41 Mesoporous Materials And Its Adsorption Properties Of The Rare Earth Ions

Posted on:2018-10-07Degree:MasterType:Thesis
Country:ChinaCandidate:Y WangFull Text:PDF
GTID:2321330518466162Subject:Applied Chemistry
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This paper aimed at the not completely recycle and serious waste of rare earth resources in the exploitation process,with the guide of green chemistry concept,we successful synthesized a kind of new functioned mesoporous silica materials with the MCM-41 as the substrate,two kinds of silane coupling agent as the modifier.Then the mesoporous silica materials were applied to the enrichment and recovery experiments of the light rare earth ions La3+,the middle rare earth ions Gd3+and the heavy rare earth ions Yb3+respectively.According to the experimental results,this paper systematic explored the adsorption and desorption behavior of low concentration of rare earth ions on the three kinds of adsorbents.First of all,we synthesis the MCM-41 molecular sieve simply and efficiently using TEOS as silica source and CTAB as template agent,which BET pore size and specific surface area of was 2.94 nm and 1114.8 m2/g.Then by joining two kinds of silane coupling agents,APTES and MPTES,we successfully synthesized two materials named NH2-MCM-41 and SH-MCM-41,which BET pore size and specific surface area were 2.15 nm,956.2 m2/g and 2.10 nm and 956.0 m2/g respectively.The coupling agent had been successfully entered into the internal MCM-41 mesoporous molecular sieve,and realized the pore surface modification.Second,with the MCM-41 ? NH2-MCM-41 and SH-MCM-41 as adsorbents,this paper studied the factors that influenced adsorption reaction conditions,including the single factors,the isothermal adsorption,thermodynamics and kinetics,adsorption mechanism and the regeneration performance.Experiment showed that at the optimal conditions,the maximum adsorption quantity of La3+,Gd3+and Yb3+on MCM-41 were 434.08 mg/g ? 418.42 mg/g and 492.40 mg/g respectively;The influence of interfering ions Fe3+,Al3+,Ca2+,Mg2+ and NH4+on adsorption quantity is: The trivalent ions can form competitive adsorption with the rare earth ions to reduce its quantity,and the influence of other ions on the adsorption quantity is very small.The optimum amino grafting amount?in N?was 1.98%,in this condition,the adsorption quantity of Yb3+on NH2-MCM-41 adsorbent was 709.70 mg/g.The adsorption process largely in line with the Freundlich isothermal model,and the dynamics can be described as the pseudo-second order kinetic equation.The best amount of graftingamount?in S?is 6.06%.Under the optimum adsorption conditions,the saturated adsorption quantity of La3+,Gd3+ and Yb3+ on SH-MCM-41 adsorbent reached to560.56 mg/g?507.85 mg/g and 540.68 mg/g respectively.Finally,this paper explored the desorption and regeneration performance of adsorbents with the hydrochloric acid ?nitric acid and the citric acid as the desorption agent respectively.Comprehensive the concept of green chemistry,the best desorption condition is HCl solution which concentration is 2 mol/L,and desorbed for 1 h,the first desorption rate of La3+?Gd3+ and Yb3+ reached 93.4%?93.4% and 95.3% on the SH-MCM-41 asdorbent respectively;After the SH-MCM-41 adsorbent has been reused for 4 times,it's adsorption rate of La3+,Gd3+and Yb3+still remained above 80%,it is indicated that the SH-MCM-41 adsorbent has good hydrothermal stability and could be recycled to save the cost of adsorption process.
Keywords/Search Tags:Rare earth ions, adsorption, desorption, MCM-41mesoporous molecular sieve, alkylation, cyclic regeneration
PDF Full Text Request
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