| Rare earth has become a key material in many cutting-edge fields due to its unique properties.China's rare earth minerals are rich in types and large in reserves.As the market's supply and demand for rare earths surge,the mining of primary mines is also increasing.However,rare earth elements are non-renewable resources.In order to alleviate the over-exploitation of primary rare earth mines,it is urgent to recycle rare earth elements in various waste materials.Ionic liquid is a new type of green extraction material.When extracting rare earth elements,compared with traditional organic extractants,the saturated vapor pressure is low,not easy to volatilize,and there is no problem that the acidic extractant needs to saponify the organic phase to improve the extraction rate,an efficient and environmentally friendly green solvent.In this paper,the main elements of ferrite boron waste,niobium and niobium,were selected,respectively,to select the mitanion ionic liquid 1-butyl-3-methylmitium hexafluol phosphate([BMIM][PF6])and quaternary ammonium salt ionic liquid[tricaprylylmethylammonium][di-2-ethylhexylphosphinate]([A336][DEHP]).As a new extractor,the effects of different extraction conditions on Nd(?),Pr(?)extraction rate in rare earth elements are investigated by using trioctylphosphine oxide(TOPO)as the auxiliary agent,and the optimal process conditions are obtained,and the extraction mechanism is analyzed and discussed.1.Based on the characteristics of liquid extraction,the hydrophobic ionic liquid[BMIM][PF6]was synthesized by microwave assist,based on the raw materials of bromine,N-methylmide,and potassium hexafluoride.The extraction of Nd(?)and Pr(?)in rare earth elements with different neutral phosphate extractors was studied in the extraction of[BMIM][PF6].The effects of time,temperature,pH and A/O on extraction efficiency were studied in the best extraction system.The results showed that the extraction time was 20 min,the temperature was 25?,the pH was 5.5,and the extraction effect was the best for Nd(?)compared with A/O=1.The extraction rate was 97.8%;The extraction time is 25min,the temperature is 25 ?,the pH=6.0,compared with A/O=1,the extraction effect of Pr(?)is the best,and the extraction rate can reach 94.2%.The system extracts Nd(?)and Pr(?)as exothermic reactions,and the reaction enthalpy change ?H is-38.43 kJ/mol and-28.76 kJ/mol,respectively.2.Based on the similarity of the properties of the rare earth elements Nd(?),Pr(?)elements and the extraction process of mitose-type ionic liquid,the extraction process of the season ammonium salt ionic liquid to Nd(?)is investigated.Functionalized ionic liquid[tricaprylylmethylammonium][di-2-ethylhexylphosphinate]([A336][DEHP])was synthesized by ions-exchange method using quaternary ammonium salt ionic liquid tricaprylylmethylammonium([A336][Cl])as precursor.The structure of the product was characterized by FT-IR and 1HNMR.3.[A336][DEHP]was used as extractant,trioctylphosphine oxide(TOPO)as synergistic extractant to investigated the extraction efficiency of Nd(?)by three extraction systems[A336][DEHP],[A336][Cl]+TOPO and[A336][DEHP]+TOPO in hydrochloric acid.The results showed that[A336][DEHP]+TOPO system exhibited better synergistic extraction effect.Reducing temperature,increasing NaCl concentration and pH value were favorable for extraction of Nd(?)Under the conditions of NaCl concentration of 0.5 mol/L,pH 5.0 and temperature of 25?,the extraction efficiency of the above corresponding extraction system was 85.6%,78.6%and 96.5%,respectively.The synergistic extraction process(?H<0)was an exothermic reaction,and lowering the temperature was beneficial to the extraction process.The extraction mechanism was ion association mechanism.In the extraction process,cation and anion ions did not exchange in the aqueous phase,so the extraction system was environment-friendly.The organic phase loaded with Nd(?)can be completely stripped by 5%hydrochloric acid.The extraction system still had good extraction effect after 5 times of recycling. |
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