| Rare earth and chromium are important+3 valence transition metal elements.Rare earths are strategic resources in China,which are irreplaceable key material in modern high-tech industries and national defense industries and have been widely used in many fields.The coexistence of lanthanide elements in minerals and the contraction of lanthanide lead to the similarity of electron layer structure and physical and chemical properties among rare earth elements,so the rare earth extraction and separation has always been the focus of research.Chromium has the advantages of hard,brittle and corrosion resistance,and plays a vital role in metallurgy,chemical industry,tanning and electroplating,etc.However,wastewater containing Chromium caused by these industries due it’s of danger,it is urgent to reduce the damagement and recover resource.The emulsion liquid membrane(ELM)method includes two processes:extraction and stripping,and its separation effect is remarkable.It has large specific surface area and fast mass transfer rate.Compared with solvent extraction,the amount of extraction agent is greatly reduced.However,the ELM method has some shortcomings such as poor stability and unsatisfactory extraction.Therefore,to solve the above two problems,the research of improving this method was carried out.For the poor stability,this paper explored the construction of ELM system.For the poor separation effect,this added the ionic liquid with excellent physical and chemical properties into the ELM to form a new ionic liquid emulsion membrane system,used to study the separation of rare earth.Not only has the ELM been further applied to the extraction and separation of metals,but the ELM system containing ionic liquid has been constructed for the extraction and separation of rare earth for the first time.The main contents of this paper are as follows:Firstly,the ELM was constructed to extract Re(Ⅲ)and study the kinetics of extracting Re(Ⅲ)and Re(Ⅲ).Secondly,Cr(Ⅲ)was recovered from stainless steel pickling waste solution by ELM and electrolysis-extraction.Thirdly,the ELM containing ionic liquid was used to extract and separate Re(Ⅲ).The following conclusions were drawn:Firstly,using Re(Ⅲ)extraction rate as the index,the ELM was composed of 6.0%D2EHPA,5.0%T154,3.0 mol·L-1 HCl solution,Roi=1.5 by single factor experiment.Kinetic study showed that:emulsification time is 5.0 min,extraction time is 6.0 min,Rew=0.5,extraction temperature is 25℃,the material liquid pH is rare earth hydrate aqueous solution(pH=5.6),ELM technology showed excellent extraction capacity in the low concentration of La3+ solution condition,as well as good enrichment.According to Fick’s first law,the mass transfer rate of La3+in ELM is k=9.35×10-10 m·s-1.Secondly,The extraction rate of Cr(Ⅲ)was used as the index to construct a W/O/W ELM system.The experimental results showed that the extraction efficiency of Cr(Ⅲ)could not be improved.Then,the method of electrolytic extraction combined to separate and recovery of Cr(Ⅲ)from the stainless pickling waste solution was adopted.Fe loss rate from sulfuric acid pickling waste liquor is only low to 30%,and recovery rate of Cr is up to 94%,to achieve the purpose of Cr recovery.Finally,six kinds of ILS-ELM were added into the organic component of traditional ELM,namely[Omim]Cl,[OPy]Cl,TOMAC,[Omim][PF6],[Omin][BF4]and[OPy][BF4].The results showed in two aspects.First,Only TOMAC,[Omim]Cl and[OPy]Cl three ILs could be dissolved in Span80 system.Next,using n-amyl alcohol as additive can only increase the solubility of the three ILs in Span80 and T154 systems,but there is no selectivity to La3+,and the stability of the liquid film system is reduced after the introduction of n-amyl alcohol.Although the stability was decreased as the TOMAC added in ELM,the static demulsification efficiency was improved.[Omim]Cl can improve demulsification efficiency on the premise of ensuring ELM stability.Second,with the addition of D2EHPA,the extraction rates of La3+and Ho3+decreased with the increase of TOMAC,[Omim]Cl and[Opy]Cl concentrations.In the T154 system,β(Ho3+/La3+)was the highest,and the corresponding maximum values of the three ILs-ELM were 3.41,6.0 and 10.23,respectively.Among them,[Opy]Cl had the best separation effect. |
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