Synthesis And Extraction Performance Of High Purity Organophosphorus Acid Extractants

Organophosphoric acid extractants have been widely used to separate nickel /cobalt and rare earths due to their high selectivity,low water solubility,and low stripping acidity.Among them,the extraction performance of bis?2,4,4-trimethylpentyl?phosphinic acid?DTMPA?is especially prominent because there are two C-P bonds and larger steric hindrance in its structure.However,there are many defects on its existing production process?PH3-route?,such as high pressure,high toxicity of raw materials,low purity of products.Therefore,the price of DTMPA is very high,which limits the application and popularization.The synthesis of DTMPA with H3PO2-route,and its extraction properties was studied in this thesis.DTMPA was synthesized in one step by using hypophosphorous acid?H3PO2?and di-isobutylene?C8H16?as raw materials and t-butyl peroxide as free radical initiator through free radical reaction.The effect of ratio of raw material,temperature and time on product yield and purity were investigated.The crude products were purified with three-phase method.NMR?1H,31 P spectrum?,IR,MS and GC,and potentiometric titrationetc were used to characterized the products.The results show that no trialkyl phosphine exists in the crude products,which make the purification process easier.The optimum synthesis parameters are: molar ratio of C8H16 to H3PO2 2.2: 1,reaction temperature 135 ?,reaction time 32 h.After purification,the purity of final product is about 98.4% with yield about 76%.Compared with PH3-route,this method has some advantages,such as fewer side reaction,higher purity and yield,free of highly toxic PH3 gas,lower reaction pressure,which make it easy to scale production.The extraction properties of Co,Ni,Cu,Fe,Al,Zn and other metal ions of the as-synthesized DTMPA has been studied.The results show that the separation coefficient?bNi / Co?of Ni/Co is 2950.The maximum loading for Co is 8.1g/L at pH 5.5,which can be completely striped by 0.16mol/L of H2SO4 at the phase ratio of 1:1.the extraction sequence of metal ions is: Fe3+ > Zn²⁺ >Al3+> Cu²⁺ > Co²⁺ > Cd²⁺ > Mn²⁺> Mg²⁺ > Ca²⁺ > Ni²⁺.Its extraction behavior is similar to that of Cyanex272?Cytec.product?,and the comprehensive performance is slightly better than that of Cynex272.In addition,measurements of physicochemical properties indicate the water solubility?S?,pKa,surface tension?s?,density?r?of DTMPA are 7.30×10-5mol/L,4.10,26.175mN/m,0.920g/mL respectively.It is displayed that DTMPA pocess good physicochemical properties as a extractant.The research results of this thesis are expected to promote the development of low-cost and high-security preparation technology,and the application in the fields of metal extraction and separation for DTMPA.