Organophosphorus acids for hydrometallurgical extraction. The synthesis of di(2-methylcyclohexyl)-, di(3-methylcyclohexyl)-, di(4-methylcyclohexyl)-, di(3,5-dimethylcyclohexyl)-, di(4-t-butylcyclohexyl)-, di(cyclohexylmethyl)- and dicyclohexyl- phosphinic; cyclohexylmethyl monocyclohexylmethylphosphonic; di(2-methylcyclohexyl)-, di(4-methylcyclohexyl)-, di(cyclohexylmethyl)- and di(cyclohexylethyl)- phosphoric acids and their evaluation as potential hydrometallurgical extractants for cobalt or nickel.

摘要

The syntheses and characterisation of di(cyclohexylmethyl),uddi(2-cyclohexylethyl), di(2-methylcyclohexyl) and di(4-methylcyclohexyl)udphosphoric acids; cyclohexylmethyl phosphonic acid monocyclohexylmethyludester, di(cyclohexylmethyl), di(4-methylcyclohexyl), di(4-tert-udbutylcyclohexyl), di(3-methylcyclohexyl), di(3,5-dimethylcyclohexy)udand di(2-methylcyclohexyl) phosphinic acids are reported.udProblems encountered and how they were resolved during theudpreparation of the above organophosphorus acids are reported anduddiscussed in detail.udThese acids are then evaluated as potential hydrometallurgicaludextractants, for the separation of cobalt from nickel in acid leachudliquors, and compared with two commercially available extractants,udnamely di(2-ethylhexyl)phosphoric acid (D2EHPA) and di(2,4-4-udtrimethylpentyl)phosphinic acid (Cyanex 272).udThe effects of variablest such as metal feed solution concentration,udextractant concentration, diluent, modifier and temperature areudexamined experimentally in order to determine which factors are importantudfor optimisation of an extraction system.udThe extraction characteristics for each acid as a function ofudpH are presented graphically and the pHO 5 values, distributionudcoefficients and separation factors are calculated.udThe dialkylphosphinic acids are found to exhibit much greaterudselectivity, for cobalt over nickel, than the dialkylphosphoricudacids.udIt is postulated, that steric crowding of the phosphorus atom,udby the hydrocarbon groups attached to the phosphorus, increases theudselectivity of an extractant. This effect is particularly apparentudin the dialkylphosphinic acids with di(2-methylcyclohexyl)phosphinicudacid giving the best selectivity; much better than the commerciallyudavailable Cyanex 272.udSeveral of the dialkylphosphinic acids, evaluated as extractantsudin this thesis, are protected by a British Patent Application.