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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.

By Surinder P. Chahal

Abstract

The syntheses and characterisation of di(cyclohexylmethyl),\ud di(2-cyclohexylethyl), di(2-methylcyclohexyl) and di(4-methylcyclohexyl)\ud phosphoric acids; cyclohexylmethyl phosphonic acid monocyclohexylmethyl\ud ester, di(cyclohexylmethyl), di(4-methylcyclohexyl), di(4-tert-\ud butylcyclohexyl), di(3-methylcyclohexyl), di(3,5-dimethylcyclohexy)\ud and di(2-methylcyclohexyl) phosphinic acids are reported.\ud Problems encountered and how they were resolved during the\ud preparation of the above organophosphorus acids are reported and\ud discussed in detail.\ud These acids are then evaluated as potential hydrometallurgical\ud extractants, for the separation of cobalt from nickel in acid leach\ud liquors, and compared with two commercially available extractants,\ud namely di(2-ethylhexyl)phosphoric acid (D2EHPA) and di(2,4-4-\ud trimethylpentyl)phosphinic acid (Cyanex 272).\ud The effects of variablest such as metal feed solution concentration,\ud extractant concentration, diluent, modifier and temperature are\ud examined experimentally in order to determine which factors are important\ud for optimisation of an extraction system.\ud The extraction characteristics for each acid as a function of\ud pH are presented graphically and the pHO 5 values, distribution\ud coefficients and separation factors are calculated.\ud The dialkylphosphinic acids are found to exhibit much greater\ud selectivity, for cobalt over nickel, than the dialkylphosphoric\ud acids.\ud It is postulated, that steric crowding of the phosphorus atom,\ud by the hydrocarbon groups attached to the phosphorus, increases the\ud selectivity of an extractant. This effect is particularly apparent\ud in the dialkylphosphinic acids with di(2-methylcyclohexyl)phosphinic\ud acid giving the best selectivity; much better than the commercially\ud available Cyanex 272.\ud Several of the dialkylphosphinic acids, evaluated as extractants\ud in this thesis, are protected by a British Patent Application.Science and Engineering Research\ud Counci

Topics: Organophosphorus acids, Hydrometallurgic extractants, Cobalt, Nickel, Separation, Phosphinic acids, Extraction characteristics, Dialkylphosphinic acids, Dialkylphosphoric acids
Publisher: Postgraduate School of Studies in Chemistry
Year: 1987
OAI identifier: oai:bradscholars.brad.ac.uk:10454/4395
Provided by: Bradford Scholars

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