SOLVENT EXTRACTION OF GOLD FROM HYDROCHLORIC ACID SOLUTIONS USING BIS(DIALKYLPHOSPHONATE)S

摘要

The extraction of gold(Ⅲ) from hydrochloric acid medium is studied by using newly synthesized extractants, the α,ω-alkane-diyl-bis(dialkylphosphonate)s (ABDAP),commonly known as the bis(dialkylphosphonate)s. Gold is most favorably extracted with these reagents at HCl concentrations above 5M and the extraction is not interfered by palladium(Ⅱ), silver(Ⅰ), copper(Ⅱ) and lead(Ⅱ) ions, when methylene bis(diiso-propylphosphonate) (MBDIPP) dissolved in 1,2-dichloroethane (DCE) is used as the extractant. In 5M HCl, the extraction of Au(Ⅲ) by MBDIPP reaches equilibrium in 1 min. through formation of a 1:1 solvating complex, MBDIPP:HAnCl_4. For ABDAPs, the extractability is affected by the alkoxy substituent attached to the phosphorus atoms while the selectivity of gold(Ⅲ) extraction is governed by the length of the hydrocarbon chain separating the two P=O sites in the diphosphonate molecule. Various extraction parameters are evaluated in relation to the recovery of the metal from acidic waste solutions and the data are compared with those of tri-n-butyl phosphate (TBP) and tri-n-octylphosphine oxide (TOPO).