“…Alkyl phosphorus acids are the most widely used acidic extractants [2][3][4]. Bis (2-ethylhexyl) phosphoric acid (HDEHP), bis(2-ethylhexyl) phosphinic acid (Cyanex ® 272) and bis(2-ethylhexyl) dithiophosphoric acid are some of the alkyl phosphorus acids extractants which are employed in extraction of metal ions [5]. In particular, HDEHP has been extensively used for the extraction of metals such as uranium, lanthanides, nickel, cobalt, zinc and other divalent transition metals [6][7][8].…”