Synthesis of N-(2-Ethylhexyl)-2-aminobenzamide and Its Extraction Properties for Precious Metals

Abstract

N-(2-Ethylhexyl)-2-aminobenzamide (EHAB=RNN) was synthesized to develop a selective extractant for precious metals. In this study, the extraction selectivity from acidic chloride media was investigated using EHAB in toluene at 303 K. EHAB exhibited a high selectivity for palladium(II), gold(III) and platinum(IV) over base metals such as copper(II), zinc(II), mercury(II) and nickel(II) from hydrochloric acid. The extraction equilibrium of gold(III) was quantitatively examined from hydrochloric acid. The extraction of gold(III) can be represented by the following reactions:
The extraction equilibrium constants were determined to be K_ex1= 1.58×10¹⁰ (mol dm^-3)^-2 and K_ex2= 3.3×10² mol dm^-3, respectively.