Efficient diglycolamic acid extractant for separating and recycling Au(III)

Abstract

The type of diglycolamic acid extractantN,N-di-2-ethylhexyldiglycolamic acid (D2EHDGAA) was examined for selective extraction and separation of Au(III) in acidic chloride solutions containing Pd(II), Pt(IV), Rh(III), and Cu(II). The separation factor βAu/Pt = 959.3 was observed in 7 M hydrochloric acid. The extraction of Au(III) was quick, and extraction equilibrium was reached in less than 5 min. The n-dodecane and kerosene diluents had a notable effect on the extraction of Au(III) with the D2EHDGAA, and the D2EHDGAA had excellent capacity in n-dodecane and kerosene. However, the selectivity coefficient of Au(III) and Pd(II) was better in n-dodecane (βAu/Pd = 1070) than in kerosene (βAu/Pd < 0.1) of 4 M hydrochloric acid. The extraction mechanisms of the Au(III) and Pt(IV) were investigated, and the results suggest that one metals ion is extracted with two and one extractants in 1 M HCl concentration. The D2EHDGAA-based n-dodecane extracting phase was easily activated using a low-concentration thiourea aqueous solution (0.01 M). The recyclability of D2EHDGAA for five cycles was investigated, and its efficiency decreased less than 4%.