Molecular tailoring of salicylaldoxime for enhancing flotation separation of malachite from calcite

Synthesis and application of a novel salicylaldoxime (EASA) for separating malachite from calcite. • The molecular behaviour of EASA and SAO were investigated. • EASA exhibited superior collecting ability and selectivity for malachite against calcite than SAO. • EASA chemisorbed on the malachite surface by formation of a six-membered chelate ring. In this paper, a novel surfactant, 4-(diethylamino)salicylaldoxime (EASA), was synthesized by introducing a diethylamino group into the salicylaldoxime (SAO) molecule, and its first application as a collector for the flotation separation of malachite from calcite. The interfacial adsorption behavior of EASA on malachite and its selectivity for malachite versus calcite were systematically investigated. DFT calculations revealed that the incorporation of the diethylamino group enhances the chelating ability of the salicylaldoxime molecule. Moreover, EASA demonstrated strong selective adsorption on malachite, which significantly increased its surface hydrophobicity, whereas its interaction with calcite was weak and exerted a negligible effect on calcite’s hydrophobicity. Such adsorption selectivity resulted in superior flotation performance, with a significantly larger recovery difference between malachite and calcite compared with conventional collectors including SAO and OHA. Mechanistic studies indicated that EASA chemisorbs onto the malachite surface via the formation of a six-membered chelate ring (−C–O–Cu(I)–N–C–), involving coordination between surface Cu(II) ions and both the –OH and C=N groups of EASA. Download: Download high-res image (158KB) Download: Download full-size image