Preparation of cinnamon hydroxamic acid and its flotation characteristics and mechanism to fine-grained wolframite

Process diagram of flotation separation of quartz wolframite with a new hydroxamic acid collector. • Cinnamon hydroxamic acid (CIHA) was introduced as a new collector for wolframite flotation. • CIHA displayed better ability to collect wolframite than sodium oleate (NaOL). • CIHA exhibited superior selectivity for wolframite against quartz. • CIHA was adsorbed on wolframite surface by chemical adsorption. • Fe and Mn were active sites that strongly adsorbed on wolframite surface and CIHA collector. A new collector—cinnamon hydroxamic acid (CIHA)—was synthesized from methyl cinnamate using the hydroxyamine method. The results of single-mineral flotation and artificially mixed-mineral flotation indicated that CIHA had good collection performance and selectivity. Adsorption-capacity test results indicated that the CIHA collector adsorbed wolframite and quartz, and the adsorption intensity of wolframite was higher than that of quartz. The adsorption mechanism was investigated via zeta-potential analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that CIHA interacted with Mn on the wolframite surface via Pb 2+ activation to form a surface Mn–O–Pb 2+ complex, which formed a new Fe–O bond with Fe. Hydroxamic acid may have formed a five-element chelated hydroxamic group with the metal on the wolframite surface. The hydrophobicity of the wolframite surface was improved, making the wolframite more easily attach to bubbles and be more easily carried to the pulp surface.