Flotation Performance And Mechanism Of Novel Dual-ligand Hydroxamic Acid On Scheelite And Wolframite

As an important strategic mineral resource in China,tungsten ore is an important metal raw material supporting modern industry,national defense and high-tech fields.The separation of scheelite and wolframite,the main tungsten minerals,from the calcium-bearing gangue minerals calcite,fluorite and the silicate gangue mineral quartz has always been a technical problem in the field of mineral processing.Novel dual-ligand hydroxamic acid collectors containing two hydroxamic acid groups sebacic acid hydroxamic acid（SHA）and dodecanoyl hydroxamic acid（DHA）were prepared and investigated the flotation performance of scheelite,wolframite,calcite,fluorite and quartz.The interaction mechanism of dual-ligand hydroxamic acid with scheelite and wolframite was explored by contact angle measurement,infrared spectroscopy analysis,Zeta potential measurement,XPS analysis and DFT calculation.The pure mineral flotation test results showed that the optimum p H of SHA and DHA for flotation of scheelite and wolframite was 8.SHA and DHA both had good flotation effect on scheelite and wolframite.SHA exhibited stronger collecting ability than benzhydroxamic acid（BHA）and better selectivity than DHA and sodium oleate（Na OL）.The inhibition effect of sodium silicate on calcite and fluorite was not strong,and the inhibitory effect of sodium humate and sodium hexametaphosphate on scheelite and wolframite ore was too strong.Citric acid had a strong inhibitory effect on fluorite and calcite and weak inhibitory effect on scheelite and wolframite.The flotation test results of artificial mixed ore showed that the WO₃ recovery in the scheelite concentrate obtained by SHA was similar to that obtained by Na OL,but the WO₃grade obtained by SHA was much higher than obtained by Na OL in the flotation separation of scheelite from calcite and fluorite.The WO₃ grade in the wolframite concentrate obtained by SHA was similar to that obtained by BHA,but the WO₃ recovery obtained by SHA was much higher than obtained by BHA in the flotation separation of wolframite from calcite and fluorite.In addition,in the flotation separation of five-element artificial mixed ore（wolframite,scheelite,calcite,fluorite and quartz）,the WO₃ grade（68.70%）and WO₃ recovery（97.61%）of tungsten concentrate obtained by SHA were 4.00%and 7.21%higher than those of BHA,respectively.,and the WO₃ grade obtained by SHA was 27.82%higher than that obtained by Na OL.The results of contact angle measurement showed that SHA could strongly increase the contact angle of scheelite and wolframite surfaces,while the contact angles of calcite,fluorite and quartz had relatively little change,showing excellent ability to enhance hydrophobicity and selectivity for gangue mineral.And citric acid inhibitor could selectively reduce the contact angle of calcite and fluorite surfaces.FT-IR analysis and Zeta potential measurement indicated that SHA had strong chemical adsorption on the surface of scheelite and wolframite,weak chemical adsorption on the surface of calcite and fluorite,and no adsorption on the surface of quartz.And citric acid can be adsorbed on the surface of calcite and fluorite to further inhibit the adsorption of SHA.XPS analysis showed that the adsorption mechanism of SHA with scheelite and wolframite was that the–CONHOH acting groups of SHA formed five-membered ring chelates with the Ca acting sites on the surface of scheelite and the Fe acting sites on the surface of wolframite,respectively.DFT calculations illustrated that C=O and N–OH groups were the main active groups of SHA molecules,playing a leading role in the process of donating electrons with metal ions of tungsten minerals.SHA had stronger chemical reactivity than BHA and oleic acid（HOL）.