Effect of metal ions on the organic small molecule depressant in the flotation separation of scheelite from calcite
Qifang Zheng, Lidong Qiao, Peilun Shen, Tianfu Zhang, Liuyang Dong, Dianwen Liu
Abstract
Both scheelite and calcite were calcium-containing oxidized minerals with similar calcium active sites, which leads to a lack of selectivity in the adsorption of collectors. Moreover, their surface chemical and solution chemical properties were similar, which makes their flotation separation extremely challenging. In this study, vanillic acid (VA) was used as a depressant for the flotation separation of scheelite and calcite. However, the difference in recovery of these two minerals was small, making it difficult to achieve effective flotation separation. The synergistic effects of Fe 3+ , Cu 2+ , and Al 3+ with VA were further investigated. It was found that Fe 3+ and Al 3+ had poor depressive effects on calcite in the presence of VA, while Cu 2+ showed the best selectively depressive effect on calcite. When the molar mass ratio of Cu 2+ to VA was 5:1 and the pH was 9.5, the flotation recovery of scheelite and calcite were 88.3 and 3.18 %, respectively. Effective flotation separation of scheelite and calcite was achieved. In addition, the selective depression mechanism of Cu 2+ and VA on scheelite was revealed. In the slurry, VA existed in the form of anions L 2– and HL – . The addition of Cu 2+ significantly improved the adsorption environment of VA on the calcite surface. Cu 2+ could form metal complexes such as CuL and CuHL + with VA. These metal complexes could selectively chemically adsorb on the oxygen atom positions on the calcite surface, resulting in strong depression of calcite. This research provides a new method for the green flotation separation of scheelite and calcite, which has potential industrial application value.