The flotation separation of scheelite from calcite using acidified sodium silicate as depressant

• Sodium oleate has collecting ability for both scheelite and calcite.
• Acidified sodium silicate is mixture of sodium silicate and oxalic acid with a ratio of 3:1.
• Acidified sodium silicate exhibits selective depression for calcite.
• The separation of scheelite from calcite is realized.

The flotation separation of scheelite from calcite using sodium oleate as collector and acidified sodium silicate as depressant has been studied. The results show that sodium oleate has collecting ability to both scheelite and calcite and the flotation separation of scheelite from calcite cannot be realized if collector is used only. The depressant acidified sodium silicate has selective depression effect on calcite and the optimum ratio of sodium silicate to oxalic is 3:1. The use of acidified sodium silicate as depressant can achieve the flotation separation of scheelite from calcite. Infrared studies and zeta potential measurements showed that the pre-adsorption of acidified sodium silicate interferes with the adsorption of sodium oleate on calcite surface while does not interfere with its adsorption on scheelite surface.