Role of calcium lignin sulfonate in brucite flotation: multi-mechanism analysis of efficient serpentine inhibition

Calcium lignin sulfonate, as a flotation depressant, exhibits an inhibitory effect on serpentine during the flotation of brucite. Its mechanism can be explained from the following aspects:

1. Chemical adsorption and covering effect: Calcium lignosulfonate molecules contain multiple functional groups, such as hydroxyl (-OH) and sulfonic acid groups (-SO₃⁻). These groups give calcium lignosulfonate good Water solubility and surface activity. In the brucite flotation system, calcium lignosulfonate can physically adsorb or chemically react with the active sites on the serpentine surface through these functional groups to form a covering layer. This process effectively prevents the collector from contacting the serpentine surface and reduces the chance of serpentine particles being carried up by air bubbles, thus achieving the purpose of inhibiting serpentine.

2. Electrostatic repulsion: Calcium lignin sulfonate carries a negative charge, which can change the charge properties of the serpentine surface, increase the electrostatic repulsion between particles, reduce the aggregation tendency between particles, and enhance the dispersion. In this way, the stable dispersion state of serpentine particles in the water phase is not easily broken by the collector, the flotation efficiency is reduced, and the serpentine is suppressed.

3. Steric hindrance effect: The macromolecular structure of calcium lignin sulfonate can form a physical barrier after it is adsorbed on the surface of serpentine, which hinders the collector molecules from approaching the effective action sites of serpentine, produces a steric hindrance effect, and further inhibits the flotation of serpentine.

4. Competitive adsorption: The competitive adsorption ability of calcium lignin sulfonate on the serpentine surface is stronger than that of some collectors. It preferentially occupies the active positions on the serpentine surface, reduces the effective adsorption points of the collector, and thus inhibits the flotation performance of serpentine.

5. Adjust the pH value of the slurry: The addition of calcium lignosulfonate may slightly adjust the pH value of the slurry, affecting the dissociation state of the serpentine surface and indirectly affecting the flotation performance. Although this is not the main mechanism of action of calcium lignosulfonate, it cannot be ignored under certain conditions.

The inhibition mechanism of calcium lignin sulfonate on serpentine is mainly through multiple effects such as chemical adsorption, electrostatic repulsion, steric hindrance and competitive adsorption, which effectively reduces the floatability of serpentine during the flotation process and achieves the goal of selectively separating brucite and serpentine.