In the production process, the flotation method is often used for the beneficiation and separation of feldspar and quartz. According to different pulp media, there are three main methods for flotation separation of feldspar and quartz, alkaline flotation, acid flotation, and neutral flotation.
1. Alkaline flotation methods
Separation of quartz and feldspar in alkaline pulp with a pH value of 11-12, alkaline earth metal ions as an active agent, alkyl sulfonate as a collector, reverse flotation preferentially floats quartz, while adding appropriate non-Ionic surfactants can significantly increase the recovery rate of quartz.
Under alkaline conditions, the neutral complexes formed by metal ions and alkyl sulfonates [such as Ca(OH)+RSO3-] play a key role. These neutral complexes combine with free sulfonate ions. It is adsorbed on the surface of the quartz, and a hydrated layer is formed on the surface of feldspar under high alkali conditions.
2. Acid flotation method
The acid flotation technique is to preferentially flotation feldspar using an anion and cation mixed collector at a pH of 2-3 acid slurry. According to the different chemicals used, the method can be divided into fluorine flotation and non-fluoride flotation.
▌Flotation with fluorine
With strong acidity and fluoride ion participation inactivation, cation collectors have used to preferentially flotation feldspar. The key to achieving flotation selectivity is to adjust the pH value of the slurry solution. When pH=2, quartz is near the zero electric point, while the general zero electric point of feldspar, pH=1.4~1.7, is negative on the surface under the activation of fluoride ions. The electric potential increases and the quartz surface is basically uncharged. Amine cations are the first to adsorb on the surface of feldspar, making the surface hydrophobic.
▌Fluorine-free flotation methods
Under strong acid conditions, mixed-use of anionic collector dodecyl sulfonate and diamine cationic collector. The anionic collector is then complexed with the diamine collector adsorbed on the surface of the feldspar to form a co-adsorption, Improve the hydrophobicity of the feldspar surface.
3. Neutral flotation
In a neutral medium, both feldspar and quartz are negatively charged, but there are still locally positively charged areas on the surface of the quartz. There is a small amount of adsorption of oleate ions with the help of electrostatic force and hydrogen bond. This adsorption is not stable. Under the action of inhibitors such as sodium hexametaphosphate, the surface adsorbed collector oleate can be removed.
The adsorption of feldspar on oleate is mainly the chemical adsorption of Al3 +, which is relatively firm, and sodium hexametaphosphate can not remove the adsorbed oleate. The amount of Al3 + on the surface of feldspar is small, and its hydrophobicity is limited, which can not make feldspar float out preferentially. However, oleate ions adsorbed on the surface of feldspar can be used as anionic active particles to adsorb amine cationic collectors. Amine cationic collectors are firmly adsorbed on the surface of feldspar to make feldspar float out preferentially, so as to achieve the purpose of sorting feldspar and quartz.
In a neutral medium, the key to the separation of feldspar and quartz is to select appropriate and effective inhibitors, which can not only desorb oleate ions adsorbed on the quartz surface but also prevent amine cationic collectors from adsorbing on the quartz surface.
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