Preparation And Flotation Mechanism Of Low Temperature Flotation Collector For Potassium Chloride

As the main agricultural fertilizer,potassium chloride is also the main raw material for producing potassium sulfate and nitrate.KCl is mainly produced by flotation methods.As a key agent in the flotation process of KCl,the collector changes the surface activity of KCl to make the hydrophobic difference between KCl and other minerals.KCl is attached to the surface of the bubble to complete the flotation separation.In the process of potassium salt flotation,the flotation yield is not only affected by the chemical components in the system,the amount of collector,but also affected by temperature to a large extent.When the temperature is below 5℃,the flotation yield of potassium chloride decrease seriously.The flotation yield of potassium chloride was improved by increasing the amount of collector at low temperature.On the one hand,it will greatly increase the cost,on the other hand,it will lead to reduced product purity.Therefore,most potash salt enterprises in Qinghai Salt Lake potash salt production base are facing the predicament of winter production.Based on the actual problems existing in the positive flotation process of KCl from Qinghai Salt Lake,this study adopted the method of reagent compounding.Attempted to prepare a new type of KCl positive flotation collector by introducing other reagents based on octadecylamine.It is expected to solve the practical problems existing in KCl production by positive flotation at low temperature.Firstly,this project attempts to compound the cationic collector dodecylamine and octadecylamine with the anionic trap sodium dodecylsulfate.The mixed collector（cationic/anionic）agents were obtained.The optimum molar ratio of mixed collector was initially determined as dodecylamine:octadecylamine:sodium dodecyl sulfate=20%:60%:20%by contact angle and surface tension measurements.Mixed collector can increase the flotation yield of KCl by 7%on average at room temperature.The mixed collector has a higher capacity for potassium chloride when a liquid phase temperature of 5℃.The mechanism of the mixed amine was explained by the determination of turbidity and precipitation particle size.In order to further improve the flotation yield and product grade of potassium chloride,the second part of the experiment mixed amines with different chain lengths to obtain a mixed amine collector.The optimum molar ratio of mixed amines was initially determined as dodecylamine:octadecylamine:eicosanamine=25%:50%:25%by contact angle and surface tension measurements.Mixed amine collector can increase the flotation yield of KCl by 7%on average at room temperature.The flotation experiment showed that flotation yield of mixed amines for KCl was significantly higher than the octadecylamine.The mixed amine collector has a higher capacity for KCl when a liquid phase temperature of 5℃.The determination of turbidity and precipitate particle size can explain the mechanism action of mixed amines.In order to further explain the action mechanism of mixed amines,the interaction of octadecylamine and mixed amines on the surface of potassium chloride and sodium chloride crystals was studied by density functional theory（DFT）in the third part.The thickness and structure of the stabilized crystal surface were determined by calculating the surface energy.Finally,the adsorption energies of H₂O molecules and collectors on the surface of KCl and Na Cl crystals were calculated.The results show that octadecylamine is more easily adsorbed on the surface of KCl crystal than Na Cl.The mixed amine has stronger adsorption capacity for KCl.Further explanation of the superiority of the mixed amines in the experimental results is provided.In brief,this study provides an experimental basis for solving the collector problem from using octadecylamine only at low temperature.At the same time,the mixed amine collector obtained by this work is a new collector choice forthe KCl production in China.