The intensified leaching behavior of potassium from phosphorus-potassium associated ore in HCl-CaF2 system with surfactant: Part Ⅰ kinetics and modelling

Abstract

The intensified leaching behavior of potassium from phosphorus-potassium associated ore in HCl-CaF2 system with different surfactants was investigated. It was found that anion surfactants could enhance the dissolution fraction of potassium and sodium dodecyl sulfate (SDS) had the best effect. The dissolution fraction increased from 89.50% to 98.01% with the addition of 0–1.25 g/L SDS, but dropped to 91.5% with 5.00 g/L SDS. The cationic surfactants could only shorten the time to the equilibrium, while the nonionic surfactant would hinder the leaching of potassium. The intensified leaching observed in the presence of 1.25 g/L SDS could be interpreted as follows: SDS was adsorbed on the surface and micro-porous cracks of mineral particles, then the adsorption film was appeared, which leaded to more SiF4 stayed in the adsorption film and more SiO2 produced, indicating the residual became smooth, thereby the ore was eroded thoroughly due to the produce of more HF. But much micelle covering on the residue was formed if the dosage such as 5.00 g/L SDS exceeded the critical micellization concentration (CMC), which hindered acid and fluorine entered into the interior of the ore, indicating dissolution fraction decreased. In addition, the leaching kinetics of potassium was successfully modeled by a semi-empirical kinetic model based on the modified shrinking-core model with chemical reaction being the rate-controlling step.