Effect Of Surfactant On The Leaching Of Potassium From Phosphorus-potassium Associated Ore

Soluble potassium resources are severely scarce in China,however,the insoluble potash ores are very abundant.Therefore,the economical and effective extraction of potassium from the insoluble potassium deposit has great strategic significance.Recently,the phosphorus-potassium associated ore with a reserve as much as 800 million tons,which contains 6¹2% phosphorus pentoxide?P2O5?,5⁹% potassium oxide?K2O?and 45-55%silicon dioxide?Si O2?,was found in Yichang city,Hubei province,China.The previous research results have shown that the dissolution fraction of potassium from phosphorus-potassium associated ore in hydrochloric acid solution can reach more than90%.However,the acid decomposition process still exists the drawbacks of large consumption of acid and additive.Hence,how to strengthen the acid leaching process of phosphorus-potassium associated ore is an important research topic.In recent years,surfactants are gaining attention in leaching processes.However,most of the previous studies have focused on the bioleaching and heap leaching,and the leaching of potassium ore,especially the intensified leaching kinetics and mechanism with surfactant has hardly been addressed in detail.Therefore,the objective of this study is to investigate the effect of surfactant on acid leaching of potassium from phosphorus-potassium associated ore.The main contents and conclusions are as follows:?1?The effect of different kinds of surfactants on the dissolution fraction of potassium from phosphorus-potassium associated ore was researched.It was found that anion surfactants could enhance the dissolution fraction of potassium and sodium dodecyl sulfate?SDS?with 1.25 g/L had the best effect.Cationic surfactant had not obvious effect and nonionic surfactant could inhibit the leaching of potassium.?2?The influence of leaching parameters with SDS 1.25 g/L were investigated.It was found that the leaching time,the reaction temperature,hydrochloric acid concentration,the liquid/solid ratio and the calcium fluoride?Ca F2?dosage are the critical factors affecting leaching behavior.The dissolution fraction of potassium is 98.01% with 1.25 g/L SDS added under the optimm reaction conditions of liquid/solid ratio?L/S,ratio of the volume of hydrochloric acid solution?m L?to the mass of ore?g??of 4:1,hydrochloric acid concentration of 22.5%,Ca F2 dosage of 4 g,reaction temperature of90 ?,and leaching time of 4h and increases by 8.5% compared with without SDS.The kinetics analysis showed that the leaching process with 1.25g/L SDS follows the modified shrinking-core model with diffusion internal as the rate-limiting step.The determined activation energy is 85.25 k J/mol,and the semi-empirical kinetic equation coupling the parametric cumulative effect is as follows:?1-X?^-2/3-1=2.98×10¹⁰C^2.5689?L/S?^3.8713M^0.9813exp?-85245.4/RT?t)?3?The intensified leaching mechanism with SDS could be interpreted by promoting the wetting,dispersion and permeation actions as well as molecular diffusion and convective diffusion,and avoiding the flow channel from enlarged fissures blocking because of unformed Si O2 produced.But much micelle covering on the residue fixed layer 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.This paper can provide basic date and theoretical support for the leaching of soluble potassium from insoluble ores.