Physical and chemical characterization and recovery of potash fertilizer from glauconitic clay for agricultural application

Glauconite is a natural occurring iron-rich, heterogeneous, phyllosilicate rock containing around 4-8% of potash (K2O) locked in the alumino-silicate matrix. An attempt has been made to develop a complete flow-sheet for the recovery of potash from a typical glauconite sample containing 3.93%K2O, 10.75% Fe2O3, 4.41%Al2O3 and 70.35% SiO2. Initially, the detail physico-chemical characterization and beneficiation study was performed to enrich the potash content from 3.93% to 5.52% by removing free silica. The enriched fraction of glauconite was further processed to recover locked potash through chemical treatment. Potassium recovery by direct acid leaching was found to be very poor and also resulted in simultaneous dissolution of iron. Therefore, a combined sulfation roasting water leaching process was developed to break the matrix and selectively recover potash. Various parameters such as sulphuric acid concentration, roasting and leaching temperature were optimized to achieve >98% potash dissolution. The potassium from the leach solution was recovered as sulfate of potash (SOP) suitable for fertilizer application. (C) 2017 Elsevier B.V. All rights reserved.