Physico-chemical treatment of glauconitic sandstone to recover potash and magnetite

Abstract

Potassium is one of the important nutrients for healthy growth and development of plants. This article explores the possibility of extracting potassium from lean grade indigenous glauconitic sandstone, which is locked in the host matrix. Detail physico-chemical and mineralogical characterization of glauconitic sandstone collected from Guneri area of Kuchchh district, Gujarat (India) was carried out by X-ray diffraction (XRD), Scanning electron microscopy (SEM) followed by Energy-dispersive X-ray (EDX), X-ray fluorescence (XRF), AtOmic absorption spectrometer (AAS) and conventional analytical tools. The major matrix of glauconite sample was found to contain 3.93% K2O,10.75% Fe2O3, 4.41% A1(2)O(3) and 70.35% SiO2. The K2O content could be enriched from 3.93% to 5.52% by simple screening and rejection of +425 mu m particles fraction. Chemical leaching of enriched fraction with hydrochloric acid (HCI) yields very low recovery (< 12%) of potassium. Therefore, a combined reduction roasting-leaching method was developed to recover potassium chloride suitable for fertilizer application. The effects of roasting temperature, coke to glauconite ratio during roasting and various leaching parameters such as acid concentration, leaching time and temperature during dissolution of potash were studied. Parameters have been optimized to achieve more than 98% potassium recovery along with recovery of iron value as magnetite. (C)2017 Elsevier Ltd. All rights reserved.