A Clean Process for the Recovery of Potash Fertilizer from Glauconitic Rock via Hydrogen Gas Pre-treatment and Mild Acid Leaching

Potassium (K) is an essential macronutrient for the healthy growth and development of crops but their conventional resources are only limited to a few countries. Deficiency of potash fertilizer in soil is a widespread problem for countries with no such potash deposits to meet the present as well as future food demands. In view of this, the present work investigates a novel interdisciplinary approach for the recovery of potash fertilizer from widely available glauconitic rocks. The rock sample containing ~ 6–8% K₂O can be considered a potential alternative source of K-fertilizer. The characterization study revealed that the quartz, glauconite and K-feldspar are the major mineral phases, and the glauconite occurs in the form of ovoidal-shaped pellets. As potassium is trapped between di-octahedral T-O-T stable structure of glauconite, a combined process involving hydrogen gas reduction followed by mild hydrochloric acid leaching was developed to enhance the effective recovery of potassium. More than 99% of potassium dissolution was achieved with 20% (v/v) hydrochloric acid leaching at 80ºC for the sample reduced at 500ºC in the presence of 20 mL/min of H₂ gas flow rate for 2 h. The leach liquor was further treated to recover potassium as muriate of potash (MOP).