Production of epsom, gypsum and other industrial products from the mill tailings of Jhamarkotra rock phosphate project, India.

At the Jhamarkotra rock phosphate mines, the low-grade Proterozoic rock phosphate containing 14-19% P 2 O 5 is beneficiated by froth flotation process to produce beneficiated rock phosphate having 32-34% P 2 O 5 , to provide raw material for fertilizer plants. The process generates considerable quantity of dolomitic tailings which contain 5-6 % P 2 O 5 , 16-18 % MgO and 32-34 % CaO, that are potentially useful in agriculture. It is therefore necessary to utilize these products to conserve the diminishing, meagre and non-renewable phosphate resources of India. About 1500-1800 tonnes per day (TPD) of dolomitic tailings is produced through the processing of -3000 TPD of the ore, which is collected in the tailing ponds. Investigation carried out on final carbonate tails (FCT) of Jhamarkotra rock phosphate froth flotation beneficiation plant revealed that good quality epsom (MgSO 4 ·7H 2 O)/fertilizer-grade magnesium sulphate, gypsum (CaSO 4 ·2H 2 O) and magnesium ammonium phosphate (MAP) can be produced by leaching FCT with dilute sulphuric acid (30%) at 60-80°C and subsequent crystallization through evaporation and cooling. MAP also can be produced, which has citrate solubility of about 96%. MAP has proved to be beneficial for rice crop on acid as well as alkaline soils. Additionally, ammonium carbonate/ carbon dioxide, hydrogen fluoride/calcium fluoride can also be produced. This scheme will certainly help reduce the wastage of these resources, mitigation of pollution and will generate additional revenue to the company.