A process for making slow-release phosphate fertilizer from low-grade rock phosphate and siliceous tailings by fusion with serpentinite

Worldwide demand of phosphate fertilizer is met essentially from phosphatic rocks. India imports most of its requirements and produces a small portion through froth flotation of Precambrian stromatolitic rock phosphate. Increasing population and consequent increase in demand for food production necessitated investigation to utilize the large reserves of low-grade rock phosphate to produce an alternative fertilizer. An acceptable phosphate fertilizer was obtained by fusion of low-grade dolomitic and siliceous rock phosphate from Jhamarkotra mines, effluents from beneficiation plants of Jhamarkotra and Maton Rock Phosphate Projects and serpentinite rejects from Rikhabdev decor stone industry, in an electric furnace followed by quick quenching with water. This scheme may be adopted for all low-grade ores in the world, which will help utilize the large reserves of low-grade phosphate. Useful by-products are also recovered and the process is environment-friendly.