Preparation of High Purity Graphite using Comminution, Pressure Leaching and Flotation

The present paper deals with the development of process flowsheet for recovery of high-grade graphite from rougher graphite concentrate for use in industrial applications. In the present investigation, since the coarser graphite flakes have a higher demand, an attempt is made at every stage of comminution, and flash flotation experiments have been carried out, and the end product obtained by stage comminution followed by flotation has been further subjected to alkali pressure leaching followed by grinding and flotation to recover industrial grade graphite concentrate. During this stage grinding, an additive, a depressant that is being used for depression of silica during flotation, has been used as grinding aid. The data indicates that at any given time of grind, the effect of grinding aid is significantly better as far as the separation efficiency of graphite. Hence, it is concluded that excessive size reduction of graphite is minimised while using a grinding aid. Based on these observations, further studies have been planned for flash flotation using a comminution circuit with grinding aids. The results of the present study reveals that number of cleaning of rougher concentrate alone will not fetch more than 75% of fixed carbon (FC) with less than 8% yield and 41% recovery. The effect of four stage cleanings continued with starvation dosage in grinding circuit followed by flash flotation indicate that the end product achieved contains 97.8% FC with 11.6% yield and 78% recovery and the overall values loss in tailings contain 3.6% FC. The end product achieved by alkali digestion method from a flotation product [97.8% FC] contains 99.2% FC with overall 10.4% yield and 71% recovery. The process adopted in the present investigation is friendly environment and process flowsheet is an innovative. The end product obtained from this process is useful for various industrial applications.