Graphite Ores Research Articles

Increasing the Fine Flaky Graphite Recovery in Flotation via a Combined MultipleTreatments Technique of Middlings

As the residual flaky graphite ores become miscellaneous and fine, a single treatment technique for the middlings from the flotation process of graphite ore cannot efficiently recover the valuable graphite in the multistage grinding-flotation technology. In the study, the existence form of graphite and relationship of graphite with the associated gangue minerals were estimated by optical microscope analysis. The results indicated that the fine flaky graphite particles embedded with gangue minerals like a honeycomb, making it difficult to be beneficiated using the typical flotation technique. A combination technique of individual process and concentrated returning for the treatment of middlings was used to increase the graphite recovery based on the co-existing relationship between graphite and gangue minerals in the middlings. The graphite recovery of the final concentrate upgraded from 51.81% to 91.14% at a fixed carbon (FC) content of 92.01% by a beneficiation process consisted of once coarse (94.41% passing 74 μm) and rougher, five stages regrinding and six stages cleaning. The proposed treatment technique for middlings is of great significance to increase the recovery of fine flaky graphite.

Insights into Alkali-Acid Leaching of Sericite: Dissolution Behavior and Mechanism

Sericite is a typical silicate impurity in microcrystalline graphite ores, and its removal is important in the preparation of high-purity graphite preparations. Alkali-acid leaching is an effective method used to purify graphite and remove silicate minerals. In this study, the dissolution behavior and mechanism of sericite in alkali-acid leaching were investigated. The dissolution of sericite was mainly affected by alkali leaching temperature, sodium hydroxide concentration, and alkali leaching time. According to the XRD, FTIR, and SEM-EDS analyses, the dissolution mechanism of sericite is a three-stage process: (1) sericite is dissolved in the form of soluble silicate and aluminate; (2) the dissolved silicate and aluminate then react with each other to form aluminosilicate; and (3) finally the aluminosilicate mainly composed of hydroxycancrinite and sodalite is almost completely dissolved in the hydrochloric acid solution.

Preparation of high-purity graphite from a fine microcrystalline graphite concentrate: Effect of alkali roasting pre-treatment and acid leaching process

ABSTRACTRemoval of silicate minerals from microcrystalline graphite ores is important to achieve high-purity graphite product. Alkali roasting pre-treatment and acid leaching process was used to prepare high-purity graphite from a fine microcrystalline graphite concentrate. The results showed that the alkali roasting pre-treatment and acid leaching process could enhance the fixed carbon of microcrystalline graphite to a higher level. Under the optimum conditions selected, a graphite product with fixed carbon content of 99.0% was obtained from microcrystalline graphite concentrate with carbon content of 90.2%. According to XRD and SEM-EDS analysis, impurities mainly composed of Fe, Si, and Al were decomposed to water soluble or acid soluble components during alkali-roasting pre-treatment and acid leaching process. The crystal structure and surface topography of microcrystalline graphite showed no change.

The dissolution behavior and mechanism of kaolinite in alkali-acid leaching process

Kaolinite is a typical silicate impurity in microcrystalline graphite ore. Removal of kaolinite from graphite ores is important to achieve high purity graphite product. Alkali-acid leaching is effective to remove silicate impurity in microcrystalline graphite. For in-depth understanding of phase transformation of kaolinite in microcrystalline graphite purification process, dissolution behavior and mechanism in alkali-acid leaching process were studied in this paper. As shown in alkali-acid leaching tests and analyses (FTIR, XRD, and SEM-EDS), silicon extraction of kaolinite was mainly affected by sodium hydroxide concentration, alkali-leaching temperature, and alkali-leaching time. The dissolution mechanism of kaolinite was regarded as a three-stage process: kaolinite firstly dissolved in alkaline solution in form of soluble silicate and aluminate. Dissolved silicate and aluminate in alkaline solution then reacted with each other and aluminosilicate transient phase with Si/Al≈1 precipitated when silicon ion concentration exceeded its equilibrium concentration. Finally, the aluminosilicate precipitate composed of nepheline and sodalite dissolved in hydrochloric acid solution. As a consequence, kaolinite dissolved completely in alkali-acid leaching process.

CHARACTERISTIC OF ENRICHMENT PROCESS OF ORES OF ZAVALLYA, BALAKHIVKA AND BURTYNSKE DEPOSIT OF UKRAINIAN SHIELD

On example of three largest deposits of graphite of the Ukrainian shield considered the problem of enrichment of graphite ores depending on the degree of their physical and chemical changes, as well as the principles of its division according to the industrial types.

Chemical demineralization of three different graphite ores from Turkey

The removal of gangue minerals from three different graphite ores (Inebolu, Akdagmadeni and Coraklidere) from Turkey by acid leaching was studied. Acid leaching experiments were applied to the flotation bulk concentrates, which were obtained in determined optimum conditions after preliminary flotation tests. The effects of acid type, acid concentration, leaching temperature and leaching time on the dissolution of gangue minerals were studied. The most suitable leaching conditions were determined to be 20% HCl + 4% HF for acid type and concentration, 85 oC for leaching temperature and 4 hours for leaching time. After removing the gangue minerals at these optimum conditions, the total carbon contents of the samples from Inebolu, Akdagmadeni and Coraklidere increased from 23.51% to 40.07%, from 37.93 to 60.47% and from 42.28 to 59.47%, respectively.

Processing of low grade graphite ores of orissa, India

Low grade graphite samples containing 12.2–13.1 % fixed carbon from Rajunagfena, Orissa, India have been investigated for characterisation and amenability to beneficiation. The graphite is of the well crystallised flaky variety, and is associated with orthoclase, quartz, plagioclase, biotite, garnet, sillimanite, kaolinite as dominant gangue minerals. The textures, microstructures and liberation of graphite and their implications in beneficiation are described in this paper. The optimum liberation size of the graphite was determined to be below 210 μm Beneficiation studies indicated that a concentrate with 79% fixed carbon, at a recovery 80.1% can be achieved by cleaning the rougher concentrate five times in a conventional flotation cell. Almost similar grade and recovery can be obtained in two stages by column flotation.