Experimental Research On The Alkali-acid Method Purification Of Graphite And Kinetics Of Desilication

Graphite is an strategic resource which plays important role in the high-tech fields and national economy. As a kind of mineral resources, graphite must be purified when used as graphite materials and then processed on the particle size and modification according to its Application. With the rapid development of science and technology, demands for high quality graphite materials are increasing in many areas. Our country existing graphite purification technology and modernization of the national economy or industrial development does not adapt. Some high technical content of graphite products also need to be imported from abroad. The key problem which restrict the development of the graphite industry in China is graphite purification.China's graphite resource reserves rank the first in the world,studying the reasonable purification technology has the significant practical significance to giving full play to this advantage resources and promoting economic development.The graphite concentrates in Inner Mongolia province is the research object in this experiment, graphite's carbon content is 84.32%, the main gangue mineral of graphite are quartz, mica and hematite. SiO2 content is 4.82%, Fe2O3 content is 4.78% and Al2O3 content is 1.80%. Used alkaline roasting-acid leaching process to purify graphite and inspected the effects of factors to purity of graphite such as sodium hydroxide dosage, roasting temperature, roasting time, ect. The products of graphite purification process were analyzed by XRD, FTIR and SEM means. And the reaction kinetics of SiO2 and Fe2O3 were studied.Experiments got the best condition of alkaline-acid process: mass ratio of NaOH to graphite 0.4:1; roasting temperature 600?; roasting time 120 min; mass ratio of HCl to graphite 0.4:1; hydrochloric acid concentration 1 mol/L; leaching time 45 min. Graphite carbon content increase from 84.32% to 99.51%. The purification effects of alkali-acid method for each size fractions graphite are different. In the same conditions, the bigger particle size of graphite, the purification effect is better. The purity of +0.589 mm graphite reached 99.92%. The main factors' effect order are as followed: NaOH dosage > leaching time > roasting temperature > roasting time > hydrochloric concentration > acid dosage. XRD test results showed that the structure of quartz and mica have changed in alkaline roasting process. Acid leaching process have a great influence on the crystallization of hematite. FTIR test results show that the silicon dioxide and sodium hydroxide react to generate sodium silicate in the process of alkaline roasting. SEM and XRD analysis results show that the alkaline roasting-acid leaching process have little effect on the structure of graphite and keep the good properties of graphite.The reaction kinetics research of SiO2 and Fe2O3 in graphite shows that: The alkaline roasting-acid leaching process has obvious effect on removal of SiO2 and Fe2O3. The reaction between SiO2 and NaOH is controlled by surface chemical reaction and diffusion.