The Removal of Impurities from Domestic Graphite Concentrate by H2SO4 Solution and NaOH Solution Leaching

Leaching tests were conducted using sulfuric acid and sodium hydroxide solutions to remove impurities from domestic graphite concentrate. As a result of the leaching experiment using sulfuric acid solution and sodium hydroxide solution, respectively, the difference of removal efficiency was insignificant when the concentration of sodium hydroxide or sulfuric acid was 2 mol/L or more. The fixed carbon content increased with increasing the temperature in the sulfuric acid solution leaching, while it remains constant above 150°C in sodium hydroxide solution. For the repeated sequential leaching tests, the leaching conditions were 2 mol/L NaOH, 200°C, 1 hour in the sodium hydroxide solution leaching and 2 mol/L H2SO4, 100°C, 1 hour in the sulfuric acid solution leaching, respectively. When sulfuric acid leaching followed by sodium hydroxide solution leaching was repeated 5 times, the fixed carbon increased to 99.95% and ash content decreased to 0.048%, while the fixed carbon increased to 99.98% and ash content was reduced to 0.018 when sodium hydroxide solution leaching followed by sulfuric acid solution leaching was repeated 5 times.