Study on Extracting Germanium from Coal Ash by Chlorination with Ammonium Chloride and Extraction with Dihydroxamic Acid as Extractant

A process for extracting germanium from coal ash by chlorination with ammonium chloride and extraction with dihydroxamic acid(DHYA) as extractant was investigated.Ammonium chloride was used to chorinate the germanium from coal ash and the chloride was vapored and enriched,the hydrolyzate of which was germanium dioxide through hydrochloric acid with a molarity lower than 6 mol/L.The optimum conditions were established based on the experimental results/ The coal ash was roasted for an hour by adding 20 % weight NaHCO3.The roasted residues were calcined for 90 minutes at 400 ℃ by adding 15 % weight ratio of ammonium chloride dosage to coal ash and the recovery of germanium was not lower than 81.5 %.1.5 % sulfuric acid(solid-liquid mass`ratio was 1∶2) was used to counter-flow leaching germanium from the chlorination roasted residues.When the pH value of the leaching liquor was 1.0,under the experimental conditions of DHYA as extractant,iso-octylalcohol as solvent,sulfonated kerosene as diluent,VO/VA=1∶4,CDHYA=0.5 mol/L,t=8 min,the three-step counter-flow was carried out to extract germanium and the orerall extraction rate was not lower than 99.5 %.2.5 mol/L NH4F solution was used for two-step reverse extracting germanium,counter-extraction rate was not lower than 99.5 %.In the process,the overall recovery rate of germanium from coal ash was greater than 95 %.