Research On The Scattered Metal Extraction From Fly Ash Of Silicon And Aluminum Recycled

Fly ash is a kind of industrial waste from coal-fired power plant, and the rapid development of China’s power industry directly causes the growing emissions of fly ash. At present, the fly ash has been widely used in building materials, construction engineering, road construction, agriculture, etc. but the recovery of useful elements is still in the research stage. Apart from large amounts of silicon and aluminum oxide, fly ash also contains trace amounts of scattered metal, with some recovery value.In this paper, the study is on the scattered metal extraction from fly ash of silicon and aluminum recycled, the main conclusions are as follows:(1) Experiment used UV-visible spectrophotometry, with accuracy analysis and small error, which can meet the condition of testing scattered metal. Scattered metal is selected from the mother liquor with NaOH solution by controlling the pH to remove Fe, Ti, Mg and Ca ions. Through single factor experiment, purify process parameters were selected:the concentration of sodium hydroxide is 6mol/L, the reaction time is 40min, the volume ratio is 3:1 and the reaction temperature is 40℃. In this condition, edulcoration can be more complete.(2) In the mother liquor of remove impurities, the mass ratio of Ga and Al2O3 is less than 1/340. The concentration of Ga cannot reach the electrolysis conditions. While the content of Ge is less than 0.2g/L, so the hydrolysis conditions are not satisfied. Therefore, the mother liquor containing scattered metal should be concentrated by adding the stage of crude aluminum sulfate recrystallization. After three times cycle, the enrichment effect of Ga and Ge is remarkable.(3) GeCl4 was separated and purified by distillation from the mother liquor of containing Ga and Ge. Single factor experiment was made to get the purify process conditions:the concentration of hydrochloric acid is 6mol/L, the ratio of liquid and solid is 4:1, the distillation temperature is 96℃ and the distillation time is 6h. The distillation recovery of GeC14 is up to 95%.(4)After distilled and enriched, GeCl4 was hydrolyzed using double distilled water. Under the condition that the volume ratio of H2O and GeCl4 is 6, it was hydrolyzed for 1.5h at 10℃. GeCl4 of containing water of crystallization was dried for 0.5h at the temperature of 200℃, and the product of GeO2 can be made. Extraction rate of Ge is 66.7%, and the purity of GeO2 products characterized by XRF and Energy Dispersive Spectrometer is up to 99.2% to 99.4%.(5)Aluminum gallium complex salt containing Ga was dissolved in the electrolyte solution of 3 mol/L sodium hydroxide, and the anode and cathode of electrode is platinum. The parameters of electrolysis is that the electric current is 200mA/L, the electrolysis voltage is 4V and the temperature is 40℃, thus the metallic gallium can be obtained. Extraction rate of Ga is 67.22%, and the purity of Ga products characterized by XRF and Energy Dispersive Spectrometer is up to 98.83% to 99.1%.