| The production amount of aluminum is large in China, and also producing a large number of waste cathode every year. The impertinent ways to deal with waste cathode such as stacking cause considerable harm to environment, and there are a lot of useful substances to industry in waste cathode, so researching a proper way to treat with and recycle it is not only reducing the pressure on the environment but also recycling the valuable substances.The material used in this study is taken from some Aluminum plant in Yunnan, by the means of chemical analyse to waste cathode, discovering that there are two harmful material-fluoride and cayanide, and waste cathode contains most of useful and recyclable substances such as Al2O3, C, Na3AlF6, NaF etc. Breaking the material to necessary siza and mixing that equably first, then by the method of alkali leaching to deal with material at first of the experiment, then processing the liquid and solid after alkali leaching by the ways of carbonization and flotation respectively, recycling the useful substances severlly.In the process of alkali leaching, the products obtained by the reactions of Na3AlF6, AI2O3, cyanide and NaOH which dissolve in water and separate from the insoluble solid, NaF also dissolve in alkali leaching solution, confirming the best leaching conditions of100g material which fineness is-200on the basic of experiment analysis of single factor:the concentration of NaOH is108.33g/L, the rate of liquid to solid is6:1, leaching time is3h, reaction temperature is100℃. The maximum leaching rate of F is86.53%and Al2O3is79.46%in this condition, the grade of C is up to60.91%increasing27.17%compared with material. By the means of carbonization to deal with the liquid after alkali leaching with the method of adding CO2, the three-phase reactions of gas、liquid and solidand happening in the same time, producing the precipitation of Na3AlF6and Al(OH)3and NaF into the solution, then confirming the best conditions:the quantity of flow of CO2is40L/h, reaction time is3h, reaction temperature is40℃. The maximum recovery of F is93.66%and Al2O3is99.92%. The substances in the solid after carbonization are Na3AlF6, Al(OH)3, Na2Al2O46·H2O, the components are the important substances to the production process of electrolytic aluminium, and the generated Na3AlF6is more pure. Obtaining the white solid which main composition is Na2CO3by evaporating and crystallizing filtrate.Washing the solid after alkali leaching and the washing liquid can be recycled to preparate alkali solution and recover NaF eventually. Processing the solid after washing by the method of flotation, and confirming the best technological process and potions system on the basic of experiment analysis of single factor:the ratio of solid which grinding fineness for-200is90%, technological process structure is once roughing and once scavenging and twice concentrating flotation, the collecting agent is diesel and the dosage for roughing is200g/t and for scavenging is100g/t, the regulator is sodium silicate mixed with six partial sodium phosphate and the rate of both is7:3and the best totals is1000g/t. Finally, the solid obtained is carbon mainly, the grade is85.16%and recovery is87.87%.Resolving the harmful fluoride and recovering the useful substances such as Al2O3, C, Na3AlF6, NaF etc. exist in waste cathode in the study, realizing the experiment purposes of ptrotecting environment and recycling resources. |
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