Alkaline Refining Bismuth Slag Mention Molybdenum And Alkali Regeneration Process

Low temperature alkaline smelting of bismuth sulphide concentrate has many remarkable advantages than traditional smelting process, but much usages of alkali make cost higher than that of traditional ones.It will draw cost down significantly and make the process environmental friendly if the alkali and molybdenum reused.The slag is easy to be oxidized and deliquesced in the presence of air, forming oxidized slag, so this thesis research two work:one is selective leaching sodium salts from oxidized slag, the other is recycling alkali and molybdenum from the slag without oxidation.Adopting two stage leaching, one at normal temperature, the other at higher one, to treat the oxidized slag, molybdenum and Na2S2O3 are mainly leached into the leachate at normal temperature, while Na2CO3 goes into hotter leachate mostly, due to the solubility difference and the effect of common ion and salt. With two stage reverse leaching, the concentration and leaching efficiency of Na2S2O3 and Mo increasing largely than only one stage leaching, but the leaching efficiency of Na2CO3 is only 33.13%, indicating primary separation of Na2S2O3 and Na2CO3. The soluble sodium salts can be leached almost completely in the hot leaching process.Using the process:water leaching, zinc oxide, causticize, carbonate, solvent extract, stripping to recycle molybdenum and to regenerate alkali.The temperature and usage of zinc oxide will affect the causticizing rate significantly, on the condition of temperature 90℃, reaction time 1.5 hour,1.5 times theory usage of zinc oxide, the causticizing rate reach up to 97%.Temperature is of significance to carbonating rate, which is higher or lower do no good to carbonating rate, but best at 40℃.Carbonating rate, reaching up to 90%, increase slightly with the flow rate of carbon dioxide when that is more than 40L/h, so the flow rate of carbon dioxide being 20～40L/h is better. After reacting 1.5h, the carbonating reaction basically completed. Under the optimal condition, the carbonating rate and the alkali recycling rate reach up to 95.21% and 54.4%,respectively.Using N235 as extractant,1:1(V/V) ammonia water as stripping agent to recycle molybdenum, the extract and stripping efficiency can reach up to 91.67% and 94% respectively.