Research On Distribution Of Sn Element In E-waste High Temperature Melting Process

As a typical example of “urban mines”,e-waste contains much more precious and precious metal resources than natural mineral resources.Currently,there are many methods for recycling e-waste,and the pyrometallurgical process is one of the most important terminal technologies.E-waste pyrometallurgical slag usually contains large amounts of alumina,There are significant differences from traditional non-ferrous smelting,and the smelting conditions are also different from the traditional non-ferrous metal concentrate smelting process.Therefore,it is of great theoretical and practical value to carry out research on the smelting and distribution behavior of rare and precious metal elements under high aluminum slag.In this study,the balance system of copper-tin alloy and Al₂O₃-FeOx-SiO₂-CaO synthetic slag was studied,and a high-temperature static thermodynamic equilibrium-quench-chemical analysis test method was used to study at 1300?and Al₂O₃ saturated smelting conditions.The effects of oxygen partial pressure,slag composition?Fe/SiO₂,CaO content?and other factors on the distribution behavior of Sn element and SnOx activity coefficient in slag,and the valence of Sn in slag were discussed.Finally,the thermodynamic test results were studied.A comparison was made between the trend of Sn element in the smelting test of end-of-life mobile phones and circuit boards.The main findings are as follows:?1?The distribution coefficient?LSns/m?of tin increases as the oxygen partial pressure increases.When the oxygen partial pressure changes from 10-9atm to 10-8atm,LSns/mincreases from 0.07 to 0.1 with a small increase;when the oxygen partial pressure changes from 10-8 atm to 10-6 atm,LSns/m increases from 0.1 to 7.36.The change is obvious.In addition,as the partial pressure of oxygen changes,the valence of Sn in the slag changes.When the oxygen partial pressure is low?10-9-10-7atm?,Sn element exists in the form of Sn2+,that is SnO,when the partial pressure of oxygen is lower.At high times?10-6 atm?Sn is present as Sn4+,that is SnO₂.?2?Under the smelting conditions of 1300? and PO₂=10-8atm,the slag composition has different effects on the change trend of LSns/m.In the slag composition,Fe/SiO₂ increased from 0.8 to 1.2,and LSns/m changed from 0.1 to 0.2.The trend of slight increase was less obvious.When Fe/SiO₂ in the slag is constant?0.8 or 1.2?,LSns/m decreases with the increase of CaO content?5wt%-20wt%?in the slag,but the rate of decrease is slightly different,when Fe/SiO₂ is 0.8.At the sametime,LSns/mdecreases quickly when the content of CaO in the slag is between5-10wt%.When Fe/SiO₂ is 1.2,the LSns/m decreases rapidly when the content of CaO in the slag is between 15-20wt%.?3?Under the smelting condition of 1300?,the activity of Sn in the slag??SnOx?increases with the increase of PO₂.At PO₂=10-9-10-7 atm,?SnO increased from 2.05 to5.31,and when PO₂ was 10-6atm,?SnO₂ was significantly increased at 32.3.Under smelting conditions of 1300? and oxygen partial pressure PO₂=10-8 atm,?SnO increases with the increase of Fe/SiO₂?0.8-1.3?in the slag composition?2.05-4.82?,and the CaO content in the slag composition.The linear increase of the increase,different linear equations when the Fe/SiO₂ content is different.The overall effect of oxygen partial pressure on ?SnOx has the greatest effect,and Fe/SiO₂ has the smallest effect on ?SnOx.?4?The LSns/m measured in this study is basically consistent with the actual smelting test results of the electronic waste in the literature,which can better guide industrial practice.