Study On Selective Precipitation Valuable Constituent In Copper Smelting Slags

Dump slags from copper smelting prove to be a valuable source of base and rare metals. A typical copper slag may have the composition of 40-50wt% iron, which is much higher than the 29.1wt% average ore grade for iron smelting. Recovery those iron constituents are important from both economical and environmental perspective. However, due to fine mineral dissemination and complex mineralogy, while iron mainly exists in the form of fayalite(Fe₂SiO₄), Recovery those valuable constituents in slag is a very meaningful task by traditional approachs.Based on the study of copper slags composition feature, concentrated iron into magnetite(Fe₃O₄) phase by selected oxidizing molten slag by air(or oxygen). As a result, the average grain size of magnetite particles grow from 25μm to 95μm and the iron enrichment in magnetite phase rised from 22% to 86% with cooling rate 5K/min after oxidizing. All those pave a way for magnetic separating the magnetite phase in copper slags.Oxidization kinetic in copper slag was investigated by blowing oxygen (or air) into molten slag. Based on the relationship between content of the Fe²⁺ and oxidizing time in different temperature, oxidizing kinetic equations were established, from which the apparent energetic E_α of those reactions were also deduced.The results show that while oxidizing by pure oxygen, apparent energetic E_α is 296.70kJ/mol, reaction rate equation expressed as:While oxidizing by air, E_α=340.30kJ/mol, reaction rate equation expressed as:The results show that ferrous oxidizing in slag is a first order heterophase reaction. In isothermal oxidizing process, content of Fe³⁺ increase rapidly, become saturation and firstly precipitate in the form of Fe₃O₄. Main phases in the slag after cooling down were magnetite (Fe₃O₄), fayalite(Fe₂SiO₄) and glass state silicate ((Fe, Ca)SiO₄). In oxidizing...