Study On Recovery Mechanism And Process Optimization Of Copper In Copper Smelting Slag By Sulfide Flotation

Copper smelting slag is one of the main industrial solid wastes.Heavy metal ions in the slag are one kind of the key pollutants in the?12th Five-Year Plan for Comprehensive Prevention and Control of Heavy Metal Pollution?.It required that copper smelting enterprises should strengthen the comprehensive recovery and reuse of smelting slag,reduce emissions and reduce environmental risks.In 2018,China produced 18.7 million tons of copper smelting slag,which is both a pollutant and a secondary resource.At present,due to its stacking,dust pollutes air and heavy metal ions pollute groundwater,causing serious environmental pollution and threatening human health.Due to the fine particle size,complex composition and various types of copper smelting slag,in addition,other factors such as the fluctuation of technical index of copper recovery from slag and lack of research on the recovery principle resulted in the harmless and comprehensive utilization of industrial technology are not satisfactory.In this paper,the recovery mechanism and process optimization of copper in copper smelting slag are studied in depth,so as to improve the comprehensive utilization level of copper and reduce the content of copper and other heavy metal ions,which is of great significance for sustainable development,promoting circular economy and protecting the environment.In this research,the waste slag from a copper smelter in Hubei Province is taken as the research object.The variation of ions precipitation and adsorption behavior in the waste slag solution is analyzed by ICP-AES,the main mineral composition in the waste slag is analyzed by XRD,and the main components in the waste slag are analyzed by FESEM-EDS.The changes of surface potential of main minerals are measured by Zeta potentiometer,and the change law of surface element composition and valence state of main minerals in waste slag is analyzed by X-ray photoelectron spectroscopy?XPS?.The recovery mechanism of main minerals in waste slag was analyzed by quantum chemistry and molecular dynamics calculation.Finally,according to the theoretical research results of activation-sulfuration,the optimization of copper recovery and utilization process in actual copper smelting slag were studied.The main research contents are as follows:?1?The species of main ions in waste slag solution were tested.The chemical equilibrium software Visual MINTEQ3 was used to calculate the concentration and existing form of main ions such as Cu?II?,Fe?III?,Ca?II?and Mg?II?.By leaching the main minerals in the waste slag,the sources of the main ions in the solution were grasped.Cu²⁺and S^2-mainly come from matte,Fe³⁺mainly comes from magnetite and matte,Mg²⁺,Al³⁺and Ca²⁺mainly come from their oxides.The variation of main ions was obtained by measuring the adsorption of various minerals in the waste slag.It was found that Cu²⁺,Fe³⁺were easily adsorbed by the waste slag.Based on this,the recovery experiments of copper-bearing pure minerals in copper smelting slag were carried out.It was found that activation of Cu²⁺and sulfuration of S^2-are beneficial to the recovery of copper minerals.?2?DFT calculation and analysis of main copper-bearing minerals in copper slag show that Cu-S bond covalence of matte is the lowest and more Cu²⁺and S^2-are easily exposed than that of copper oxide when the crystal is broken.The reconstructed surface of copper matte model?001?-S results in the formation of disulfide and S-S covalent bond.By calculating the adsorption energy of reconstructed surface,it is found that the adsorption energy of HS^-on the surface of matte?001?is lower and belongs to preferential adsorption,which is beneficial to the activation of matte.The calculation results of the density of states of the adsorption model show that the Fe and S sites are the active sites of adsorption,and new stable chemical bonds S-S and S-Fe are formed during the adsorption process,which is conducive to air flotation.?3?By measuring the surface potential of copper-bearing minerals in copper smelting slag,when the pH value is 10,sodium sulfide can increase the electronegativity of matte and copper oxide,and copper sulfate can further increase their electronegativity.It is proved theoretically that activation-sulfuration is beneficial to the recovery of copper minerals.The variation of sulfur,copper and iron components in copper mineral solution was tested by ICP,and the results showed that sodium sulfide adsorbed on copper-bearing minerals well.When Cu²⁺or Fe³⁺existed,the adsorption of sodium sulfide was further increased.In order to further study the existing forms of copper,iron and sulfur elements on the surface of copper minerals in waste slag,XPS was used to systematically analyze.The results indicating that sulfur elements were elemental sulfur S₀,Monosulfide S^2-and polysulfide S_k^2-exist on the surface of copper-bearing minerals and form a sulphur-rich environment.The addition of copper ions increases the proportion of polysulfide S_k^2-on the surface of matte and copper oxide,which confirms the enhancement of sulphurization effect.?4?In order to enhance the recovery of copper minerals from waste slag and further enhance the adsorption of air flotation agent xanthate on matte,the adsorption kinetics of butyl xanthate on matte was studied.The fitting results showed that the adsorption of butyl xanthate on matte at all solution temperatures was in accordance with pseudo-second-order adsorption kinetics.Combined with the intraparticle diffusion equation phase,the relevance analysis showed that in the second stage of the adsorption process?within 100-300 s?,the diffusion rate of butyl xanthate particles on the surface of matte determined the efficiency of the whole adsorption process.Thermodynamic calculation results showed that the activation energy of butyl xanthate adsorbed on the surface of iceberg was low,only 312±10J/mol,which proved that the adsorption was a fast process.?5?On the basis of theoretical research results,the activation and sulfurization process of copper recovery from copper smelting slag was developed.Optimum design experiments show that the copper concentrate with a copper grade of 24.56%and a recovery rate of 95.94%can be obtained from the actual copper smelting slag under the new copper recovery process of copper sulfate activating and sodium sulfide sulphidizing with 80%content of fineness of-0.074 mm.The copper grade of tailings is 0.2%,which is lower than the lowest copper content standard of the first type construction land stipulated by the Ministry of Ecological Environment of China.Compared with the original technology,the grade of copper concentrate increased by0.55%and the copper recovery rate increased by 4.33%.Compared with the original technology,the grade of copper concentrate increased by 0.55%and the recovery rate of copper increased by 4.33%,which is equivalent to an annual increase of 321,000tons of copper metal and an additional profit of 800 million yuan.In this paper,by systematically studying the types,sources and changing rules of main ions in the air flotation solution of copper smelting slag,combined with the analysis and characterization of pure mineral flotation,Zeta potential,adsorption capacity and XPS,the mechanism of Cu²⁺activation and S^2-sulfidation in favor of recovery of copper minerals and enhancement of sulfidation effect of copper ions has been found.Quantum calculation of the structure model of matte shows that Fe and S sites are the active sites of adsorption,Fe is the preferred adsorption site,HS^-is the preferred adsorbate,which proves that S-S bond and S-Fe bond are beneficial to sulfur adsorption mechanism.Based on the theoretical research results,the process of activation-sulfuration treatment of copper smelting slag has been optimized,and ideal technical indexes have been obtained.The comprehensive utilization level of copper in copper smelting slag has been improved,and the pollution of heavy metal ions in waste slag to groundwater has been reduced.It is of great significance to the sustainable development of copper industry and environmental protection in China.