Study On Properties And Application Of Copper Smelting Slag

Copper smelting slag（CSS）is a solid waste produced in the process of copper smelting.With the rapid development of China’s economy,the copper output increases year by year,resulting in an increasing total amount of CSS.However,most enterprises stack CSS in the open air for a short or long time,which not only wastes land resources,but also pollutes the surrounding environment.At present,high value utilization of CSS and effective recovery of valuable metals such as Fe,Zn and Pb are prominent problems in the research of CSS.Therefore,the research on the recycling and reduction of CSS has important practical significance.Firstly,the composition,phase and morphology of CSS were analyzed by XRF,XRD and SEM,and the leaching characteristics of valuable metal elements and toxic and harmful metal elements in CSS under different pH conditions were explored by pH static experiment.The main components of CSS are Fe and Si,and also contain Ca,Al,Cu,Zn,Pb,As,Mg,Cr and other elements.Among them,Zn and Pb have great economic benefits for recycling.Through XRD and SEM characterization analysis,it is determined that the main phases in CSS are Fe₂SiO₄and Fe₃O₄,the main morphology is lamellar particle agglomeration structure,and the properties are relatively stable.The leaching concentration of toxic and harmful elements Cu,As,Cd and Pb in CSS exceeds the maximum limit of integrated wastewater discharge standard（GB8978-1996）.Therefore,in the process of resource utilization of CSS,it is necessary to carry out environmental risk assessment,and pay attention to the environmental risk caused by open stacking.Secondly,this paper uses the activation method of ball milling with different activators to explore the feasibility of preparing cement active materials with CSS as the main raw material.The experimental results show that the optimum process parameters for ball milling activation with CaO are as follows:CaO content 15%,ball milling time 90 min,ball mill speed 400 r/min,compressive strength of mortar block up to 38.9 MPa and activity index 89%（>75%）;The optimum process parameters of adding CaCO₃for ball milling activation are as follows:CaCO₃content of 5%,ball milling time of 90min,ball mill speed of 500 r/min,compressive strength of mortar test block up to 39.82 MPa and activity index of 93.7%（>75%）.Both materials meet the requirements of fly ash used in cement and concrete（GB/T 1596-2017）.XRD and SEM results show that ball milling and CaO have a synergistic mechanism on the activation of copper tailings.Ball milling can activate silicate groups in iron olivine（Fe₂SiO₄）by reducing particle size and increasing surface active groups.In addition,CaO can form a large number of C-S-H active groups on the surface of activated particles,so as to significantly improve its compressive strength.The addition of CaCO₃ball milling can reduce the proportion of iron olivine（Fe₂SiO₄）in CSS and increase the content of amorphous substances.After ball milling,the lattice of CSS is distorted and the original and orderly structure of minerals is destroyed.After making mortar test block,due to the introduction of CO₃^2-,it can preferentially react with C₃A.The generated ettringite acts as a skeleton and overlaps with each other in the cement system,making the interior of mortar test block more compact and the strength significantly improved.The leaching toxicity concentration of harmful substances of the two cement active materials meets the requirements of the integrated wastewater discharge standard（GB 8978-1996）.Finally,using CSS as the main raw material,copper tailings based chemical bonding material（CSS-CBC）was prepared by ball milling and alkali excitation reaction,and applied to the removal of Cd²⁺in water.The effects of CSS-CBC dosage,initial pH of solution,interfering ions,reaction temperature and other factors on the removal of Cd²⁺were explored,and the removal mechanism of CSS-CBC for Cd²⁺was analyzed by XRD,BET,SEM,FTIR and XPS.The results show that the optimal dosage of CSS-CBC for adsorbing Cd²⁺is 4.8g/L and the optimal pH of the solution is7.0.Under these conditions,the removal rate of Cd²⁺can reach more than 95%and the maximum adsorption capacity can reach 19.35mg/g.The adsorption of Cd²⁺by CSS-CBC conforms to the quasi second-order kinetic model and Langmuir isothermal adsorption model.The adsorption of Cd²⁺by CSS-CBC is mainly realized through chemical precipitation and complexation.Some Cd²⁺forms metal silicate precipitation and amorphous carbonate precipitation;Another part of Cd²⁺coordinates with Fe₃O₄to form a surface complex.