New Process For Producing Copper Powder From Waste Printed Circuit Boards By Mechanical And Physical Method

The waste printed circuit boards contain a large amount of pure copper,which is mixed with valuable metals such as Sn,Pb,Fe and Zn,and also contains non-metallic materials such as resin,glass fiber,and ceramics.The traditional recycling process mainly uses hydrometallurgical or pyrometallurgical processes to recycle copper and other valuable metals,with long process flow,high energy consumption and high pollution.In this paper,the metal concentrate obtained from the waste printed circuit boards are used as raw materials,the raw material particle size is more than 2 mm,the metal content is 83.22 wt.%,and the Cu content is 51.8 wt.%.Based on the analysis of the physicochemical properties of raw material,a new process for the recycling of copper by the mechanical and physical method is proposed and implemented.The obtained copper powder can be directly applied to powder metallurgy.The Main conclusions are summarized as follows:(1)The magnetic separation and crushing process of raw materials is studied.The results show that when the feeding speed is 460 kg/h and the magnetic field strength is 0.09 T,it is a better magnetic separation process condition.Under this condition,the removal rate of iron reached 97.2%,and the copper recovery rate reached 94.84%.The material after iron-removing was crushed by a hammer crusher,and the dissociation effect of the materials in different particle sizes is studied.The results show that the smaller the particle size,the more the material dissociation is.(2)The separation process of metal and non-metal in the metal concentrate is studied.The crushed materials were separated by hydraulic shaking table,and the influence of table inclination,water flow and shaking table frequency on metal grade and recovery rate is studied.The results show that when the table inclination,water flow and shaking table frequency reach 1.5 °,15 L/min,380 times/min,respectively,the recovery rate of copper is 94.35% and metal grade is 96.66 wt.%.The material after the separation of the hydraulic shaking table is processed by ball milling,which can effectively remove non-metallic impurities and a part of the solder.When the rotation speed of ball milling,liquid-material ratio and the time of ball milling reach 400 r/min,0.3 ml/g,4 h,respectively,the removal rate of non-metallic impurities and solder reached 96.36% and 67.71%,the recovery rate of copper reached 88.07%.(3)The separation process of Cu and other impurity metals such as Fe,Sn and Pb in copper concentrate is studied.The material obtained by physical separation is treated by hydrochloric acid leaching,and the impurity metals such as Fe,Sn and Pb can be effectively removed.When the hydrochloric acid concentration,liquid-solid ratio,the time of leching and the temperature of leching reached 10mol/L,1.5 ml/g,60 min and 75 ?,the leaching rates of Fe,Sn and Pb were 99.36%,97.30% and 99.32%,respectively.(4)The ball milling pulverization method for large particle copper is studied.The results show that when cyclohexane is used as a process control agent,under the conditions of a ball milling speed of 400 r/min and a liquid-to-material ratio of 0.2 ml/g,the copper powder with a particle diameter of 100 to 250 ?m was ball milled for 7 hours,and all copper powders was refined to 7 to 45 ?m.(5)After the raw materials are processed through the whole process,the purity of the obtained fine copper powder reaches 99.39%,and the direct yield of copper directly applicable to powder metallurgy reaches 67.7%.Moreover,the waste liquid and tailings produced in the process can be treated by a suitable process to achieve its harmlessness and recovery of valuable components therein.(6)The new process flow for the preparation of copper powder from waste printed circuit boards by mechanical and physical method proposed in this study.The main processes include: mechanical fracture-pneumatic separation-mechanical pulverization-hydraulic shaking table separation-ball milling to remove impurities-acid leaching-ball milling refining particle size.The process avoids the metallurgical process,has the characteristics of short process flow,low energy consumption and low pollution,and the obtained copper powder can be used for powder metallurgy to realize direct material application.The research provide an efficient,environmentally friendly and economically viable process for the recycling and reuse of waste printed circuit boards copper resources,and also provide a technical reserve for recycling of electronic waste.