Study On New Process Of Recovering Copper From Waste Printed Circuit Boards And Preparing Ultrafine Copper Powder

A hydrometallurgical process for copper recovery and MLCC copper partales from the waste Printed Circuit Boards (PCB) was proposed in this study. The main process include:physical pretreatment of raw materials-leaching in NH3-(NH4)2SO4-H2O system-deep purification by solvent extraction-stripping enrichment of copper sulfate solution-preparing copper power used in MLCC through two-step restore. The obtained research fruits were listed as follows:(1) After mechanical pretreatment of raw materials, the high-density and low-density were separated by water power shaker. The electricity beneficiation can separate metal and nonmetal of low-density part. The recovery of copper in the high-density part was up to99.67%, and the recovery of non-metallic material in the low-density part reached84.88%.(2) The high-density part was raw material in leaching experiment, and air was blew into solution as the oxidant for leaching copper in NH3-(NH4)2SO4-H2O system, while the leaching residue was treated by physical method. It’s a promising choice for choosing air as oxidant to leach copper because of its good effect, economic and environmental friendly characteristics. Based on amount of experimental data, the optimum conditions were determined that solid-liquid ratio of1:20, the leaching temperature at25℃, air flow at8m3/h, the ammonium sulfate concentration of2mol/L, the ammonia concentration of2mol/L, the leaching time of4h. Under these optimum conditions, the leaching rate of copper was up to96.67%. Leaching residue was obtained by electrostatic separation and magnetic separation.(3) LIX84IT was used as extractant, and high content and purified copper stripping solution was obtained though extraction-sulfuric acid stripping. The optimal conditions of extraction process was determined as follows:the extractant concentration (volume fraction) of50%, phases ratio(O/A) of1:1, TBP concentration of0.1mol/L, extraction temperature at25℃, the oscillation frequency of150times/min, contact time of3min.Under the optimal conditions, the copper extraction rate reached98.87%. The suitable conditions in stripping process were obtained, which inclueded concentration of sulfuric acid2mol/L, phase ratio(O/A) of2:1, the oscillation frequency of150times/min, contact time of5min, the copper stripping rate reached93.34%. After evaporative cooling and crystallization of the stripping solution, CuSO4·5H2O which had low impurity content and met the requirement for preparation of ultrafine copper powder requirements was prepared.(4) By Glucose pre-restore-the hypophosphite secondary restore, we prepared ultrafine copper powder that achieved the requirements of MLCC. the proper experimental conditions for the copper powder using in MLCC was summarized as follows:preparation of Cu2O suspension, the dosage of PVP seed6g, the stirring speed of400rpm, the dosage of NaH2PO2·H2O seed four times of the stoichiometric quantity, NaH2PO2solution was added through two steps.Ultrafine copper powder used in MLCC was obtained, which have uniform particle size, high crystallinity, no agglomeration and satisfied the technological application requirements.After above process for the waste printed circuit boards, ultrafine-copper particles used in MLCC was prepared.