Waste Printed Circuit Boards Liberation And Gold Recovery By Iodide Process

The printed circuit boards，as an important part of electronic products, containcomplex components which include large amounts of valuable metals and harmfulsubstances like Pb、Hg、Cd、Cr⁶⁺、halogen flame retardant etc. Therefore the recoveryis significant to the resources and environment.In this paper, the waste printed circuit boards were crushed，and their crushcharacteristics，compositions，metal distribution and liberation state were analyzed.The study found that：the complete liberation granularity of metals and non-metals inthe printed circuit boards was0.45mm，and the main metal elements in circuit boardswere Cu、Ca、Al、Pb、Sn，and the non-metallic elements were Si and Br. Metals weremainly distributed in the grain size of+0.20mm，and its contents generally reducedwith the decrease of granular level. The flotation method was used to separate metalsand nonmetals in circuit boards. When the mass concentration of slurry was90g/L，aeration rate was0.22m3/h，the dosage of foaming agent （octanol）was210g/t，theflotation results of-0.45mm grade powders as followed：the metal contents insediments reached at87.32%，and the metal recovery was90.11%. The leaching testsfor metal powders after pretreatment were obtained by iodide method, under theconditions of initial iodine concentration1.1%，molar ratio of iodine and potassiumiodide was1:10，solid to liquid ratio1:9，hydrogen peroxide dosage1%，leaching time3h，room temperature, and leaching solution pH was natural value of the solution，theleaching rate for gold was95.53%. Crush-flotation-iodide leaching process canrecycle effectively the gold in the printed circuit boards.