| At present,the production of electronic and electrical equipment is one of the fastest growing areas in manufacturing industry of China.After the abandonment of electrical equipment,a lot of electronic waste will be generated at the same time.In recent years,with the continuous expansion of market economy in China,especially the innovation of science and technology,the total amount of waste electronic and electrical equipment has increased rapidly.If the electronic waste with high metal content is not properly processed,it will cause serious environmental damage.Recycling and utilization of electronic waste is imperative.The method of mechanical treatment is to enrich the valuable substances in electronic wastes according to the differences in physical properties between them.Compared with other methods,its main advantages are light environmental pollution and low cost,while there are some problems such as low concentrate grade and poor metal recovery for fine particles separation experiments.In order to solve the problem of difficult separation for fine particles,new technologies are needed to efficiently separate of fine particles.Flotation is suitable for the treatment of fine and ultra-fine materials.Besides,flotation has the advantages of low cost,simple equipment and technology,high recovery rate and little secondary environmental pollution.The application of flotation to the resource utilization of electronic waste will be beneficial to recycling high value metals,realizing the recycling of resources,to alleviating the resource crisis and obtaining considerable economic benefits.In this paper,the current researchs of resource utilization of waste printed circuit boards and the development of sorting methods at home and abroad were introduced and the related researchs on reverse flotation recovery of metals in printed circuit boards was systematically discussed.In the experiments,the broken particles of circuit boards after disassembly of components were selected as feed materials of the reverse flotation and the metal content of the flotation feed and concentrates was analyzed.Copper with the highest content in the feed is the most important recovery metal.The recovery rate and beneficiation efficiency were selected as evaluation indexes.Single factor and response surface tests were carried out through factors such as feed particle size,feed concentration,agitation speed and aeration rate and the best operation parameters were analyzed.Finally,the reverse flotation test was carried out to analyze the influence of roasting.The following conclusions can be drawn:When the grain is too large or too small,the effect of the reverse flotation test will be worse.The optimum particle size is –0.25 mm,and the circuit board is broken to –0.25 mm by cutting type commininder and vibration mill prototype as the reverse flotation feed.Kerosene and MIBC were determined to be collectors and foaming agents for reverse flotation and the optimum amount is 200 g/t.The operation parameters of reverse flotation process are feed concentration of 100 g/L,agitation speed of 1700 r/min and aeration rate of 200 L/h.After roasting,the indexes of concentrate copper content,copper recovery and copper beneficiation efficiency have been improved except for the decrease of concentrate yield.Taking into account the change of loss rate,the selected roasting conditions are 4 minutes and 200 centigrade,while the copper content of the concentrate is 57.33%,the copper beneficiation efficiency reaches 60.85% and the copper recovery rate is 92.8%. |
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