The Catalytic Oxidation Electronic Waste In Three-phase Reactor

A new technics of gold recovering from the waste printed circuit board(PCB) is put forward in this article. This technics is basis on the analysis of more than 20 kinds of metal ultimate in a certain waste PCB with Atomic Absorption Spectrometry(AAS). In this PCB,the content of low-priced metal is very high, such as copper,iron and plumbum etc. So the catalytic oxidation pretreatment system technique is used to lixiviate these low-priced metals,the enlarge scale experiments on the application of the process are carried out three-phase reactor.and the gold left in the dregs is by soaked out with low toxicity drug.The result of the test shows:under certain terms,this pretreatment craft can soak effectively out such elements as the lowpriced metal copper, iron and plumbum etc, the catalytic oxidation enlarge scale experiments in three-phase reactor also obtained the satisfying result.the recovery rate of gold is more than 93% with the low toxic durg as sulphur urea,sodium thiosulphate;at the same time,though treating properly with the waste water and waste residue produced in gold recovering course,will not cause the secondary pollution to the environment,achieve resource recovery and in-noxious double purpose.The catalytic oxidation system with nitric acid can effedtive lixiviated out the metal as copper,iron and plumbum inside waste PCB.The best response terms:liquid-solid ration 5:l,sulfate acid 7ml, nitric acid 3ml, reaction temperature 60℃, leaching time 2h,the recovering rate of metal may up to 92.87%. with the characteristic that nitric oxides produced by the oxidation reduction reaction the nitric acid participated in can be absorbed in water and nitric acid is reproduced.The waste PCB was leached by ferric chloride acid solution under normal pressure is feasible.the optimum conditions: reaction temperature 60 °C, oxidation leaching time lh,hydrochloric acid 3ml.the recovering rate of copper and iron may up to 95%, the plumbum recovering rate is more than 90%. with the characteristic that ferric chloride produced by the oxidation reduction reaction bichloride can be reaction oxvgn and nitric acid is reproduced.The catalytic oxidation system enlarge scale experiments in three-phase reactor test shows: the catalytic oxidation system leaching waste PCB is feasible,the low demand for the equipments,without other special matching equipments. The best response terms:the waste PCB50g, sulfate acid 85ml, nitric acid 15ml,water 650ml, liquid-solid ration 15:1, reaction temperature 60°C, leaching time 2h, the recovering rate of metal may up to 92%.The experiment of leaching gold in waste PCB with thiourea indicates that gold leaching with thiourea is possible and effective . and that its suitable leaching conitions are the ratio of solid to liquid is 1:5, leaching temperature 40°C , thiourea concentration 10g/l, FeJ+concentration 0.3%,leaching perio 2h> H2SO4concentration 10%.the gold recovering rate can be up to 95%.The sodium thiosulphate soaking gold goes on in the alkaline system,having the advantages of low requiring to the equipment,fast reaction speed.The best response condition of gold recovery with sodium thiosulphate: the ratio of solid to liquid is 1:5,leaching temperature 60°C , leaching period 2h, thiosulfate concengration 0.4M, Cu2+concentration0.04M,ammonia concentration 0.45M,PH=9.5, SO32 ~ concengration 0.2%, Speed of air 11/min, the gold recovering rate can be up to 93%.Innovate to some exent on the technological process,feasiblely and simple/this gold-recovering technics have double benefit of economy and environment.ZhongFeiWen (Environmental Engineering)Supervised by professor Li DengXin...