Study Of Gold Recovery From The Waste Printed Circuit Board

A new technology of gold recovery from the waste printed circuit board ( PCB ) is putting forward in this article. This technology is based 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 copper and iron are very high. So the oxidizing-acid soaking pretreatment technique is used to lixiviate these metals, and the gold left in the dregs is by extracted out with three different methods: solvent extraction method, emulsion liquid membrane technology and the multi-emulsion liquid membrane technology. As one traditional precious metal extraction method, The solvent extraction method has an advantage for high extraction efficiency of gold, such as good separation effort, big industry productivity , fast and continuous operation , safer processing, easy for automatic control and so on. And it has become one of the promising processing methods for electric waste in future. The other two kinds of extraction method known as the liquid emulsion membrane method and multi-liquid emulsion membrane method, have a simulation of biology cell's concentrated function and has an advantage of continuous and automated function. It has caused the attention in the electric waste processing field fortheir high selectivity, fast mass transfer speed, short extraction time, few solvent extract amount, and moderate reaction condition.The pretreatment experiment takes 70-200mu electronic printed circuit board as the processing object, the test result indicates.- In the leaching pretreatment of copper, iron, with the hydrogen peroxide solution -sulfuric acid and under the certain condition, they can be effectively leached out. And it's environment friendly and also a clean and effective pretreatment method. When taking the waste circuit board 2g, the best pretreatment react condition is: Hydrogen peroxide solution lOmL, sulfuric acid: water(volume) Is 1 r 2, reaction time 2h, temperature 25°C , fluid solid ratio(sulfuric acid volume: The sample quality) is 3: 1. The leaching rate of copper may achieve 93 %.In the solvent extraction experiment, the gold density is 0.9mg/L. MIBK is used as the extract. And magnetic force mixer, the tap funnel, PHS2 acid are used to research the compare rate, pH value and the temperature influence to the gold extraction rate. The experimental result indicates, when compare rate is 0.3, and the extract time is lOmin under the constant temperature, the gold extract rate may reach 95 % , but the pH value change doesn't influent the gold extract rate obviously.In the emulsion liquid membrane experiment, the gold density is 0.9mg/L. Span8Ck MIBK^ liquid paraffin wax are used. The analytical balance, constant temperature water bath, emulsification mixer (JRJ300-S) are used to study the internal phase reagent(Na2SO3)density, the carrier (MIBK) density, pH value, rotational speed and the impurity ion concentration that effect the gold extract rate. The experimental result indicates when the carrier density is 4%, the internal phase reagent density is 5xlO"6mol/dm3, pH value is 2.5, mixing speed is 4000rpm, the gold extract rate achieved 94.1 %.In the multi-emulsion liquid membrane experiment, the gold density is 0.9mg/L. Span8(h Tween8(h MIBK^ liquid paraffin wax are used. The analytical balance, constant temperature water bath, emulsification mixer (JR.I300-S) are used to study the internal phase reagent(Na2SC>3)density, the carrier (MIBK) density, pH value, rotational speed and the impurity ion concentration that effect the gold extract rate. The experimental result indicates when the carrier density is 4% , the internal phase reagent density is 8X1CT 'mol/dm', pH value is 2.5, mixing speed is 3000rpm, the gold extract rate achieved 96.8%.