Study On The Separation And Analysis Of Platinum Spent Catalyst In Organic Silicon Synthesis

This paper proceeds from the valuable precious metals in the industrial spent catalyst and studies the redemption of precious metals. The main recovery technologies including the hydrometallurgical, the pyrometallurgical and the hydrometallurgical-pyrometallurgical methods were compared through reading abundant documents about separation and analysis of precious metals in China and abroad. The recovery process was chosen which pretreatment was with pyrometallurgy, and leaching separation was with hydrometallurgy.The innovative point of this paper is that the leaching process of platinum from spent catalyst with complex components and low grade was researched. The technical process was determined. The influence factors and the optimum technical conditions of the leaching process were found.The experiment object is the spent catalyst in organic silicon synthesis which contained 50% of moisture and acids, less than 0.1% of platinum, and 50% of organic silicon polymer. Considering that the content of platinum is too low and the difficulty of leaching is very big, the main research was concentrated on the analysis sampling method and the leaching separating technology of Platinum. At last a H2PtCl6 solution of lmg/mL was made for reuse. The chief process of recovery platinum includes pretreatment, analysis experiment and leaching process with the oxidant and HCl.It was found that low analysis result and bad stability after studying on different traditional analysis methods of precious metals can not determine an accurate data. The key point of the research was the sampling process for analysis because the form of samples is complex. Some shortage of the routine sampling method with aqua regia was found, and then was mended by adding HF to dissolve silicon through comparing different sampling methods. The content of platinum was analysed with SnCl2 photometry after completely solving sample with HF dissolving silicon and with aqua regia dissolving platinum. The conditions of the sampling process are as follows:The sample was dissolved in conditions of aqua regia of 5ml/g for dissolving platinum, concentrating HCl of lml/g for removal nitrate, HF of 4ml/g for dissolving silicon, concentrating H2SO4 of 2ml/g for removal fluoride, all processes with heating to drying; and then the sample was diluted to a 100ml solution. The analysis data of platinum content is higher than those of other methods, average at 0.833mg/g.It is the key point in the separation experiment to find out the best suitable system and conditions of platinum leaching. The optimum conditions were found in the leaching system by single-factor experiment and orthogonal experiment. In the system of HCl-NaC103, the catalyst was leached at 90℃for 3h in a solution of 6mol/L HCl2ml/g and 0.3mol/L NaC103 2ml/g, just as the ratio of solid to liquid of 4ml/g. The leaching ratio of platinum is about 90%. And in the system of HCl-H2O2, the catalyst was leached at 85℃for 3h in a solution of 6mol/L HCl 2ml/g and 2ml/g H2O2 (30%), just as the ratio of solid to liquid of 4ml/g. The leaching ratio of platinum is 94.3%. The concentration of H2PtCl6 for reuse is more than lmg/mL. The leaching ratio in the system of HCl-H2O2 is higher than that that in the system of HCl-NaClO3, without the second pollution on environment. The leaching system of HCl-H2O2 is an economical method for recycling precious metals from spent catalyst in organic silicon synthesis.