Wet Desorption Of Mercury From Waste Mercury Catalyst

The issue of mercury pollution has been attracted human's wide concerns as result of mercury and its compounds have mobility,highly toxicity,persistence and bioaccumulation.The treatment of mercury-containing waste is also getting more and more attention.The waste mercury catalyst generated during the production of PVC is a solid waste with a high mercury content.This project used chloride system and thiosulfate system to desorpt and recover mercury from waste mercury catalyst,the reason was that the mercury can react with chloride or thiosulfate to form soluble mercuric-chloride or mercuric-thiosulfate complex.The results was as follows:The characterization of waste mercury catalyst showed that the moisture content of waste mercury catalyst was 6.55%,the mercury content was 4.09%(the approximate content of mercury compounds was about 5.5%),the carbon content was 62%,KCl,SiO2 and CaO accounted for about 13%,other substances accounted for about 12.95%.The results of the study on the system of chloride and thiosulfate desorpted mercury from waste mercury catalyst showed that the desorption rate of mercury in the waste mercury catalyst by the thiosulfate system was higher than of the chloride system under the same temperature and same concentration.When the desorption conditions were:the S2O32-concentration is 1 mol/L,the solution pH is 11,the desorption temperature is 60?,the liquid-solid ratio is 100:1,stirring speed is 200 r/min,the desorption rate of mercury in the waste mercury catalyst was the highest,which was 96.37%.The desorption rate of mercury gradually descended with the extension of time after reaching the maximum in 10 minutes.The results of the addition of additives to the desorption of mercury in waste mercury catalyst showed that:the addition of SO42-inhibited the desorption of mercury;the addition of a small amount of SO32-,the desorption rate of mercury gradually descended with the extension of time after reaching the maximum in 30 minutes.With the increase of SO32-content,the desorption rate of mercury didn't decrease with the prolongation of time.Adding SO32-can significantly inhibit the decomposition of mercury-thiosulfate complex.Cyclic desorption of mercury in waste mercury catalyst showed that:(1)Waste mercury catalyst was repeatedly desorbed:the first desorption rate of mercury in waste mercury catalyst was 91.09%,the second desorption rate was 2.4%,the third desorption rate was 0.41%,indicating that nearly all of the mercury was basically desorpted for the first time;(2)Desorption solution desorpted the mercury from untreated waste mercury catalyst repeatedly:the first desorption rate was 99.09%,the second desorption rate was 87.31%,the third desorption rate was 66.92%.With the increase of desorption cycle times,the desorption rate of mercury gradually decreased.The results of the study on the recovery of mercury from desorption solution by sulphidation precipitation showed that the sulfide precipitation reaction is fast,and A maximum mercury recovery ratio of 98.12%can be achieved when the ratio of sulfur to mercury is 5.Untreated waste mercury catalyst was desorbed,with desorption solution after mercury recovery,the desorption rate of mercury was 97.47%.The desorption solution has the ability to desorb the mercury from the waste mercury catalyst after mercury recovery by sulfide precipitation.