| Rhodium, a member of platinum group in the periodic table, has been widely applied in heterogeneous and homogeneous catalytic reactions as center mental of catalysts. Rhodium catalysts have a variety of application with features as longevity and high activity, selectivity. However, the less reserves, higher price and lower amount of production make it important to develop a technique for the recovery of (?)oble metal rhodium considering its remarkable economic benefits.In this thesis, we investigated the process of recovery of noble metal rhodium in the following aspects:1. Resin adsorption and elution process.Using D401 macroporous chelating resin, static process was performed directly n the Hydrogenated Nitrile-butadiene Rubber(HNBR) organic phase and dynamic process was performed in the waste rhodium-containing water phase, in which YT(a water soluble extractants) is used to extract the used triphenylphosphine rhodium catalysts from organic phase into water phase, respectively. The results were as following:The static process:(1)A 4.9% (by weight) of HNBR organic solution is adsorbed five times with 30 grams new resin in each performance, the total adsorption recovery was 87.10%.(2)60 grams resin were used to adsorb five 3.6% of HNBR solutions one by one, after each adsorption, the resin is washed with 10ml iimethylbenzene four times, adsorption recovery for each glue solution was more :han 50%, and for 2.9% of HNBR solutions, adsorption recovery was more than 60%. (3) Static elution process:Eluting rhodium-adsorbed resin with Y for 2 hours, the elution recovery were 16.24,22.51% and 29.26% for the 4.9%,3.6% and 2.9% of HNBR solutions respectively, that means the lower the concentration of HNBR was, the better the elution recovery was.The dynamic process:The adsorption rate was 27.23% by passing through the resin column two times in three hours and 45.95% four times in six hours. Elution rate was 11.94% for one time in 2 hours using Y as elution agent. Resin is still capable of adsorption after regeneration.Recovery process.Heating and reducing process.The waste rhodium-containing water phase is obtained by transferred used rhodium catalysts from hydrogenated NBR organic phase to the aqueous phase with a patent method. The optimal conditions of the process were studied. The experimental results showed that by heating (160℃) and evaporating 50ml aqueous phase to 7～8ml residual in 2 and half hours under atmospheric pressure,89.59% rhodium can be reduced as element rhodium in black precipitate. 2. Pure rhodium was obtained by electrolyzing rhodium chloride solution obtained by sampling elemental rhodium precipitated in the heating and reducting process or rhodium-containing elution solution from resin adsorption and elution process. Using self-made electrolyte cell, the operation parameters we used were as following:the electrolyting voltage was 3 V, the concentration of the NaCl supporting electrolyte was 1 moL/L and both cathodic and anodic electrodes were pure graphite. The yield of rhodium was 1.23mg/h.cm3.3. Sampling and determination.(1)Rhodium catalysts were treated with Na2O2-H2O2 The optimum conditions were determined. Using 0.5g Na2O2, 10mL H2O2 and 1moL/L HCl solution, 0.01800g rhodium catalysts can be sampling thoroughly. The recovery of rhodium was 99.99%.(2)Carbonization-acid dissolving method were investigated for both rhodium-containing water phase and organic phase. The recoveries of rhodium were 94.97% and 99.05% respectively.(3) Investigated dissolvoing black elemental rhodium with aqua regia.(4)Using stannous chloride-potassium iodide colorimetric system, concentration of rhodium was determined by standard addition method with simple, sensitive, accurate and repeatable features. |
PDF Full Text Request