Research On Recovery Of Palladium From The Spent Pd/Al₂O₃ Catalyst

Palladium is a kind of scarce platinum group metal and itsusing amount is increasing every year.Palladium has become the world s largest consumptive platinum metals.Because of its catalytic performance,it is widely used in catalytic manufacture.During the use of palladium catalyst,the activity decreases,fails and finally discarded.But palladium still exists in the spent catalyst,whose grade is much higher than that in nature.So it has high collection value.In this paper,a kind of a-alumina-based protein spent petroleum catalyst recovered by a precious metal recycling enterprise was used as raw material.Based on the factory conditions and the composition of raw material,hydrochloric acid and sodium chlorate was used as leaching agent,and adsorbed by anion exchange resin DL201-I then desorbed byhydrochloric acid resin obtained solution was treated by conventional methods to get high purity sponge palladium.The results were shown as follows:(1)Spent catalyst was a-alumina-supported protein-based catalyst confirming by XRD and SEM Ball milling was proposed based on its morphology which may break the catalyst to dislodge the catalyst support against the palladium.(2)In the HCl-NaCl leaching spent catalyst system five factors and four levels orthogonal experimentswere designed,such as temperature,milling time,sodium aluminate addition,liquid-solid ratio and leaching time.The optimum leaching conditions were shown as follows:temperature 80 ?,ball milling time 4 min,sodium chlorate dosage 0.4 g,liquid to solid ratio 4:1,leaching time 2 h,hydrochloric acid 6 mol·L-1 and the leaching rate of palladium reached 99.74%.(3)In static adsorption experiments,[PdC14]2-was extracted by anion exchange resin DL 201-1.According to single factor experiments,the optimal adsorption conditions were shown as follows:adsorption time 2 h,amount of resin 5 times,pH = 0,and the adsorption rate of palladium was 94.74%.(4)When hydrochloric acidwas used as desorption agent,the optimum desorption conditions were shown as follows:desorption time 1h,desorption volume 40ml,desorption temperature 50?,hydrochloric acid 5 mol-L-1 and desorption rate of palladium was 82.33%.After concentrating with two chlorine diammine palladious precipitation,the hydrazine reduction can be obtained with purity of 99.5%sponge palladium.If 8%thiourea was added,desorption rate was 94.49%under the suitable conditions.(5)The direct yield was 81.53%if this technology was used.