Research On The Process Of The Recovery Of Zinc From Waste Catalyst

Catalyst plays a very important role in petroleum, chemical and medicinal industry, there are large quantities of waste catalyst produced in the world every year, because catalyst would lose activity after a period of time and are replaced by fresh catalyst. Waste catalyst has been not able to recycled reasonably for many years. Some were taken to landfill or piled up directiy, in that case, It not only squanders secondary resources, but also pollutes the ecological environment and human health. With the growing shortages of mineral resources, the recycle of valuable metals from waste catalyst could accomplish the recycle of resources and has important social significance.This experiment used waste catalyst as raw materials, and the recovering of zinc from the waste catalysts by NaOH and NH3-NH4HCO3leaching methods have been studied in this paper, and the optimum experimental conditions were obtained through a series of experimental research.Factors influencing on zinc leaching rate including concentration of NaOH, liquid-solid ratio, temperature and reaction time were studied in the leaching system of NaOH solution and got the optimum conditions. The leaching ration of Zn can amount to90%when the concentration of NaOH was5mol/L, liquid-solid ratio was25:1, the mixing speed was300r/min, and leaching2hours at80℃, meanwhile, nickel was enriched in residue which can also be used as nickel smelting raw materials. The species of impurity element were less in Leaching solution because of high selectivity of alkaline leaching agent. The purified solution obtained by one-stage purification of alloy zinc powder and the concentration of Fe was1.03mg/L, Pb was0.245mg/L, Ni was1.42mg/L in the solution after purification. ZnS were synthesized by using Na2S to precipitate in the paper, and It decided to adopt Hydrothermal method to synthetize ZnS basing on the comparison of the direct precipitation method and Hydrothermal method. Zinc sulfide with the purity of95.4%were obtained under the optimum conditions including n(Na2S)/n(ZnO22-) of 1.2, reacting for12hours at150℃.The leaching conditions of zinc including concentration of ammonia, liquid-solid ratio, temperature, reaction time and the pH of ammonia solution were studied in the system of NH3-NH4HCO3solution and got the optimum conditions. The results showed that under the leaching conditions of the pH of9.5, the concentration of ammonia of7.5mol/L liquid-solid ratio of8:1, temperature of80℃, mixing speed of300r/min, and leaching time of2h, the zinc leaching was up to94.0%. The leaching solution need to be purified before preparation of ZnO because Pb, Ni and Cu also complexed with ammonia in ammonia solution. The purified solution obtained by one-stage purification of alloy zinc powder and and the concentration of Fe was0.97mg/L, Pb, Ni and Cu was very low in ammonia solution which has meet the requirements of the deep purification. ZnO was prepared of ammonia leaching solution.The effect of factors on the yield and purity of ZnO were investigated, including ammonia stilling time and calcining temperature. The purity of zinc oxide powder reached99%when ammonia pure solution was evaporated for2.5hours and then calcined for2hours at500℃.