| The waste denitration catalysts(vanadium-titanium based) have been treated as hazardous waste, if it hasn’t be recyclied reasonably, casuing not only the waste of resources but also environment damage for leaching toxicity. Regeneration is priority method for inactive denitration catalysts, but for the destoryed and unregenerated denitration catalysts, the metal resources of V, W and Ti shoud be recycled as far as possible. Therefore, how to extract V, W and Ti from waste SCR catalysts become an hot research project. Currently, main problems for recycling waste SCR catalysts are low leaching rate of V and W, and the separation of V and W in leaching solution. For resolving these problems, this paper mainly studies ultrasound or microwave assisted enhancemnet in V and W leaching from waste SCR catalysts, and extraction and separation of vanadium from tungsten, mainly involves the leaching and kinetics of vanadium and tungsten from waste SCR catalysts by sodium carbonate roasting- ultrasound assisted leaching, the leaching of vanadium from waste SCR catalysts using sulfuric acid by traditional leaching and microwave leaching, and also studys the selection of extracting agents for seperation of vanadium and tungsten and extraction mechanism. This work has important application and reference value.In this work, waste SCR catalysts serving as raw materials, the leaching and kinetics of V and W enhanced by ultrasound with sodium carbonate roasting – water leaching were studied. Results showed that: ultrasound assisted leaching method was more efficient for V and W recovery than conventional leaching. The leaching rates of V and W enhanced with ultraound were 77.48% and 69.87% respectively for 3 min, and improved by 23.08% and 2.59% respectively compared with conventional leaching. The optimal conditions for ultrasonic leaching are: 90 min ultrasonic leaching time, liquid to solid ratio of 12:1 and ultrasonic power of 500 W. The leaching rates of V and W reached at 89.01% and 96.05% ultimatly. The dissolution kinetics curves of V and W from waste SCR catalysts could be well fitted with the Stumm model. The dissolution of V was first-order reaction, while the dissolution of W was second-order reaction.The leaching and kenitics of vanadium from waste SCR catalysts using sulfuric acid was researched. Results showed that the optimum conditions for conventional leaching are: 5 M sulfuric acid concentration, liquid to solid ratio of 10:1, 2% assisted leaching reagent, leaching temperature of 110 ℃ and 5 h leaching time. The leaching rate of V reached at 79.3% ultimatly. The leaching kinetics of vanadium from waste SCR catalysts could be in line with the shrinking core model, implied that the leaching process was controled by interfacial mass transfer and solid membrane diffusion process, and Ea was 24.57 KJ /mol.The effect of microwave on V leaching and leaching factors in microwave-assisted V recovery from waste SCR catalysts using sulfuric acid were investigated. Results showed that microwave assisted leaching method was more efficient for V recovery than conventional leaching. Leaching rate of V enhanced with microwave leaching was 92.3% by 30 min, increasing by 31.8% compared with conventional acid leaching. The greater of microwave power, the higher of V leaching rate. When microwave power increased from 300 W to 600 W, V leaching rate increased from 63.8% to 92.3%, improved by 28.5%.The selection of extracting agents for seperation of vanadium and tungsten and extraction mechanism including extracting agents selection, extraction conditions and extraction mechanism of vanadium with A/B were studied. Results showed that: Compared with other extracting agents, A/B showed synergistic effect and was more efficient for separation of V and W. The optimum conditions for the separation of V and W with A/B are: initial pH = 5.7, volume ratio of extractant A: B of 1:1, 1.5 M NaOH solution as stripping agent. The extraction rate of V was 91.4% by three countercurrent extraction, while the extraction rate of W was 5.9%. Characterization and analysis showed that 1 mol V3O93-extracted needed 1 mol A and 1 mol B respectively, and V3O93- combied with LIX 63 and Alamine 336 respectively, synthesising larger organic compound easily extracted. |
