| With the rapid development of communication and household appliance industry, the demand for nickel-cadmium batteriese is also increasing gradually, but the problem of environmental pollution is becoming more and more serious. Cadmium is a rare and precious metal, as well as toxic metal. The cadmium has great content in nickel-cadmium batteries, the problem of environmental pollution caused by the waste nickel-cadmium batteries is mainly due to cadmium pollution. So we should recycling the cadmium in waste nickel-cadmium batteries, it has important practical significance, whether from the point of view of resource recycling, or from the point of view of environmental protection.In this experiment, selected to synthesize the ionic liquid: 1-butyl-3-methylimid-azolium hexafluorophosphate([Bmim]PF6) and 1-butyl-3-methylimidazolium hexafluorophosphate([Beim]PF6), and then investigated the influence factors of synthesis rate such as reaction time, reaction temperature, ratio of reactants and dosage of solvent. Combination the ionic liquid and liquid membrane separation technique, use trioctylamine(TOA) as carrier, sulfuric acid as back-extraction. In this paper, studied the enrichment and separation effect of cadmium in cadmium nitrate solution by using this technology, and investigated the influence factors as reaction time, the amount of carrier, p H value of solution and concentration of sulfuric acid. Finally, this technology was applied to treat pretreatment solution of waste nickel-cadmium batteries, testing its effect on separation and enrichment of cadmium. The results of this experiment are as follows:1. The best parameters of synthesize the intermediates as [Bmim]Br and [Beim]Br were N-methylimidazolium or N-ethelimidazolium concentration is 0.1mol/L, n-butyl bromide concentration is 0.12mol/L, the concentration of carrier is 0.03mol/L, reaction time is 24 hours and reaction temperature is 60℃. The best conditions of synthesize the ionic liquid as [Bmim]PF6 and [Bmim]PF6 were the concentration of [Bmim]Br or [Beim]Br is 0.1mol/L, the concentration of KPF6 is 0.11mol/L, reaction temperature is 50℃ and reaction time is 24 hours. Finally, the synthetic rate of [Bmim]PF6 is 88.2%, [Bmim]PF6 is 90.6%. The products have been identified by Infrared Spectroscopy(IR).2.Combination the ionic liquid and liquid membrane separation technique to treat the cadmium nitrate solution, the concentration of this solution is 5×10-4mol/L. The best reaction conditions of this experiment we will choose [Bmim]PF6, carrier concentration is 9×10-4mol/L, p H value of solution is 5, extraction time is 80 min, the concentration of sulfuric acid is 1.5mol/L, back extraction time is 60 min. Then the separation and enrichment rate of cadmium is 91.9%. Adding nickel and cobalt as interference ions has minimal impact on the separation and enrichment rate of cadmium. The ionic liquid can be realized to recycle after purification treatment.3.Using this technology to treat pretreatment solution of waste nickel-cadmium batteries, the experiment achieved the expected processing effect under the best parameter conditions. In the end of experiment, the separation and enrichment rate of cadmium is 91.9%, nickel is 3.5%, cobalt is only 2.1%, to realized the separation and enrichment of cadmium.Using the technology in this paper, the reaction operation is simple and the reaction process is green, safe and non-polluting. It can be used to separate and enrich the cadmium in nickel-cadmium batteries, the experiment achieved the expected effect. |
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