Experimental Study On N263 Extraction Of Zinc From Galvanized Pickling Waste Liquid Of Structural Parts

Hot-dip galvanizing is a common method for steel corrosion protection.Pickling is one of the treatment steps before galvanizing of structural parts.According to its process,the spent pickling solution is inevitably contaminated by zinc ions.The iron concentration in the spent pickling solution is about 150g/L,which can be used as a high-quality raw material for water purifiers,however,a small amount of heavy metal zinc ions makes it unable to be used as a high-quality water purifier raw material.At present,only neutralization,distillation and roasting can be used for simple disposal of spent pickling solution,and there is a lack of efficient methods for removing zinc ions.This paper proposes a new method of selective removal of zinc ions under a new extraction system.The effects of extraction time,phase ratio,hydrogen ion concentration,temperature and extractant concentration on the selective separation of zinc from spent pickling solution were studied.In the stripping stage,the effects of phase ratio,time and stripping agent concentration on the stripping rate of zinc in the loaded organic phase and the regeneration effect of Na Cl solution on the organic phase were investigated.In addition,the stability of the extraction system was further studied by using extended experiments.Based on the study of extraction process parameters,the extraction mechanism was analyzed by slope method,infrared spectroscopy and nuclear magnetic resonance spectroscopy.The specific research results are as follows:（1）When the mass ratio of N263 to secondary octanol is 1:1,the third phase in the extraction process can be eliminated.The N263 extraction system not only has a high extraction rate for Fe（Ⅲ）in the spent pickling solution,but also reduces the extraction of zinc ions in a single-stage extraction.The Fe（Ⅲ）can converted to Fe（Ⅱ）after iron powder is used to reduce the waste acid,meanahile,single-stage extraction rate of zinc is greatly improved.（2）Under the optimal experimental conditions of extraction time of 10 min,phase ratio O/A of 1.5:1,and temperature（20±3）℃,the single-stage extraction rate of 30%organic relative to zinc reaches 87.3%,the zinc-iron separation coefficient is 142.9;the three-stage countercurrent extraction rate of 25%organic relative to zinc is 99.99%.（3）Under the experimental conditions that the stripping time is 15 min and the phase ratio O/A is 2.5:1,the single-stage stripping rate of 0.5 mol/L NaOH to the loaded organic phase containing 23.4g/L zinc is 99.4%.（4）The organic phase is regenerated by using NaCl with a concentration of 1 mol/L.After ten extraction-stripping cycles,the extraction capacity of the organic phase can still reach85.4%of the fresh organic phase.In the expanded experiment,the single-stage extraction rate of zinc was 74.3%and the zinc-iron separation coefficient was 61.2 under the conditions of 30%organic phase stirring time 15 min,stirring speed 400 rpm and O/A 1.5:1.（5）Through slope method,infrared spectroscopy and nuclear magnetic resonance spectroscopy analysis,it is concluded that the reaction mechanism of N263 extracting zinc ions in spent pickling solution is anion exchange,and the extraction compound is[R₃CH₃N⁺]_2·[ZnCl₄^2-].In summary,after the three-stage countercurrent extraction,the zinc ion concentration in the spent pickling solution is reduced to 10 ppm,which is better than the zinc ion requirement of the water purifier.The research results of this article can provide research and development ideas and theoretical basis for the high-value deep processing of spent pickling solution in the structural parts hot-dip galvanizing industry.