Preparation Of Nanocrystal Basic Zinc Carbonate

Nanocrystal basic zinc carbonate was a new type of basic zinc carbonate.It could be used as skin protective agent in the pharmaceutical industry.It also could be used as basic raw materials in the production of cosmetics.Because it was a kind of high-end fine chemical product,so the requirements of the targets were strict.The targets were as follows:grain size (9 - 10.4nm);the content of the main elements Zn(≥56%),Mg(1-2%);the content of impurity elements:Fe(≤20ppm),Cu(≤20ppm),Cd(N/A),Pb(≤5ppm),Co(N/A),Ni(N/A), As(N/A).In order to enlarge the production in industry in the future,industrial ZnSO₄·7H₂O was selected as zinc source of raw materials.But it contained a large number of impurity elements, and the contents of them were high.Therefore,it was necessary to purify zinc sulfate solution furtherly before adding precipitator to it.Firstly,impact of each factor that effected the removal of impurities was saw about,after repeated experimental studies,optimum conditions were obtained.After treatment in the optimum conditions,the impurity content of the samples were as follows:Fe(9ppm),Cu(0.5 ppm),Cd(N/A),Pb(5ppm),Co(N/A),Ni(N/A),As(N/A),met the target requirements.Then,the process of the grain refinement of basic zinc carbonate was studied stressly.A certain mass of MgSCO₄·7H₂O was mixed into ZnSO₄ solution which had been purified, NH₄HCO₃ was used as precipitating agent,a system of nanocrystal basic zinc carbonate was prepared.Through XRD analysis,to draw a small amount of Mg ion incorporation to the basic zinc carbonate can reduce the grain size,and would not give rise to changing in the structure phase of basic zinc carbonate.Through single-factor and orthogonal experimental study,the optimum conditions obtained:(1)ZnSO₄ solution concentration:2.5 mol/L; (2)NH₄HCO₃ solution concentration?3 mol/L;(3)Mg:Zn(mass ratio):1.02:22;(4)stirring speed:350 r/min;(5)NH₄HCO₃ droping speed:12.5 mL/min;(6)temperature:60℃.Three repetitive tests were carried out in above optimal conditions,the results of analysis showed that the repeatability of the process conditions was well,grain size(9.5-9.6 run),the content of zinc(56.09-56.13%) and the content of magnesium(1.04-1.11%),in full compliance with the requirements of target.