Study On Preparation Process Of High Purity Stannous Pyrophosphate

This thesis includes three parts．Part I．The establishment of quantitative analysismethods for stannous pyrophosphate．Part Ⅱ．Study on dissolution properties andhydrolysis properties of stannous pyrophosphate. Part Ⅲ．Study on preparation processof high purity stannous pyrophosphate．Part I. The establishment of quantitative analysis methods for stannouspyrophosphate.At present, the industry standard HG/T4206-2011is applied to quantify analysis theproduct. The purity of stannous pyrophosphate is evaluated by the content of tin ions(Ⅱ)in products, which is measured in the oxidation-reduction titration method. It isinaccurate to evaluate the purity of stannous pyrophosphate only by the content of tinions(Ⅱ), the content of the pyrophosphate radical ion in the products should also bemeasured, which is not included in the industry standard.1. The quantitative analysis method of phosphate radical ion was established by usingphosphorus molybdenum blue spectrophotometry. The influences of ammoniummolybdate dosage, the concentration of reductant, pH, temperature, time andinterfering ions (tin ions) on analysis method were investigated. The results showedthat the concentration and absorbance form a good linear relationship when content ofphosphorus ranged from0.01mg to0.06mg. This method has an advantage of reagentblank color, simple color system, short chromogenic time, simple operation. It wasbetter to eliminate interference ion effects on quantitative analysis by adding excessivemasking agent EDTA-2Na.2. The quantitative analysis method of phosphate radical ion was established by usingRaman spectroscopy. A good linear relationship between concentration of P2O74-andthe intensity ratio of Raman spectral characteristics peak of P2O74-and NO3-isdisplayed by using potassium nitrate as an internal standard and keeping the pH ofmeasured solution at11. The linear regress equation is Y=1.2110X+0.1515，and thecorrelation coefficient R2is0.9996.3. According to the test and improvement on the industry standard of HG/T4206-2011,the quantitative analysis method of tin (ii) was established. Comparing to the methodof Raman spectroscopy, this method showed a great advantage in evaluation ofpyrophosphate purity of the tin sample by measuring the concentration ofpyrophosphate ion, the relative error was less than0.03%. 4. Quantitative analysis method of trace tin in the solution was established by usingspectrophotometric method, the results showed that: if using H2O2as oxidant,phenylfluorenone solution as the chromogenic agent, CTAB (cetyl trimethylammonium bromide) as the surfactant, solution pH=0, concentration and absorbancecurve had a good linear relationship when content of tin range from0.025mg to0.225mg, and the linear regress equation is Y=5.6387X-0.0054，the correlationcoefficient R2is0.9989. Quantitative analysis of more tin ion in the solution wasestablished by complexometric titration method and this method was quick and easy.Add excess hydrogen peroxide in the solution and divalent tin could be transformatedinto tetravalent tin trough oxidation. In that case, total tin content of divalent tin andtetravalent could be tested.Part Ⅱ. Study on dissolution properties and hydrolysis properties ofstannous pyrophosphate.1. The solubility of stannous pyrophosphate was determinated by determinating thecontent of total tin in solution. The results showed that the pyrophosphate stannouswas difficult to dissolve in distilled water, anhydrous ethanol, ammonium chlorideaqueous solution, sodium chloride and potassium chloride aqueous solution, butslightly soluble in aqueous solution of dilute hydrochloric acid, soluble in concentratedhydrochloric acid, and soluble in high concentration of potassium pyrophosphatesolution.2. The total content of the phosphorus and free phosphate in solution of pyrophosphatewere measured by phosphorus molybdenum blue spectrophotometry. Then thehydrolysis degree of pyrophosphate, potassium pyrophosphate and stannouspyrophosphate were obtained. The results showed that increase of temperature wouldstimulate the hydrolysis process, but increase of pH value would inhibit thehydrolysis process. The separation conditions pyrophosphate radical ion andphosphate radical ion by zinc chloride was studied. The results showed thatpyrophosphate radical ion could be completely precipitated by zinc chloride whenpH=1.8, and phosphate radical ion could not be completely precipitated.Part Ⅲ． Study on preparation process of high purity stannouspyrophosphate．The influences of reaction temperature, reaction system pH value and washing timeson the quality of stannous pyrophosphate sample were studied by using pyrophosphoricacid, ammonia and stannous chloride as the raw material. The main results included:1. The influence of reaction temperature on the quality of stannous phosphate samples was studied. The results showed that the purity of pyrophosphate stannous sampleincreases gradually as the increase of the temperature, and the optimum reactiontemperature was70℃.2. The influence of pH in reaction system on quality of stannous phosphate samples wasstudied. It could be concluded that when pH was3, pyrophosphate stannous samplecould be achieved with the highest purity.3. The influence of washing times on quality of stannous phosphate samples was studied.The results showed that when the washing number was3, the purity of pyrophosphatestannous sample was more than99.00%. In order to avoid loss in the process ofwashing, the optimum washing times should be3.