High Purity Silver Nitrate Preparation And Production Practice

As one of the main chemical product of silver, the silver nitrate has a widespread application in very many domains; at the same time the silver nitrate also is raw material of many silvers fine chemical product. It is foundation of producing many high added value silver fine chemical product such as photosensitive material,the silver catalyst,the electronic contact material, the antibacterial material, the Silver oxide and the superfine silver powder and the silver paste etc.When take silver nitrate as material to prepare fine chemical product including photosensitive material,silver catalyst,silver oxide and so on, the production process has a very high request to the silver nitrate purity. Because of the photosensitivity characteristic and the mechanism it is extremely high requested to the silver nitrate purity while preparing photosensitive material, when producing top grade photosensitive material used for the color photos, it requests the concentration of almost all the impurity ion of silver nitrate under 0.1ppm.The factory can produce this high pure silver nitrate is very few domestically. Because the pure silver nitrate has a very high added value, and its market demanding is also very big, relying on the experience of many years silver production, as well as the abundant fund superiority, Chenzhou Jingui company decides to get a potential achievement in the high pure silver nitrate production field. On the foundation of cooperation with the photosensitive chemistry institute of Chinese Academy of Sciences, the company has developed a new craft to produce the high pure silver nitrate, and has carried on a pilot experiment after the small trial in the laboratory, and directly turn to industrial production later. This article introduces the development of the entire craft and the case of the industrial production process systematically. It has obtained a very good result after research the craft theory also.In this craft the silver is used to react with the nitric acid to synthesize silver nitrate, the silver used as raw material may be 1# also may be the mixed silver; Partial silver nitrate is used to react with the analytically pure sodium hydroxide to prepare the silver oxide, than adding the silver oxide to the solution to use up the remaining nitric acid, the surplus silver oxide in the solution hydrolyze, enables the solution pH value to achieve about 8, the impurity ions existing in the silver nitrate solution is 7precipitated as hydroxide form from the solution when the pH value, but the impurity ions can't be removed completely as sedimentation because the limited pH value could achieved, the remained impurity ion could adsorbed by the silver hydroxide flocculation which is brought in by the reaction between silver oxide and water, thus further reduces it concentration in the solution, Through the whole process, a qualified silver nitrate solution is obtained; The impurity ions in the qualified silver nitrate solution is further removed from the solution in the crystallization process, the concentrated over saturation silver nitrate solution is slowly stirred and naturally cooled to crystallize, the superior grade pure silver nitrate crystal is obtained when the crystallization efficiency at 70% time, the crystal obtained in the first crystallize process is returned to the impurity removing step and treated in the following again, after the second crystallization the silver nitrate to basically satisfies the photography top grade request, but concentration of the no-precipitated-thing by hydrochloric acid and the sulfate is still up the standard. After the last step pickling by the thin nitric acid, the completely satisfied standard photography top grade silver nitrate product is attained.On the foundation of the small trial, the Jingui Company has carried on the industrialization enlargement experiment; the entire product satisfies the standard besides the front two batches tested. After the enlargement experiment, we turn to industrial production directly, after a nearly three month-long productions, the product qualified rate had achieved above 90%, silver returns-ratio is more than 99%, each working procedure runs very good, and the craft is very stable. Many production experiences is obtained through the industrialization production, this has laid a foundation for the further development, and also accumulated the precious material for the preparing of the high net product particular.