Chair of Non-Ferrous Metals and Gold, National University of Science and Technology “MISiS”, Moscow, Russia:

A. P. Lysenko, Assistant Professor, e-mail: reikis@yandex.ru

A. Yu. Nalivayko, Leading Electronics Engineer

This paper shows the mechanism of precipitation of aluminum hydroxide in experimental-industrial electrolytic cell. There was defined the influence of various current carrying reagents on the process indicators. In the time of obtaining of aluminum hydroxide by electrolysis in sodium chloride-containing salt solution, there was found the contamination of final product, connected with adsorption of sodium aluminate and sodium salts on Al(OH)3 surface with subsequent introduction of sodium in alumina structure. This paper describes a new method of production of pure aluminum hydroxide by electrolysis, which is possible by replacing of NaCl by NH₄Cl or NH₄NO₃. There was shown a method of “self-cleaning” of aluminum electrodes during anodic dissolution of aluminium: if ammonium chloride and ammonium nitrate are used as electrolytes, there can be formed the acids, which will react with basic aluminum impurities on electrode surface for formation of water soluble chlorides and nitrates. Three individual zones were found in experimental-industrial electrolytic cell workspace: – sol zone (the biggest part of this zone consists of aluminum hydroxide; generated hydrogen is adsorbed onto the newly formed particle of Al(OH)₃ and delivers it onto the bath surface, where the particles are coagulated so long as the density of aluminum hydroxide will not be higher than the density of the middle zone); – transition zone (the biggest part of this zone consists of electrolyte; falling interconnected particles of aluminum hydroxide are carried out in this zone); – zone of sediment (seal and accumulation aluminum hydroxide are carried out in this zone). There was carried out the research, aimed at identification of dependence of distribution of working zones in electrolytic cell on electrolyte concentration. There was defined the concentration of coagulation threshold activating current-carrying agent. There was established that aluminum hydroxide is sedimented much faster at the found concentration of currentcarrying agent.

1. Lysenko A. P., Bekishev V. A., Seredkin Yu. G., Zenkovich G. S. Sposob polucheniya oksida alyuminiya, prigodnogo dlya proizvodstva monokristallov korunda (Method of obtaining of aluminium oxide, applied for production of monocrystalline corundum). Patent RF, No. 2366608. Applied : May 08, 2008. Bulletin No. 25. 

2. Seredkin Yu. G., Lysenko A. P. Razrabotka tekhnologii polucheniya tonkodispersnogo gidroksida alyuminiya elektroliticheskim sposobom (Development of obtaining technology of fine aluminium hydroxide by electrolytic method). Tsvetnye Metally = Non-ferrous metals. 2013. No. 5. pp. 49–57. 

3. Nalivayko A. Yu., Vdovina A. K. Podgotovka syrya dlya proizvodstva leykosapfirov — oksida alyuminiya vysokoy chistoty (Preparation of raw materials for production of leucosapphires — high-purity aluminium oxide). Sbornik tezisov “68-e dni nauki studentov MISiS” (Collection of articles “68-th science days in MISiS”). Moscow : Publishing House “MISiS”, 2013. p. 406. 

4. GOST 11069–2001. Alyuminiy pervichnyy. Marki. Pereizdanie s popravkoy (State Standard 11069–2001. Primary aluminium. Grades. Corrected re-edition). Moscow : Publishing House of Standards, 2008. 

5. Glinka N. L. Obshchaya khimiya (General chemistry). 24-th edition, corrected. Leningrad : Khimiya, 1985.