Home – Home – Jornals – Chemistry for Sustainable Development 2022 number 1

The literature data and experimental results of the authors on the state of bismuth in the solutions of chloric and nitric acids, as well as on the synthesis of various bismuth compounds with the participation of polynuclear complexes, are systematized and summarized. It is shown that hydrolytic processing of bismuth-containing nitric solutions through bismuth precipitation at the process temperature of 65±5 °C and рН 0.7-1.0 in the form of compound [Bi6O4(OH)4](NO3)6 • H2O, followed by its transformation by means of washing with water into the compound [Bi6O5(OH)3](NO3)5 • 3H2O allows efficient separation of bismuth from impurity metals, which leads to a high-purity product with lead, silver and copper content less than 1 • 10-5 %. It is established that these compounds may be used as precursors to obtain high-purity compounds: basic bismuth carbonate, gallate, succinate, as well as medium bismuth nitrate, citrate, ditartrate trihydrate. It is stated that the complex [Bi6O4(OH)4]6+ is the initial cationic form for hydrolytic precipitation of bismuth from solutions; only the ratio of bridging oxo and hydroxo groups changes during hydrolysis, with the conservation of the Bi6O82+ core, which serves as the central structural unit. It is shown that the addition of sodium tribromophenolate to the bismuth-containing nitric solution results in the formation of bismuth oxohydroxotribromophenolate [Bi6O6(OH)2](C6H2Br3O)4. It is determined that bismuth precipitates from chloric and nitric solutions after the addition of even oxohydroxocarboxylates in the form of the compounds with the composition Bi6O4(OH)4(СnH2n + 1COOO)6 (n = 2-22), where (СnH2n + 1COOO)- is the carboxylic acid anion. Bismuth precipitation from nitric solutions in the form of laurate and stearate allows efficient purification of bismuth from impurity metals. A comparison of bismuth extraction with di-2-ethylhexylphosphoric acid from nitric solutions in the form of solvated complex Bi(C16H34O2POO)3 • 2C16H34O2POOH and oxohydroxodialkylphosphate Bi6O4(OH)4(C16H34O2POO)6 is carried out. In the latter case, extracts concentrated with respect to bismuth can be obtained, which provides substantial broadening of the possibilities to use extraction-based processes in the technology of obtaining bismuth compounds.