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Mathematical modeling of processes in flow-through 3D electrode with account for reactions preceding to reduction of metal ions to metallic phase

“…Flow-through 3D electrodes (F3E) of carbon fiber materials (CFMs) are used for treatment of mul ticomponent solutions containing ions that can par ticipate in oxidation and reduction reactions [1][2][3][4][5][6][7][8]. Such complex multicomponent systems are formed in hydrometallurgical processes of metal recovery from mineral and industrial raw components, e.g., in the processes of electrodeposition of gold, silver, plati num group metals, accordingly, from multicompo nent basic cyanide and sulphate thiourea solutions, nitrite-nitrate solutions for treatment of nuclear waste, silver electrodeposition from bleaching baths.…”

“…Such complex multicomponent systems are formed in hydrometallurgical processes of metal recovery from mineral and industrial raw components, e.g., in the processes of electrodeposition of gold, silver, plati num group metals, accordingly, from multicompo nent basic cyanide and sulphate thiourea solutions, nitrite-nitrate solutions for treatment of nuclear waste, silver electrodeposition from bleaching baths. The solutions contain metal ions capable of stagewise reduction [1,3,5,6,8]; some metal ions are reduced to less electropositive forms without formation of a metal phase. Stagewise electrooxidation of metal ions is also possible, as recovery of iridium from sul furic acid solutions by ion exchange or extraction includes the preliminary stage of converting iridium from Ir 2+ to Ir 6+ via Ir 3+ → Ir 4+ by electrooxidation on a flow-through fiber carbon electrode; herewith, the parallel reaction of Fe 2+ → Fe 3+ is possible [7].…”

“…Let us point out that the equation similar to equa tion (6) is also applicable in the case of oxidation of certain component k to the state, in which type j ions are present. However, to formulate all model equa tions for the given process, one has first to consider in detail all possible electrochemical reactions in a flowthrough 3D electrode.…”