Extracting noble metals from industrial solutions and waste waters with biosorbents

The chemical composition of various industrial solutions of the Shchelkovo Plant of Secondary Noble Metals is evaluated. It is established that the excess content of heavy metals with respect to gold and silver is larger by a factor of more than 1000. The microbial biomasses of various systematic groups are approved for extracting Au and Ag from solutions with a high salt background. The appropriateness of selectively extracting heavy metals from such complex solutions is shown. The behavior of heavy metals is investigated for sorption on biosorbents from individual solutions within the pH limits of 1.0–6.0 for the medium. The decisive significance of the pH of the solution (within the limits 1.0–3.0) on selectively extracting Ag from industrial solutions is determined. The notion that silver and heavy metals are attributed to different groups of metals by varying the degree of sorption with microorganisms, depending on the pH medium, is confirmed. The specific behavior of the biomass cells in the acidic medium also promotes the separation of these elements. Testing the biosorbed extraction of silver from the industrial solution on a granulated lincomycin biomass is approved under industrial conditions. The average degree of extraction was Cu ≤ 8.1, Ni 4.2, Zn 4.0, Fe 15.5%. The losses of biosorbent are about 70 g/m³ of the solution.     

Extraction of noble metals from the recycle slag of refining production

Results of investigations of concentration of metallurgical slag using electrical separators, jugs and flotation machines, sluices, concentration table, and Itomack centrifugal separator are presented. As a result, two production flowsheets are suggested, wet and dry, which provide recovery of ～95% silver and ～89% gold mixed with a ～15.5% metal content.     

Thermodynamics of interaction between sulfite-thiosulfate solutions and noble metals

The thermodynamic probability of dissolution of noble metals in aqueous solutions of sodium thiosulfate, sodium sulfite, and their mixture under standard conditions (without heating of the solution) is considered. The influence of impurities and catalysts (divalent copper, elemental sulfur, oxygen access into the solution, and ammonia) is evaluated. Theoretical calculations of reaction rates are performed. As a result of theoretical investigations, a conclusion about the usefulness of applying sulfite-thiosulfate solvents of noble metals from ores and concentrates is made.     

Reaction of rare-earth metals with boron and aluminum

We have used x-ray phase analysis to establish the phase equilibria at 600°C for the systems Gd-Al-B, Tb-Al-B, and Ho-Al-B (the boron-rich sites have not yet been studied). We determined the crystalline structure of the new borides HoAlB₄ and ErAlB₄ (space group Pbam, YCrB₄ type, a=59283(7), b=1.1553(1), c=0.35306(5) mm for HoAlB₄ and a=0.59955(9), b=1.1487(2), c=0.35284(8) nm for ErAlB₄). We synthesized the compound Tm_1?xAl_1?yB₁₄ with MgAlB₁₄ type structure (space group Imma, a=0.5826(2), b=1.0380(2), c=0.8176(2) nm) by the method of crystallization from an aluminum melt.