Abstract: Experimental production methods of Chevreul’s salt
being an intermediate stage product in copper recovery were
investigated on this article. Chevreul’s salt, Cu2SO3.CuSO3.2H2O,
being a mixed valence copper sulphite compound, has been obtained
by using different methods and reagents. Chevreul’s salt has an
intense brick-red color. It is highly stable and expensive. The
production of Chevreul’s salt plays a key role in hydrometallurgy.
Thermodynamic tendency on precipitation of Chevreul’s salt is
related to pH and temperature. Besides, SO2 gaseous is a versatile
reagent for precipitating of copper sulphites, Using of SO2 for
selective precipitation can be made by appropriate adjustments of pH
and temperature. Chevreul’s salt does not form in acidic solutions if
those solutions contains considerable amount of sulfurous acid. It is
necessary to maintain between pH 2–4.5, because, solubility of
Chevreul’s salt increases with decreasing of pH values. Also, the
region which Chevreul’s salt is stable can be seen from the potentialpH
diagram.
Abstract: The proof of concept experiments were conducted to
determine the feasibility of using small amounts of Dissolved
Sulphur (DS) from the gaseous phase to precipitate platinum ions in
chloride media. Two sets of precipitation experiments were
performed in which the source of sulphur atoms was either a
thiosulphate solution (Na2S2O3) or a sulphur dioxide gas (SO2). In
liquid-liquid (L-L) system, complete precipitation of Pt was achieved
at small dosages of Na2S2O3 (0.01 – 1.0 M) in a time interval of 3-5
minutes. On the basis of this result, gas absorption tests were carried
out mainly to achieve sulphur solubility equivalent to 0.018 M. The
idea that huge amounts of precious metals could be recovered
selectively from their dilute solutions by utilizing the waste SO2
streams at low pressure seemed attractive from the economic and
environmental point of views. Therefore, mass transfer characteristics
of SO2 gas associated with reactive absorption across the gas-liquid
(G-L) interface were evaluated under different conditions of pressure
(0.5 – 2 bar), solution temperature ranges from 20 – 50 oC and acid
strength (1 – 4 M, HCl). This paper concludes with information about
selective precipitation of Pt in the presence of cations (Fe2+, Co2+,
and Cr3+) in a CSTR and recommendation to scale up laboratory data
to industrial pilot scale operations.