From the Wastewater of Copper Production with Use of Different Reagents

PRECIPITATion of isotope osmium-187

from the wastewater of copper production with use of different reagents

Z.S. Abisheva, A.N Zagorodnyaya, Ye.G. Bochevskaya*, A.S.Sharipova,

E.A. Sargelova

Centre of Earth Sciences, Metallurgy and Ore Beneficiation

Shevchenko st. 29/133, 050010, Almaty, Kazakhstan

*Сorresponding author е-mail: ; tel. +7(727)2984527

ABSTRACT

Sulfide copper ores of Zhezkazgan deposit in Kazakhstan are unique in terms of the rhenium and osmium content. Osmium more than 90 % of these ores is represented by isotope osmium-187. In the pyrometallurgical processing of copper concentrates, osmium is distributed between slag and gas phase, dust and solutions from washing metallurgical gases (further wastewaters).

Thus, osmium is recovered into solutions up 40 % of its content from the copper mixture. Osmium is recovered from 15 to 25 % as a result extraction with rhenium. However, the major part of osmium (75 – 80 %) is discharged into the wastewaters and is lost.Its concentration in the wastewaters amounts to 0.3 – 1.2 mg/L. Efficiency of such a method as precipitation allows considering the wastewaters of copper production as an additional raw material to produce the isotope osmium-187.

The work shows results of experiments on selection of the optimal conditions of maximum osmium precipitation from the wastewaters. The concentration, duration and temperature influence on the process of Os precipitation by different reagents – precipitators: thiosulphate Na2S2O3 and sodium sulphide Na2S was studied.

It was found out that the main factor influencing on the efficiency of osmium recovery in the precipitate with the optimum quantity of added reagents is temperature.

The material and chemical compositions of the precipitates produced from the wastewaters of copper production by Na2S2O3and Na2S using a set of physical analysis methods were studied.

It was established that both reagents collectively precipitate osmium from solutions under the selected optimum conditions: addition of sodium thiosulphate to have its concentration in the solution as 2.0 g/L or sodium sulphide 3.0 g/L, temperature is 90 °С, duration is 2 h. The efficiency of osmium recovery was achieved at ~ 80 %.

An osmium precipitation mode is offered with the presence of Na2S2O3 with addition of potassium iodide KI from the new type of wastewaters. The wastewaters were produced after rhenium extraction from industrial ammonia solutions representing combined mother solutions of operations of solid-phase re-extraction and dissolution of pulp of crude ammonium perrhenate. They have a significantly higher osmium concentration varying from 5 to 15 mg/L.

It was established that use of KI allowed reducingNa2S2O3 consumption for osmium precipitation operations 4 to 5 times if compared to the method existing in the production. Optimum conditions of precipitation of isotope osmium-187 from the new type of wastewaters are: KI concentration into the solution 0.65 g/L, addition of Na2S2O3 to the solution to have the concentration of 5.0 g/L, temperature 90 °С, and duration - 5 h. During the experimental period Os recovery in the Os-containing precipitation was achieved at 58 %.

The proposed method could be used at the copper industry enterprises, where wastewaters with similar chemical composition exist.

KEYWORDS

Wastewater, Precipitation, Isotope osmium-187, Recovery, Precipitate