For effective preparation of hardly concentrating ores to leaching there are considered to be perspective the methods of two-phased oxidation, which is based on photo electrochemical influence on solutions of reagents with formation of strong oxidants (active forms of oxygen) with the following biooxidation of hard minerals, which are realized in ditch version.
An examination of peculiarities of photo electrochemical influence and bacterial oxidation on the change of material surface structure and the process of dissection of mineral medium was carried out on the polished selection of sulfide minerals of Kokpatassk, Daugyztausk (Uzbekistan), Bugdainsky, Darasun, Teremkinsk (Transbaikalia) deposits. On the base of the analysis of received information of two-phase oxidation it was stated that, by the photo electrochemical influence the sulfide oxidation degree increased by 19,9 % (from 44,2 to 64,1 %) – 26,1 % (from 64,1 to 90,2 %), sulfide sulphur – by 15,9 % (from 40,4 to 56,3 %) – 21,9 % (from 63,1 to 85,0 %). By the photo electrochemical oxidation of minerals the facts of X-ray phase analysis testify the formation of new mineral phases: magnetite, hematite, scorodite, element sulphur. General tendency of sulfides oxidation is confirmed by the results of Eh change from 480 to 780 мВ, рН from 4,5 to 2,0, iron concentration change from 5,1 to 70 g/l and arsenic concentration change from 110 to 180 mg/l in liquid phase.
During the examination of polished selections by incident light it was visually defined that the volume of emptiness till the biooxidation was in average 5-15 %, and – 40-50 %. Softening of mineral matrix by the photo electrochemical influence and formation of nanoaccumulation of element sulphur in optimal regimen stimulates the bacterial oxidation, fastening the leaching of metals by 2-3 times. An iron output into solution in 24 hours in the variants with photo electroactivation was 30-35 g/l, in 36-48 hours – 33,2-70 g/l. when in variants without preliminary treatment – only 8-10 and 20-25 g/l accordingly. Long treatment didn’t improve the showings of leaching.
Experimental researches of the two-stage oxidation influence on dissection of hard minerals were carried out on the sulfide ore of Daugyztausk deposits.
On the base of experimental researches there were received new results, which testify the high effectiveness of preparation of hard raw materials with two-stage oxidation to gold leaching: there was received an increase of gold extraction by the cyanidation of oxidized sulfide ore in 46,9 % (from 40,2 to 87,1 %) into a liquid phase and in 41,1 % (from 48,4 to 89,5 %) into a resin.
Firstly on the base of processing of experimental facts of two-stage oxidation with the use of mathematical statistics by the method of Protodyakonov there were received following empirical dependences:
1) degree of material oxidation depends on the duration of photo electrochemical oxidation:
degree of photo electrochemical oxidation of sulfide minerals
У3’(β’sulph.min) = 10·(0,84 + 1,01 + log(Х) – 0,21 + log(Х)·2),
degree of photo electrochemical oxidation of sulfide sulphur
There were experimentally stated rational parameters: duration of photo electrochemical oxidation (Хopt = t1 = 6-12 ч) and degree of photo electrochemical oxidation of minerals (β’sulph.min = 40-52 %; );
2) degree of two-stage oxidation depends on the parameters of photo electrochenical influence:
degree of two-stage oxidation of sulfide minerals
У3(βsulph.min) = 48,72 + 10,30·log(tsplash lubrication) + 10,41·log(Uэ) + 2,20·log(tsplash lubrication)·log(Uэ) +
+ 10,32·log(tirradiation) + 2,18·log(tirradiation)·log(tsplash lubrication) + 2,21·log(tirradiation)·log(Uэ) + 10,48·log(Р) +
+ 2,22·log(Р)·log(tsplash lubrication) + 2,24·log(Р)·log(Uэ) + 2,22·log(Р)·log(tirradiation),
degree of two-stage oxidation of sulfide sulphur
log(tsplash lubrication) + 2,20·log(tirradiation)·log(Uэ) + 10,39·log(Р) + 2,19·log(Р)·log(tsplash lubrication) +
+ 2,22·log(Р)·log(Uэ) + 2,21·log(Р)·log(tirradiation),
where Р – consumption of NaCl, g/t;
tsplash lubrication – duration of splash lubrication, hours; tirradiation – duration of irradiation, hours; Uэ – voltage on the electrodes in electrolyzer, V.
There were experimentally stated the rational parameters of photo electrochemical influence:
tirradiation = 5-8 min,
tsplash lubrication = 1,5-2,0 h, Uэ = 20-30 В,
Р = 10-20 g/t, duration of biooxidation
(t2 = 48-50 h), degree of two-stage oxidation
(βsulph.min = 90-94 %; ).
The work was submitted to International Scientific Conference «Engineering and modern production», France (Paris), 14-21, October 2012, came to the editorial office on 05.09.2012.