Environmental conditions affecting the oxidation of thiosalts in treated mine milling effluent
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Date
2000
Authors
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Journal ISSN
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Publisher
University of New Brunswick
Abstract
The production of thiosalts (S203
2~, Sn06
2 \ etc.) in the milling of sulfide rich ore is
inevitable with today's technologies. There is no economically feasible way of treating
for thiosalts in milling effluent at the present time. They will pass through conventional
lime treatment and eventually be released into effluent streams. Periodically the pH of
the effluent streams will drop due to the oxidation of the thiosalts, leading to undesirable
conditions for aquatic life. This only occurs a few times a year and although it is
consistent with seasons, the time frame is relatively unpredictable. The key to this
problem is to determine what conditions contribute to thiosalt oxidation in order to
predict these pH depressions. From here, treatment times can be optimized to cut down
on cost.
This report indicates a number of conditions that contribute to pH depressions and
thiosalt oxidation in a mine effluent stream in northeastern New Brunswick. A
multivariate regression model has been formulated, using Minitabl2 statistical software,
to help predict pH drops in stream receiving effluent from the mine. This model can be
seen below.
pHl 111/1112 = 5.66 +2.0E-06 (thiosalts)2 + 0.503(Rel Temp./thiosalts) - 7.53E-04(Rel.Temp)2
The model is able to predict pH depressions in range from 5.05 to 6.55 and
predicts the time of these drops within ± 2 weeks of the measured drops. This is the first
attempt at predicting the time frame for thiosalt treatment.