Manganese oxide which is used in the production of primary batteries usuall
y has some heavy metals associated with its mineral sources. One of the hyd
rometallurgical procedures to remove these impurities is sulfuric activatio
n. This consists of a controlled sulfuric acid leach aimed at the solubiliz
ation of some heavy metals and minimum manganese extraction. The goal of th
is work is to evaluate some sulfuric activation parameters in the treatment
of the Mina do Azul (Brazil) manganese ore for maximum heavy metals remova
l. Laboratory bench-scale experiments were carried out to study the more im
portant variables, viz.: activation time, solid-liquid ratio, sulfuric acid
concentration in the activation solution and stirring intensity. The evalu
ation of the variables and their interactions on the manganese and heavy me
tals extraction was made by statistical experimental design using the compl
ete factorial method for four variables at two experimental levels. The sul
furic acid concentration showed the greatest influence on the experimental
responses for manganese, nickel and cobalt extraction. The solid-liquid rat
io was the most significant variable as regards iron and copper extraction.
The optimization was accomplished by the use of the ascendent step statist
ical methodology and it allowed the determination of the best experimental
conditions for maximum heavy metals extraction by sulfuric activation of th
e manganese ore under study. The experimental results obtained under the op
timum conditions were 15.0% for manganese extraction while the maximum nick
el, iron and copper extractions were 74.4%, 37.4% and 41.2%, respectively.
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