Sulfuric activation of a Brazilian manganese ore for heavy metals removal

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. (C) 1999 Elsevier Science B.V. All rights reserved.