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Stability of bubble size in the pulp zone and froth control is an important param

The water from several artesian wells in the metropolitan area of Recife presents high iron content, preventing its use in some industrial processes. The possibility of removing the iron by the use of precipitate flotation using sodium dodecyl sulphate (SDS) as collector was studied. The tests were carried out in a glass column 65 cm high, fed by a constant airflow. At pH 8, where the isoelectric point of colloidal iron hydroxide [Fe(OH)3] was observed, the size of the precipitate increases with conditioning time and facilitates the removal of iron ions by flotation. The results showed that an increase in conditioning time, from 5 to 20 minutes, resulted in a reduction of the residual concentration of iron from 13.2 to 0.2 ppm. The decrease in precipitate specific surface area rendered a decrease in the collector consumption possible. The iron ion removal process by flotation using SDS as collector was shown to be quite efficient. A removal of 99% of Fe3+ contained in the original solution was obtained.

A study was carried out to investigate the combined effect of released ions in the pulp by pH regulator and mineral surface on dolomite flotation. The tests were carried out using a dolomite sample in a bench flotation cell with automatic froth remover. Zeta potential measurements, solution conductivity and FTIR analysis were done to support the interpretation of the results. The main reagents used for pH adjustment in the alkaline range (calcium hydroxide, sodium hydroxide, and sodium carbonate) were compared using amine or sodium oleate as collector. Dolomite is a sparingly soluble-type calcium mineral (as calcite, apatite, fluorite and scheelite), releasing different amounts of calcium and magnesium ions in the pulp. Amine adsorbs mainly by a chemical complexation mechanism between the molecular specie RNH 2 with calcium and magnesium ions present on the dolomite surface. In this system calcium hydroxide must be used because in addition to adjusting the pH it is a calcium ion supplier, thus increasing the collector adsorption. In turn, in the dolomite flotation with oleate, the pH must be regulated with soda ash that precipitates Ca 2+ and Mg 2+ as carbonate allowing for higher adsorption of the collector.

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