INFLUENCE OF IONIC STRENGTH ON THE REMOVAL OF As⁵⁺ BY ADSORBING COLLOID FLOTATION

Abstract

The aim of this work was to study the influence of ionic strength (IS) (with NaCl and Na₂SO₄) on the removal of As⁵⁺ by adsorbing colloid flotation (ACF), using as collector sodium dodecylsulfate (SDS). The morphology of the precipitate retained in the foam was analyzed by scanning electron microscopy (SEM/EDS).

The effect of an increase in the IS by adding NaCl proved to be insignificant on the As⁵⁺ removal by ACF. On the other hand, by adding SO₄ ²⁻ ions, the same increase in IS resulted in a removal decrease of 62.2%. By introducing, however, 80 mg L⁻¹ of Al³⁺ such deleterious effects from IS were minimized since an increase in As⁵⁺ floatability (37.7% without Al³⁺ and 76.5% with Al³⁺) was noticed.

Through SEM/EDS analyses, it was possible to observe that both morphology and composition of the precipitate produced in the solution and retained in the foam depend on the physico-chemical conditions of the system, i.e., on the species present in the solution.

Keywords:

• Adsorbing colloid flotation
• Foam separation
• Ionic strength
• Arsenic

ACKNOWLEDGMENTS

The authors gratefully acknowledge CAPES and FAPERJ for their financial support.