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 SO42- 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 physicochemical conditions of the system, i.e., on the species present in the solution.