Removal of Direct Red from aqueous solution by foam separation techniques of ion and adsorbing colloid flotation

Experimental investigations on the removal of Direct Red from an aqueous solution were carried out through two foam separation techniques: ion flotation and adsorbing colloid flotation with Fe(III). The residual concentration of Direct Red can be lowered to below 0.5 ppm in 3 minutes by ion flotation and below 0.1 ppm in 2 minutes by adsorbing colloid flotation. The optimum pH for the removal of Direct Red was found to be 4 for ion flotation and 3-5 for adsorbing colloid flotation. The effects of surfactant, foreign ions, and Al(III) addition on the removal of Direct Red are discussed.