Removal of Azo dyes with Xanthan

Abstract

The interaction among Xanthan (XANT) and three azo dyes: Direct blue 1 (DB1), Direct red 81 (DR81), and Direct black 22 (DB22) was studied. The Xanthan-dye-Al product was formed after the addition of AlCl3 to a Xanthan-Dye adduct containing solution. It was proposed that polyhydroxyoxoaluminum clusters named CAL-13 and CAL-30 react with this adduct producing a Xanthanate aluminum network, XANT-Al, and as a consequence a decrease in dye concentration in an aqueous medium was observed. The removal efficiencies obtained were the following: DB1 (99 %), DB22 (99 %) and DR81 (94 %), demonstrating that this dye removal method is very efficient. The Zimm-Bragg model adequately described the experimental data and the order observed in the Ku (nucleation) and U (aggregation) parameters from this model was the following: DB1>DB22> DR81. Evidence suggests that physicochemical properties of dyes such as charge, molecular weight, aggregation ability and the capacity of XANT-Al to trap dye molecules are involved in the high removal values. Moreover, the dye binding mechanisms include: electrostatic, hydrogen bonding and hydrophobic interactions that determine the magnitude of the parameters Ku and U. These findings suggest that the XANT polymer is a good option to remove azo dyes from an aqueous medium.