Role of acid blue 25 dye as active site for the adsorption of Cd2+ and Zn2+ using activated carbons

The adsorption of acid blue 25, Cd2+ and Zn2+ on a physically activated bituminous carbon and a phosphoric activated carbon from wood was studied using single and binary (dye/metal) solutions, at 30 °C and pH 5. Results showed a synergic effect of acid blue 25 in the adsorption of Cd+2 and Zn+2. Thus, the amount of metal ions adsorbed on both activated carbons increased with the initial concentration of acid blue 25. The effect was especially remarkable in the case of the adsorption of Zn2+ ions on the wood-based carbon. For this particular system, the metal uptake increased up to 60 times in presence of acid blue 25, when compared to the results obtained for the mono-component (Zn2+-only) solutions. Modeling of the adsorption results showed that a surface response methodology approach was required to attain an adequate description of the multi-component adsorption.

► The adsorption of acid blue 25, Cd2+ and Zn2+ was studied in single and binary solutions on activated carbons.
► The presence of acid blue 25 favors the adsorption of these metal ions on both carbons.
► For Zn2+ ions the metal uptake increases up to 60 times when the acid blue 25 is present in the solution.
► The acid blue 25 can be act as active site for the adsorption of heavy metals.