Treated residue from aluminium lamination as adsorbent of toxic reactive dyes - a kinetic, equilibrium and thermodynamic study

The residue generated in the aluminium cold lamination (TTR) was submitted to a direct burning and then it was calcined at 500 degrees C. BET, FTIR, SEM with EDX and TGA techniques were performed to characterize the adsorbent before and after the adsorption. BET analysis showed that TTR specific surface area was 55.37 m(2) g(-1) and there were no significant changes after the adsorptive process. Afterwards, the TTR was applied as adsorbent of the reactive Drimaren Blue (DB), Drimaren Red (DR) and Drimaren Gold (DG). Its employment consists in a sustainable alternative for the treatment of textile wastewater, once the TTR was used as low-cost adsorbent of textile dyes. Kinetic studies showed that the process reached the equilibrium state between 5 and 10 min. The pseudo-second-order model better fitted the adsorption kinetics, with kinetic rate constants 10.51, 34.71 and 31.51 mg min g(-1) for DB, DR and DG respectively. The equilibrium experiments were performed to obtain the adsorption parameters for each dye; moreover, the maximum adsorption capacity was 6.27, 0.42 and 1.23 mg g(-1) for DB, DR and DG, respectively. Thermodynamics studies allowed to obtain the values of enthalpy for DB, DR and DG, -7.90, 14.03 and -17.75 kJ mol(-1), respectively. Furthermore, the negative values of Gibbs free energy confirmed the spontaneity of the adsorption. The results point to the physisorption characteristic of the process, in which the temperature negatively influenced the adsorption for the DB and DG; the opposite result was observed for the DR.