Adsorption of reactive dyes onto thermally treated waste from aluminum lamination

The lamination process of aluminum sheets generates a flammable oil-soaked waste, which had been thermally treated (TTW) and used as adsorbent of reactive Remazol Black B (RB) and Remazol Red RB133 (RR), two of the most used dyes in the printing processes on textile industries, with reported carcinogenic and toxic properties. The adsorbent was characterized by Brunauer-Emmett-Teller (BET)-specific surface area, scanning electron microscopy and X-ray diffraction analysis. Kinetic and equilibrium studies were performed to evaluate the TTW adsorption parameters and the isotherm model which best represented the process. It was observed that the system reached the equilibrium state after 5 min for both dyes and obtained their maximum adsorption capacity (qm) at pH 4: 0.69 mg·g−1 and 2.89 mg·g−1, for RB and RR respectively; moreover, the pseudo-second-order model better fitted the adsorption kinetics. The equilibrium data were better fitted to Langmuir isotherm compared to Freundlich's for the RB and RR adsorption. The maximum removal efficiency obtained in the experiments was 80.2% for RB and 80% for RR; moreover, after the acid activation of TTW, the RB removal efficiency increased from 84.9% to 93.7%.