Modeling Adsorption of Copper(II), Cobalt(II) and Nickel(II) Metal Ions from Aqueous Solution Onto a New Carboxylated Sugarcane Bagasse. Part II: Optimization of Monocomponent Fixed-bed Column Adsorption

In the second part of this series of studies, the monocomponent adsorption of Cu, Co and Ni onto STA adsorbent in a fixed-bed column was investigated and optimized using a 2 central composite design. The process variables studied were: initial metal ion concentration and spatial time, and the optimized responses were: adsorption capacity of the bed (Q), efficiency of the adsorption process (EAP), and effective use of the bed (H). The higher Q for Cu, Co and Ni were 1.060, 0.800 and 1.029 mmol/g, respectively. The breakthrough curves were modeled by the original Thomas and Bohart-Adams models. The changes in enthalpy (ΔH°) of adsorption of the metal ions onto STA were determined by isothermal titration calorimetry (ITC). The values of ΔH° were in the range of 3.0-6.8 kJ/mol, suggesting that the adsorption process involved physisorption. Desorption (E) and re-adsorption (E) of metal ions from the STA adsorbent were also investigated in batch mode, and the optimum conditions were applied for three cycles of adsorption/desorption in a fixed bed column. For these cycles, the lowest values of E and E were 95 and 92.3%, respectively, showing that STA is a promising candidate for real applications on a large scale.