Elucidation of interactions between metal ions and Ca alginate-based ion-exchange resin by spectroscopic analysis and modeling simulation

In this study, a cost-effective calcium alginate-based ion-exchange resin (CABIER) was employed for treatment of metal waste streams. pH, concentration, and presence of competitive metal ions played important roles in the removal. The X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) analysis indicated that the functional groups on the carbohydrate backbone (i.e., C-O-R and COO-1) were responsible for the binding of metals. It was found that the lead abstraction was driven by the ion exchange between Ca2+ and Pb2+. On the contrary, the Cu2+ ion was stripped via both ion exchange with Ca2+ and coordination of the other functional groups. A new mathematical model based on ion exchange (between metal and calcium) and elementary coordination (among metals and functional groups) reactions successfully described and predicted the metal removal under various conditions (e.g., pH, concentration, and existence of competitive metal ions). It was found from the modeling that metal binding follows a decreasing order of Pb2+ > Cu2+ > Ca2+.