Preparation of dumbbell manganese dioxide/gelatin composites and their application in the removal of lead and cadmium ions.

The nano-sized sorbents restrict their practical application in flow-through system due to excessive pressure. In this study, dumbbell MnO2/gelatin composites were synthesized based on the protein-assisted synthesis technology. Then they were immobilized on the amino-modified polymethyl methacrylate (PMMA) plate. SEM, TEM, XRD, XPS and FT-IR were employed to study the surface properties and the adsorption mechanism of MnO2/gelatin composites. Adsorption experiments for Pb(II) and Cd(II) ions were performed to study the adsorption isotherms, kinetics, and thermodynamics as well as the influencing factors. The maximum adsorption capacities of Pb(II) and Cd(II) ions were 318.7 mg g-1 and 105.1 mg g-1 respectively. The adsorption process met the pseudo-second-order kinetic model. Subsequently, MnO2/gelatin composites modified plates were used to remove the heavy metal ions in surface water and wastewater samples. The removal efficiencies of Pb(II) ion was changed from 83% (wastewater) to 100% (surface water), when the initial concentration was 10 mg L-1. This device exhibited great application prospect in the removal of heavy metals taking advantage of its high removal efficiency, excellent stability and reusability and ease of operation.