An environmental-friendly magnetic bio-adsorbent for high-efficiency Pb (II) removal: Preparation, characterization and its adsorption performance

In this paper, environmental friendly magnetic composite adsorbent (MSAL), exhibited excellent adsorption capacity for lead ions in the solution, was successfully prepared using two non-biologically toxic materials including L-cysteine and sodium alginate. Batch experiments were carried out to discuss the influences of different parameters like pH, adsorbent dosing, initial concentration and contact time on adsorption performance. Results showed sorption process followed by pseudo-second-order kinetic model and Langmuir isotherm model, which suggested the adsorption was limited by the chemical process dominated by the molecular layer. Based on Langmuir isotherm model, the maximum Pb(II) adsorption capacity was about 330 mg/g, which was better than a large amount of other lead adsorbents. Various analytical methods, such as SEM-EDS, FTIR, VSM, TGA, XPS and Zeta potential, were applied to characterize the performance of this adsorbent as well as exploring the adsorption mechanism. Characterization results found this adsorbent exhibited a large contact area, good thermal stability, sufficient adsorption sites and excellent magnetic responsiveness. It also has been found that the adsorption mechanism mainly included ion exchange and chelation between amino, carboxyl and lead ions. After 5 cycles, the adsorption capacity decreased from 98.04% to 87.40% and still maintained at high level. The average iron ions concentration in the adsorbed solution sample or in the regeneration solution were 0.34 mg/L and 0.15 mg/L. Overall, all above results imply that MSAL is a promising reusable adsorbent for removing Pb(II) in solution.