Particles and porous tablets based on Fe0/ZSM-5 composites prepared by ball-milling for heavy metals removal: Dissolved Fe2+, pH, and mechanism.

Novel, low-cost Fe0/ZSM-5-based particles and porous tablets were prepared by a ball-milling method and used for the removal of Pb2+ in solution. Solid-phase characterization by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) and transmission electron microscopy (TEM) revealed that the Fe0 microparticles were evenly loaded and tightly immobilized on the surface of ZSM-5 because of the extrusion/welding impact during ball-milling. For different Pb2+ concentrations, batch experiments indicated that the removal of Pb2+ increased with the decline of dissolved Fe2+ and pH value in the solution for particles; opposite results were obtained for the tablets. The differences in the contact between both materials and Pb2+ were the main factor controlling Pb2+ removal in the solution. Investigation into the effect of initial pH value revealed that high pH reduced the number of electrons released from Fe corrosion. Consequently, low levels of removed Pb2+ and dissolved Fe2+ were synchronously observed. Also, simulated electroplating wastewater was treated using the prepared particles and porous tablets, and the removal order of Pb2+>Cr6+>Cu2+≈Cd2+ was observed. The Fe0/ZSM-5 particles and tablets prepared through ball-milling show potential as materials for treatment of Pb2+ and other toxic metals.