Development of polymeric iron/zirconium-pillared clinoptilolite for simultaneous removal of multiple inorganic contaminants from wastewater

Excessive levels of ammonium, phosphate, and heavy metals in surface water are serious environmental concerns that could potentially cause eutrophication and health issues. In this study, a novel iron/zirconium-pillared clinoptilolite (nano Fe/Zr-PC) was developed by intercalating Fe3+/Zr4+ polyhydroxy-cations into clinoptilolite for the simultaneous removal of ammonium, phosphate, and cadmium (Cd (II)). The obtained material was characterized using a transmission electron microscope (TEM), BET analysis, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR), which indicated that nanoscale Fe or Zr particles were successfully formed on the surface and pore structures of clinoptilolite. Batch experiments were conducted to investigate the effects of varied operation parameters on the adsorption behavior. The results show that nano Fe/Zr-PC achieved high removal efficiencies for ammonium, phosphate, and Cd (II) over a wide pH range (4-8), indicating higher adaptability towards varying environmental conditions. In addition, kinetic analysis suggested that the adsorption process was best represented by the pseudo-second-order kinetic model, suggesting the rate-limiting step for removing ammonium, phosphate, and Cd (II) on nano Fe/Zr-PC may be the chemical adsorption stage. The underlying mechanism was also assessed using X-ray photoelectron spectroscopy (XPS) analysis. Ammonium, phosphate, and Cd (II) were captured via a cation exchange reaction, electrostatic attraction and ligand exchange, and surface precipitation, respectively. Overall, the analysis and the characterization results revealed that nano Fe/Zr-PC is a highly efficient adsorbent for the simultaneous removal of ammonium, phosphate, and Cd (II) with an excellent adaptability to varying and undesirable environmental conditions.