Removal of cadmium and copper from water by a magnetic adsorbent of PFM: Adsorption performance and micro-structural morphology

Abstract

In this study, a novel magnetic composite of polyacrylamide-modified Fe3O4/MnO2 (PFM) was successfully synthesized and introduced to remove cadmium and copper ions from water. The characterization methods of vibrating sample magnetometry, X-ray diffraction, scanning electron microscopy with energy dispersive spectrometer, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller were applied to examine the ferromagnetism, to compare the crystal structure, to examine the crystal shape change and elemental composition change, to examine the composition change, and to compare the specific surface area, respectively. The effects of various factors, including adsorbent dosage, initial ion concentration, and adsorption time, were evaluated. Under the condition of 50 mg/L Cu2+ or Cd2+ concentration, 1.6 g/L nano-PFM, and pH 6, the adsorption equilibrium was considered to have been reached when the solution has been adsorbed for an adsorption time of 400 min. Using the condition of 50 mg/L Cu2+ or Cd2+ solution as an example, the removal efficiency of Cu2+ and Cd2+ reached 96.91% and 78.10% and the adsorption capacity of them reached 30.285 mg/g and 39.052 mg/g, respectively. Additionally, a competing ions adsorption experiment was carried out to determine which ion’s adsorption capacity is larger in aqueous solution of both Cd2+ and Cu2+ ions. The result indicated that Cu2+ binds more easily with the active sites on the surface of the nano-PFM. An experiment of five consecutive adsorption–regeneration cycles confirmed that the adsorbent can be reused successfully for Cd2+ and Cu2+ adsorption and that it has promising potential for practical application.