The lead removal from aqueous solution by magnetic Fe₃O₄@polydopamine nanocomposite using Box–Behnken design

The polydopamine modified with magnetic nanoparticles (Fe3O4@PDA) was prepared and used for Pb2+ removal from aqueous liquids. The resulted Fe3O4@PDA nanocomposite was characterized with Fourier transform infrared spectra (FTIR), vibrating sample magnetometer (VSM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The optimized Pb2+ ions adsorption process was studied by response surface methodology (RSM) considering with 3-variable-3-level Box–Behnken design (BBD). The lead ions adsorption capacity were verified regarding three parameter effects, that is, pH, contact time and initial concentration of Pb2+ ions. The optimal conditions for the lead removal were obtained as 5.8, 5.4 hr and 92 mg/L, for the liquid pH, contact time and the initial lead ions concentration, respectively. Moreover, adsorption isotherms were studied to understand the mechanism of adsorbing Pb2+ ions by Fe3O4@PDA nanocomposite. The models represented the experimental data well. Furthermore, regeneration and reuse of adsorbent for the removal of Pb2+ ion in four cycles was studied. The results show the maximum lead adsorption capacity was 297 mg/g and Fe3O4@PDA nanocomposite could be used as a reusable adsorbent with convenient conditions. HIGHLIGHTS• Polydopamine coated magnetite nanoparticles were used to remove Pb2+ ions.• Lead adsorption process parameters are optimized using Response Surface Method.• The effect of different factors on the adsorption are investigated.• pH shows the greatest effect, time and Pb2+ concentration have significant effect• The adsorption isothermal parameters are studied.• Possible mechanisms of adsorption process have been discussed in detail.