Abstract
Reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) composites were prepared by chemical deposition method and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, N2-sorption and X-ray photoelectron spectroscopy (XPS). Operating parameters for the removal process of Pb(II) ions, such as temperature (20–40 °C), pH (3–5), initial concentration (400–600 mg/L) and contact time (20–60 min), were optimized using a quadratic model. The coefficient of determination (R2 > 0.99) obtained for the mathematical model indicates a high correlation between the experimental and predicted values. The optimal temperature, pH, initial concentration and contact time for Pb(II) ions removal in the present experiment were 21.30 °C, 5.00, 400.00 mg/L and 60.00 min, respectively. In addition, the Pb(II) removal by nZVI/rGO composites was quantitatively evaluated by using adsorption isotherms, such as Langmuir and Freundlich isotherm models, of which Langmuir isotherm gave a better correlation, and the calculated maximum adsorption capacity was 910 mg/g. The removal process of Pb(II) ions could be completed within 50 min, which was well described by the pseudo-second order kinetic model. Therefore, the nZVI/rGO composites are suitable as efficient materials for the advanced treatment of Pb(II)-containing wastewater.
Highlights
Heavy metals are one of the most important classes of pollutants due to their wide sources, non-degradability and high toxicity [1,2]
Many studies have been carried out on the use of porous materials to support Nanoscale zero-valent iron (nZVI), for example, nZVI particles supported on resin, were used to remove Pb(II) ions in aqueous solution, and the results showed that the reaction rates for Pb(II) ions were up to 30 times higher than that using iron fillings or powder [17]
It was found that the nZVI nanoparticles were aggregated (Figure 1a), while these nanoparticles were dispersed well on reduced graphene oxide (Figure 1b), because the rGO could enhance the dispersion of nZVI nanoparticles
Summary
Heavy metals are one of the most important classes of pollutants due to their wide sources, non-degradability and high toxicity [1,2]. The use of lead compounds causes large amounts of industrial wastewater containing the high quantity of Pb(II) ions. Lead is a potent neurotoxin, childhood lead poisoning has an impact on many developmental and biological processes, most notably intelligence, behavior, and overall life achievement [5]. The reason for this is that children can absorb 40% to 50% of an oral dose
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