Experimental Study of the Relationship Between Dissolved Iron, Turbidity, and Removal of Cu(II) Ion From Aqueous Solutions Using Zero-Valent Iron Nanoparticles

In this study, nanoscale zero-valent iron has been prepared through the reduction method by sodium borohydride and then was used for removal of Cu(II) from aqueous solutions. The XRD analysis proved the high crystallinity of synthesized nZVI particles, and the calculated particle size was found to be 72 nm, which corresponds to a specific surface area of 10.68 m 2 /kg. The SEM analysis provided images about the morphologies of nZVI particles before/after Cu(II) adsorption, which revealed that the nZVI particles are spherical and tend to aggregate together in chain-like agglomerates. Besides, after Cu(II) adsorption, the SEM image evidenced a disparity in the structure of nZVI particles. The mineral composition of nZVI particles before/after Cu(II) adsorption was examined using XRF, which demonstrated that the nZVI particles were mainly composed of iron metal by up to 74.16%, and further proved the successful adsorption for Cu(II) onto nZVI particles. Kinetics, isotherms, and thermodynamics studies were showed that the adsorption process obeyed the pseudo-second-order, well-fitted to monolayer Langmuir isotherm with a maximum adsorption capacity of 54.35 mg/g, and have endothermic spontaneously nature, respectively. Both the released dissolved iron ions and the yielded turbidity that co-occurred along with the nZVI/Cu reaction were monitored. The dissolved iron concentrations recorded the highest value reached up to 106.3 mg/L at pH 1.0, while the turbidity dramatically increased to 32, and 35 NTU with increases in nZVI dosages and initial Cu(II) ion concentrations, respectively. Finally, some explanations have been suggested to represent the Cu(II) ion removal mechanisms onto nZVI particles.