Cu²+ and Zn²+ Adsorption to Synthetic Iron Oxides and Natural Iron Ore Powder

Cu²⁺ and Zn²⁺ adsorption onto the synthetic iron oxides prepared in laboratory including ferrihydrite (amorphous), goethite and hematite, and natural iron ore powder were investigated. The results showed that Cu²⁺ and Zn²⁺ adsorption onto the iron oxides: ferrihydrite, goethite, hematite and iron ore powder could be described by non-linear Langmuir, linear Freundlich, and Temkin models with significant correlation (R>p=0.7646, n=8, alpha<0.01). The amount of Cu²⁺ and Zn²⁺ adsorbed by synthetic iron oxides was more than that by natural iron ore powder, moreover, Cu²⁺ and Zn²⁺ adsorption onto the synthetic iron oxides was in order as follows: ferrihydrite > goethite > hematite, and the synthesized ferrihydrite was considered to be of the maximum adsorption capability (18.38 mmol/mol Fe for Cu²⁺ and 10.72 mmol/mol Fe for Zn²⁺, respectively), due to its amorphous structure based on the X-ray diffraction (XRD) analysis. Comparison with iron oxides extracted from the natural surface coatings collected in natural aquatic environments, the synthetic ferrihydrite in the present study could be more suitable than other iron oxides to substitute iron oxides in the natural surface coatings in aquatic environments to investigate the transport, transform and fate of metals in laboratory conditions.