Kinetic study on removal of copper(II) using goethite and hematite nano-photocatalysts

Goethite and hematite nanomaterials (nano-goethite and nano-hematite) can be synthesized using a coprecipitation method. Nano-hematite is synthesized via the reaction of HCl and FeCl(3) solution at 100 degrees C for 2 days, while nano-goethite is prepared by adding Fe(2)(SO(4))(3) into the 2.5 M NaOH solution for 4h, and then heated at 40 degrees C for 2 days. Afterward the photocatalytic decomposition of methylene blue solution is performed by UV-light irradiation, and the adsorption procedure is carried out by batch experiments. It is observed that both nano-hematite and nano-goethite exhibit some photocatalytic activity and possess a high adsorption capacity for copper ions. The maximum Cu(II) adsorption capacity is 149.25 and 84.46 mg/g for nano-goethite and nano-hematite, respectively. Further, the experimental data are well fitted to the pseudo-second-order equation. It also suggests that the Langmuir isotherm is more adequate than the Freundlich isotherm in simulating the adsorption isotherm of Cu(2+), and the Cu(2+) adsorption onto nanomaterials is a spontaneous process. Therefore, these findings indicate that nano-goethite and nano-hematite are effective materials for Cu(2+) removal and, together with its photocatalytic activity, may be applied in the removal of heavy metal ions from aqueous streams.