مشخصات پژوهش

Background and aims: Chromate ion is considered as one of the important environmental pollutants. Therefore, the development of an effective method for pre-concentration of chromate in environmental samples is important. Magnetic nano-composites are used to control and eliminate heavy metals from industrial effluents through the mechanisms of adsorption, ion exchange and electrostatic forces. This study is focus on the application of a magnetic nanocomposite (NC) based on nickel oxide/nickel ferrite/layered double hydroxide (NiO/NiFe2O4/LDH) as a sorbent for the solid-phase extraction and pre-concentration of chromate ion from industrial wastewater samples [1,2]. Methods: Ni-Fe LDH was performed using a facile hydrothermal method for 14 h at 140 °C. After being cooled to the room temperature, the product was washed several times with deionized water and absolute ethyl alcohol and dried in vacuum drying oven for 8 h at 60 °C. NiO-NiFe2O4 NC was obtained after calcinating for 4 h at 500 °C. For preparation of NiO/NiFe2O4/LDH, appropriate amounts of Al and Ni nitrate salts was added into the solution containing NiO/NiFe2O4 and transferred final solution into the autoclave, which was heated at 140 °C for 6 h. Results: The synthesized magnetic NC was demonstrated to be homogeneous, and having a magnetic property. The structure of magnetic adsorbent was investigated by XRD, SEM, TEM, FT-IR, and VSM techniques. Under the optimized experimental conditions (amount of adsorbent; 0.1 g, sample volume; 100 mL, 1 mL hydroxyl ammonium chloride 10% (w/v) as a suitable eluent, and adsorption and desorption times; 15 min), the calibration graph was linear in the concentration range of 0.2‒100 ng mL−1. The limit of detection and the pre-concentration factor were 0.06 ng mL−1 and 100, respectively. Conclusion: Magnetite nanocomposite have high competency for solid-phase extraction of chromate from industrial wastewater, and extraction efficiency is reversely related to pH. The method