Fabrication and characterization of Fe3O4@Ag nanoparticles adsorbent for the simultaneous measurement of chromium and manganese in steel factory effluent samples by X-ray fluorescence using experimental design optimization

A rapid and simple method was optimized through experimental design and validated for the separation of chromium and manganese with magnetic sorbent of Fe₃O₄@Ag and 2-(2-thiazolylazo)-p-cresol ligand from the effluent of a steel factory. The adsorbed metals on the magnetic sorbent were simply separated using a magnet and collected on filter paper to measure with an X-ray fluorescence device. The infrared spectroscopy, ultraviolet–visible spectroscopy, field emission scanning electron microscopy, and wavelength-dispersive X-ray spectroscopy were used to characterize and follow the steps of the constructed sorbent synthesis. The surface response methodology was used to achieve better figures of merit and more accuracy. Optimal values for the three effective parameters of the response pH, sorbent amount, and sample solution volume were obtained to be 6.0, 4.0 mg, and 50.0 mL, respectively. Under optimum conditions, the detection limits of 0.5 µg mL⁻¹ and 1.6 µg mL⁻¹ for chromium and manganese ions were achieved, respectively. The acceptable linear range of 2.0–100.0 and 5.0–100.0 µg mL⁻¹ was obtained for chromium and manganese, respectively. To show the efficiency of the method, the heavy metals of chromium (20.0 µg mL⁻¹) and manganese (30.0 µg mL⁻¹) were measured with a high accuracy (n = 3), and the recovery was 98% and the relative standard deviation was 2.1% in the real samples of the effluent of a steel factory.