Abstract
This work describes the preparation, the characterization, and the magnetic properties of a series of three mixed NiZn ferrite nanoparticles and the study of their efficiency for the adsorption-desorption of Eriochrome black T (EBT) dye. The nanoferrites were produced by the coprecipitation method. The produced powders were pure phases with a cubic spinel-type ferrite structure. They consisted of almost spherical nanoparticles with an average size ranging from similar to 13.5 to 16 nm. The smallest size was observed with the ferrite (abbreviated to as NiZn1) which exhibited the largest Zn content. Magnetic study revealed a superparamagnetic behavior at room temperature with a reasonable saturation magnetization and a relatively high Curie temperature. Adsorption, desorption, and regeneration study of EBT onto the nanoparticles was achieved by varying the nanoparticle nature, the pH, the nanoparticle dosage, the contact time, and the dye concentration. Regarding the effect of the nanoparticle nature on the removal of EBT, the smallest nanoparticles (NiZn1) were noticeably more performant. For these nanoparticles, the removal efficiency was found to increase with the decrease of pH. At pH 2.0, the adsorption of EBT onto NiZn1 nanoparticles was fast and the uptake capacity was found to decrease with the adsorbent dosage. Three kinetic models were tested. The best fitting to the kinetic data (R-2 > 0.986) was with the pseudo-second-order model. The adsorption capacity, q(e), of NiZn1 was found to increase with the increase of the adsorbate concentration. For instance, for the EBT dosage of 4.0 g L-1, q(e), was found to range from 12.5 for 50 to 34.4 mg g(-1) for 250 mg g(-1). The selected NiZn1 nanoadsorbent was tested in six adsorption-desorption-reuse cycles without significant loss in sorption/desorption performance.