The magnetic NiFe2O4 nanoparticles have been synthesized and used as adsorbents for removal of an azo dye, Eriochrome black-T (EBT) from aqueous solution. The NiFe2O4 nanoparticles were characterized by scanning electron microscope (SEM), Transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR). The adsorption studies were carried out under various parameters, such as pH, adsorbent dosage, contact time and initial dye concentration. The experimental results show that the percentage of adsorption increases with an increase in the adsorbent dosage. The maximum adsorption occurred at the pH value of 6.0. The equilibrium uptake was increased with an increase in the initial dye concentration in solution. Adsorption kinetic data were properly fitted with the pseudo-second-order kinetic model. The experimental isotherms data were analyzed using Langmuir and Freundlich isotherm equations. The best fit was obtained by the Langmuir model with high correlation coefficients (R2 = 0.9733) with a maximum monolayer adsorption capacity of 47.0 m g/g.

In this study, NiFe 2 O 4 /hydroxyapatite/graphene quantum dots (NiFe 2 O 4 /HAP/GQDs) as nano-adsorbent to remove cadmium (Cd 2+) from aqueous solution were synthesized. This nano-adsorbent was depicted by some techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR). Adsorption studies were conducted to investigate the effect of contact time, pH, adsorbent dosage and initial cadmium ion concentration on removal efficiency. To determine the most fitting kinetic model, the suitability of pseudo-first-order and pseudo-second-order models was compared. The adsorption isotherm was described well by the Langmuir isotherm and maximum equilibrium uptake capacity (q e) was 344.83 mg g −1. Studies revealed that adsorption process is not a physical process and formation of complexes (bidentate and monodentate complexes) between-COO − and-OH functional groups on the surface of NiFe 2 O 4 /HAP/GQDs and Cd 2+ ions may occur. In addition, the adsorbent can simply be removed by an ordinary filtration process.

A novel nanomagnetic basic catalyst of caesium carbonate supported on hydroxyapatite-coated Ni 0.5 Zn 0.5 Fe 2 O 4 magnetic nanoparticles (Ni 0.5 Zn 0.5 Fe 2 O 4 @HAP-Cs 2 CO 3 ) was prepared. This new catalyst was fully characterized using Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, X-ray diffraction and vibrating sample magnetometry techniques, and then the catalytic activity of this catalyst was investigated in the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives. Also, Ni 0.5 Zn 0.5 Fe 2 O 4 @HAP-Cs 2 CO 3 could be reused at least five times without significant loss of activity and could be recovered easily by applying an external magnet. Thus, the developed nanomagnetic catalyst is potentially useful for the green and economic production of organic compounds.

The present research studied the antibacterial effect of silver-coated Ni 0.5 Zn 0.5 Fe 2 O 4 magnetic nanoparticles on Gram-negative bacteria Escherichia coli (E. coli) from water. The effects of pH (6, 7 and 9), disinfectant dose (2, 5 and 10 g/L) and contact time (10, 20 and 30 min) have been also investigated. To obtain important factors, the interactions between factors and optimal experimental design in surface response method were used based on Box-Behnken design. According to the research findings, the system is efficient in eliminating E. coli. The results showed that E. coli elimination efficiency intensified through increasing the amount of nanoparticles from 2 to 10 g/L. The results also demonstrated no significant change in E. coli elimination through pH increasing of 6 to 9. Expanding contact time from 10 to 30 min also heightened E. coli elimination rate. R 2 for E. coli elimination is 0.9994 indicating a good agreement between model experimental data and forecasting data.

Acacia Nilotica seed shell ash supported Ni 0.5 Zn 0.5 Fe 2 O 4 magnetic nanoparticles were synthesized by a low-cost, simple, and environmentally benign procedure. The adsorbent was characterized by several methods including X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. Then, the potential of Acacia Nilotica seed shell ash supported Ni 0.5 Zn 0.5 Fe 2 O 4 magnetic nanoparticles was investigated for adsorption of Pb(II). The effect of different parameters including contact time, pH, adsorbent dosage and initial Pb(II) concentration on the Pb(II) removal yield was studied. The experimental data were fitted well with the pseudo-second order kinetic model (R 2 ¼ 0.999). The adsorption isotherm was described well by the Langmuir isotherm (R 2 ¼ 0.900) with a maximum monolayer adsorption capacity of 37.6 mg g -1 . The process for purifying water treatment presented here is easy using the magnetic nanoparticles. Therefore, this adsorbent was found to be useful and valuable for controlling water pollution due to Pb(II) ions.