Nickel ferrite (NiFe2O4) nanoparticles are prepared through different routes (microwave, co-precipitation, and pyrolysis) and
tested for water purification applications through adsorption removal of an acid red dye B as a model organic pollutant. The
characterizations of the prepared samples were done using XRD, FT-IR, SEM, TEM, BET, UV-Vis absorbance, Raman spectrum, and vibrating sample magnetometer (VSM). All samples showed an inverse spinel crystal structure. The obtained results
pointed out to the effect of the synthetic route on the morphology, particle size, optical, and magnetic properties of the prepared
ferrites. Magnetic measurements showed super-paramagnetic behavior for all samples. The magnetic saturation (Ms) of the
sample prepared by pyrolysis, was found to possess the highest saturation value, 34.8 emu/g. Adsorption experiments were
performed under the change in several parameters, such as pH, adsorbent dosage, and initial dye concentration. A dye removal
percentage of 99% was reached under the optimum state. The isothermal adsorption of the acid red dye was investigated using
several models, in which the experimental data could be best described by the Freundlich model. Several kinetic and equilibrium
models were inspected by linear regression analysis and showed best fitting for the adsorption data through pseudo-second-order
model. The calculated thermodynamic parameters indicated that the adsorption of acid red dye onto all the ferrite samples is a
spontaneous and endothermic physical adsorption process.