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Abstract
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of the major environmental problems, because not only does it damage the esthetic nature of the
contaminated water, but also causes inhibitory effect on photosynthesis activity in aquatic systems. In
addition, some dyes may degrade into the compounds, causing toxic, mutagenic, and carcinogenic effects
on living organisms [1]. Therefore, the dye removal from industrial effluents, before being released to the
environment is of great importance. The removal of pollutants by adsorption is one of the most attractive
techniques for treatment of contaminated water. Recently, magnetic nano-sorbent have gained much more
attention because these materials possess the advantages of the nano-scale sorbent and magnetic separation
simultaneously [2].
In this study, nickel ferrite (NiFe2O4) nanoparticles (NFNs) was prepared and used as magnetic
nano-sorbent for the adsorption removal of Reactive Blue B25 (RB B25) as a model of azo dye. The NFNs
was synthesized by co-precipitation method using nickel nitrate and ferric nitrate [3]. Optimization and
modeling of the RB B25 using NFNs were performed through the response surface methodology (RSM)
based on central composite design (CCD). The structure and morphology of the prepared nano-sorbent were
characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Effect of the
important factors on the adsorption of Reactive Blue B25 including solution pH, initial concentration of the
dye, adsorbent dose, contact time and temperature was considered as input variables for RSM. The analysis
of variance showed a high correlation coefficient (R2=0.992) between experimental and predicted response.
The removal efficiency of the dye was more than 99 % at the optimum conditions proposed by RSM.
Furthermore, the adsorption kinetic studies revealed that the adsorption process followed the pseudosecond-
order model. Moreover, adsorption isotherms investigation indicated that the experimental data
were well fitted to Langmuir i
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