(Zn–Magn) nanoparticles and their corresponding sodium tripolyphosphate–functionalized nanoparticles
(Zn–Magn@STPP) was investigated in details. The pristine nanoparticles (Zn–Magn) were prepared by the
classical coprecipitation method, while the Zn–Magn@STPP ones were obtained by reacting colloid of the former
nanoparticles with a STPP solution in an acidic pH. The produced powders consisted of single crystals of
spinel–type ferrite ultrasmall (~10 nm) almost spherical magnetic nanoparticles. Additionally, the
Zn–Magn@STPP showed a robust-dense anchoring of STPP moieties onto the nanoparticles’ surface. Regarding
the adsorption properties, the effect of various influencing parameters on CV removal was elucidated. A clear
enhancement of Zn–Magn@STPP nanoparticles for the removal of CV over the uncapped nanoparticles was
evidenced. Preliminary results showed that pH is the most important factor that controls the dye adsorption and
the optimum removal efficiency was determined for the natural pH (pH ~7). Further, the adsorption process was
very fast reaching an equilibrium in 15 min. Additionally, modeling of the adsorption kinetics data showed that
the third order Ritchie (R3) model kinetics mechanism prevails and that the overall rate of the dye adsorption
onto Zn–Magn@STPP appeared to be controlled by the chemisorption process. The last result correlates the
multilayer adsorption model (corrected BET model) retained in the adsorption isothermal studies. Adsorption
involved a chemisorbed monolayer enveloped by a multilayered framework of physisorbed CV moieties.
Furthermore, thermodynamic studies indicated that the adsorption was feasible, spontaneous and endothermic.
The desorption study demonstrated that the Zn–Magn@STPP could be readily regenerated using 0.1 M acetic
acid. Moreover, adsorption-desorption studies indicated that the nanoadsorbent had an excellent regeneration–
reusability capability.