Removal of ferrous ions from their aqueous solutions onto NiFe2O4-alginate composite beads

This paper deals with the experimental investigation related to the removal of Fe(II) from aqueous solutions by synthesized NiFe2O4-alginate composite beads and nano-NiFe2O4 at different temperatures and constant stirring rate of 150 rpm. The adsorption process was optimized by Response surface methodology RSM/CCD and studied as a function of contact time, pH and adsorbent mass. The results revealed that the maximum adsorption capacities were 158.4 and 69.8 mg/g for NiFe2O4-alginate composite beads and nano-NiFe2O4 when the initial Fe(II) concentrations were 350 and 250 mg/L at 318 K, respectively. The kinetics of Fe(II) removal by synthesized materials were best described by the pseudo-second-order model and the adsorption isotherms were seen to be consistent with Langmuir's adsorption isotherm. Also, the thermodynamic parameters of the adsorption (Gibbs free energy, entropy, and enthalpy) were discussed. Therefore, the results demonstrated that the adsorption process was spontaneous and endothermic and the synthesized NiFe2O4-alginate composite beads material could act as a highly-effective nano-adsorbent of Fe(II) removal more than nano-NiFe2O4 from the aqueous solutions.