Removal of Cu(II) and Ni(II) Metal Ions from Aqueous Solutions Using Modified Hydroxyapatite by Zero-Valent Iron Nanoparticles

In this study, hydroxyapatite-supported zero-valent iron nanoparticle was synthesized by the sodium borohydride reduction method. To evaluate the performance of adsorbent for the removal of Cu(II) and Ni(II) ions, the influence of different sorption parameters, such as contact time, temperature, initial concentration of metal ions, the dosage of adsorbent, and pH value of the solutions were investigated. The highest removal efficiency of both metals occurred under the optimal conditions of 7, 45 min, 0.1, 50 ºC, and 5 mg/l for pH, contact time, adsorbent mass, temperature, and initial concentration, respectively. The kinetic and equilibrium data were well fitted by the pseudo-second-order model and Langmuir- Freundlich model, respectively. The maximum adsorption capacities of adsorbent towards Cu(II) and Ni(II) were 138 and 108 mg/g, respectively. The results indicated that the adsorbent could remove the majority of metals (95%) within 40 min without pH control. Thermodynamic parameters, i.e., ΔG°, ΔH°, and ΔS°, indicated that the sorption process was spontaneous and thermodynamically favorable.