Comparative Study of Cu Ion Adsorption by Nano-Hydroxyapatite Powder Synthesized from Chemical Reagents and Clam...

Area of Science:

• Materials Science
• Environmental Chemistry
• Nanotechnology

Background:

• Heavy metal contamination of water sources is a growing environmental concern.
• Development of efficient and sustainable adsorbent materials is crucial for water remediation.
• Nano-hydroxyapatite (HA) shows potential for heavy metal ion adsorption.

Purpose of the Study:

• To evaluate nano-hydroxyapatite (HA) powders synthesized from chemical reagents (Chem-HA) and clam shells (Bio-HA) as adsorbents for copper (Cu) ions.
• To compare the adsorption performance, kinetics, thermodynamics, and energy efficiency of Chem-HA and Bio-HA.
• To investigate the mechanism of Cu ion adsorption onto HA.

Main Methods:

• Synthesis of HA powders using microwave irradiation.
• Characterization of synthesized powders using X-ray diffraction (XRD).
• Adsorption experiments to determine adsorption capacity (Langmuir isotherm), kinetics (pseudo-second-order model), and thermodynamics.
• Analysis of activation energy and post-adsorption phase identification.

Main Results:

• Both Chem-HA and Bio-HA synthesized as nano-sized rod-like HA particles.
• Bio-HA exhibited higher crystallinity (67.5%) and superior adsorption capacity (436.8 mg/g) compared to Chem-HA (426.7 mg/g).
• Adsorption followed pseudo-second-order kinetics, with Bio-HA showing faster equilibrium and higher rate constant.
• Adsorption was spontaneous and endothermic, with Bio-HA demonstrating lower energy requirements.
• XRD confirmed the formation of Cu$_{2}$(OH)PO$_{4}$ post-adsorption, indicating Ca ion replacement by Cu ions in the HA lattice.

Conclusions:

• Bio-HA derived from clam shells is a highly efficient and sustainable adsorbent for Cu ions.
• The superior performance of Bio-HA is attributed to its higher crystallinity.
• Utilizing waste materials like clam shells for adsorbent synthesis offers environmental benefits and reduces overall environmental impact.