Comparative Study of Cu Ion Adsorption by Nano-Hydroxyapatite Powder Synthesized from Chemical Reagents and Clam Shell-Derived Calcium Sources

• Published in: Nanomaterials (Basel, Switzerland) Switzerland), 2024-09, Vol.14 (17), p.1431
• Main Authors: Wu, Shih-Ching, Hsu, Hsueh-Chuan, Ji, Hong-Yi, Ho, Wen-Fu
• Format: Article
• Language: English
• Subjects: Adsorbents; Adsorption; Aqueous solutions; Biomass; Calcium ions; Chemical synthesis; clam shells; Comparative studies; Copper; Cu ions; Endothermic reactions; Energy consumption; Energy efficiency; Environmental impact; Equilibrium; heavy metal adsorption; Heavy metals; Hydroxyapatite; Ion adsorption; Ions; Irradiation; Manufacturing; Metals; Methods; Microwave radiation; microwave synthesis; Microwaves; Plating; Pollutants; Reagents; Recyclable materials; Shells; Spectrum analysis; Sustainable development; Waste materials; Water pollution; X-ray diffraction
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano14171431

The increasing contamination of water sources by heavy metals necessitates the development of efficient and sustainable adsorption materials. This study evaluates the potential of nano-hydroxyapatite (HA) powders synthesized from chemical reagents (Chem-HA) and clam shells (Bio-HA) as adsorbents for Cu ions in aqueous solutions. Both powders were synthesized using microwave irradiation at 700 W for 5 min, resulting in nano-sized rod-like particles confirmed as HA by X-ray diffraction (XRD). Bio-HA exhibited higher crystallinity (67.5%) compared to Chem-HA (34.9%), which contributed to Bio-HA's superior adsorption performance. The maximum adsorption capacities were 436.8 mg/g for Bio-HA and 426.7 mg/g for Chem-HA, as determined by the Langmuir isotherm model. Kinetic studies showed that the Cu ion adsorption followed the pseudo-second-order model, with Bio-HA achieving equilibrium faster and displaying a higher rate constant (6.39 × 10⁻ g/mg·min) than Chem-HA (5.16 × 10⁻ g/mg·min). Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic, with Bio-HA requiring less energy (ΔH° = 39.00 kJ/mol) compared to Chem-HA (ΔH° = 43.77 kJ/mol). Additionally, the activation energy for Bio-HA was lower (41.62 kJ/mol) than that for Chem-HA (46.39 kJ/mol), suggesting better energy efficiency. The formation of a new Cu (OH)PO phase after adsorption, as evidenced by XRD, confirmed that the Cu ions replaced the Ca ions in the HA lattice. These findings demonstrate that Bio-HA, derived from natural sources, offers environmental benefits as a recyclable material, enhancing heavy metal removal efficiency while contributing to sustainability by utilizing waste materials and reducing an environmental impact.