Synthesis of hydroxyapatite from mussel shells for effective adsorption of aqueous Cd(II)

• Published in: Water science and technology 2019-10, Vol.80 (7), p.1226-1237
• Main Authors: Meski, S, Tazibt, N, Khireddine, H, Ziani, S, Biba, W, Yala, S, Sidane, D, Boudjouan, F, Moussaoui, N
• Format: Article
• Language: English
• Subjects: Adsorbents; Adsorption; Animals; Aqueous solutions; Bivalvia; Cadmium; Durapatite; Endothermic reactions; Equilibrium; Fourier transforms; Hydrogen-Ion Concentration; Hydroxyapatite; Immobilization; Ion exchange; Kinetics; Metals; Mollusks; pH control; Phosphoric acid; Pollutants; Pollution; Room temperature; Shells; Solutions; Synthesis; Temperature; Thermodynamics; Water Pollutants, Chemical
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2019.366

We report the synthesis of hydroxyapatite (HAP) powder from waste mussel shells (decomposed to CaO) and phosphoric acid at room temperature without pH control. The powder synthesized was utilized for cadmium removal from aqueous solutions using the batch technique. The effects of solution pH, adsorbent dose; initial Cd concentration, contact time, and temperatures were examined. Furthermore, the adsorption process revealed a pseudo-second-order reaction model and the Langmuir isotherm is the best-fit model to predict the experimental data and adsorption capacity was found to be 62.5 mg/g. Thermodynamic analysis revealed that because of the negative values of ΔG and the positive value of ΔH , the adsorption process was spontaneous and endothermic. Cadmium immobilization occurs through a two step mechanism: rapid ion exchange followed by partial dissolution of hydroxapatite and precipitation of cadmium containing hydroxyapatite.