Preparation of anionic-cationic co-substituted hydroxyapatite for heavy metal removal: Performance and mechanisms

• Published in: Journal of solid state chemistry Vol. 280; p. 120960
• Main Authors: Zeng, Rongying, Tang, Wenqing, Ding, Chunxia, Yang, Lihua, Gong, Daoxin, Kang, Zhuo, He, Zhimin, Wu, Yuming
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.12.2019
• Subjects: Adsorption isotherm; Adsorption mechanism; Cadmium ion; Lead ion; Na-SiCHAP; Na-SiCHAP; Lead ion; Cadmium ion; Adsorption mechanism; Adsorption isotherm
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2019.120960

Sodium, silicate and carbonate ions co-substituted hydroxyapatite adsorbent (Na-SiCHAP) was prepared by sonochemistry coprecipitation. The effect of a variety of parameters on the adsorption of Pb2+ and Cd2+ by Na-SiCHAP were performed. The adsorption process of heavy metal ions was found to follow the pseudo-second-order kinetic equation and Langmuir adsorption model. The maximum absorption capacity (Qm) of Na-SiCHAP for Pb2+ and Cd2+ ions in 303 K were 698.68 and 129.60 mg g−1 according to the Langmuir adsorption model, respectively. The thermodynamic parameters (ΔG0 <0, ΔS0 >0, ΔH0 >22kJ·mol-1) indicated that the absorption of Pb2+ and Cd2+ on the Na-SiCHAP was spontaneous and endothermic, and the Na-SiCHAP adsorbed mainly via chemical adsorption. Ion exchange of Pb2+ and Cd2+ for Ca2+ and Na+ was one of the principal mechanisms, followed by precipitation and electrostatic interactions. Furthermore, the well stability properties of the Na-SiCHAP adsorbent were confirmed by recycling assays. These data indicate that Na-SiCHAP may be a good adsorbent for the rapid removal of heavy metal ions from aqueous solutions. The schematic illustration of lead and cadmium ions sorption mechanisms on Na-SiCHAP (Ion exchange of Pb2+ and Cd2+ for Ca2+ and Na+ was one of the principal mechanisms, followed by precipitation and electrostatic interactions.) [Display omitted] •An effective adsorbent (Na-SiCHAP) was prepared by sonochemistry coprecipitation.•Na-SiCHAP was used for Pb2+ and Cd2+ adsorption with a Qm of 698.68 and 129.60 mg g−1 at pH 5.5 under 303 K , respectively.•Mechanism studies showed that ion exchange was one of the principal mechanism.