Efficient removal of uranium (VI) by 3D hierarchical Mg/Fe-LDH supported nanoscale hydroxyapatite: A synthetic experimental and mechanism studies

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2020-07, Vol.392, p.123682, Article 123682
• Main Authors: Guo, Yadan, Gong, Zhiheng, Li, Chenxi, Gao, Bai, Li, Peng, Wang, Xuegang, Zhang, Bingcong, Li, Xiaomeng
• Format: Article
• Language: English
• Subjects: Adsorption; Hierarchical; Hydroxyapatite; Mechanism; Mg/Fe-LDH; U(IV)
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2019.123682

[Display omitted] •Fe/Mg-LDH@nHAP composites were facilely synthesized by ultrasonic-assisted method.•The adsorption capacity reached 845.16 mg/g in simulated uranium-containing wastewater.•The adsorbent showed good stability and selectivity.•Removal mechanisms includes ion exchange, surface complexation and dissolution-precipitation. 3D hierarchical Mg/Fe-LDH supported nanoscale hydroxyapatite materials (Mg/Fe-LDHs@nHAP) were facilely synthesized by the ultrasound-assisted synthesis method. Various techniques for characterization, such as X-ray diffraction (XRD), Fourier transformed infrared (FT-IR), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area measurements, disclosed that Mg/Fe-LDHs@nHAP composites had hierarchicallayered structure with large BET surface area (231.4 m2/g) as well as plentiful phosphate-containing and hydroxyl-containing groups. The results of batch adsorption experiments showed that U(VI) removal by Mg/Fe-LDHs@nHAP composites was less influenced by other coexisting ions, suggesting the high selectivity of U(VI) by Mg/Fe-LDHs@nHAP composites. The pseudo-second-order models and intra-particle diffusion model can well represent the removal kinetics of U(VI) on Mg/Fe-LDHs@nHAP, and the maximum U(VI) capture capacity of Mg/Fe-LDHs@nHAP reached 845.16 mg/g calculated by Langmuir model at pH = 6.0 and 298 K. The regeneration experiment demonstrated that Mg/Fe-LDHs@nHAP composites held good stability and reusability for extraction of U(VI). The removal mechanisms of U(VI) on Mg/Fe-LDHs@nHAP involved ion exchange, surface complexation and dissolution-precipitation by XPS, EDX and FT-IR spectra investigation. Accordingto the XRD analysis, the absorbed U(VI) was finally formed into a chernikovite precipitate with a flower-like shape induced by phosphate-containing groups. The work indicated that the as-synthesized Mg/Fe-LDHs@nHAP composites are effective adsorbents for the removal of U(IV) in wastewater.