Enhanced phosphorus adsorption performance of ZnAl-LDO by fluorine‑chlorine co-doping and synergistic mechanism exploration

• Published in: The Science of the total environment 2024-12, Vol.955, p.177102, Article 177102
• Main Authors: Yang, Anzhou, Fu, Yongping, Huang, Fuqiang
• Format: Article
• Language: English
• Subjects: adsorbents; adsorption; chlorides; chlorine; density functional theory; environment; fluorine; Fluorine‑chlorine co-doping; Layered double oxides; Phosphate adsorption; phosphates; phosphorus; pollution control; Synergistic effect
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.177102

Layered double hydroxides (LDHs) and their calcined products layered double oxides (LDOs) are widely used as adsorbents for pollutant removal. Their adsorption performance are significantly influenced by intercalated ions, while previous studies primarily focusing on the impact of individual ions. For the first time, this paper reports the mechanism of the synergistic enhancement of phosphate adsorption properties of LDO by bicomponent interlayer ions. The ZnAl-LDO by fluorine‑chlorine co-doping (F, Cl-ZnAl-LDO) exhibits excellent adsorption capacity of 158.9 mgP/g, surpassing that of single-component intercalation Cl-ZnAl-LDO and F-ZnAl-LDO, as well as most LDH-based adsorbents. Further research and density functional theory calculations indicate the differential adsorption enhancement mechanism of the interlayer ions. Chlorine functions as the exchanged anion, whereas fluorine facilitates the complete replacement of chloride ions and hydroxyl groups by phosphate. This finding highlights the potential of utilizing the synergistic effects between different interlayer ions to design and synthesize advanced phosphate adsorbent materials. The co-doping of fluorine and chlorine has been demonstrated to significantly improve the phosphorus adsorption capabilities of ZnAl-LDO. Chlorine serves as the exchanged ion, while fluorine facilitates the complete substitution of chloride ions and hydroxyl groups with phosphate ions. [Display omitted] •Fluorine and chlorine synergistically enhance the H2PO4− adsorption performance.•Fluorine and chlorine act distinct mechanisms in the adsorption process.•Relationship was elucidated between anions content and H2PO4− adsorption capacity.