Phosphate interactions with iron-titanium oxide composites: Implications for phosphorus removal/recovery from wastewater. (1st May 2023)

• Record Type: Journal Article
• Authors: Cui, Jinli; Yang, Jinsu; Weber, Mischa; Yan, Jia; Li, Ruohong; Chan, Tingshan; Jiang, Yi; Xiao, Tangfu; Li, Xiaoyan; Li, Xiangdong
• Is Part Of: Water research. Volume 234(2023)
• Publication Date: 2023-05-01
• Subjects: Phosphorus -- Removal -- Bimetal oxide composite -- Surface complexation and precipitation -- Ternary complexes; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2023.119804
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Ti component in Fe-Ti composite leads to less Fe dissolution and FePO4 precipitate. Ca enhanced P removal at pH 7 by precipitating surface-adsorbed P as hydroxyapatite. Acetate increased Fe dissolution and favored FePO4 formation. Fe-Ti composite is effective in P removal and recovery from wastewater. Abstract: Understanding the interactions between phosphate (P) and mineral adsorbents is critical for removing and recovering P from wastewater, especially in the presence of both cationic and organic components. To this end, we investigated the surface interactions of P with an iron-titanium coprecipitated oxide composite in the presence of Ca (0.5–3.0 mM) and acetate (1–5 mM), and quantified the molecular complexes and tested the possible removal and recovery of P from real wastewater. A quantitative analysis of P K-edge X-ray absorption near edge structure (XANES) confirmed the inner-sphere surface complexation of P with both Fe and Ti, whose contribution to P adsorption relies on their surface charge determined by pH conditions. The effects of Ca and acetate on P removal were highly pH-dependent. At pH 7, Ca (0.5–3.0 mM) in solution significantly increased P removal by 13–30% by precipitating the surface-adsorbed P, forming hydroxyapatite (14–26%). The presence of acetate had no obvious influence on P removal capacity and molecular mechanisms at pH 7. At pH 4, the removal amount of P was not obviously affected by the presence of Ca and acetate. However, acetate and high Ca concentration jointly facilitated the formation of amorphous FePO4 precipitate, complicating the interactions of P with Fe-Ti composite. In comparison with ferrihydrite, the Fe-Ti composite significantly decreased the formation of amorphous FePO4 probably by decreasing Fe dissolution due to the coprecipitated Ti component, facilitating further P recovery. An understanding of these microscopic mechanisms can lead to the successful use and simple regeneration of the adsorbent to recover P from real wastewater.