Zn induced surface modification of stable goethite nanoparticles for improved regenerative phosphate adsorption
C. Belloni (Wetsus, European Centre of Excellence for Sustainable Water Technology, TU Delft - RST/Fundamental Aspects of Materials and Energy)
L. Korving (Wetsus, European Centre of Excellence for Sustainable Water Technology)
Geert Jan Witkamp (TU Delft - BT/Environmental Biotechnology, King Abdullah University of Science and Technology)
E.H. Brück (TU Delft - RST/Fundamental Aspects of Materials and Energy)
A.I. Dugulan (TU Delft - RID/TS/Instrumenten groep, TU Delft - RST/Fundamental Aspects of Materials and Energy)
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Abstract
Iron oxide-based adsorbents showed potential to reach ultra-low phosphorus (P) concentrations to prevent eutrophication and recover P. High affinity, high capacity at low P concentrations (<1 mg L−1), good stability, and reusability of the adsorbent are key factors for economic viability. In this study, nanoparticles of goethite (α-FeOOH), a highly stable phase, have been synthesized with increasing Zn2+-doping, 0–20 %at. Zn/Fe, to manipulate the surface properties, following the results of a previous work. Mössbauer spectroscopy showed preserved goethite phase and increased point of zero charge (pzc) at low Zn-doping percentages, while at higher percentages (>5%at.) co-existing phases with increased specific surface area formed. Low concentrations (0.1–10 mg L−1) batch adsorption tests showed increased P removal per unit mass with increasing doping. However, the highest pzc, affinity and P removal per unit area were observed for the 5%at. doped sample, suggesting this dopant concentration to provide the most effective surface. A regeneration test, performed at a lower pH than usual, showed preserved, even improved P desorption with increasing doping. Mössbauer spectroscopy showed that the nanoparticle phase and composition, up to 5%at., doping was preserved throughout the process. These results are promising to develop a stable effective Zn-doped goethite-based adsorbent for P recovery at ultra-low concentrations.