Phosphate removal by iron oxide-coated diatomite: Laboratory test of a new method for cleaning drainage water

Gry Lyngsie*, Konstantina Katika, Ida Lykke Fabricius, Hans Christian Bruun Hansen, Ole Kragholm Borggaard

*Corresponding author for this work

    Research output: Contribution to journalJournal articleResearchpeer-review


    Transport of phosphate (P) in drainage water from P rich agricultural fields to freshwaters via drains may cause open water eutrophication. One way to reduce this transport is by installation of P sorbing filters at drain outlets. As drainage water flows and P concentrations can be highly fluctuating, suitable filter must have good hydraulic conductivity and high P sorbing efficiency, i.e. rapid sorption with high affinity and capacity. To fulfill these requirements, we tested a new concept for filter material design comprising porous and stable calcined diatomaceous earth particles (CDE, 2e4 mm) coated with thin layers of high affinity P sorbing amorphous iron oxide. According to NMR and MICP analyses the material had a bimodal pore size distribution with average diameters of around 1 μm and 100 μm. The coating formed a thin film on the CDE internal and external surfaces and markedly increased the P sorption efficiency. Thus, P in 0.1 and 0.5 mg P/L solutions was almost quantitatively sorbed within 1½ min at a solution:solid ratio of 100. SEM-EDX demonstrated that P quickly penetrated into the porous structure of the CDE granules and that all Fe in the coating was active in P bonding. This conceptual investigation demonstrates that porous CDE is a useful host into which Fe oxides can be precipitated resulting in an effective P sorbing material.
    Original languageEnglish
    Pages (from-to)884-890
    Publication statusPublished - 2019


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