Title: The Implications of Pulsating Anode Potential on the Electrochemical Recovery of Phosphate as Magnesium Ammonium Phosphate Hexahydrate (Struvite)
Abstract: A sustainable approach to address the limited availability of rock phosphate is to electrochemically recover phosphorus (P) as struvite (magnesium ammonium phosphate hexahydrate, MgNH 4 PO 4 .6H 2 O) fertilizer. On Mg surfaces, however, magnesium hydroxide (Mg(OH) 2 ) and/or struvite form resistive films that limit the release of divalent Mg ions and reduce struvite precipitation. The present work enhances struvite recovery through the application of a dynamic voltage with a sinusoidal waveform. Compared to a constant potential, our results demonstrated that a dynamic potential could enhance the rupture of the passivating film, and facilitate the release of Mg 2+ from the metal anode, thereby overcoming passivation problems. Ammonium dihydrogen phosphate (NH 4 H 2 PO 4 , 10 mM) solutions at neutral pH were used as test solutions. A 160-192% increase in magnesium release was observed versus constant voltage applications, resulting in a 1.3x increase in phosphate recovery. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) characterizations indicated that the precipitate recovered contained struvite. An analysis of electrode surfaces using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) confirms a greater extent of passivating film breakdown under dynamic voltages.
Publication Year: 2022
Publication Date: 2022-01-01
Language: en
Type: article
Indexed In: ['crossref']
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