Quantitative determination of vivianite in sewage sludge by a phosphate extraction protocol validated by PXRD, SEM-EDS, and 31P NMR spectroscopy towards efficient vivianite recovery

WATER RESEARCH

卷:202

Article

Wang, Qian¹  Kim, Tae-Hyun^1,2  Reitzel, Kasper³  Almind-Jorgensen, Nina⁴  Nielsen, Ulla Gro¹ 

[1] Univ Southern Denmark, Dept Phys Chem & Pharm, DK-5230 Odense M, Denmark

[2] Seoul Natl Univ Sci & Technol, Dept Environm Engn, Seoul 01811, South Korea

[3] Univ Southern Denmark, Dept Biol, DK-5230 Odense M, Denmark

[4] VandCtr Syd VCS, DK-5000 Odense C, Denmark

关键词: Phosphate recovery;    Sewage sludge;    Vivianite;    Circular economy;    Solid-state P-31 NMR;   

DOI  :  10.1016/j.watres.2021.117411

来源: Elsevier

【 摘 要 】

Vivianite (Fe-3(PO4)(2.8)H2O) is a potential phosphorus (P) recovery product from wastewater treatment plants (WWTPs). However, routine methods for quantification of vivianite bound P (vivianite-P) are needed to establish the link between vivianite formation and operating conditions, as current approaches require specialized instrumentation (Mo spacing diaeresis ssbauer or synchrotron). This study modified a conventional sequential P extraction protocol by insertion of an extraction step (0.2% 2,2 '-bipyridine + 0.1 M KCl) targeting vivianite-P (Gu et al., Water Research, 2016, 103, 352-361). This protocol was tested on digested and dewatered sludge from two WWTPs, in which vivianite (molar Fe:P ratios of 1.0-1.6) was unambiguously identified by optical microscopy, powder Xray diffraction, and scanning electron microscopy with energy dispersive X-ray spectroscopy. The results showed that vivianite-P was separated from iron(III)-bound P (Fe(III)-P) in the sludge. Vivianite-P constituted about half of the total P (TP) in the sludge from a Fe dosing chemical P removal (CPR) WWTP, but only 16-26% of TP in the sludge from a WWTP using a combination of Fe dosing CPR and enhanced biological P removal (EBPR). The modified protocol revealed that Fe-bound P (Fe-P, i.e., vivianite-P + Fe(III)-P) was the dominant P fraction, in agreement with quantitative P-31 nuclear magnetic resonance (NMR) experiments. Moreover, it was shown that the conventional P extraction protocol underestimated the Fe-P content by 6-35%. The established protocol represents a reliable in-house analytical method that can distinguish and quantify vivianite-P and Fe(III)-P in sludge, i.e. facilitate optimized vivianite production at WWTPs.

【 授权许可】

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