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Synergistic Runoff Particulate‐Bound Phosphorus Extraction by Oxalate and Citrate Ligands in a Mixed Aqueous Extractant System
Author(s) -
Gaviglio Katie,
Shields Shaun,
Mondala Andro
Publication year - 2019
Publication title -
clean – soil, air, water
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 66
eISSN - 1863-0669
pISSN - 1863-0650
DOI - 10.1002/clen.201700499
Subject(s) - chemistry , oxalate , extraction (chemistry) , citric acid , phosphorus , aqueous solution , kinetics , particulates , chromatography , environmental chemistry , inorganic chemistry , organic chemistry , physics , quantum mechanics
Recovering nonpoint phosphorus (P) losses in particulate runoff is considered a significant step toward closing the P loop for nutrient and water sustainability. The objectives of this study are to examine how process conditions affect P extraction efficiency using an abiotic 2:1 mM oxalate/citrate extractant mixture and investigate the sediment P extraction kinetics in this system in comparison to a pure citrate extraction process. High P removal and solubilization are favored at low sediment loading (5 g/100 mL), low initial pH (3), and high initial organic acid loading (75 mM), with P recovery efficiencies up to 99.6% achieved under these conditions, similar to a pure citrate system. Initial and equilibrium extractant pH levels near oxalate and citrate pKa 2 s (4.19 and 4.74, respectively) appear conducive for optimal and/or synergistic oxalate ligand exchange and citrate ligand‐induced particulate P release. P solubilization kinetics and P speciation dynamics analysis indicate better performance by the oxalate/citrate mixture through a higher initial P solubilization rate by rapidly extracting Fe‐P from the sediments within the first 30 min of extraction, indicating potential synergism between the oxalate and citrate ligands. From a process development standpoint, the results suggest that operating the extraction under fed‐batch or semi‐continuous modes with pH control may maximize runoff particulate P recovery efficiency using a mixed low molecular weight organic acid (LMWOA) extractant.