Title

Extraction of Runoff Sediment-Bound Inorganic Phosphorus Using Low Molecular Weight Organic Acids: Solubilization Kinetics and Speciation Dynamics

Date of Award

6-2018

Degree Name

Master of Science in Engineering

Department

Chemical and Paper Engineering

First Advisor

Dr. Andro Mondala

Second Advisor

Dr. Betsy Aller

Third Advisor

Dr. James Springstead

Fourth Advisor

Dr. Brian Young

Access Setting

Masters Thesis-Abstract Only

Restricted to Campus until

6-2028

Abstract

Continued food security in the future is constrained by the need for an uninterrupted supply of phosphorus (P) for use as a fertilizer nutrient in commercial-scale agriculture. Researchers at the WMU chemical engineering program pioneered the development of a phosphate solubilizing fungi (PSF)-mediated bioextraction process designed to recover P from agricultural runoff sediments, which represent a major pathway for losses of the valuable P resource. In this study, solubilization kinetics and speciation dynamics of P from P-rich sediment during a 120-minute extraction process using aqueous low molecular weight organic acid (LMWOA) reagents containing 2:1 (mM ratio) oxalate-to-citrate and pure citrate were investigated. Results show that between 70-90% of the total P solubilized occurs within the first 30 minutes of the extraction process, likely through a ligand exchange mechanism. After 30 minutes, P is solubilized likely through a ligand-promoted dissolution mechanism, and the rate of P solubilization decreased drastically. P speciation dynamics was found to be dependent mainly on the type of LMWOAs used in the treatment process. LMWOA mixtures appear to exhibit a synergistic effect that allowed for greater P solubilization than would be possible with individual LMWOAs. The 2:1 oxalate-to-citrate LMWOA mixture appears to be more suitable for P solubilization from runoff sediments compared to pure citrate, and its use is recommended in the PSF-mediated bioextraction process to maximize P recovery.

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