Abstract Anion exchange membranes (AEMs) are widely used to assess soil phosphorus (P) cycling. However, the routine reuse of AEM for soil extractions may impact the surface properties of AEM and thus phosphate‐P exchange. We evaluated changes in AEM surface morphology, chemical composition, and phosphate‐P exchange capacity after varying degrees of use: never, lightly (20–30 extractions), and intensively (>100 extractions). Scanning electron microscopy and elemental analysis revealed increased surface roughness and accumulation of metal‐containing particles (e.g., Al and Fe) on reused AEMs compared to never used AEMs. Fourier‐transform infrared (FTIR) spectroscopy corroborated the presence of Fe/Al‐based minerals on the surface of reused AEM. Phosphate‐P exchange capacity increased with AEM reuse: +24% for lightly used and +95% for intensively used AEM relative to never used AEM. Kinetic experiments revealed phosphate‐P exchange rate increased with AEM reuse, suggesting that soil‐derived coatings provided additional binding sites. Regardless of usage degree, however, AEM showed reduced phosphate‐P exchange in the presence of competing anions (i.e., chloride, nitrate, and sulfate), indicating that the polymeric head groups remained critical for exchange reactions on reused AEM. Further research should investigate the degree to which specific soil minerals may modify AEM and the extraction of phosphate‐P.
Li et al. (Thu,) studied this question.