Phosphate binding to allophane and ferrihydrite with implications for volcanic ash soils

The occurrence of allophane and ferrihydrite in volcanic ash soils contributes to the high P sorption capacity soils. objective this study was investigate distribution phosphate between systems their mixtures as a function sorbed aqueous citrate concentrations. results were compared with those from rich ferrihydrite. Phosphate adsorption isotherm for allophane–ferrihydrite described linear combination Freundlich models each single compound system. across single- binary-compound decreased increasing Phosphorus K-edge X-ray absorption near edge structure (XANES) showed that had higher affinity than ferrihydrite, particularly at low intermediate Such preferential attenuated 10 mM Changes full width half-maximum height white-line peak XANES spectra provided evidence Al-phosphate precipitation allophane-ferrihydrite mixtures, but not systems. demonstrated 61–92% associated Al, thus confirming Al over Fe