ABSTRACT Phosphorus availability in soils is low due to its strong retention by inner-sphere complexation on minerals in the clay fraction with pH-dependent charges, such as goethite. On the other hand, sulfur has greater availability because it is retained mainly by electrostatic attraction. We evaluated the intensities of the inner-sphere complexation of orthophosphate and sulfate (H2PO4-/HPO42- and SO42- – generically treated as PO4 and SO4) under different experimental conditions (pH, goethite purity, and contact times) on synthetic goethite samples to […]

The adsorption of two humic acids (HA) was carried out on a natural Oxisol (natural LR) and on an ammonium-oxalate treated sample (treated LR), in order to investigate the adsorption mechanisms and the main functional groups involved and relate the adsorptive capacity with the chemical and molecular characteristics of the adsorbates. The HA extracted with 0.5 N NaOH solution from a coal sample (HAc) and from a Mollisol sample (HAs) were characterized by elemental analysis and 13C-NMR spectroscopy. The experimental […]