Phosphate Sorption‐Desorption Behavior of Some Acidic Soils of South and Southeast Asia

Abstract

The equilibrium phosphate sorption and release behavior and the kinetics of adsorption were studied in some acidic soils of South and Southeast Asia. Phosphate sorption data at 25 °C were fitted to the Tempkin, Freundlich, and Langmuir adsorption isotherms. The soils varied widely in their capacity to sorh and retain P. During desorption, the amount of sorbed P at a given equilibrium P concentration was always higher than that during sorption, indicating low desorbability of the sorbed P. The kinetic P sorption data at 21 and 35 °C were fitted to a modified Freundlich type of kinetic equation to obtain a parameter related to the sorption rate coefficient. The effect of temperature on the kinetics of sorption was small, suggesting the process is diffusion controlled. Equilihrium and kinetic P sorption parameters were found to he closely correlated with clay and organic matter contents and surface area of soils. A negative correlation between specific P sorption by clay or organic matter and clay or organic matter content of the soils suggests an association between the two colloidal components of the soils, causing loss of effective P‐sorhing surface area. An attempt was further made to evaluate the differential change in free energy of P sorption at infinite dilution from the corresponding thermodynamic equilibrium constant for P sorption by the given soils. The results suggest that the stability of the P sorption reaction products in the given soils contribute to the P‐fixing characteristics of these soils.

Sorption of isoxaflutole by five different soils varying in physical and chemical properties

“…This is because the Freundlich equation, although originally empirical, implies that the af®nity for sorption decreases exponentially with increasing solution concentration, which is closer to reality. 14,15 Values of n were close to unity in all soils, suggesting partitioning as a dominant adsorption mechanism. Hence, it was possible to compare the K F values and determine the comparative sorption capacities of the soils.…”

Sorption of Phosphorus from Swine, Dairy, and Poultry Manures

“…Organic matter has been shown to reduce P sorption to soils by competing with P for sorption sites as well as complexing with metal oxyhydroxides (Bhatti, Comerford, and Johnston 1998;Ohno and Crannell 1996;Ohno and Erich 1997;Singh and Jones 1976;Violante, Colombo, and Buondonno 1991). On the other hand, studies have also reported increased P sorption due to the presence of organic matter (Guppy et al 2005a;Harter 1969;Redding, Shatte, and Bell 2006; Sanyal, De Datta, and Chan 1993). Possible mechanisms include the attachment of P to DOM through metal-chelate linkages (Guppy et al 2005a;Zhou, Rhue, and Harris 1997) or inhibiting metal oxide crystallization (Borggaard et al 1990).…”

Phosphorus Accumulation Pattern in a Subsurface Constructed Wetland Treating Residential Wastewater

“…However, OM accumulation can potentially contribute to the clogging of pore space, thus decreasing the wetland purification potential. The relationship between P sorption and organic matter content can vary, with some studies reporting a negative correlation [27,43] and others a positive correlation [44]. In the Sadowa wetland, the correlation between OM content and P accumulation in the bed substrate was weak.…”