Application of Elovich Equation to the Kinetics of Phosphate Release and Sorption in Soils

Abstract

Experimental data on the phosphate release and sorption in soils, when inadequately described by a first‐order kinetic reaction, are often interpreted as a combination of two or three simultaneous first‐order reactions. A simple modified Elovich equation in the form: q = (1/β) ln (αβ) + (1/β) ln t was derived to fit the reported experimental data in literature that failed to conform to a single first‐order kinetic equation. In this equation, q is the amount of phosphate released or sorbed, and α and β are constants. The equation successfully described the data as a single straight line that covers the entire course of reaction time. It also appears that constants of α and β may be used for comparison of reaction rates of phosphate release or sorption in different soils.

Kinetics of phosphorus sorption in soils in the state of Paraíba¹

“…In general, the data fit the equations proposed by Kuo & Lotse (1974), Barrow & Shaw (1975) and Panda (1978) (Table 3), but not the equation proposed by Chien & Clayton (1980). Lack of fitting to the equation of Chien & Clayton (1980) possibly occurred because the assumption of the equation (αβ t > 1) was not met.…”

“…Lack of fitting to the equation of Chien & Clayton (1980) possibly occurred because the assumption of the equation (αβ t > 1) was not met. Thus, the data of the coefficient of this equation were not presented.…”

“…In order to assess the kinetics of P sorption, the equations suggested by Kuo & Lotse (1974); Barrow & Shaw (1975); Panda et al (1978) and Chien & Clayton (1980) were used.…”

“…Panda et al (1978) suggested the equation: C = K.t -n , where C is the phosphate concentration (mg L -1 ) measured in time t (min), the constant K denotes a P concentration in the equilibrium solution (mg L -1 ) and the index is related to the phosphate sorption rate in soil. Chien & Clayton (1980) modified the equation of Elovich and used it to assess the kinetics of phosphate adsorption and desorption in soils: q = (αβ) (1/β) t (1/β) , q: adsorbed P and a and b are constants used to compare the reaction rates.…”

“…Moreover, the relative simplicity of the equations makes it difficult to describe the complex sequence of steps of the fast and slow sorption stages (Cheung & Venkitachalam, 2006). The equations proposed by Kuo & Lotse (1974), Barrow & Shaw (1975), Panda et al (1978) and Chien & Clayton (1980) are widely used.…”