Cristobal Valenzuela-Calahorro

Lithium adsorption by acid and sodium amberlite

In this paper we used a previously reported model for examining the adsorption of nonelectrolytes in solution by solid adsorbents to study the adsorption of lithium(I) cations by acid and sodium amberlites, which is an ion-exchange process. Based on the results, both are equilibrium processes and obey a kinetic law with a unity partial order in the Li+ concentration. The kinetic results were used to calculate the specific rate constants and thermodynamic activation functions involved. Also, equilibrium isotherms were used to determine the corresponding ion-exchange capacities, the individual equilibrium constants, and the thermodynamic functions for the overall process.

Retention of progesterone by four carbonaceous materials: study of the adsorption kinetics

The process by which progesterone in an ethanol solution is retained by four carbonaceous materials involves a reversible mechanism that conforms to a kinetic equation of unity partial order in both the progesterone concentration in solution, the coverage fraction (u ) of the adsorbing surface and (1� /u ). Over the temperature range 10 � /40 8C, the specific rate constant varies from 5.29 � /10 � 4 to 44.85 � /10 � 4 s � 1 . The formation of the activated species involved in the adsorption process is an endothermal, exoentropic step. The rate of the adsorption � /desorption process is primarily determined by diffusion of progesterone molecules in the pores of the sorbent. # 2003 Elsevier B.V. All rights reserved.

Retention of Progesterone by an Activated Carbon: Study of the Adsorption Kinetics

The process by which progesterone in an ethanol solution is retained by Merck granular activated carbon involves a reversible mechanism that conforms to a kinetic equation of unity partial order in both the progesterone concentration in solution, the coverage fraction (θ) of the adsorbing surface and (1−θ). Over the temperature range 10–40°C, the specific adsorption rate varies from 5.8·10−5 to 1.3·10−4 s−1. The thermodynamic activation functions for the process are ΔH*=41.6 kJ/mol and ΔS*=−0.20 kJ/K· mol. The rate of the adsorption-desorption process is primarily determined by diffusion of progesterone molecules in the pores of the sorbent.