Kinetic Uptake Studies of Powdered Materials in Solution.

Mohamed Mohamed,Lee Wilson

doi:10.3390/nano5020969

Abstract

Challenges exist for the study of time dependent sorption processes for heterogeneous systems, especially in the case of dispersed nanomaterials in solvents or solutions because they are not well suited to conventional batch kinetic experiments. In this study, a comparison of batch versus a one-pot setup in two variable configurations was evaluated for the study of uptake kinetics in heterogeneous (solid/solution) systems: (i) conventional batch method; (ii) one-pot system with dispersed adsorbent in solution with a semi-permeable barrier (filter paper or dialysis tubing) for in situ sampling; and (iii) one-pot system with an adsorbent confined in a semi-permeable barrier (dialysis tubing or filter paper barrier) with ex situ sampling. The sorbent systems evaluated herein include several cyclodextrin-based polyurethane materials with two types of phenolic dyes: p-nitrophenol and phenolphthalein. The one-pot kinetics method with in situ (Method ii) or ex situ (Method iii) sampling described herein offers significant advantages for the study of heterogeneous sorption kinetics of highly dispersed sorbent materials with particles sizes across a range of dimensions from the micron to nanometer scale. The method described herein will contribute positively to the development of advanced studies for heterogeneous sorption processes where an assessment of the relative uptake properties is required at different experimental conditions. The results of this study will be advantageous for the study of nanomaterials with significant benefits over batch kinetic studies for a wide range of heterogeneous sorption processes.

Highlights

IntroductionThe study of conventional kinetic uptake experiments for two phase (e.g., solid-solution) systems is often met with several experimental challenges [1,2,3]
The study of conventional kinetic uptake experiments for two phase systems is often met with several experimental challenges [1,2,3]
There are challenges for the study of adsorption processes of powdered materials depending on their relative particle size when using conventional batch methods

Summary

Introduction

The study of conventional kinetic uptake experiments for two phase (e.g., solid-solution) systems is often met with several experimental challenges [1,2,3]. An additional challenge concerning the rapid separation of multi-phase systems occurs when employing batch methods for the study of uptake kinetics at variable temperature. One-pot sorption experiments have been employed which rely on sampling of aliquots in a multi-phase system as a function of time This method often neglects the loss of adsorbent during sampling of heterogeneous fractions which contain the sorbent phase residues that are often unaccounted for during the serial sampling process [6]. Batch kinetics of multiple samples can overcome these challenges but the method is time consuming, labor-intensive, requires substantive amounts of sorbent material, and may be inapplicable to solid-solution systems with rapid uptake kinetics due to the aforementioned systematic errors over the sampling interval [2]

Methods

Results

Conclusion