Adsorption equilibria of di(2-ethylhexyl)phosphoric acid at the water-dodecane-interface. Effects of additional electrolytes

Table of Contents

1 Introduction

2 Experimental

3 Modelling

4 Results

5 Summary

Research Objectives and Topics

This work aims to simulate the equilibrium interfacial tension of the joint adsorption of the monomer and anion of the cation exchanger D2EHPA at the water-dodecane interface, specifically accounting for the influence of electrolytes and micelle formation. The research seeks to overcome limitations in conventional modelling by incorporating a pseudo-nonionic strategy that considers counterion adsorption and dissociation equilibria.

• Pseudo-nonionic modelling of interfacial tension
• Influence of electrolyte concentrations and pH on D2EHPA adsorption
• Coupling of Langmuir and Stern isotherms for multicomponent systems
• Impact of micelle formation on interfacial activity
• Verification of the model through pendant drop tensiometry

Excerpt from the Book

Chapter Summary

1 Introduction: This chapter highlights the significance of interfacial adsorption for process design in fluid engineering and discusses the limitations of existing models for D2EHPA systems.

2 Experimental: This section details the pendant drop method and the temperature-controlled setup used to measure equilibrium interfacial tension with high precision.

3 Modelling: This core chapter introduces the pseudo-nonionic strategy, utilizing Langmuir and Stern isotherms to simulate the adsorption of monomeric and anionic forms of D2EHPA while accounting for electrolyte effects.

4 Results: This chapter presents the validation of the proposed model by comparing experimental data with simulation results under varying chemical conditions, demonstrating high accuracy.

5 Summary: This final section concludes that the pseudo-nonionic model successfully describes the interfacial tension, emphasizing the critical role of counterion adsorption in the system.

Keywords

Di(2-ethylhexyl)phosphoric acid, interfacial activity, adsorption equilibrium, counterion adsorption, pseudo-nonionic modelling, liquid-liquid-interface, interfacial tension, D2EHPA, cation exchanger, micelle formation, Langmuir isotherm, Stern isotherm, mass transfer, surfactant, extraction process

Frequently Asked Questions

What is the primary focus of this research?

The research focuses on the modelling and simulation of the equilibrium interfacial tension of D2EHPA at liquid-liquid interfaces, considering the effects of electrolytes and dissociation.

What are the central thematic fields?

The core themes include chemical thermodynamics, interface science, surfactant adsorption, and hydro-metallurgical extraction processes.

What is the primary goal of the study?

The objective is to develop a robust pseudo-nonionic modelling strategy that accurately simulates interfacial tension even when counterion adsorption and micelle formation are present.

Which scientific method is applied?

The study combines experimental pendant drop tensiometry with theoretical derivation based on the Gibbs adsorption equation, Langmuir isotherms, and the Stern isotherm.

What topics are covered in the main body?

The main body covers the theoretical modelling strategy, the experimental setup, the mathematical integration of the adsorption equations, and the comparison of calculated results against empirical data.

Which keywords characterize this work?

Key terms include D2EHPA, interfacial tension, pseudo-nonionic modelling, counterion adsorption, and liquid-liquid extraction.

Why is the Stern isotherm necessary in this model?

The Stern isotherm is included to account for the accumulation and influence of counterions at the interface, which significantly impacts the interfacial tension.

How is the micelle formation addressed?

Micelle formation is treated as a self-assembly process using a monodisperse approximation that does not affect chemical reaction equilibria but influences the available quantity of interfacially active agents.

What experimental limitation occurred with sodium hydroxide?

With a 0.1 molar sodium hydroxide solution in contact with one molar D2EHPA, a stable microemulsion formed, making the measurement of interfacial tension impossible.