MOLECULAR VALIDATED MODEL FOR ADSORPTION OF PROTONATED DYE ON LDH

B M Braga,D V Gonçalves,S M P Lucena,M A G Paiva

doi:10.1590/0104-6632.20160331s00003451

B M Braga, D V Gonçalves + Show 2 more

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https://doi.org/10.1590/0104-6632.20160331s00003451

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Abstract

Hydrotalcite-like compounds are anionic clays of scientific and technological interest for their use as ion exchange materials, catalysts and modified electrodes. Surface phenomenon are important for all these applications. Although conventional analytical methods have enabled progress in understanding the behavior of anionic clays in solution, an evaluation at the atomic scale of the dynamics of their ionic interactions has never been performed. Molecular simulation has become an extremely useful tool to provide this perspective. Our purpose is to validate a simplified model for the adsorption of 5-benzoyl-4-hydroxy-2-methoxy-benzenesulfonic acid (MBSA), a prototype molecule of anionic dyes, onto a hydrotalcite surface. Monte Carlo simulations were performed in the canonical ensemble with MBSA ions and a pore model of hydrotalcite using UFF and ClayFF force fields. The proposed molecular model has allowed us to reproduce experimental data of atomic force microscopy. Influences of protonation during the adsorption process are also presented.

Highlights

Layered double hydroxides (LDH) are an important class of natural compounds and obtained by synthesis
LDHs can exchange anions that lie between the layers
LDHs with magnesium and aluminum atoms on their layers are known as hydrotalcite and the framework of the layers are similar to brucite (Mg(OH)2)

Summary

Introduction

Layered double hydroxides (LDH) are an important class of natural compounds and obtained by synthesis. They have a permanent positive charge on their surface. LDHs can exchange anions that lie between the layers. For these characteristics, these compounds are of great scientific and technological interest and are used as ion exchange materials (Dutta et al, 1991), catalysts (Reichle et al, 1986) and modified electrodes (Itaya et al, 1987). LDHs with magnesium and aluminum atoms on their layers are known as hydrotalcite and the framework of the layers are similar to brucite (Mg(OH)). We can imagine a starting structure, electrically neutral, being composed by one brucite layer (Figure 1a)

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