A colloid chemistry route for the preparation of hierarchically ordered mesoporous layered double hydroxides using surfactants as sacrificial templates

Gábor Varga,Zoltán Somosi,Zoltán Kónya,Ákos Kukovecz,István Pálinkó,Istvan Szilagyi

doi:10.1016/j.jcis.2020.08.118

Gábor Varga, Zoltán Somosi + Show 4 more

Open Access

https://doi.org/10.1016/j.jcis.2020.08.118

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Journal: Journal of Colloid Science	Publication Date: Sep 9, 2020
Citations: 27	License type: cc-by

Affiliation: University of Szeged

Abstract

An efficient synthetic route was developed to prepare hierarchically ordered mesoporous layered double hydroxide (LDH) materials. Sodium dodecyl sulfate (SDS) was used as a sacrificial template to tune the interfacial properties of the LDH materials during the synthetic process. The SDS dose was optimized to obtain stable dispersions of the SDS-LDH composites, which were calcined, then rehydrated to prepare the desired LDH structures. Results of various characterization studies revealed a clear relationship between the colloidal stability of the SDS-LDH precursors and the structural features of the final materials, which was entirely SDS-free. A comparison to the reference LDH prepared by the traditional co-precipitation-calcination-rehydration method in the absence of SDS shed light on a remarkable increase in the specific surface area (one of the highest within the previously reported LDH materials) and pore volume as well as on the formation of a beneficial pore size distribution. As a proof of concept, the mesoporous LDH was applied as adsorbent for removal of nitrate and dichromate anions from aqueous samples, and excellent efficiency was observed in both sorption capacity and recyclability. These results make the obtained LDH a promising candidate as adsorbent in various industrial and environmental processes, wherever the use of mesoporous and organic content-free materials is required.

Highlights

Layered double hydroxide (LDH) materials, named as hydrotalcites after their naturally occurring form, are lamellar anionic clays, i.e., they possess anion exchange capacity, which is extensively utilized in applications including drug delivery [1], catalysis [2] or environmental remediation [3]
Like in Method 1, the sodium dodecyl sulfate (SDS) content was removed by calcination at 510 °C for 12 h leading to layered double oxide (LDO) formation, which was again transformed to layered double hydroxide (LDH) by rehydration
C-LDH3, cLDH10 and c-LDH30 materials were prepared by Method 2 using the standard co-precipitation technique

Summary

Introduction

Layered double hydroxide (LDH) materials, named as hydrotalcites after their naturally occurring form, are lamellar anionic clays, i.e., they possess anion exchange capacity, which is extensively utilized in applications including drug delivery [1], catalysis [2] or environmental remediation [3]. LDH materials of lower surface charge density, but higher pore sizes are good candidates to immobilize and deliver larger biomolecules [7], while high surface charge and area are required for the most efficient anion absorbers in water decontamination [8] In the latter case, significant effort was made to remove inorganic toxic anions including nitrate and chromate from aqueous environmental or industrial systems [3,9]. Despite the fact that numerous hard (e.g., solid particles) or soft (e.g., surfactants) template-based processes have been developed to build up porous LDHs, significant increase in the sorption capacity was not achieved. This tendency might be attributed to two issues. The presence of macropores lead to formation of hollow spheres [10] around the template and this resulted in a significant decrease in the microporous surface area [11]

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