Effect of Ultrasound on the Structural and Textural Properties of Al–Fe Pillared Clays in a Concentrated Medium

Abstract

A modification of bentonite with the Al-Fe mixed system in a concentrated medium was performed, assisting the intercalation with ultrasound. The solid pillaring agent and clay powder were placed in a dialysis membrane in contact with a minimum amount of water, and ultrasound was used to promote species exchange. Al-Fe pillared clays (2, 5 and 10 mol% Fe) were characterized by XRF, CEC, XRD, H 2 -TPR and N 2 adsorption at 77 K, revealing changes in the structural and textural properties of the modified clays in the presence of ultrasound during the intercalation. The catalytic properties of pillared clays were evaluated by using the catalytic wet peroxide oxidation of phenol in a diluted aqueous medium, showing an activity comparable to that of a solid modified through the conventional method.

Pillared montmorillontes from unusual antiperspirant aqueous solutions: Characterization and catalytic tests

“…Although this method has had success in laboratory synthesis of pillared clays, it is not an ideal preparation technique for large scale production because large amounts of water and heat are necessary [14]. New procedures for the synthesis of pillared clays were proposed, using microwave irradiation or ultrasonic waves in order to decrease the consumption of three industrially-important parameters: time, water consumption and energy [15,16]. The high stability of the pillared clays prepared by ultrasonic was attributed to the uniform pillaring obtained by the use of ultrasonics, which did not alter properties such as acidity and catalytic activity [16].…”

Influence of Synthesis Conditions on the Physicochemical Properties and Catalytic Activity of Fe/Cr‐Pillared Bentonites

“…This observation indicates that there is a beneficial effect of using ultrasound treatment and by adding the pillaring solution slowly to the clay suspension on amount of iron that incorporated into the structure. The use of ultrasound in the intercalation stage probably increases exchange of pillars and improves the dispersion and homogenization of the suspended solids [10]. Furthermore, from EDS analysis results, it was observed that, by changing the Fe/Fe + Cr ratio in the pillaring solution, the Fe/Cr ratio in pillared clay could be changed; the success of the replacement of iron and chromium in the structure was increased by pillaring with a solution containing an Fe/Fe + Cr ratio of 0.75.…”

“…For this reason, studies related to developing a more rapid synthesis of these materials have recently become important. At this point in the development of pillared clay catalysts for the industrial scale, it is important to improve their physicochemical and catalytic properties as well as to develop synthesis methods that decrease their production time and water use [6][7][8][9][10].…”

Development of Pillared Clays for Wet Hydrogen Peroxide Oxidation of Phenol and Its Application in the Posttreatment of Coffee Wastewater

“…Thus, it has become possible to decrease the volume of water by the use of concentrated suspensions, both clay and the pillaring agent [106][107][108][109][110][111]. Also, the time of intercalation of montmorillonite with chlorhydrol has been reduced through the use of ultrasound, having led to the obtaining of Al-PILC with a high thermal stability and textural properties superior to those of clay modified with an exchange time of 24 h. In overall, during the intercalation, treatment with ultrasound [51,112,113] and microwaves [107,[114][115][116] has been proved to be an adequate method for reducing the contact time between clay and the pillaring agent [57].…”

“…Although, in the past 30 years, several studies highlighting some applications of industrial pillared clays have been published, such materials have not been used as commercial catalysts primarily due to the difficulty of extending the laboratory synthesis to an industrial scale [57]. However, in 2005, a procedure for pillaring clays with aluminum, which minimizes the processing time and the amount of water used, allowing its extension to an industrial level was developed.…”