Comparison of Surface Properties of Sepiolite and Palygorskite: Surface Energy and Nanoroughness

Abstract

The surface properties of two sepiolite samples and one palygorskite sample were compared using inverse gas chromatography (IGC). Samples were previously conditioned at appropriate temperatures for the removal of all zeolitic water. Dispersive (or Lifshitz–van der Waals) component of the surface energy (γsd), specific interactions (−ΔGas) with π electron donor bases (1-alkenes), and nanomorphology indices (IMχT) based on the injections of cycloalkanes and a branched alkane were measured. From IGC data, at 240 °C, it was found that the palygorskite was clearly distinguished from the sepiolites. The palygorskite possessed a lower γsd, larger −ΔGas with 1-alkenes, and remarkably higher IMχT. Slight differences could also be observed between the two sepiolite samples with the same origin. The results were rationalized in terms of the structural features of the two studied minerals. The larger channels of the sepiolite allow for a better insertion of the n-alkanes (longer retention times) while excluding the bulkier probes, such as cyclooctane or 2,2,4-trimethylpentane. Accordingly, the corresponding γsd values were larger and the IMχT values were lower (higher surface nanoroughness) for the sepiolites. Regarding Lewis acid–base properties, all the sample’s surfaces evidenced a very strong amphoteric character. The present results highlight the potential of the evaluated samples for, e.g., adsorption processes with volatile organic compounds or matrix–filler interactions regarding the production of composite structures with Lewis acid–base matrices.

Preparation of Hybrid Nanopigments with Excellent Environmental Stability, Antibacterial and Antioxidant Properties Based on Monascus Red and Sepiolite by One-Step Grinding Process

“…Compared with APT, Sep is a magnesium hydrosilicate with larger nanochannels (1.06 nm × 0.37 nm) and fibrous morphology, which is also formed by two continuous tetrahedral sheets of silicon oxides linked by discontinuous octahedral sheets of magnesium oxides [11]. The reversal period of the apical oxygen in every three silicate chairs results in the existence of numerous silanol (Si-OH) groups on the surface and the formation of parallel tunnels and channels arranged along the fibers [12,13]. The unique porous structure is filled with weakly bound zeolitic H 2 O that forms the hydrogen bridge with the tetrahedral sheet and with tightly bound structural OH 2 coordinated to the magnesium at the ribbon borders [14,15].…”

Influence of Organic-Modified Inorganic Matrices on the Optical Properties of Palygorskite–Curcumin-Type Hybrid Materials

“…In this sense, the clays were modified with layer swelling compounds or organic substances with high affinity for bio-active compounds, so as to increase their adsorption capacity [7][8][9][10]. In some studies, palygorskite (attapulgite, (Mg, Al) 2 Si 4 O 10 (OH) 4 (H 2 O)), a magnesium aluminum phyllosilicate with a fibrillar structure, in monoclinic crystalline systems [11][12][13], is preferred for such applications. At the same time, palygorskite is known to be one of the oldest clays used to make hybrid materials (Maya blue pigment) obtained by the adsorption of natural indigo [14,15].…”