Surface and Structural Properties of Clay Materials Based on Natural Saponite

Abstract

Because they are so widespread, the use of saponites is significant in many industries. The modification of saponite-rich clay minerals is known to improve their existing characteristics and may provide new functional properties. The objective of the present paper was to characterize the effects of adding nanosized graphene-like molybdenum (Mo) and tungsten (W) sulfides on the textural and surface characteristics of composites based on native saponite and saponite pre-modified with nanoscale magnetite. The textural characteristics were investigated by the nitrogen adsorption-desorption method and scanning electron microscopy. The total acidity, Hammett Brönsted centers, and Quasi-Equilibrium Thermo Desorption (QE-TD) Lewis centers were characteristics used to probe the acid-base properties of the modified composites. In all cases, modification proved to have a significant effect on both the surface and textural properties of the clay matrix. Modification of the native saponite by graphene-like Mo and W sulfides resulted in a decrease in the specific surface area, except a slight increase in the surface area of the magnetite-containing saponite was observed. Analysis of the acid-base characteristics of native and magnetite-modified saponite (MMS) indicated the ability of modified MoS2 and WS2 additives to alter the acid-base state of the surface. The addition of graphene-like Mo and W sulfides increased the total acidity of native and MMS, with MoS2 modification being more promising because, in almost all the samples, saponite composite materials increased the number of both Brönsted and Lewis active centers compared with WS2, which was determined by the corresponding methods. The acid-base characteristics of the saponite-containing samples, which were studied in an aqueous medium by various methods, are in good correlation with each other, and are consistent with the sorption activity of cationic and anionic dyes.

“In-water” Dehydration Reaction of an Aromatic Diol on an Inorganic Surface

“…The other possible factor is a pH change on the saponite surface. It was reported that saponite surfaces are weakly acidic, , and the effect of pH on the MQu + equilibrium was examined at pH = 2, 3, and 6. As can be seen in Figure S12, the absorption spectra of MQu + did not depend on pH at all.…”

“…Many studies have been reported on the unique effects of the interface between a saponite surface and an aqueous solution. − Our group has reported unique phenomena of adsorbed species on a saponite surface. − , For example, the emission enhancement of adsorbed species − and photoisomerization control on the saponite surface have been reported. These examples can be interpreted mainly as steric effects of the saponite surface on “intra”-molecular reactions and processes.…”

“…In addition, saponite nanosheets can be dispersed stably and the surface is chemically stable in water. The aqueous solution including dispersed saponite is optically transparent and thus is a pseudo-homogeneous solution system. ,,, These characteristics indicate that the saponite nanosheet can act as an intersection of the traditional in-solvent synthesis systems and the on-surface synthesis systems.…”

Preparation, stretch‐induced crystallization and thermo‐oxidative aging behavior of poly (lactic acid)/saponite grafted polystyrene nanocomposites films

“…Natural saponite is a very unique modifier, saponite nanoparticles have great specific surface area, surface free energy, high mechanical strength and reinforcing capacity. 17,18 However, the large number of hydroxyl groups on the surface of saponite makes it extremely hydrophilic and prone to agglomeration, thus limiting its use in hydrophobic polymer matrices, and it can lead to the formation of stress concentrations resulting in poor reinforcement. 19 To overcome these challenges, several researchers have performed various modifications to saponite, not only retaining the advantages of PLA itself, but also giving it new functions.…”

“…The properties of PLA can be further enhanced by the addition of various inorganic nanoparticles such as fibers, 12 hydrotalcite, 13 hydroxyapatite, 14 bumpy rods, 15 calcium carbonate, 16 etc., aiming to enhance the various properties of PLA to broaden its applications. Natural saponite is a very unique modifier, saponite nanoparticles have great specific surface area, surface free energy, high mechanical strength and reinforcing capacity 17,18 . However, the large number of hydroxyl groups on the surface of saponite makes it extremely hydrophilic and prone to agglomeration, thus limiting its use in hydrophobic polymer matrices, and it can lead to the formation of stress concentrations resulting in poor reinforcement 19 .…”