Ultrasound assisted preparation of chitosan–vermiculite bionanocomposite foams for cadmium uptake

Thermal insulation with 2D materials: liquid phase exfoliated vermiculite functional nanosheets

“…Moreover, ultrasounds cause a substantial decrease in particle size reaching nanometer dimensions along the [00l] lattice direction. 33,44,45,47,48 Importantly, mixed layer (micavermiculite) minerals always produce better exfoliation than pure vermiculite, giving rise to materials with higher specific surface area and expansive capacity, 34 whereas pure vermiculite does not undergo exfoliation or does so only to a smaller extent. 35 Ultrasound-assisted exfoliation of vermiculite is generally conducted in water or hydrogen peroxide solutions during long period of time (up to 150 h) 47 using low ultrasonic frequencies (20 kHz) and high output power (350 -750 W).…”

“…49 To the best to our knowledge, the production of ultrathin vermiculite flakes using ultrasonication in acidic solutions has not been investigated to date. Vermiculite, as well as other analogous minerals (e.g., montmorillonite, kaolinite), are used in combination with organic molecules and polymers to obtain functionalized clay materials, ordered self-assembled nanostructures 50 and polymer-based nanocomposites, 48,51,52 displaying interesting and improved physical and chemical properties. In particular, materials with enhanced stiffness, toughness, strength and thermal stability can be obtained, 53,54 exhibiting increased affinity towards organic pollutants 43 and metal ions, 48,55,56 enhanced gas barrier and thermal insulating properties.…”

Multicomponent bionanocomposites based on clay-nanoarchitectures for electrochemical devices

“…In contrast, a decrease in the compression modulus (1.4 MPa) was found for the sample with a higher content of chitosan (72 %), suggesting a synergic effect of both clays as reinforcing fillers of the polymer and as adhesive agent, which is required to improve the mechanical properties for the designed samples [46][47]. The obtained compression modulus is comparable to values measured for other chitosan/clay foams (1.4 MPa) [47] and significantly higher than those of self-assembled graphene hydrogels (0.03-0.3 MPa) [48]. Notably, the specific modulus of the bionanocomposite foams was 50 kNm kg -1 , which is considerably higher than values reported for silica aerogels (5-20 kNm kg -1 ) [49] and is on par with polystyrene foams (10-100 kNm kg -1 ) [45] and other bionanocomposite graphene-clay foams (77 kNm kg -1 ) [39].…”

“…This tendency can be correlated to the strong interactions between the chitosan matrix and the sepiolite fibres as well as to an increase in the relative density that produces a decrease in porosity, commonly related to a smaller pore size and a lower tendency to collapse as in case of larger macropores [44,45]. In contrast, a decrease in the compression modulus (1.4 MPa) was found for the sample with a higher content of chitosan (72 %), suggesting a synergic effect of both clays as reinforcing fillers of the polymer and as adhesive agent, which is required to improve the mechanical properties for the designed samples [46][47]. The obtained compression modulus is comparable to values measured for other chitosan/clay foams (1.4 MPa) [47] and significantly higher than those of self-assembled graphene hydrogels (0.03-0.3 MPa) [48].…”

Building Up Functional Bionanocomposites from the Assembly of Clays and Biopolymers

“…These materials were also effective to remove negatively charged organic pollutants like tannic acid or the dye Congo red . Similarly to smectite‐based materials, in a recent work we developed bionanocomposite foams based on vermiculite and chitosan for Cd 2+ uptake . Usually, the synthesis of nanocomposites based on vermiculite is difficult, as the high charge density per unit cell in its layers limits the entrance of high molecular polymers to the interlayer space.…”