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Nanoarchitectural strategy for design of highly active catalysts with CoMoS encased in 50-nm diameter aluminosilicate tubes (halloysite nanoclay) serving as an abundantly available natural support was proposed. This encapsulation conception implies the protection of active metal sulfides from aggregation, coking and leaching. Synthesized nanocatalytic system was investigated by TEM, XPS, N2 adsorption, hydrogen temperature programmed reduction and desorption of ammonia techniques. Using of Mo-heteropolyacid anionic precursor complex (ca. 10 wt%) possess selective loading of molybdenum oxide into 15-nm diameter inner cavity of the nanotubes (covered with positively charged alumina) by an electrostatic attraction. Subsequent sulfidation results in formation of CoMoS particulate core inside the aluminosilicate shell. These tubular nanoreactors were pelletized using alumina binder to produce a mechanically strong mesoporous catalyst efficient for hydrotreatment of diesel petroleum fraction to clean fuels.

Polymer matrix composites are replacing traditional materials in space, defense, marine and many other engineering applications. This fact is owed to the fact of the mass to strength ratio that can be tailored/ engineered in polymer matrix composites. Using a compatibilizer, polycarbonates (PC) were blended with polypropylene (PP) in specific weight percentages to achieve optimum properties followed by the introduction of Halloysite Nanotubes (HNT). Ultimate tensile strength (UTS) reached a maximum value (28.36 N/mm2) when the HNT is 3%. Thermal properties were measured using thermogravimetric analysis and differential scanning calorimetry and showed no dependence with HNT loading with respect to degradation peak and crystallization temperature.

Pt-nanoparticles supported on halloysite-nanotubes (HNTs) were selectively deposited onto the inner (Pt(IN)/HNT) or outer (Pt(OUT)/HNT) surface of the support to evaluate their operational stability on the cleaner and efficient hydrogenation of nitro compounds to produce their corresponding anilines. The formation of Pt0-aggregates on the inner or outer surfaces was observed, with mean particles sizes of 2.4–2.9 nm. The catalysts were evaluated using ethanol as solvent and nitrobenzene as a model substrate at a temperature of 298 K, under 1 bar of H2 pressure. The Pt(IN)/HNT catalyst showed better catalytic performance than Pt(OUT)/HNT, which was mainly attributed to the confinement effect of the Pt-nanoparticles inside the HNTs. However, the operational stability showed that Pt(OUT)/HNT retained its catalytic performance after 15 cycles, while the Pt(IN)/HNT catalyst suffered deactivation after the 5th cycle. The best catalytic system showed a moderate-to-high efficiency in the efficient hydrogenation of 7 nitro compounds used to produce their corresponding anilines, which are important pharmaceutical building blocks.

Halloysite nanotubes (HNTs) have been considered as a promising flame retardant fillers for polymers. In this work, the polyhedral oligomericsilsesquioxane (POSS) containing amino group was covalently grafted on the surface of HNTs with 3-(2,3-epoxypropoxy)propytrimethoxysilane as a chemical bridge. The POSS modified HNTs (HNTs-POSS) dispersed uniformly in the thermoplastic polyurethane (TPU) matrix and endowed TPU nanocomposites with enhanced tensile properties and fire safety. Cone calorimeter tests revealed that the introduction of 2 wt% HNTs-POSS to TPU matrix remarkably reduced the peak of heat release rate (PHRR) and total heat release (THR) by 60.0% and 18.3%, respectively. In addition, the peak CO production rate and total smoke release (TSR) could be significantly suppressed by the addition of HNTs-POSS. The well dispersed HNTs in combination with the ceramified silicon network from the thermal decomposition of POSS contributed to the formation of a continuous and compact char layer, exhibiting a tortuous effect by inhibiting heat diffusion and evaporation of volatile gaseous. In addition, the released crystal water from HNTs could dilute the combustible volatiles and then decline the combustion intensity. The tensile tests demonstrated that introduction of 2 wt% HNTs-POSS would enhance the maximum stress of TPU nanocomposite with a slight decrease of elongation at break. The combination of HNTs and POSS through the construction of effective interfacial interactions provides a feasible way to effectively enhance the fire safety of TPU nanocomposites without scarifying ductility.

Heavy metal-containing wastes pose long-term environmental threats. In the present work, cementitious binders in the presence of halloysite nanotubes (HNTs) at 1 wt%, 3 wt%, and 5 wt% by mass were used to immobilize lead (Pb(II)). Semi-dynamic leaching tests were used to quantify the Pb(II) leaching up to 64 days. The results showed that the addition of 1 wt%, 3 wt%, and 5 wt% HNTs particles strongly reduced the Pb(II) release. The optimal dosage of HNTs was 3 wt%, which decreased the cumulative release of Pb(II) by around 40.5% after 64 days. Isothermal calorimetry, X-ray diffractometry (XRD), thermogravimetry (TG), mercury intrusion porosimetry (MIP) and compression tests were then used to investigate better immobilization effect with HNTs addition. The results showed that HNTs particles promoted cement hydration, refined the pore structure of the hardened cementitious binders, decreased permeability, and enhanced mechanical strength. Zeta potential measurements indicated that the negative surface charge of the HNTs particles could adsorb Ca2+ ions from the pore solution of cement hydration, then facilitating adsorption of Pb(OH)3−.

In this study, naturally occurring clay halloysite has been used to synthesize novel halloysite functionalized sulfonic acid in two steps, i.e. functionalization followed by oxidation, and its catalytic activity has been estimated for one-pot synthesis of Hantzsch 1,4-dihydropyridines under green solventfree conditions. Spectroscopic studies such as FTIR, TGA, elemental analysis and first-principles-based quantum chemical studies have been employed to characterize the catalyst. Recyclability without significant loss of catalytic activity has been observed for several runs.

This experimental study emphasizes on the effect of ultrasonication, degassing and stirring process of purenanotubular Halloysite (HNT) on epoxy based composite. This process includes hydraulic compression and moderate pressurized hold under a pressure of 1.1 MPa for the expansion restriction of the composite during solidification. Synthesized composite were evaluated accordance to the processing effect on the microstructure and its interfaces. A compact discussion on the microstructure of the each composite and generated interface has been illustrated. A consolidated effect of processing parameters as ultrasonication, degassing and stirring is observed on the microstructure and XRD results of the synthesized composite. Microstructure results reveal that dispersion of HNT enhanced linearly with an addition of HNT particulates.

In this study, porous halloysite nanotube ceramics were prepared by the foam-gelcasting method using sodium carboxymethyl cellulose (CMC) as a foam stabilising agent, Isobam 104 as a dispersant and triethanolamine lauryl sulphate (TLS) as a foaming agent, respectively. Then, the effects of firing temperature on the phase composition, microstructure, and pore size distribution of porous halloysite nanotube ceramics were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunner-Emmet-Teller (BET), thermogravimetry (TG) and differential scanning calorimetry (DSC). The results showed that the prepared porous ceramics contained both mesopores (10–50 nm) and macropores (100–300 μm). As the firing temperature rose, the linear shrinkage and compressive strength of samples increased, while the porosity decreased. When the porosity was as high as 75.7%, the samples still remained the compressive strength of 1.1 MPa, and had the lowest thermal conductivity, reaching 0.194 W/(m·K) (at a testing temperature of 100 °C).

Halloysite nanotubes (HNTs) represent a versatile core structure for the design of functional nanosystems of biomedical interest. However, the development of selective methodologies for the site-controlled functionalization of the nanotubes at specific sites is not an easy task. This study aims to accomplish a procedure for the site-selective/specific, “pin-point”, functionalization of HNTs with polydopamine (HNTs@PDA). This goal was achieved, at pH 6.5, by exploiting the basicity of ZnO nanoparticles anchored on the HNTs external surface (HNTs@ZnO) to induce a punctual polydopamine polymerization and coating. The morphology and the chemical composition of the nanomaterial was demonstrated by several techniques. Turbidimetric analysis showed that PDA coating affected the aqueous stability of HNTs@PDA compared to both HNTs@ZnO and HNTs. Notably, hyperthermia studies revealed that the nanomaterial induced a local thermic rise, up to 50 °C, under near-infrared (NIR) irradiation. Furthermore, secondary functionalization of HNTs@PDA by selective grafting of biotin onto the PDA coating followed by avidin binding was also accomplished.

In present work, Acrylnitrile-Butadiene-Styrene (ABS) copolymer and Poly Vinyl Chloride (PVC) polymers have been blended with injection molding technique. To improve the thermo-mechanical properties of ABS/PVC blend, Halloysite Nanotubes (HNTs) at different concentration like (0, 0.5, 1, 1.5 and 2 wt%) also added. To obtain the best results, the percentage concentration of PVC is maintained at 10 % in ABS. The results of this work showed that due to addition of HNTs up to 1.5 wt% tensile and impact properties improve by 71.73 % and 32.6 % respectively. In addition to this, HNTs also showed the improved thermal stability of composites which is explained with the help of Differential Scanning Calorimetry (DSC). ABS/PVC composites will find applications in the piping and electrical insulation systems.

The control and inhibition of microbial infection are of critical importance for patients undergoing dental or orthopedic surgery. A critical requirement is the prevention of bacterial growth, subsequent bacterial colonization of implant surfaces, and biofilm formation. Among biofilm-forming bacteria, S. aureus and S. epidermidis are the most common bacteria responsible for causing implant-related infections. The ability to produce customized and patient-specific antimicrobial treatments will significantly reduce infections leading to enhanced patient recovery. We propose that 3D-printed antimicrobial biomedical devices for on-demand infection prophylaxis and disease prevention are a rational solution for the prevention of infection. In this study, we modified 3D printed polylactic acid (PLA) constructs using an alkali treatment to increase hydrophilicity and functionalized the surface of the constructs using a suspension of Zinc/HNTs-Ag-Chitosan Oligosaccharide Lactate (ZnHNTs-Ag-COS). The morphologies of printed constructs were analyzed using Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS), and chemical analysis by Fourier-transform infrared spectroscopy (FTIR). Assessment of the antimicrobial potential of our constructs was assessed using agar diffusion and biofilm assays. The surface of 3D printed PLA constructs were chemically modified to increase hydrophilicity and suspensions of COS-ZnHNTs-Ag were adsorbed on the construct surface. Surface adsorption of ZnHNTs-Ag-COS on PLA printed constructs was determined to be a function of relative pore size. Morphological surface characterization using SEM-EDS confirmed the presence of the suspension coatings on the constructs, and FTIR analysis confirmed the presence of COS-ZnHNTs-Ag in the coatings. The inhibition of bacterial growth was evaluated using the agar diffusion method. Results obtained confirmed the antimicrobial potential of the PLA constructs (which was a function of the Ag content in the material).

Injectable hydrogels have been known as promising materials for the regeneration of irregular shape tissue defects. In this study, novel thermosensitive methylcellulose (MC) hydrogels containing bassorin (Ba) and halloysite nanotubes (HNTs) have been developed for application in bone tissue engineering. Bassorin isolated from gum tragacanth (GT) with the concentration of 0.25-1.5 w/v% was blended with MC. The best MC/Ba gel (containing 0.5% bassorin) was chosen based on the results of injectability and rheological tests. HNTs (1-7%) were added to this formulation and tested for the physicochemical, mechanical, rheological, degradation, swelling, and biological properties. In vitro biological evaluations including cell proliferation (by MTT assay), cell attachment (by SEM), osteogenic activity (by Alizarin Red staining and alkaline phosphatase assay), and osteogenic gene expression (by quantitative real-time polymerase chain reaction) were done using MG-63 cells. Results showed that bassorin led to the increased gel-forming ability (at a lower temperature) and mechanical properties of MC hydrogel. The presence of HNTs and bassorin affected the degradation rate and swelling degree of MC-based hydrogel. Results showed significant enhancement in cell proliferation, differentiation, and mineralization, as well as higher bone-specific gene expression of the cell on bassorin and HNTs incorporated MC compared to pure MC hydrogel.

Nanopartides with light-to-heat conversion properties play vital roles in the design of photothermal materials that can be remotely heated via light activation. Halloysite nanotubes (HNTs), versatile natural clay nanoparticles, were converted into efficient photothermal agents by functionalizing them with polydopamine, a polymer with light-to-heat conversion properties. By varying the polydopamine functionalization reaction conditions such as dopamine concentration, reaction time, and the nature of the HNTs, HNT-polydopamine (HNT-PDA) nanohybrids comprising different amounts of polydopamine were obtained. HNTPDA nanohybrids presented significant temperature elevations when irradiated with 808 nm laser light, reaching 250 degrees C in 2 min, and were demonstrated to be effective photothermal agents, whose light-to-heat conversion properties and the degree of lightactivated temperature elevations can be easily tuned by controlling the polydopamine content through reaction conditions. The photothermal effect of HNT-PDA nanohybrids was demonstrated to be stable over multiple laser light-activation cycles, allowing their reusability. In addition to infrared laser light activation, HNT-PDA nanohybrids were also shown to be activated by other light sources of more practical importance such as a solar simulator, an infrared incandescent lamp, and a light-emitting diode (LED) lamp, demonstrating their versatility as photothermal agents. As one of the potential applications of HNT-PDA nanohybrids, their light-activated antibacterial activity was evaluated. The viability of Staphylococcus aureus (S. aureus) treated with HNT-PDA nanohybrids was reduced by 6.3 log when irradiated with infrared laser light for 5 min, whereas bacteria not treated with the nanohybrids stayed alive under the same irradiation conditions. Comprising natural, nontoxic, cost-effective components, HNT-PDA nanohybrids are promising nanoparticles as versatile clay-based photothermal agents that can be utilized in various photo-driven applications.

Nanotechnology has proven as progressive technology that enables to contribute, develop several effective and sustainable changes in food products. Incorporating nanomaterials like TiO2, SiO2, Halloysite nano clay, Copper sulfide, Bentonite nano clay, in carrageenan to develop innovative packaging materials with augmented mechanical and antimicrobial properties along with moisture and gas barrier properties that can produce safe and healthy foods. Intervention of carrageenan-based bio-nanocomposites as food packaging constituents has shown promising results in increasing the shelf stability and food quality by arresting the microbial growth. Nanomaterials can be incorporated within the carrageenan for developing active packaging systems for continuous protection of food products under different storage environments from farm to the fork to ensure quality and safety of foods. Carrageenan based bio nanocomposite packaging materials can be helpful to reduce the environmental concerns due to their high biodegradability index. This review gives insight about the current trends in the applications of carrageenan-based bio nanocomposites for different food packaging applications.

Metal–organic frameworks (MOFs) have received great attention in environmental remediation application. In particular, one-dimensional (1D) MOF materials have excellent catalytic degradation perfor...

The development of polymer-based composites with self-healing and recyclable capability has attracted the attention of several researchers for resource recycling and environment protection. In this work, Halloysite nanotubes (HNTs) reinforced polyurethane materials (PU) with self-healing and recyclable ability were constructed by in situ polymerization method. The mechanical, thermal amd morphological properties of PU and related composites were studied. The morphology of samples fracture surface ensured the homogeneous dispersion of HNTs in the polymer matrix. Moreover, thermal stability was improved with the incorporation of the HNTs. The tensile test showed strength increased with HNTs content increased. The tensile strength of composites increases from 23.38 to 34.92 MPa at 2 wt% HNTs. Therefore, the designed strategy provides a simple approach for preparing high mechanical properties, reprocessing and self-healing ability polyurethane composites.

In this study the compressive strength and durability of soft clay soil stabilized with halloysite nanotubes are investigated. Halloysite nanotubes are novel 1D natural nanomaterials which are widely used in reinforcing polymer, pollution remediation, and as nanoreactors for biocatalyst. The wide use of halloysite nanotubes is due to their high aspect ratio, appropriate mechanical strength, high thermal stability, nature-friendly and cost-effectiveness. However, the use of halloysite nanotubes as a stabilizing agent for improving the durability of soil is not clear. In this research, halloysite nanotubes was used in the amounts of 2%, 5% and 10% by the weight of dried soil. Unconfined compressive strength, wet/dry cycles and freeze/thaw cycles tests were performed to evaluate the strength and durability of stabilized soft clay soil. Experimental results showed that halloysite nanotubes considerably improves the compressive strength and durability of soft clay soil. The optimum amount of halloysite nanotubes for soil stabilizing in terms of compressive strength and durability was 5%. The compressive strength of soft clay increased as much as 129% by applying 5% halloysite nanotubes. Also, the specimen containing 5% halloysite nanotubes showed the least strength loss after wet/dry and freeze/thaw cycles. The soil sample containing 5% halloysite nanotubes lost 20% of its initial compressive strength after 8 cycles of freezing and thawing, while the soil sample without any halloysite content lost 100% of its compressive strength after the same number of freezing and thawing. Based on the obtained results, the use of halloysite nanotubes in order to enhance the strength and durability of soft clay is strongly recommended.

Chitosan (CTS) functionalized Halloysite Nanotubes (HNT) have been used as receptive nano-supports for the grafting of copper (Cu) and laccase (Lac) for the degradation of chlorpyrifos. The developed nanocomposite Lac@Cu-CTS-HNT showed 83.4% Lac immobilization which was further characterized by TEM, SEM-EDX, FTIR, XRD, DSC and TGA. The chlorpyrifos degradation studies were performed under constant stirring for 24 h with both free enzyme and Lac@Cu-CTS-HNT and were analysed through HPLC. Percentage degradation of chlorpyrifos with the nanocomposite went as high as 97% for 50 μg/mL chlorpyrifos at neutral pH and room temperature. Variable pesticide and nanocomposite concentration, pH, and temperature studies for pesticide degradation were also performed, followed by reusability studies. The nanocomposite maintained its degradation ability at ~97% even at variable temperature and pH conditions. Reusability study was performed 5 times wherein the degradation percentage remained the same after 5 cycles (~95%). Degradation kinetics were also performed for the nanocomposite in the presence and absence of the immobilized enzyme. Through this study, it is suggested that Lac@Cu-CTS-HNT can be a potential nano-catalyst for the degradation of chlorpyrifos in aqueous environment.

A defective interphase section in polymer halloysite nanotubes (HNT) system is considered and the influences of required interfacial shear strength for effective stress conveying via interphase zone (τc) and interfacial shear strength (τc) on the effective interphase depth, effective filler amount and percolation onset are stated. Additionally, a novel model is progressed for the strength of nanocomposites after percolation onset assuming these terms. The calculations of the established model at numerous series of all factors are analyzed and several tentative facts for various examples are compared to model's estimations. The nanocomposite's strength reaches 75 MPa at τc = 10 MPa and HNT volume fraction of 0.03, but τc = 50 MPa cannot toughen the system at various HNT contents. τ = 30 MPa and HNT radius (R) = 60 nm cannot strengthen the nanocomposites, while τ = 100 MPa and R = 20 nm maximize the strength of system to 138 MPa. HNT length of 900 nm cannot reinforce the samples at various ranges of percolation onset, whereas the strength of nanocomposites grows to 200 MPa at HNT length of 3.1 μm and percolation onset of 0.002. These results are valuable to optimize the main factors yielding the tough nanocomposites.

This paper focuses on the role played by the clay minerals and microorganisms in the deterioration process of Coptic architecture units at the church of Virgin Mary, Wadi El-Natrun region. For this purpose building materials (mainly mortars and plasters) from the studied church were examined using X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), in order to identify their composition and were investigated petro-graphically to determine the real response of the masonry structure to the deformation imposed at the endogenous factors. Wall gypsum mortars in the church contain halloysite as a dominant clay mineral while plaster is clay free, concerning microorganisms, the fungal flora Aspergillus glaucus represent the most dominant fungi constituting (22.22%), Aspergillus flavus, Aspergillus flavus, Aspergillus fumigatus, Aspergillus occhraceus, and Aspergillus caudidus were also isolated.

The present study focused on the dynamic mechanical performance and thermal behavior of epoxy composites reinforced utilizing pristine halloysite nanotubes (HNTs). A comprehensive analysis was carried out on the viscoelastic behavior and structure–property relationship of neat and various HNTs-reinforced epoxy nanocomposites with varying weight percentage loading of pristine HNTs. FTIR, XRD, SEM, DSC, and TGA analyses were performed to characterize the composite samples. Storage modulus (E′), loss modulus (E″), frequency sweep, and damping factor (Tan δ) were studied as a function of temperature (30–120 °C) by DMA. Furthermore, temperature-dependent dynamic parameters were investigated at oscillation frequencies of 1, 25, and 50 Hz and correlated with DSC results. SEM analysis and Cole–Cole plot confirmed the homogeneity of HNTs in an epoxy matrix. Overall, HNTs imparted an improved viscoelastic behavior to the epoxy matrix at their optimized weight percentage loading of 2% featured to have a 48% rise in storage modulus (E′) and 135% rise in loss modulus (E″) at 40 °C. HNTs were found to have plasticizing effect for epoxy nanocomposites revealed from a slight decrease in their Tg. Thus, naturally occurring environmentally benign HNTs were found a promising reinforcing agent for tailoring viscoelastic behavior of epoxy matrix with low adverse physical effects as an efficient alternative to expensive carbon nanotubes (CNTs).

Halloysite nanotubes (HNTs) were incorporated into an EPDM/SBR rubber/styrene-butadiene rubber (SBR) composite by melt blending of HNTs into the EPDM/SBR blend. The mechanical properties, abrasion and swelling resistance of HNTs ranging from 2 parts per hundred rubber (phr) to 10 parts per hundred rubber (phr) were investigated in EPDM/SBR base rubber. Tensile strength, 100% modulus (modulus at 100 percent elongation), elongation at break and tear strength were evaluated at ambient temperature using electric universal tensile testing equipment in accordance with ASTM D-412. Hardness, abrasion and swelling resistance were determined using Shore-A Durometer, DIN abrader and immersion techniques, respectively. The results show that increasing HNT content increased tensile strength, tear strength, hardness (stiffness), and crosslink density. The surface morphology of tensile-fractured material was studied using field-emission scanning electron microscopy (FE-SEM). According to FE-SEM results, the most roughness of the surface was seen at HNTs filled rubber nano-composites.

The objective of this research was to comprehensively compare the effects of two different types of nanoclay, namely layered double hydroxide (LDH) and halloysite nanotube (HNT) on the physical, mechanical, and dynamic mechanical properties of compression-molded composite panels fabricated from reed flour (RF) and polyvinyl chloride (PVC). To achieve the desired properties in the composites, the clay nanoparticles were modified with surfactant (mLDH and mHNT) before usage. The results showed that the composite specimens with mLDH exhibited higher tensile and flexural properties (strength and moduli) than with mHNT at low content. Compared with the maximum flexural strength and tensile modulus of 21.56 MPa and 2186.16 MPa for the specimens made with mHNT, the highest flexural strength and tensile modulus were found in the specimens incorporated with mLDH (23.05 MPa and 2227.44 MPa). Moreover, at high content, the composite specimens with mHNT presented greater hydrophobicity. The comparative analysis exhibited that that the water uptake of the composites including mHNT (5.03%) was approximately 15% lower than that of the mLDH (5.73%) based composite. The DMTA results indicated that the composite specimens with mLDH demonstrated better molecular restriction and larger storage modulus than with mHNT. Besides, the loss-tangent (tan δ) peak was shifted to a higher temperature for the samples including both mLDH and mHNT than without ones. The specimens made with mLDH had the highest glass transition temperature values (70.67°C) compared with 70.12°C for the specimens treated with mHNT. Morphological observations showed that the nanoparticles were predominantly dispersed uniformly within the polymer matrix. Overall, it is found that the addition of 3 phc mLDH clay was the most effective in the composite formulation; it has significantly enhanced the properties of the wood-plastic composites.

Taking inspirations from nature, we endeavor to develop catalytically self-propelled nanojets from a type of tubular clay minerals, halloysite nanotubes (HNTs), and utilize them as catalysts targeted for catalysis where the traditional means of mechanical agitation cannot be implemented. Nanojets of Fe3O4@HNTs/Pt were prepared by impregnating platinum nanoparticles (Pt NPs) in lumens of HNTs and selective grafting of magnetite (Fe3O4) particles on the external surface. The HNT-based nanojets were validated to be highly suitable both in free bulk solution and in microfluidic flow. An example of Fenton degradation catalyzed by these jets was demonstrated. The powerful movement of Fe3O4@HNTs/Pt (368 ± 50 μm·s-1) fueled by 5.0% wt. H2O2 was found to follow a bubble propulsion mechanism, and the motion exhibits collective behavior as swarms. The clay tubes were for the first time observed to self-assemble into fish-like aggregates during swimming, reflecting natural occurrence of motion-evolution philosophy. Guided motion was realized by employing magnetic manipulation which makes jets feasible for reactors with complex microchannels/reactors.

In this study, halloysite nanotubes (HNTs) filler particles were treated in a basic solution with a pH of 11 for their better dispersion during incorporation in Pebax-1657 matrix by 1, 2, 5, 10, 15 wt.% loadings to prepare some HNTs-Pebax nanocomposite membranes. The treated HNTs were evaluated by XRD analysis and the prepared nanocomposite membranes were characterized by DSC, TGA, and FESEM analysis. Treatment of the HNTs in basic solution increased their porosity, pore volume, and specific surface area. CO2 adsorption capacity of the raw and the modified HNTs were measured as 45.7 and 48 mol/kg adsorbent and those of CH4 were evaluated as 34.6 and 32.4 mol/kg adsorbent, respectively. Gas permeation performance of the neat Pebax-1657 and the modified HNTs-Pebax nanocomposite membranes were investigated for CO2/CH4 separation. The 10 wt.% loaded raw HNTs membrane's CO2 permeability and ideal CO2/CH4 selectivity increased to 132.1 Barrer and 18.6 from those for the neat Pebax as 98.4 Barrer and 13.6 while those of 10 wt.% loaded modified HNTs were measured as 144.4 Barrer and 27.2, respectively. The modified HNTs-Pebax nanocomposite membranes’ separation performance considerably approached the Robeson upper bound limit of 2008.

The use, in veterinary practice, of a three-dimensional biopolymer matrix (based on chitosan, agarose, and gelatin and doped with halloysite nanotubes) as a vehicle for mesenchymal stem cells (MSCs) to repair bone defects is reported here. The nanocomposite, combined with allogenic adipose-derived stem cells, was suitable for the repair of bone defects in dogs when paired with standard surgery involving metal Kirshner wires. The absence of inflammatory reactions to biopolymer matrices with allogenic stem cells was revealed in the case of an animal prone to inflammatory and allergic reactions. In addition, positive dynamics in the fusion of chronic bone defects without rejection reactions was observed after using a biopolymer matrix with MSCs.

Industrial hydrogenation catalysts must be not only selective and active but also resistant to feedstock impurities, including water. We report the strategy of preparing catalytic core-shell nanoreactors based on hydrophobized aluminosilicate nanotubes loaded with ruthenium. The modification of halloysite with alkyltriethoxysilanes enhances hydrophobicity of the clay nanotubes (water contact angle up to 122°) and enables their selective loading with 4-nm ruthenium particles. Such a core-shell tubular nanoreactors provide shielding of active sites from deactivation by admixed water and prevent metal leaching. Produced mesoscale catalysts were active in the hydrogenation of aromatics both in organic and aqueous media at 80 °C and a hydrogen pressure of 3 MPa. Benzene hydrogenation in the biphasic system with water resulted in a complete conversion with 100 % selectivity to cyclohexane over halloysite modified by C18-triethoxysilane supported ruthenium catalyst with turnover frequency (TOF) of 4371 h−1. This catalytic system remained stable after ten cycles of benzene hydrogenation, providing 98 % conversion. The demonstrated synthetic strategy is promising for the design of industrial catalysts for the hydroprocessing water-containing organic feedstock and may be upscaled due to the abundant availability of halloysite clay nanotubes.

The paper comparatively assesses the physicochemical properties of natural aluminosilicate nanotubes (halloysite) provided by domestic (HNT-Ch) vs. foreign (HNT-A) manufacturers, as well as the catalytic activity of ruthenium catalysts synthesized therefrom. The composition, structure, and textural properties of the materials were measured by a combination of physicochemical methods, such as TEM, ED–XRF, low-temperature nitrogen adsorption/desorption, and H2–TPR. The activity of the synthetic catalysts was examined in benzene hydrogenation at 80°C and a hydrogen pressure of 3 MPa in both a hydrocarbon and aqueous–hydrocarbon system. The catalysts supported on HNT-Ch and HNT-A were found to have similar physicochemical properties and to exhibit high activity in benzene hydrogenation, both in the monophasic and biphasic systems, thus ensuring quantitative substrate conversion with 100% cyclohexane selectivity.

In the present work, halloysite nano-clay (HNTs) based hydrogel was fabricated and their efficiency for the removal of methylene blue dye was studied. The hydrogel films were prepared with varying amount of halloysite nano-clay via facile solution casting method. Effect of halloysite clay on adsorption performance of composite was investigated. The hydrophobic thermoplastic synthetic polymer, polylactic acid (PLA) was blended with hydrophilic polymer polyvinyl alcohol (PVA) and HNTs to synthesize hydrogels. Swelling behavior and antimicrobial efficiency was also evaluated. The halloysite incorporating films showed excellent antibacterial activity. Swelling capacity of hydrogel with increased halloysite content was reduced due to increased crosslinking among polymer chains. Halloysite incorporated hydrogel exhibited higher adsorption ability as compared to film comprising of only PVA and PLA and dye removal followed pseudo first order kinetics. Film with 0.03 g HNTs rapidly attained adsorption-desorption equilibria and removed the dye completely within 30 min. Results confirmed that synthesized film could be potentially used for the removal of cationic dye and fabricated hydrogel film have promising potential for wastewater treatment since a higher adsorption capacity was observed for halloysite nano-clay incorporated hydrogel.

In the current research, halloysite nanoclay was functionalized by 3-aminopropyltriethoxysilane to immobilize endoinulinase for the preparation of fructooligosaccharides (FOSs) from inulin. Response surface methodology (RSM) was used for optimization of immobilization technique onto halloysite nanoclay. Maximum enzyme activity yield (57.20%) and immobilization yield (67.15%) was achieved, under optimized conditions (3-aminopropyltriethoxysilane 1.50% (w/v), sonication time 3.50 h, coupling-time 2.00 h and enzyme load 55 IU). Immobilized endoinulinase shown a shift in both pH optima (pH 5.0) and temperature optima (60 °C) with broad pH (4.0–8.5) and temperature (50–70 °C) stability than its free form. An increase (13-fold) was recorded in half-life of enzyme after immobilization. An increase in Km and decrease in Vmax of endoinulinase for inulin was observed after immobilization. Hydrolytic conditions for inulin hydrolysis by immobilized endoinulinase were also optimized by RSM software. Under optimal conditions, viz. inulin concentration (7.0%), endoinulinase load (77 IU), agitation rate (100 rpm) and hydrolysis time (12 h), maximum FOSs yield (99.56%) was obtained. TLC chromatogram and densitogram analysis confirmed FOSs preparation contained 36.68% kestose, 27.34% nystose, 10.11% fructofuranosylnystose and 25.43% FOSs of DP 5–9. Immobilized biocatalyst retained half of its activity upto third batch cycle of FOSs production from inulin.

This work aimed to synthesise a magnetic photocatalyst based on Ag-TiO2 nanoparticles supported on Algerian Halloysite clay (HKDD3) loaded with magnetite Fe3O4 through a solvothermal method. The pr...

The chitosan/polyvinyl alcohol/halloysite nanoclay (CS/PVA/HNC) loaded with cephradine drug electrospun nanofibers (NFs) were fabricated and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) techniques. FTIR analysis confirmed the hydrogen bonding between the polymer chain and the developed siloxane linkages. SEM analysis revealed the formation of uniform NFs having beads free and smooth surface with an average diameter in 50–200 nm range. The thermal stability of the NFs was increased by increasing the HNC concentration. The antimicrobial activity was examined against Escherichia coli and staphylococcus strains and the NFs revealed auspicious antimicrobial potential. The drug release was studied at pH 7.4 (in PBS) at 37 °C. The drug release analysis showed that 90% of the drug was released from NFs in 2 h and 40 min. Hence, the prepared NFs could be used as a potential drug carrier and release in a control manner for biomedical application.

This paper illustrates the experimentation activities on rammed earth and nanotechnologies. The experimental research was carried out with the aim of improving the performance of rammed earth bricks with clay nanotubes, creating a ‘new material’ with reduced embodied energy and low CO2 emissions into the atmosphere. Specifically, the analysed performances are related to the compressive strength that expand their area of use as a building material.

Abstract The treatment of stone surfaces for their protection from ageing caused by natural and anthropogenic effects is an open issue in materials development for Cultural Heritage. We thought interesting to verify the suitability of a modified cellulose biofilm filled with halloysite nanotubes as wax compatibilizers to design a protecting layer. A hydraulic mortar was selected as a stone prototype. To improve the physico-chemical properties of the covering layer, wax microparticles have been incorporated to control transport, consolidation and wettability features. In particular, different application protocols have been studied, namely brushing and spraying, to assess whether the proposed procedures can be scaled up. Colorimetric analysis has been carried out to evidence the applicability in terms of color alteration after the treatment. Water adhesion was investigated by measuring the contact angle values as a function of time to obtain information on spreading and adsorption phenomena. These physico-chemical properties have been correlated to the microstructure evidenced by both electron and optical microscopies. Graphic abstract

For the first time, in this study, two novel glycogen-graphene oxide/halloysite nanotubes (GO-Gly/HNTs) and guar gum-graphene oxide/halloysite nanotubes (GO-GG/HNTs) nanocomposites were synthesized as the adsorbents for removal of Pb(II) from water, and the ionic liquid was used in the synthesis as a green solvent. According to the SEM, TEM, EDS, BET, zeta potential, FTIR, and XRD results, GO-Gly/HNTs and GO-GG/HNTs were synthesized successfully. Response surface methodology (RSM) was applied to optimize the experimental conditions. Nanocomposites followed the Langmuir equilibrium model and were best fitted to the pseudo-second-order model. According to the thermodynamic model, the adsorption process was endothermic. Due to several features, these two novel nanocomposites can be considered the proper candidate for Pb(II) removal from water and wastewater. First, these nanocomposites have good adsorption capacity for Pb(II) removal, which is 219 mg/g for GO-Gly/HNTs and 315 mg/g for GO-GG/HNTs. Moreover, nanocomposites can be recycled with proper adsorption capacity after four repeated cycles. These materials can be used to remove Pb(II) from water in the presence of other contaminants because nanocomposites have selective tendency toward Pb(II) in the presence of other pollutants such as Cd2+, Cu2+, Cr2+, and Co2+. In addition, the presence of Ca2+, Mg2+, Na+, and K+ improve Pb(II) removal. Finally, possible mechanisms for each nanocomposite were represented.

This work reported the one-pot synthesis of the promising, cheap and green heterogeneous nanocatalyst for biodiesel production. The halloysite nanotube (HNT) was impregnated with 40 wt% NaAlO2 (SA) and the assistance of ultrasonic helped to achieve a better and more stable modification. The resulting 0.4SA/HNTs-UI catalyst was applied in catalyzing the transesterification of palm oil with methanol, using a GA_BP neural network to train and predict the optimal values of reaction parameters. The test results proved the prediction accuracy of the model with R2 = 0.989. The catalyst possessed excellent performance, and the maximum biodiesel yield of 99.15% was achieved with the catalyst loaded amount of 8.82 wt%, methanol to oil molar ratio of 16.79 and transesterification temperature of 65.12 °C. Besides, the physicochemical properties of the purified transesterification product were in accordance with the ASTM D 6751 standard of biodiesel.

In the research, graphitic carbon nitride (g-C3N4) was synthesized using modified halloysite via a calcination method. The improvement of photocatalytic activity mainly benefits from the reduced e-/h+ pairs recombination rate, the improved electron separation yield. The photocatalytic activity of nanocomposite was evaluated through the Synozol red HF-6BN dye degradation, the degradation efficiency approached 99% after 30 mins irradiation under the solar light, and the performance is slightly reduced to 94 % after three consecutive tests. These results have demonstrated an effective method to synthesize g-C3N4 photocatalysts with nanostructures using crude clay minerals.

A facile approach of using halloysite nanotubes (HNTs) was proposed to address the durability performance demands of natural rubber (NR)/ethylene propylene diene monomer rubber (EPDM) blends and to protect them from the deleterious effects of the service environment including ozone, chemicals, abrasion, and cyclic loading. The introduction of HNTs substantially improved the stability of NR/EPDM when exposed to ozone (over fourfold enhancement with the addition of 5 phr HNTs). Moreover, the HNT-filled NR/EPDM vulcanizates offered approximately 66% reduction in the solvent-mediated swelling in comparison to the unfilled sample. Fatigue life studies showed that the HNT-reinforced NR/EPDM composite could withstand 30% more cycles to failure than the un-reinforced NR/EPDM blend. The effect of various HNT loading on the morphological, mechanical, physical, and rheological properties of nanocomposite vulcanizates based on NR/EPDM was also investigated. The morphological investigations revealed that the introduction of HNT into the NR/EPDM rubber matrix caused a rough morphology in fracture surface and a well-dispersed structure was obtained with the addition of up to 5 phr of HNTs. These findings were further supported by rheological, mechanical, and thermodynamical results.

There are few modeling papers on the mechanical behavior of halloysite nanotubes (HNT)-based system, which restrict the applications of these materials in advanced fields. In this paper, a model fo...

Despite all recent advances in medical treatments, infectious diseases remain dangerous. This has led to intensive scientific research on materials with antimicrobial properties. Silver nanoparticles (Ag-NPs) are a well-established solution in this area. The present work studied the nucleation of silver on halloysite substrates modified by chemical treatment with NaOH. The resulting stabilized Ag-NPs were characterized by X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The nucleation was characterized by thermogravimetric analysis and differential scanning calorimetry. The antimicrobial properties of the Ag-NPs were investigated against E. coli and S. aureus. The potential of the Ag-NPs for industrial application was tested by dispersing them into low-density polyethylene. The importance of the chemical affinity between matrix and additive was tested through coating the Ag-NPs with dodecanethiol, a non-polar surfactant. The resulting composites were characterized by scanning electron microscopy and in terms of surface antimicrobial activity. The results demonstrate that the Ag-NPs synthesized in this work are indeed antimicrobial, and that it is possible to imbue a polymeric matrix with the antimicrobial properties of Ag-NPs.

Composite materials of polyethylene terephthalate with silanized halloysite nanoclay were prepared and characterized. Halloysite was first functionalized with benzoyloxypropyltrimethoxysilane and then incorporated it into the polymer matrix via melt extrusion at 0.5, 1, and 2 wt% clay load ratios. The modified clay was characterized by means of elemental carbon quantification, thermogravimetric analysis, X-ray diffraction, and nitrogen adsorption–desorption. The silanization was confirmed to have taken place with an approximate reaction yield of 5%. While the silanization did not significantly affect the crystal structure or the morphological properties of the clay, a mass loss starting from 190 °C attributed to the organosilane compound used to modify the clay was observed in the reacted samples, along with increased thermal stability. The composite materials exhibited an increase in Young’s modulus and a decrease in the ultimate strain, but not a significant change in the oxygen permeability of the composites with respect to the neat PET. Graphical abstract

The primary concern of fiber-reinforced polymers (FRPs) subjected to seawater environment is losing their initial mechanical performance since water can diffuse into the composite and deteriorates the fiber-matrix interface. Recent studies related to aging performance in the seawater environment have shown that introducing halloysite nanotubes (HNTs) into the polymer matrix offers a combination of an efficient barrier effect and an improved fiber-matrix interface. Hereupon, the principal objective of this study was to experimentally investigate the impact of HNTs on shear and mode II fracture performances of the seawater aged basalt fiber (BF) reinforced epoxy (EP) composites. After six months of aging in seawater, the findings indicated that HNTs reinforced multi-scale composites exhibited 34 and 46% higher shear strength and mode II delamination toughness compared to the neat specimens. Moreover, according to the dynamic-mechanical analysis, higher glass transition temperatures (8%) were obtained for the multi-scale composites. The reduction in mechanical performances induced by fiber-matrix interfacial degradation was also confirmed by scanning electron microscopy analysis. Chemical deterioration of the polymer matrix was explored by Raman spectroscopy to reveal the efficiency of HNTs induced barrier effect. As a result of these investigations, HNT modified BF/EP multi-scale composites were offered for future advanced engineering applications.

In many porous catalyst supports, the accessibility of interior catalytic sites to reactant species could be restricted due to limitations of reactant transport through pores comparable to reactant dimensions. The interplay between reaction and diffusion in porous catalysts is defined through the Thiele modulus and the effectiveness factor, with diffusional restrictions leading to high Thiele moduli, reduced effectivess factors, and a reduction in the observed reaction rate. We demonstrate a method to integrate ceramic nanostraws into the interior of ordered mesoporous silica MCM-41 to mitigate diffusional restrictions. The nanostraws are the natural aluminosilicate tubular clay minerals known as halloysite. Such halloysite nanotubes (HNTs) have a lumen diameter of 15-30 nm, which is significantly larger than the 2-4 nm pores of MCM-41, thus facilitating entry and egress of larger molecules to the interior of the pellet. The method of integrating HNT nanostraws into MCM-41 is through a ship-in-a-bottle approach of synthesizing MCM-41 in the confined volume of an aerosol droplet that contains HNT nanotubes. The concept is applied to a system in which microcrystallites of Ni@ZSM-5 are incorporated into MCM-41. Using the liquid phase reduction of nitrophenol as a model reaction catalyzed by Ni@ZSM-5, we show that the insertion of HNT nanostraws into this composite leads to a 50% increase in the effectiveness factor. The process of integrating nanostraws into MCM-41 through the aerosol-assisted approach is a one-step facile method that complements traditional catalyst preparation techniques. The facile and scalable synthesis technique toward the mitigation of diffusional restrictions has implications to catalysis and separation technologies.

A novel 3D microsphere fabricated with halloysite nanotubes was reported in our previous work. The hollow tubular structure in nano-scale of halloysite and the hollow structure in micro-scale of microsphere have attracted our attention. In this paper, phase change materials (methylmyristate and n-dodecane) were loaded in the spaces for the construction of anti-icing surface, and the related behavior and mechanism were investigation. The anti-icing performance of slippery liquid-infused porous surfaces (SLIPSs) were characterized by ice adhesion strength, freezing temperature and ice nucleation rate. The results showed that the phase change materials loaded in anti-icing coating eliminated the possibility of water vapor condensation in porous structure, greatly reduced the probability of nucleation on a concave surface, thus showed better anti-icing effect. Phase change materials play an important role in supercooling, effectively increasing the substrate temperature by 5.4 °C. Phase change anti-icing coating is a kind of functional material with great development potential.

The main properties of halloysite, natural aluminosilicate nanotubes, are briefly considered in the review. Published data on the adsorption immobilization of proteins by halloysite and on catalytic properties of enzyme adsorption layers on the halloysite surface are analyzed and summarized. The results of authors’ studies dealing with physicochemical properties of halloysite samples are summarized. Data are given on the synthesis of zeolites, mesoporous molecular sieves, and nanotubes of silicon and aluminum oxides from halloysite. Possible pathways of halloysite synthesis under laboratory conditions are considered.