Functionalized Halloysite Nanotubes Research Articles

Effect of functionalized halloysite nanotubes on fire resistance and water tolerance of intumescent fire-retardant coatings for steel structures

To improve the comprehensive performance of intumescent fire-retardant coatings, the functionalized halloysite nanotubes (HNTs-D, HNTs@Fe3O4, and HNTs-D@Fe3O4) were synthesized as synergistic flame retardants and incorporated into intumescent fire-retardant coatings (IFRC) for steel structures, demonstrating significant flame retardant properties. Among these modified halloysite nanosheets, HNTs-D@Fe3O4 showed the best flame retardancy and water resistance. Adding the optimal addition amount (3 wt%) of HNTs-D@Fe3O4 can increase the residual weight of coating from 28.10 % to 38.40 % and reduce the backside temperature of the coated steel plate from 288 °C to 177 °C, indicating that HNTs-D@Fe3O4 can effectively improve the thermal stability and insulation performances of intumescent fire-retardant coatings. Cone calorimetric analysis showed HNTs-D@Fe3O4 can effectively suppress the heat and smoke release of the intumescent fire-retardant coatings. Compared with the unmodified coating sample, the total heat release (THR) and total smoke release (TSR) of the HNTs-D@Fe3O4-containing coating sample were reduced by 66.04 % and 11.36 %. HNTs-D@Fe3O4 facilitates the formation of dense char layers confirmed by the micro morphology characterization. Further mechanism analysis shows that HNTs-D@Fe3O4 has obvious catalytic carbonization effect and is helpful to construct the dense expanded char layer with higher graphitization degree. The uniformly dispersed HNTs-D@Fe3O4 improved the water resistance of intumescent fire-retardant coatings, which is mainly due to the hydrophobicity and barrier effect, thus effectively preventing the loss of water-soluble components.

Polyhydroxybutyrate/poly(ε‐caprolactone)‐based electrospun membranes loaded with amoxicillin‐potassium clavulanate halloysite nanotubes for biomedical applications

AbstractBiopolymers exhibit distinct properties for biomedical applications. Different biopolymer classes are utilized for various applications, for example antibacterial properties, drug delivery, tissue engineering, tissue scaffolds etc. In the present investigation, a nano‐bioengineering approach was followed to prepare polyhydroxybutyrate and polycaprolactone polymer‐based drug‐loaded halloysite nanotube electrospun membranes for biomedical applications. Functionalized halloysite nanotubes ((3‐aminopropyl)triethoxysilane acid treated halloysite nanotubes) at different weight percentages (1, 3, 5 and 7 wt%) were loaded with a broad‐spectrum antibiotic amoxicillin trihydrate‐potassium clavulanate, incorporated into the electrospun membranes, and characterized by different techniques such as XRD, FTIR, SEM, TEM and TGA. Different physical and mechanical properties were evaluated, such as porosity, water uptake, water vapor transmission rate, wettability and tensile properties. The developed membranes exhibited good in vitro biological properties, for example antibacterial, effective cell migration and less toxicity, as confirmed by disk diffusion, MTT (3‐(4,5‐dimethylthiazolyl‐2)‐2,5‐diphenyltetrazolium bromide) and cell scratch assays. A sustained drug release profile was observed from all the developed membranes. Overall results on the characterization of the developed membranes confirm the suitability of their use for different biomedical applications and as a wound dressing application. © 2024 Society of Chemical Industry.

Dopamine hydrochloride and L-arginine Co-functionalized halloysite nanotubes for modification of polyethersulfone ultrafiltration membrane with improved separation performance

In recent years, a range of high-performance ultrafiltration membranes have been developed, but maintaining high retention without sacrificing high throughput remains a serious challenge. In this paper, functionalized halloysite nanotubes is constructed by copolymerization and by a one-step reaction of L-arginine and dopamine hydrochloride using halloysite nanotubes as carriers. Subsequently, modified polyethersulfone membranes are prepared by blending them as additives through non-solvent-induced phase transition separation. As the synthesized nanofillers is rich in functional groups, negative electronegativity, and unique structures, the study focuses on adding nanofillers’ effect on the membrane structure and physicochemical properties. The addition of appropriate nanofillers enhances the membrane surface wettability and negative electronegativity, and the enlarged internal pores and the dense layer that remains flat and homogeneous effectively promote the flux of small molecules, the retention of large molecules, and the cyclic stability of the membrane. The prepared polyethersulfone membranes demonstrate exceptional cycle stability, high separation efficiency (almost 100 % for Congo red), and significantly improved permeation performance (initial permeate flux up to 316.5 L m-2h−1). The results demonstrate the high potential of the modified prepared polyethersulfone membranes for pertinent environmental separation processes.

Silicotungstic acid catalyst supported onto functionalized halloysite nanotubes (HNTs) utilized for the production of 5-hydroxymethylfurfural (5-HMF) from fructose

5-Hydroxymethylfurfural (5-HMF) is a valuable organic compound commonly derived from sugars such as fructose and glucose. Silicotungstic acid (HSiW), a unique Keggin-type heteropolyacid, is a typical catalyst for organic compound production. To synthesize 5-HMF from fructose, we developed a novel catalyst, HSiW@F-HNTs, by combining HSiW and functionalized halloysite nanotubes (F-HNTs) modified with (3-amino-propyl) triethoxysilane (APTES), 2,4,6-trichloro-1,3,5-triazine (TCT), and l-arginine. We analyzed the physicochemical properties of HSiW@F-HNTs using the FT-IR, XRD, BET, FESEM, EDS, and XPS characterization techniques, confirming their suitability for fructose-to-5-HMF conversion. Through response surface methodology (RSM), we investigated and optimized the effects of reaction conditions on 5-HMF production yield. Optimal conditions were found to be a 102 °C reaction temperature, a 65 min reaction time, and an 8.5 wt.% catalyst loading, resulting in a 95 % yield of fructose-to-5-HMF conversion. We also conducted the kinetic and thermodynamic analyses to determine the reaction rate and activation energy (Ea) and estimate the changes in Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) of the catalytic conversion reaction. Additionally, the prepared HSiW@F-HNTs catalyst could be recycled up to 9 times without a significant loss in activity, demonstrating its high stability for real-world applications.

Pesticide Nanoformulations Based on Sunlight-Activated Controlled Release of Abamectin.

A controlled release system that enables the sunlight-triggered release of a model agrochemical, abamectin (abm), is presented. The release system consists of polydopamine functionalized halloysite nanotubes (HNT-PDA) utilized as photothermal nanocarriers to encapsulate 25 wt % abm and 37 wt % lauric acid (LA), a phase change material, that acts as a heat-activable gatekeeper stopping or facilitating the abm release. When exposed to sunlight for 20 min at 1 and 3 sun light density, the temperature of the photothermal nanocarriers reaches 51 and 122 °C, respectively, which triggers the melting of LA and the consequent release of abm from the nanocarriers. Abm was shown to be released gradually over a period of 10 days when nanohybrids were exposed to sunlight for 6 h per day and to remain stable and kill Myzus persicae (Sulzer) (Hemiptera: Aphididae), green peach aphids, at a mortality rate of over 70% for at least 10 days. Aqueous dispersions of the LA/abm@HNT-PDA nanohybrids were studied in terms of their potential as aqueous sprayable pesticide nanoformulations and presented over 30% suspensibility, 36 mg/cm2 foliar retention, strong rainwater resistance, and a 50% mortality rate for M. persicae at a concentration of 9 mg/mL. The proposed sunlight-activated controlled release system based on photothermal, LA-functionalized HNT-PDA nanocarriers holds great potential as controlled release pesticide nanoformulations.

Highly carboxylate functionalized halloysite nanotube as an efficient and recyclable adsorbent for methylene blue

Halloysite nanotubes (Hal) have drawn intensive attentions because of their unique nanotubular structure and large surface area. However, limited adsorption capacity and poor recyclability severely impeded their practical application for water remediation. Herein, to overcome the deficiencies of pristine Hal, we deliberately designed and prepared a series of anhydride and carboxylate functionalized Hal (Hal@PDM-COO−) via self-stabilized precipitation polymerization. Owing to the merits of both nanotubular structure of Hal and high-density carboxylate ions in the shell layer, the Hal@PDM-COO− possessed a remarkable pH-dependent adsorption performance towards methylene blue (b-MB). As the solution pH increased from 3 to 11, the sorption capacity increased remarkably from 179.1 to 459.1 mg/g. Furthermore, all sorption processes were better-fitted with pseudo-second-order and Langmuir models, exhibiting a maximum sorption amount of 302.1 mg/g at pH = 7. These results indicate that electrostatic attraction between positive b-MB molecules and negative carboxylate groups plays a dominant role during sorption process, and carboxylate groups distribute homogeneously in the shell layer of Hal@PDM-COO−. More importantly, Hal@PDM-COO− possessed outstanding recyclability, and the removal rate of b-MB kept >95% after five recycle runs. Considering the highly enhanced adsorption capacity, rapid adsorption rate and excellent reusability, the Hal@PDM-COO− showed significant potential for wastewater treatment.

3D printing polypropylene composites reinforced with functionalized halloysite: Balance between stiffness and impact resistance

AbstractIn this work, a new nano‐reinforced polypropylene filament was produced and fabricated by 3D printing to create a nanocomposite with a good balance between stiffness and impact resistance properties. Nanocomposite filament with 0.5, 1.0, and 1.5 wt% of functionalized halloysite nanotubes was prepared. The chemical modification was carried out to obtain a reinforcement that could act as an improved β‐nucleating agent and characterized by infrared spectroscopy. The spectrum showed the appearance of two new bands at 1571 and 1410 cm−1, which could indicate an interaction between the pimelic acid molecules and the oxygenated surface of the halloysite nanotubes. Energy dispersive X‐ray spectroscopy analysis confirmed a good dispersion of the modified reinforcement along the surface of the nanocomposite filament. Wide‐angle X‐ray scattering and differential scanning calorimetry analyses showed the improvement of the β‐nucleating ability of the halloysite nanotubes through new chemically functionalized, obtaining percentages of β‐crystal of 80% for the nanocomposite reinforced with 0.5 wt%. The dynamic mechanical analysis showed that the 3D‐printed functionalized nanocomposites presented higher storage and loss modulus (an increase of 148% and 122%, respectively). Finally, the impact strength properties increased by 90%, 108%, and 21% for the functionalized nanocomposites with 0.5, 1.0, and 1.5 wt%, respectively.Highlights Chemical functionalization of a natural reinforcement as a ‐nucleating agent. 3D printing polypropylene nanocomposites with enhanced properties. Good balance between impact and stiffness properties of nanocomposites.

Quantitative XPS analysis of amine-terminated dendritic functionalized halloysite nanotubes decorated on PAN nanofibrous membrane and adsorption/filtration of Cr(VI)

Quantitative XPS analysis of the active functional groups on the surface of nanofiber membranes is an important issue for evaluating the potential efficiency of the membranes in removing heavy metals from aqueous solutions. This research is developing a novel composite nanofiber for accessibility adsorption groups on the surface of the electrospun membrane for effective removal of Cr(VI). For this purpose, three generations (G1, G2, and G3) of poly(amidoamine) dendrimers (PAMAM) were grafted onto the surface of halloysite nanotubes (HNTs). Functionalized HNTs (F-HNTs) were decorated on the surface of polyacrylonitrile (PAN) nanofiber layers in different ratios by simultaneous electrospinning and electrospraying techniques. The results showed that the decoration with F-HNTs made the surface of the membranes superhydrophilic. The removal efficiency of the optimal sample with 10 % third-generation F-HNTs (PAN/HNTs-G3-10 %) reached 96 % within 5 min. The mechanism for the removal of Cr(VI) ions in the PAN/HNTs-G3-10 % membrane was electrostatic interaction, chelation, and reduction. X-ray photoelectron spectrometer (XPS) analysis was used to characterize the quantitative and qualitative correlation dependencies between the removal of Cr(VI) and the amine functional groups of different generations decorated onto the electrospun layer. Quantitative analysis of the amine-terminated dendritic groups has revealed that the percentage of Cr(VI) removal is proportional to the number of terminal amine groups. Furthermore, PAN/HNTs-G2 and PAN/HNTs-G3 composite nanofiber membranes showed significantly lower leachability of nanoparticles and higher mechanical strength compared to other membranes due to the formation of ionic bonds between the amine-terminated dendritic of HNTs-G2 and HNTs-G3 and the cyanide groups of PAN. Effects of competing heavy metal ions on Cr(VI) adsorption follow the order of Zn(II) > Cu(II) > Ni(II).

Synthesis of polypyrrole (PPY) functionalized halloysite nanotubes (HNTs): An electrochemical sensor for ibuprofen

Over-the-counter availability of non-steroidal anti-inflammatory drugs (NSAIDs) without prescription, for medicinal use has led to abuse in accidental and intentional suicides. In this context, the present study accentuates on the development of simple and reliable electrochemical sensor based on the HNTs coated with in-situ polymerized polypyrrole (HNT/PPY) for detection of ibuprofen (IBP). Surface functionalization of HNTs with PPY increased the electron rich centres on the electrode surface with an evident ∼8 fold increase in electrochemical active surface area (EASA) as compared to bare electrode, facilitating electron transfer rate. The analytical and electrochemical characterization of the sensor was carried out with TEM, EDX-mapping, FTIR, XPS, XRD, CV and DPV. The proposed sensor exhibited a sensitive response towards oxidation of IBP with linear dynamic range (LDR) of 0.1–100 µM and offers a fairly good limit of detection (LOD) of 0.9 µM. The practical utility of the sensor was tested for real time detection of IBP from biological matrix (urine). Sensitive, selective and stable response of HNT/PPY towards electrochemical oxidation of IBP suggested it is a promising platform for IBP detection and can be used in forensic field and clinical set ups.

Fluorinated‐polyhedral oligomeric silsesquioxane (F‐POSS) functionalized halloysite nanotubes (HNTs) as an antifouling additive for epoxy resin

AbstractAntifouling epoxy resin serves as a member of advanced nanocomposite coatings and engineered surfaces. Nevertheless, developing an antifouling epoxy composites is a state‐of‐the‐art technology. Herein, a complex nanostructure is tailored to be served as an advanced additive giving the antifouling characteristics to the epoxy resin. F‐POSS@HNT hybrid nanostructure, that is, halloysite nanotubes (HNTs) decorated with fluorinated polyhedral oligomericsil sesquioxane (F‐POSS), was synthesized and characterized. Chemical structure changes, thermal stability and morphology of hydroxylated HNTs (hHNTs) intermediate and F‐POSS@HNT ultimate nanostructures were analyzed by FTIR spectroscopy, TGA and TEM, respectively. The F‐POSS@HNTs catalyzed the epoxy‐amine crosslinking reaction, taking “Good” or “Excellent” crosslinking tags an quantified by the “Cure Index.” The apparent activation energy values were calculated for the epoxy (reference), epoxy/hHNTs, and epoxy/F‐POSS@HNTs systems (26, 51, and 47 kJ mol−1, respectively). Contact angle measurements were performed via dynamic tests demonstrating improved hydro‐ and oleophobicity of the thermoset composites. The advancing contact angle with diiodomethane increased 36% and 30% for nanocomposites containing 5 and 10 wt.% of the developed hybrid nanostructure, respectively, compared with the neat epoxy. Likewise, 54% and 67% reduction in paraffin fouling in the same order confirmed their antifouling ability. Regarding self‐cleaning characteristics, 24% and 33% surface recovery were observed, respectively.Highlights Antifouling surface was achieved in epoxy thermoset nanocomposites for potential industrial applications. Self‐cleaning behavior correlated with low wetting and antifouling properties. F‐POSS@HNT nanofillers were synthesized and successfully added to epoxy matrix. Both hHNT and F‐POSS@HNT showed a beneficial autocatalytic effect on epoxy‐amine reaction yielding satisfactory polymer crosslinking. Activation energy was reduced by incorporating F‐POSS@HNT compared with hHNT, signature of facilitated crosslinking.

Exploring the effect of one-dimensional halloysite based bionanocomposite hydrogel for bone regeneration

Bone disorders are a significant public health issue with detrimental social and economic effects. Bone-related disorders are on the rise, and they are mostly associated with ageing, an unhealthy lifestyle, and bio-medical conditions like osteoporosis and bone cancer that led to bone loss and/or decay. Fortunately, intriguing hydrogels are considered one of the most promising options for bone regeneration due to their distinct 3D network structure and high aqueous content and functional capabilities. In the current study, functionalized halloysite nanotubes (fHNT) were prepared and were subsequently trapped in sodium alginate/hydroxyapatite to provide a fascinating hydrogel with bone regeneration properties. FTIR and XRD were used to characterize the synthesized hydrogels and their swelling ratio was investigated by immersing them in phosphate buffer solution. Field emission scanning electron microscopy (FESEM) analysis of the fabricated material revealed dense, layered-like patterns of the hydrogel. The thermal properties of the hydrogel reinforced with halloysite nanotubes were significantly improved. The contact angle was evaluated to discover if the hydrogel was hydrophilic or hydrophobic. The antimicrobial efficiency of hydrogel was tested using both gram-positive and gram-negative bacteria, and the outcome revealed that hydrogel had maintained its good antibacterial activity. The hemolysis assay revealed that the fabricated hydrogels are hemocompatible in nature. Moreover, osteoblast-like cells (MG-63) were used to investigate how cells interact with hydrogel. Also, hydrogel exhibited excellent attachment and proliferation of human osteoblast like cells (MG-63) on 9 days of culture period. The findings suggested that this combination of materials in the fabricated hydrogels will play a promising role in bone regeneration.

Hierarchical 3D architecture NiCo–layered double hydroxide decorated functionalized halloysite nanotubes composite. An efficient electrocatalyst for ractopamine detection

As a nutrient partitioning agent and a growth stimulator, ractopamine (RCT) enhances the feed efficiency in animal-based food products and further it is employed clinically in certain pharmaceuticals. Subsequently, metabolites of RCT have long shelf life in animals associated with deleterious repercussions in humans. It is thus, vital to develop an effective design for screening method towards RCT detection to ensure human health, food and environmental safety. Thus, we present an integrate electrocatalyst hydrothermally designed by employing NiCo–LDH (NiCo- Layered Double Hydroxides) and F-HNT (functionalized- Halloysite nanotubes) and further utilized in the electrochemical sensing of RCT. The novelty of the present work shed light upon the unique assembly of the two individual NiCo–LDH and F-HNT components with superior structural features that resulted in a hybrid matrix. The outcomes of CV and i-t analysis under optimum conditions demonstrate outstanding electrochemical performance of the NiCo–LDH/F-HNT modified GCE sensor with a wide linear range 0.003–631 μM and low detection limit 1.1 nM, enhanced selectivity towards the detection of RCT. The uniquely engineered electrode material has therefore been applied to quantitate RCT levels in real-world samples in terms of practical applications.

Surface engineering of halloysite with graphene oxide via primary and secondary forces, characterizations, and electrokinetic properties

The functionalization of halloysite nanotubes (HNT) with graphene oxide (GO) can improve the electroactive smart behaviors such as electrorheology, which is the fibrillation of dispersed particles inside an insulating oil under externally applied electric field. Therefore, it is important to reveal electrokinetic properties of HNT/GO composites in aqueous and non-aqueous media. In this study, two types of composites, (HNT/GO)PF and (HNT/GO)SF, were prepared by the modification of HNT surfaces with GO through different molecular interactions namely: primary and secondary forces. Their differences were illuminated by series of techniques such as DLS, ATR-FTIR, Raman, XPS, XRD, SEM-EDX, TEM, and TGA analyses. Further electrokinetic studies in aqueous media were carried out to expose the changes in the surface charges by measuring zeta (ζ) − potentials under different pH, electrolytes, surfactants, and temperature conditions. The results revealed that the surfaces of HNT/GO composites are dominated characteristically with GO and HNT for (HNT/GO)PF and (HNT/GO)SF, respectively. The ζ − potentials, electrophoretic mobilities and conductivities of the composites in aqueous and non-aqueous media were also studied to identify the dispersed particles behaviors. The results exhibited that the electric field induced electroactive behaviors might differentiate in dispersions due to the higher electrophoretic mobility of (HNT/GO)PF and the higher conductivity of (HNT/GO)SF.

Functionalized Halloysite Nanotubes as Potential Drug Carriers

The aim of the work was to examine the possibility of using modified halloysite nanotubes as a gentamicin carrier and to determine the usefulness of the modification in terms of the effect on the amount of the drug attached, its release time, but also on the biocidal properties of the carriers. In order to fully examine the halloysite in terms of the possibility of gentamicin incorporating, a number of modifications of the native halloysite were carried out prior to gentamicin intercalation with the use of sodium alkali, sulfuric and phosphoric acids, curcumin and the process of delamination of nanotubes (expanded halloysite) with ammonium persulfate in sulfuric acid. Gentamicin was added to unmodified and modified halloysite in an amount corresponding to the cation exchange capacity of pure halloysite from the Polish Dunino deposit, which was the reference sample for all modified carriers. The obtained materials were tested to determine the effect of surface modification and their interaction with the introduced antibiotic on the biological activity of the carrier, kinetics of drug release, as well as on the antibacterial activity against Escherichia coli Gram-negative bacteria (reference strain). For all materials, structural changes were examined using infrared spectroscopy (FTIR) and X-ray diffraction (XRD); thermal differential scanning calorimetry with thermogravimetric analysis (DSC/TG) was performed as well. The samples were also observed for morphological changes after modification and drug activation by transmission electron microscopy (TEM). The conducted tests clearly show that all samples of halloysite intercalated with gentamicin showed high antibacterial activity, with the highest antibacterial activity for the sample modified with sodium hydroxide and intercalated with the drug. It was found that the type of halloysite surface modification has a significant effect on the amount of gentamicin intercalated and then released into the surrounding environment but does not significantly affect its ability to further influence drug release over time. The highest amount of drug released among all intercalated samples was recorded for halloysite modified with ammonium persulfate (real loading efficiency above 11%), for which high antibacterial activity was found after surface modification, before drug intercalation. It is also worth noting that intrinsic antibacterial activity was found for non-drug-intercalated materials after surface functionalization with phosphoric acid (V) and ammonium persulfate in the presence of sulfuric acid (V).

Designing Hybrid Lanthanum Stannate/Functionalized Halloysite Nanotubes as Electrode Material for Electrochemical Detection of 4-(Methylamino)phenol (Metol) in Environmental Samples

Electrochemical applications such as electrical conductivity, sensitivity, selectivity, cost-effectiveness, and sampling techniques of different forms of pyrochlore oxide have been a field of current interest. In this regard, pyrochlore structured lanthanum stannate nanoparticles (LSO) decorated with functionalized halloysite nanotubes (f-HNT) were prepared via hydrothermal followed by sonochemical synthesis. The obtained samples were characterized through various spectroscopic and microscopic methods to investigate the LSO@f-HNT structure and morphology. Electrocatalytic studies of LSO@f-HNT were performed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The beneficial response of LSO interacting with the hollow structured f-HNT groups of aluminol (Al–OH) and siloxane (Si–O–Si) enhances the electron transmission channel and active site size, both of which contribute to improved electrocatalytic performance. The fabricated sustainable LSO@f-HNT electrocatalyst exhibits outstanding selectivity and linear range (0.01–480 μM) with a detection limit of 2.1 nM and produces good recovery results (97.8–99.68%) under the optimized measurement conditions. This study discusses the design of the LSO@f-HNT composite and its application as an electrode material for the sensitive and focused electrochemical detection of hazardous Metol. This research demonstrates that LSO and f-HNT (LSO@f-HNT) is an excellent electrode material for electrochemical detection of Metol in real-world samples.

Construction of Biomass Tea Polyphenol-Functionalized Halloysite Nanotubes Enabling Green and Sustained-Release Antioxidants for Highly Antiaging Elastomers

The strategy of using sustainable biomass resources instead of traditional petrochemical products has been established as an environmentally friendly way to achieve the “green rubber” industry. Meanwhile, rubber antioxidants possessing high efficiency, long-lasting protection, migration resistance, and green multifunctional properties have attracted intensive investigation for rubber protection. Herein, a naturally extracted substance of tea polyphenol (TP)-functionalized halloysite nanotubes (HNTs), which generates the slow release of free-radical capturing activity and excellent interfacial interaction in the natural rubber matrix, is fabricated by vacuum-pumping and surface-decorating methods (denoted as HNTs-s-TP). Interestingly, the nontoxic and natural antioxidant HNTs-s-TP exhibited remarkable thermo-oxidative aging resistance and stability in a natural rubber (NR) matrix compared to that of TP directly pumped into the tubes due to the further modification of the chemical anchor TP on the outer surface of HNTs. In addition, we have systematically investigated the mechanism for highly efficient and sustainable antioxidation in the rubber matrix via the natural antioxidant HNTs-s-TP derived from the constructed galloyl structure. We envision that this new natural antioxidant fabrication technology will provide significant insights into the innovation for the construction of green and eco-friendly functionalized rubber additives.

Incorporation of Functionalized Halloysite Nanotubes (HNTs) into Thin-Film Nanocomposite (TFN) Nanofiltration Membranes for Water Softening

Incorporating nanoparticles (NPs) into the selective layer of thin-film composite (TFC) membranes is a common approach to improve the performance of the resulting thin-film nanocomposite (TFN) membranes. The main challenge in this approach is the leaching out of NPs during membrane operation. Halloysite nanotubes (HNTs) modified with the first generation of poly(amidoamine) (PAMAM) dendrimers (G1) have shown excellent stability in the PA layer of TFN reverse-osmosis (RO) membranes. This study explores, for the first time, using these NPs to improve the properties of TFN nanofiltration (NF) membranes. Membrane performance was evaluated in a cross-flow nanofiltration (NF) system using 3000 ppm aqueous solutions of MgCl2, Na2SO4 and NaCl, respectively, as feed at 10 bar and ambient temperature. All membranes showed high rejection of Na2SO4 (around 97-98%) and low NaCl rejection, with the corresponding water fluxes greater than 100 L m-2 h-1. The rejection of MgCl2 (ranging from 82 to 90%) was less than that for Na2SO4. However, our values are much greater than those reported in the literature for other TFN membranes. The remarkable rejection of MgCl2 is attributed to positively charged HNT-G1 nanoparticles incorporated in the selective polyamide (PA) layer of the TFN membranes.

Triazine diphosphonium tetrachloroferrate ionic liquid immobilized on functionalized halloysite nanotubes as an efficient and reusable catalyst for the synthesis of mono-, bis- and tris-benzothiazoles.

Aminopropyl-1,3,5-triazine-2,4-diphosphonium tetrachloroferrate immobilized on halloysite nanotubes [(APTDP)(FeCl4)2@HNT] was prepared and fully characterized using different techniques such as FT-IR, thermogravimetric analysis (TGA), SEM/EDX, elemental mapping, TEM, ICP-OES, and elemental analysis (EA). This nanocatalyst was found to be highly effective for synthesis of various benzothiazole derivatives in excellent yields under solvent-free conditions. Furthermore, bis- and tris-benzothiazoles were smoothly synthesized from dinitrile and trinitrile in the presence of this catalytic system. High yields and purity, easy work up procedure, high catalytic activity (high TON and TOF) and easy recovery and reusability of the catalyst make this method a useful and important addition to the present methodologies for preparation of these vital heterocyclic compounds.

Functionalized Halloysite Nanotubes and Graphene Oxide Nanosheets Fillers Incorporated in UF Membranes for Oil/Water Separation

Functionalized Halloysite Nanotubes and Graphene Oxide Nanosheets Fillers Incorporated in UF Membranes for Oil/Water Separation

Functionalized halloysite nanotubes endowing epoxy resin with simultaneously enhanced flame retardancy and mechanical properties

In order to impart epoxy resin (EP) with desired flame retardancy, thermal stability and mechanical properties, a novel flame retardant HNT@PZM@Fe(OH)3 with hierarchical core–shell-dot structure was successfully constructed in this work. The shell layer composed of polyphosphazene (PZM) effectively facilitated the interface interaction between halloysite nanotube (HNT) and polymer matrix, and significantly reinforced the EP nanocomposites (26.6 % increase in tensile strength and 31.5 % increase in impact strength when introduced with 5 wt% HNT@PZM@Fe(OH)3). Owing to the interfacial catalysis of transition metal compounds and barrier effect of HNT, EP/HNT@PZM@Fe(OH)3 performed remarkably in flame retardancy and smoke suppression. Upon the incorporation of 5 wt% HNT@PZM@Fe(OH)3, EP nanocomposites possessed the limiting oxygen index (LOI) of 30.8 %, reaching UL-94 V-0 rating. Cone calorimeter tests proved a distinct fall in the peak of heat release rate (PHRR) and smoke production rate (SPR) of EP/5HNT@PZM@Fe(OH)3, being respectively 65.8 % and 57.1 % compared to EP. The relevant tests revealed that the interfacial charring catalysis of transition metal oxides was beneficial to the formation of residual char structure with higher graphitization degree, which further improved the fire safety. Our work has provided aresearch basisand promising prospect for the production of high-efficient flame retardant EP nanocomposites.