Attapulgite Nanofibers Research Articles

Tribological behaviors of an attapulgite-graphene nanocomposite as an additive for mineral lubricating oil.

In this work, an attapulgite-graphene nanocomposite was prepared. The tribological properties of the prepared attapulgite-graphene nanocomposite as an additive for 200SN mineral lubricating oil were investigated using an SRV-IV tribometer through ball-on-disk contact mode for the first time. The characterization of the prepared nanocomposite indicated that attapulgite nanofibers are enveloped by the graphene nanosheets and present fine combination. The tribological test results show that the friction-reducing and antiwear properties of 200SN were obviously improved by adding the attapulgite-graphene nanocomposite. Through the characterization and analysis of the worn surface and cross-section, it was found that a tribofilm composed of Fe, Fe3O4, FeO, Fe2O3, FeOOH, graphite, graphene, SiO2 and organic compounds was formed on the worn surface. Furthermore, the bonding between the tribofilm and steel matrix is tight. The tribofilm and lubricating oil achieve a solid-liquid coupling lubrication effect, which is responsible for the improvement of the friction-reducing and antiwear properties.

In situ self-exsolved ultrasmall Fe2P quantum dots from attapulgite nanofibers as superior cocatalysts for solar hydrogen evolution.

Developing highly active, stable, and cost-efficient cocatalysts for photocatalytic H2 evolution is pivotal in the area of renewable energy conversion. Herein, we present a straightforward, low-temperature phosphidation strategy for in situ exsolving doped Fe ions from natural attapulgite (ATP) nanofibers into a supported Fe2P cocatalyst for the photocatalytic H2 evolution reaction (HER). The resulting Fe2P QDs/ATP features highly dispersed Fe2P QDs with an average size of <2 nm and a strong interfacial interaction between self-exsolved Fe2P QDs and the ATP substrate, thus providing ample and stable active sites for the photocatalytic HER. When employed as a cocatalyst, Fe2P QDs/ATP exhibits superior catalytic activity and notable stability in a molecular system with low-cost xanthene dyes as the photosensitizer under visible light irradiation. More importantly, Fe2P QDs/ATP can also efficiently and stably catalyze the photocatalytic HER when simply combined with various semiconductor photocatalysts (g-C3N4, TiO2, and CdS). This strategy of exsolving transition metal ions from substrates is an effective yet simple approach for the development of highly active supported HER cocatalysts for renewable and clean energy conversion.

Preparation of oriented attapulgite nanofibers using evaporation induced self-assembly

Aligned nanofibers have great application prospects in the field of electron transport and separation. In this work, a nano-attapulgite-based alignment technique was developed. The suspension was prepared from nano attapulgite (ATP), and polystyrene sulfonate sodium (PSS) was introduced to promote the dispersion and stability of ATP. The PSS can adjust the zeta potential of ATP from − 15 to − 50 mV. And the molecular dynamics results also showed that the appropriate PSS can increase the repulsion between ATP by 1.1 × 104 KJ·mol−1. Then ATP layer on the glass substrate was prepared by drop coating and induced evaporation. The results showed that the stability of the suspension played a decisive role in the alignment effect of ATP. ATP would be aligned from the three-phase contact line of air, suspension and substrate, and the width of the alignment interval can reach 1.2 mm, when the content of ATP and PSS was 2 mg·mL−1 and 1 mg·mL−1, respectively. On this basis, an improved alignment technique called “restricted evaporation” was proposed. The three-phase line was pinned many times during the restricted evaporation process, which was beneficial to the alignment of ATP, and the directional alignment interval can be increased to about 20 mm.

Carbon fiber modified by attapulgite for preparing ultra‐high molecular weight polyethylene composite with enhanced thermal, mechanical, and tribological properties

AbstractThe attapulgite nanofibers (ATP) were grafted on the surface of carbon fibers (CF) by polyetherimide (PEI) with long chain to reinforce the thermal, mechanical properties, and fretting wear resistance of ultra‐high molecular weight polyethylene. The results showed that the surface roughness of CF modified by ATP nanofibers were highly increased. Meanwhile, the thermal, mechanical, and tribological properties of the ATP‐PEI‐CF/UPE composite were significantly improved, especially the enhancement in heat distortion temperature, compressive modulus, and wear resistance. The improvement mechanisms of the corresponding properties were mainly attributed to the increase of mechanical interlocking of the matrix and the hybrid fillers, which could not only transfer the load and heat applied to the matrix to the fibers, but also impede the friction damage of the matrix during fretting wear process.

Ball Milling Medium May Tune the Self-Curing Property and Root Canal Microleakage of β-Dicalcium Silicate-Based Cement.

It is still a challenge to overcome the extended setting process of pure Ca-silicate as root canal fillers. We investigated the effects of attapulgite (a basic hydrous silicate of magnesium and aluminum) and ball-milling liquid medium on the self-curing properties of conventional β-dicalcium silicate (C2Si)-based cements. It was shown that a minor amount of attapulgite nanofibers (1–4%) had only a slight influence on setting time but caused a large increase in compressive resistance and structural stability. In particular, the ball milling media with different acetone/water ratios (3:0, 2:1, 1:2, 0:3) could directly influence the particle size distribution of C2Si powders, and the co-existence of liquid media (2:1 or 1:2) may be beneficial for shortening the setting time, enhancing early-stage compressive strength, and significantly improving the anti-microleakage ability of cement. Moreover, the composite cements also exhibited appreciable antibacterial efficacy in vitro. These findings demonstrated that the physicochemical properties of the Ca-silicate powders could be tuned by adding a minor amount of inorganic silicate nanofibers and a simple ball milling condition, and such a facile strategy is favorable for developing novel (pre-mixed) Ca silicate-based cements as root canal sealers.

Reinforced UHMWPE composites by grafting TiO2 on ATP nanofibers for improving thermal and tribological properties

A hybrid of attapulgite (ATP) nanofibers loaded with titanium dioxide (TiO2) nanoparticles was prepared by a steam-based method, and different contents were used for the reinforcement of ultra-high molecular weight polyethylene (UHMWPE) matrix. The results show that the thermal conductivity of the composites increased with increasing ATP-TiO2 content, and its optimal wear resistance was obtained at 5 wt% filler content, reducing of friction coefficient and wear loss by up to 33.3% and 49.4%, respectively. With the homogenous distribution of an appropriate amount of the ATP-TiO2 hybrid in the matrix, the network structure formed by the fillers was conducive to heat conduction and thus improved the thermal stability of the composites. Furthermore, the fillers promoted the formation of transfer film that prevented severe damage caused by metallic counterpart. This study of the microstructure and transfer behavior of ATP-TiO2 hybrid reinforced UHMWPE paves the way for expanding its application to fretting wear conditions.

Significant friction and wear-reduction role of attapulgite nanofibers compounded in PEEK-Based materials

Attapulgite is one kind of phyllosilicate minerals of abundant reserves and rather low costs, and the unique structure of attapulgite have attracted wide attention from fields of photocatalysis and dye adsorption etc. In the present work, exfoliated attapulgite nanofibers were incorporated into polyetheretherketone (PEEK) and PEEK filled with short carbon fibers (CF), respectively. Role of attapulgite in tribo-performance of the PEEK-based materials was explored. Our results demonstrate that addition of attapulgite into pure PEEK reduces substantially wear of the polymeric matrix. More interestingly, adding low-loading attapulgite nanofibers into CF-reinforcing PEEK lowers greatly the friction and wear. The hybrid nanocomposites developed in the present work is very promising for applications under harsh sliding conditions. Thorough characterizations of the worn surfaces reveal that physio-chemical products of attapulgite nanofibers exert an important influence on growth of a resilient tribofilm.

Design and controllable preparation of Bi2MoO6/attapulgite photocatalyst for the removal of tetracycline and formaldehyde

Herein, based on the natural attapulgite nanofibers and bismuth molybdate photocatalyst, a composite photocatalyst with a unique structure was designed and prepared via a simple solvothermal method. Compared with pure Bi2MoO6, Bi2MoO6/attapulgite had stronger formaldehyde and tetracycline treatment ability. The tetracycline oxidation reaction rate constant and formaldehyde mineralization rate using Bi2MoO6/attapulgite catalyst was 0.0109 min−1 and about 58%, respectively, which was about 1.70 times higher than that of pure Bi2MoO6, respectively. The introduction of attapulgite improved the adsorption performance of Bi2MoO6/attapulgite, increased the light-receiving area and active sites, thus ameliorated the mass transfer efficiency and photon efficiency in the reaction process. The material showed excellent reusability and environmental adaptability and has good application potential. This study proposed a high application prospect of organic waste gas and wastewater treatment technology.

A novel ceramic microfiltration membrane fabricated by anthurium andraeanum-like attapulgite nanofibers for high-efficiency oil-in-water emulsions separation

Anthurium andraeanum-like Fe3O4-attapulgite (FATP) fibers were prepared by anchoring nano-Fe3O4 particles on the surface of attapugite (ATP) via chemical coprecipitation. Then a novel ceramic microfiltration membrane with superhydrophilic and underwater superoleophobic performance was fabricated based on the FATP fibers. Ascribed to the hydrophilic performance of Fe3O4 and micro-nano structure of FATP fibers, the underwater oil contact angles of the FATP membrance for various types of oils are larger than 158° and the membrane also possesses rather low adhesion force with oil droplets. After 3 cycles of oil-in-water (O/W) emulsion separation, the steady flux of FATP membrane is 209 L m−2 h−1, 44% higher than that of ATP membrane. Moreover, the FATP membrane is stable and easy to clean, its oil rejection maintains at 98.7% and flux can recover by 86.5% using hot water as cleaning agent. The as-developed anthurium andraeanum-like structure in membrane surface provides promising guidance to improve the O/W purification performance of membrane.

Enhanced fretting wear performance of UHMWPE composites by grafting Co–Ni layered double hydroxides on attapulgite nanofibers

In this study, attapulgite (ATP) nanofibers were modified by hydrotalcite-like cobalt-nickel via hydrothermal (named ATP-CoNi(H)) and co-precipitation (named ATP-CoNi(C)) method, respectively. The morphology and the composition of the ATP-CoNi hybrids were investigated. Meanwhile, the fretting wear properties of ultra-high molecular weight polyethylene (UHMWPE)-based composites reinforced by ATP and two kinds of ATP-CoNi hybrids at 2 wt% content were investigated. The results show that ATP-CoNi hybrids exhibit better fretting wear properties than pure ATP in the UHMWPE matrix. Thereinto, the ATP-CoNi(C) nanofibers present the best antifriction property that the friction coefficient and wear volume severally decreased by 27% and 47%. It is attributed to the optimal interfacial bonding between the nanofibers and the matrix, which makes the dense structure of the composite.

Tribological behaviors of natural attapulgite nanofibers as an additive for mineral oil investigated by orthogonal test method

Natural attapulgite nanofibers were added into lubricating oil to improve the tribological behaviors. Orthogonal experiment design was performed to study the effects of load, frequency, duration and concentration on the tribological properties of the additive by SRV reciprocating wear tester. Results indicate that the order that affects the tribological performances of the additive is load, concentration, frequency and duration. A tribolayer consisting of oxides, ceramics, silicates and graphite has generated on the rubbing surface lubricated by the attapulgite oil. Such layer with good lubricity, high hardness and hardness/elastic modulus ratio is conducive to the excellent tribological behaviors of the attapulgite. The formation is considered to be related to the special physico-chemical properties of attapulgite and tribological test conditions.

Attapulgite nanofibers and graphene oxide composite membrane for high-performance molecular separation

Graphene oxide (GO) based membranes are widely adopted in molecular separation based on size exclusion effect by stacked GO sheets. Both high flux and efficient rejection of GO-based membranes for long-term operation are highly expected for practical applications. Here, an attapulgite (ATP) nanofibers/ GO composite (ATP/GO) membrane is assembled by filtration of mixed aqueous colloidal suspensions of ATP and GO. Due to the modification of interlayer distance and surface property of GO membrane by ATP, the ATP/GO membrane demonstrates excellent separation performance, with a high water flux of 221.16 Lm-2 h-1bar−1, 7.7 times higher than that of pure GO membrane. Meanwhile, the rejection of ATP/GO is also slightly improved comparing with that of GO membrane. It is also found that increasing the thickness of the membrane is effective to enhance rejection percentage. The ATP/GO membranes reported here show high efficiency for molecular separation, which demonstrates potential applications in water purification and environmental protection.

Ultrathin g-C3N4 films supported on Attapulgite nanofibers with enhanced photocatalytic performance

A novel visible-light-responsive photocatalyst is fabricated by introducing g-C3N4 ultrathin films onto the surface of attapulgite (ATP) via a simple in-situ depositing technique, in which ATP was pre-grafted using (3-Glycidyloxypropyl) trimethoxysilane (KH560) as the surfactant. A combination of XRD, FT-IR, BET, XPS, UV–vis, TEM and SEM techniques are utilized to characterize the composition, morphology and optical properties of the products. The results show that with the help of KH560, g-C3N4 presented as ultrathin layer is uniformly loaded onto the surface of ATP by forming a new chemical bond (SiOC). Comparing with g-C3N4 and ATP, ATP/g-C3N4 exhibits remarkably enhanced visible-light photocatalytic activity in degradation of methyl orange (MO) because of its high surface area, appropriate band gap and the synergistic effect between g-C3N4 and ATP. To achieve the best photocatalyst, the ratio of g-C3N4 was adjusted by controlling the mass portion between ATP-KH560 and melamine (r = m (ATP-KH560)/m (melamine)). The highest decomposition rate of methyl orange (MO) was 96.06% when r = 0.5 and this degradation efficiency remained unchanged after 4 cycles, which is 10 times as that of pure g-C3N4 particles. Possible photocatalytic mechanism is presented.

Purification of cellulase fermentation broth via low cost ceramic microfiltration membranes with nanofibers-like attapulgite separation layers

Abstract This paper reports the study of low cost ceramic microfiltration membranes with a separation layer of attapulgite nanofibers (attapulgite microfiltration membrane), used to clarify the cellulase fermentation fluid in order to enhance the quality of cellulase products. Based on resistance-in series model, the influence of membrane microstructure and operating conditions on the decline in membrane flux was investigated. The appropriate method for cleaning membranes that had undergone fouling was also found. The results show that an attapulgite microfiltration membrane with mean pore size of 0.12 μm is suitable for treating a cellulase fermentation fluid. The appropriate operating conditions were found to be the following: T = 30 ± 3 °C, ΔP = 0.10 MPa, and v = 4 m/s. The dominant component of the total resistance ( R t ) was the reversible fouling resistance ( R rev ), whereas the irreversible fouling resistance ( R irr ) was less important. In conditions of low trans-membrane pressure and high velocity, the fouled attapulgite microfiltration membrane could be satisfactorily regenerated using water rinsing and chemical cleaning. The results obtained in this work indicated that attapulgite microfiltration membrane separation may represent a feasible pretreatment for cellulase fermentation broth. The resistance-in-series analysis may provide additional insight into the relative importance of different fouling mechanisms.

Attapulgite Nanofiber-Cellulose Nanocomposite with Core-Shell Structure for Dye Adsorption

Nanocomposite particle used for adsorption has attracted continuous attention because of large specific surface area and adjustable properties from nanocomponent. Herein nanocomposite particle with cellulose core and attapulgite nanofibers shell was prepared. The size of cellulose core was about 2 mm and the thickness of nanofibers shell is about 300 μm. Adsorption capacity of nanocomposite particle to methylene blue can reach up to 11.07 mg L−1and the best adsorption effect occurs at pH = 8; pseudo-first-order equation and the Langmuir equation best describe the adsorption kinetic and isotherm, respectively; repeated adsorption-desorption experimental results show that 94.64% of the original adsorption capacity can be retained after being reused three times.

Preparation of a new ceramic microfiltration membrane with a separation layer of attapulgite nanofibers

To improve the performance of ceramic membranes and reduce their costs, a new ceramic microfiltration membrane with a separation layer made of attapulgite nanofibers was fabricated by dip-coating on the inner surface of ɑ-alumina tubular supports. The membrane has a separation layer of attapulgite nanofibers without evident defects and exhibits excellent interface properties, showing good adherence to the ɑ-alumina substrate. The nanofiber membrane has an average pore size of 0.250μm, thickness of approximately 6.7μm, and a pure water flux of 1540L/(m2hbar). The membrane was able to reject all the calcium carbonate particles in suspension, and showed a steady permeate flux of approximately 980L/(m2hbar). In addition, the membrane can be easily regenerated by backwashing without any damage, and therefore used repeatedly.

Ultradrawing properties of ultra-high molecular weight polyethylene/hydrochloric acid treated attapulgite fibers

Investigation of the influence of the purified and acid treated attapulgite (ATP) contents on the ultradrawing properties of ultrahigh molecular weight polyethylene/purified attapulgites (UHMWPE/ATP, F100Ay) and UHMWPE/acid treated ATP (F100AxM-y) as-prepared fibers is reported. In which, acid treated ATP nanofibers were treated with varying concentrations of hydrochloric solutions for various amounts of time. Similar to those found for the orientation factor values, the achievable draw ratios of the F100Ay and F100AxM-y as-prepared fibers and tensile strength values of their drawn fibers approach a maximal value as their purified ATP and/or acid treated ATP contents reach the optimal values at 0.05 and 0.025 wt%, respectively. In which, the maximal Dra values of F100AxM-0.025 as-prepared series fiber specimens and the tensile strengths and moduli of the drawn F100AxM-0.025 fiber specimens are significantly higher than those of the F100A0.05 drawn fiber specimens prepared at the same draw ratios and optimal ATP contents but without acid treatment. Moreover, it is worth noting that the maximal Dra values of the F100AxM-0.025 as-prepared fiber specimens and the tensile strengths and moduli of the drawn F100AxM-0.025 fiber specimens reached another maximal value as their ATP nanofibers were treated by 5 M HCl solutions for 60 min. To understand the interesting ultradrawing, orientation and tensile properties of F100Ay and F100AxM-y fiber specimens, Fourier transform infra-red, specific surface areas, scanning electron microcope and elemental analyses of the purified and acid treated ATP nanofibers, and/or morphological and thermal analyses of the F100Ay and F100AxM-y fiber specimens were performed in this study.

Effect of Attapulgite Modification on Properties of Polypropylene Nanocomposites

Polypropylene nanocomposites were prepared by means of melt mixing using attapulgite as inorganic components. The relation between surface free energy and mechanical properties of polypropylene nanocomposites and elasticized mechanism analysis of modified attapulgite nanofibers were mainly studied. The results showed that the modulus, fracture strength, fracture extensibility, tensile strength, yield strength, bend strength, flexural modulus and dynamic ductility properties of nanocomposites all enhanced obviously after modified attapulgite nanofibers were filled up. Surface free energy of attapulgite nanofibers and impact toughness properties of nanocomposites were in approximate inversely-proportion quadratic function relationship, which could provide a new way of thinking in the field of nanocomposites research.

Drawing and ultimate tenacity properties of polyamide 6/attapulgite composite fibers

AbstractThe drawing and ultimate tenacity properties of the Polyamide 6 (PA6)/Attapulgite (ATP) composite fiber specimens prepared at varying modified ATP (mATP) contents and drawing condition were systematically investigated. As evidenced by Fourier transform infrared (FTIR) and morphological analysis, demarcated translucent resins were found firmly attached on the surfaces of ATP nanofibers. The specific surface areas of the mATP specimens reached a maximum value at 381 m2/g as the weight ratios of silane coupling agents to ATP nanofibers reached an optimum value at 1.0. The percentage crystallinity and melt shear viscosity values measured at varying shear rates of PA6x(mATP)y specimens increased consistently as their mATP contents increased. In contrast, melting temperatures of PA6x(mATP)y specimens reduced slightly as their mATP contents increased. At a fixed drawing temperature and rate, the achievable draw ratio (Dra) values of PA6x(mATP)y as‐spun fiber specimens approach a maximum value, as their mATP contents are close to the 0.2 wt % optimum value. The maximum Dra values obtained for PA699.8(mATP)0.2 as‐spun fiber specimens reached another maximum, when their drawing temperatures and rates approached the optimum values at 120°C and 50 mm/min, respectively. At a fixed draw ratio, the tenacity values of PA6x(mATP)y drawn fiber specimens drawn at the optimum drawing temperature and rate reached a maximum value, as their mATP contents approached the 0.2 wt % optimum value. Possible reasons accounting for the interesting morphological, specific surface area, drawing, orientation, and ultimate tenacity properties found for the PA6x(mATP)y fiber specimens are proposed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Characterization of Alcohol Dehydrogenase from Permeabilized Brewer's Yeast Cells Immobilized on the Derived Attapulgite Nanofibers

Alcohol dehydrogenase (ADH) from permeabilized brewer's yeast was immobilized on derived attapulgite nanofibers via glutaraldehyde covalent binding. The effect of immobilization on ADH activity, optimum temperature and pH, thermal, pH and operational stability, reusability of immobilized ADH, and bioreduction of ethyl 3-oxobutyrate (EOB) to ethyl(S)-3-hydroxybutyrate ((S)-EHB) by the immobilized ADH were investigated. The results show the immobilized ADH retained higher activity over wider ranges of pH and temperature than those of the free. The optimum temperature and pH were 7.5 and 35 degrees C, respectively, and 58% of the original activity was retented after incubation at 35 degrees C for 32 h. More importantly, in bioreduction of EOB mediated by immobilized ADH, the conversion of substrate and enantiomeric excess (ee) of product reached 88% and 99.2%, respectively, within 2 h and retained about 42% of the initial activity after eight cycles.