Magnetic MWCNTs Research Articles

Immobilization of Candida rugosa lipase on optimized polyamidoamine dendrimer functionalized magnetic multiwalled carbon nanotubes for green manufacture of butyl butyrate ester

Mineral acid catalysis in Fisher-Speier esterification is hazardous and have other disadvantages. The objective of the study was immobilization of Candida rugosa lipase onto iron oxide (Fe3O4) impregnated magnetic mutiwalled carbon naotubes (MMWCNTs) using amine functionalized polyamidoamine (PAMAM) dendrimers for manufacture of butyl butyrate ester. Dendrimers were synthesized from reaction of ethyl methacrylate with varying chain length of diamines 1, 4 diaminobutane (DAB) / 1, 3 diaminopropane (DAP) / ethylene diamine (ED). The effect of aliphatic alkyl chain length (CH2) of functionalizing agents ED, DAP and DAB, and dendrimer generations on amount of terminal NH2 group, surface charge, protein loading and immobilized enzyme activities were analysed. Magnetic MWCNTs support surface modified with third generation PAMAM using ethylene diamine showed highest protein load 220.1 mg g−1 and enzymatic activity 8,276.21 U g−1 support. The immobilized enzyme particles were characterized by HRTEM, FTIR, XRD, TGA, VSM and Zeta potential analysis. The immobilized enzyme showed improvement in the dispersion, activity, stability and reusability characteristics. Maximum esterification yield 92.67 % and reuse upto 11 cycles with 65.2 % yield obtained. The immobilized preparation showed 2.3 folds esterification than free enzyme. Developed nanobiocatalyst expects to possess potential for various other applications of lipase catalysed reactions.

Ti-MOF@Metal-polyphenol network derived TiN0.9@NC/magnetic MWCNTs composites for microwave absorption

Magnetic carbon-based microwave absorption materials (MAMs) derived from metal-organic frameworks (MOFs) have been regarded as promising candidates for addressing the electromagnetic pollution. The construction of magnetic carbon-based MAMs derived from MOFs with ferromagnetic centers (Fe, Co, Ni etc.) and their composites has become a mainstream in recent years. However, MOFs with non-magnetic centers have received less attentions due to the challenges in achieving magnetic-dielectric synergistic effect and proper impedance matching in their derivatives. In this work, a facile metal-polyphenol network coating strategy has been proposed to facilitate the construction of magnetic MWCNTs decorated TiN0.9/NC absorber derived from non-magnetic MIL-125(Ti). The regulation effect of carbothermal temperature on magnetism, defect density, graphitization degree as well as electromagnetic parameters of absorbers have been systematically investigated. The obtained composites exhibit outstanding microwave absorption performance due to the magnetic-dielectric synergistic effect and improved impedance matching. The minimum reflection loss reaches −42.55 dB at 1.91 mm and the effective absorption bandwidth reaches as wide as 4.6 GHz with an ultra-thin thickness of only 1.38 mm. It is believed that this study provides a new way to construct efficient magnetic carbon-based MAMs with non-magnetic metal-based MOFs and a meaningful exploration for the preparation of ultra-thin absorbers.

Magnetic Composite Based on Carbon Nanotubes and Deep Eutectic Solvents: Preparation and Its Application for the Determination of Pyrethroids in Tea Drinks

In this study, a novel composite material prepared by using deep eutectic solvent (tetrabutylammonium chloride-dodecanol, DES5) functionalized magnetic MWCNTs-ZIF-8 (MM/ZIF-8@DES5) was employed as an adsorbent for the magnetic solid-phase extraction of six pyrethroids from tea drinks. The characterization results show that MM/ZIF-8@DES5 possessed sufficient specific surface area and superparamagnetism, which could facilitate the rapid enrichment of pyrethroids from tea drink samples. The results of the optimization experiment indicated that DES5, which comprised tetrabutylammonium chloride and 1-dodecanol, was selected for the next experiment and that the adsorption properties of MM/ZIF-8@DES5 were higher than those of MM/ZIF-8 and M-MWCNTs. The validation results show that the method has a wide linear range (0.5-400 μg L-1, R2 ≥ 0.9905), low LOD (0.08-0.33 μg L-1), and good precision (intra-day RSD ≤ 5.6%, inter-day RSD ≤ 8.6%). The method was successfully applied to the determination of pyrethroids in three tea drink samples.

Selective and efficient adsorption of anionic dyes by core/shell magnetic MWCNTs nano-hybrid constructed through facial polydopamine tailored graft polymerization: Insight of adsorption mechanism, kinetic, isotherm and thermodynamic study

It is a big challenge to design advanced adsorbents that have high adsorption capacity and excellent selectivity to efficiently remove organic dyes from complex environmental systems. Herein, by utilizing the adhesion property of polydopamine (PDA) and its crosslinking reaction with polyethyleneimine (PEI), a novel core/shell magnetic MWCNTs/Fe3O4@(PDA + PEI) nano-hybrid that carries superior adsorption performance of dyes was constructed through facile polydopamine tailored graft polymerization. In such hierarchical structure, the inner shell of Fe3O4 nanoparticles and outer shell of (PDA + PEI) contributed to the abundant active adsorption sites, large specific surface area (126 m2/g) and high saturation magnetization value (10.91 emu/g). As a result, the prepared adsorbent exhibited highly selective adsorption performance toward multiple anionic dyes, including MB, CR, and MO with maximum adsorption capacity of 1449, 1006, and 935 mg/g at 298.15 K, respectively. It was found that the main adsorption mechanism was attributed to the hydrogen bonding and electrostatic interaction. The kinetics data fitted well with the pseudo-second-order model, and both the Langmuir and Freundlich isotherm models presented well fit to the isotherm data. The investigation of thermodynamic study indicated that the adsorption of anionic dyes onto core/shell magnetic MWCNTs/Fe3O4@(PDA + PEI) nano-hybrid was spontaneous and endothermic. More importantly, the adsorbent presented excellent regeneration property after multiple adsorption-desorption cycles and prominent stability in harsh environments, especially in the alkaline condition. Therefore, these results revealed the promising applications of hierarchical MWCNTs/Fe3O4@(PDA + PEI) nano-hybrid in water remediation.

Simultaneous capture of methyl orange and chromium(vi) from complex wastewater using polyethylenimine cation decorated magnetic carbon nanotubes as a recyclable adsorbent.

Most recently, the continuous deterioration of the aquatic environment triggered by both heavy metals and synthetic organic dyes has imparted serious threats to the ecosphere and drinking water safety. However, it is still extremely challenging to treat complex wastewater containing these two classes of pollutants via a one-step method owing to the significant differences in their physicochemical properties. In the current work, versatile magnetic MWCNTs decorated with PEI (denoted as MWCNTs@Fe3O4/PEI) was fabricated by a facile, rapid and reproducible strategy and applied to as a robust adsorbent for simultaneously removing methyl orange (MO) and Cr(vi) from aqueous solutions. The physicochemical properties of the as-designed nanohybrid were investigated using various analytical techniques, i.e. XRD, FT-IR, SEM, TEM, VSM, zeta potential, etc. It was found that the surface charge properties of the MWCNTs as well as its dispersion in aqueous solution were greatly changed after the introduction of PEI molecules. The resulting nanohybrid exhibited attractive adsorption capabilities toward anionic MO and Cr(vi). In the perspective of a mono-pollutant system, the time-dependent adsorption process matched well with a pseudo-second-order kinetics equation, the adsorption isotherm data at r.t. were well fitted by a Langmuir model with maximum monolayer uptake capacity of 1727.6 mg g−1 for MO and 98.8 mg g−1 for Cr(vi), and the removal process of both pollutants was thermodynamically spontaneous and exothermic. In the MO-Cr(vi) binary system, the uptake of Cr(vi) by the as-prepared adsorbent was evidently enhanced by the presence of MO, while the coexisting Cr(vi) exerted a small negative effect on the sorption of MO; which was attributed to the different adsorption mechanisms of both pollutants on the as-recommend adsorbent. The much better adsorbing performance of the resulting MWCNTs@Fe3O4/PEI for MO and Cr(vi) than that of the pristine MWCNTs or the MWCNTs/Fe3O4 composite was mainly ascribed to the high surface area of the MWCNTs, the high density of protonated N-rich groups of PEI as well as the excellent dispersion and solubility of the resulting nanocomposites. Moreover, the obtained nanohybrids can be easily recovered after being used by a permanent magnet and still retained high stability and excellent reusability after consecutive adsorption–desorption cycles, implying its great potential in practical applications. Therefore, the as-fabricated MWCNTs@Fe3O4/PEI composite could be recommended as a promising candidate adsorbent for the simultaneous capture of MO and Cr(vi) from complex wastewater via multiple uptake mechanisms (e.g. electrostatic attraction, π–π stacking and hydrogen bonding).

Solid phase extraction and determination of indium using multiwalled carbon nanotubes modified with magnetic nanoparticles

In this work MWCNTs-Fe3O4 nanocomposite was used as an adsorbent for extraction and preconcentration of indium from aqueous solutions. The magnetic MWCNTs with adsorbed analytes were easily separated from the aqueous solution by applying an external magnetic field. After elution of the adsorbed analytes, the concentration of indium was determined using inductively coupled plasma optical emission spectrometry determination. The effects of pH, sorbent amount, eluent type, chelating reagent concentration, sample volume and time on the recovery of the In(III) were investigated. Under the optimum conditions, the detection limit for In(III) was 0.28 μg L−1. The precision of the method, evaluated as the relative standard deviation obtained by analyzing a series of ten replicates, was 3.1 %. The method was successfully applied for the determination of In(III) in environmental water samples.

Adsorption and removal of organophosphorus pesticides from environmental water and soil samples by using magnetic multi-walled carbon nanotubes @ organic framework ZIF-8

In this study, the functional adsorbent metal–organic framework ZIF-8/magnetic multi-walled carbon nanotubes (M-M-ZIF-8) was successfully prepared for removal of eight organophosphorus pesticides from environmental water and soil samples. The M-M-ZIF-8 was characterized and their adsorption capacity was evaluated based on their isothermal adsorption curves. The results suggest that ZIF-8 particles are deposited on the surface of the magnetic MWCNTs via coordination–polymerization strategy. In addition, M-M-ZIF-8 has high static adsorption capacities for organophosphorus pesticides because of its high specific surface area and porous structure. The static adsorption data fit the Freundlich adsorption model better than the Langmuir model. Under the optimized conditions, M-M-ZIF-8 was successfully applied to remove the eight organophosphorus pesticides from environmental water and soil samples. A possible mechanism is valence-electron-driven adsorption by sharing or exchanging of electrons between the organophosphorus pesticide molecules and the vacant active sites of M-M-ZIF-8. Therefore, M-M-ZIF-8 is a promising hybrid adsorbent for adsorption and removal of organic pollutions from the environment.

Determination of phthalate acid esters (PAEs) in carbonated soft drinks with MSPE/GC–MS method

In this study, at first were prepared novel multi-walled carbon nanotubes modified with catalytic nanoparticles of iron oxide and silver (MWCNTs-Fe3O4/Ag) by mixing the magnetic particles. Due to their excellent absorption and desorption capability towards hydrophobic compounds, the magnetic MWCNTs were used as adsorbent of magnetic solid-phase extraction (MSPE) to extract phthalate acid esters (PAEs). Our results showed the highest concentration of phthalate esters of bis(2-ethylhexyl)phthalate (DEHP) which is much higher than the standard level in the four samples (6766.6, 9201, 9301.6, and 14,008 ng/L). Finally, the established MSPE-GC/MS method was successfully applied to the determination of PAEs from carbonated soft drinks and the MSPE-GC/MS method developed in current study provides a new option for the detection of PAEs from carbonated soft drinks with complex matrices.

Synthesis of Magnetic MWCNTs Nanohybrids and Application in Remediation of Chromium Ions in Refinery Wastewater

This study presents the preparation of Magnetic - Multiwall Carbon Nanotubes (M-MWCNTs) as adsorbents, MWCNTs/Fe3O4 nanocomposite, in which multiwall carbon nanotubes were coated to magnetic Fe3O4 particles by simplistic sol-gel techniques. The synthesized MWCNTs/Fe3O4 nano-composites were measured via Fourier Transform Infrared spectroscopy (FTIR), X -Ray Diffraction spectrometry (XRD), and Scanning -electron microscopy (SEM). The adsorption behaviors of the MWCNTs/Fe3O4 nanocomposites will be evaluated intended for the elimination of chromium ions in diluted refinery wastewater.

MWCNT-Fe3O4 as a superior adsorbent for microcystins LR removal: Investigation on the magnetic adsorption separation, artificial neural network modeling, and genetic algorithm optimization

Magnetic multi-wall carbon nanotube (MMWCNT) was prepared by simple protocol and its structural features were characterized using SEM, TEM, and XRD analysis. The association between removal (%) and variables such as pH(3−11), adsorbent amounts (0.005, 0.1, 0.25, 0.5, 0.75, and 1g/L), reaction time (5–180min), and concentration of microcystins-LR (10, 25, 50, 75, and 125μg/L) was investigated and optimized. The results of the isotherm study indicated that Langmuir offered high determination coefficients (R2=0.993, 0.996, and 0.998, for the three different working temperatures of 20°C, 35°C, and 50°C respectively) and was the optimum isotherm to anticipate adsorption of MC-LR (microcystins-LR) by magnetic MWCNT adsorbent. The kinetic study revealed that the adsorption kinetics of MC-LR could be better defined using the pseudo-second-order model. A three-layer model of an artificial neural network was applied to forecast the MC-LR removal efficiency by magnetic MWCNTs over 66 runs. To forecast the MC-LR removal efficiency, the minimum mean squared error of 0.0011 and determination coefficient (R2) of 0.9813 were obtained. The use of the artificial neural network model achieved a good level of compatibility between the acquired and anticipated data.

Application of Ni:ZnS nanoparticles loaded on magnetic multi-walled carbon nanotubes as a sorbent for dispersive micro-solid phase extraction of phenobarbital and phenytoin prior to HPLC analysis: experimental design

Ni:ZnSNPs loaded on magnetic MWCNTs are introduced for dispersive micro-solid phase extraction for the first time.

Determination of puerarin in rat plasma using PEGylated magnetic carbon nanotubes by high performance liquid chromatography.

This paper described a novel application of PEGylated magnetic carbon nanotubes as solid-phase extraction nanosorbents for the determination of puerarin in rat plasma by high performance liquid chromatography (HPLC). A solvothermal method was employed for the synthesis of monodisperse magnetites anchored onto multi-walled carbon nanotubes (MWCNTs@Fe3O4). In order to enhance the water solubility of MWCNTs@Fe3O4 that ensured sufficient contact between nanosorbents and analytes in the sampling procedure, the obtained nanomaterials were further noncovalently functionalized using a phospholipids-polyethylene glycol (DSPE-PEG). The PEGylated MWCNTs@Fe3O4 nanomaterials had an extremely large surface area and exhibit a strong interaction capability for puerarin with π-π stacking interactions. The captured puerarin/nanosorbents were easily isolated from the plasma by placing a magnet, and desorbed by acetonitrile. The experimental variables affecting the extraction efficiency were investigated. The calibration curve of puerarin was linear from 0.01 to 20 μg/ml, and the limit of detection was 0.005 μg/ml. The precisions ranged from 2.7% to 3.5% for within-day measurement, and for between-day variation was in the range of 3.1-5.9%. The method recoveries were acquired from 95.2% to 98.0%. Moreover, the analytical performance obtained by PEGylated magnetic MWCNTs was also compared with that of magnetic MWCNTs. All results showed that our proposed method was an excellent alternative for the analysis of puerarin in rat plasma.

Influence of magnetic MWCNTs on the antimicrobial activity of cephalosporins

The purpose of this study was to analyze the antimicrobial activity of cephalosporin antibiotics adsorbed on the surface of magnetic MWCNTs, against microbial cells in suspension and adhered to the substrate, in order to highlight potential improvements of antimicrobial activity parameters of these antibiotics. Magnetic MWCNTs were obtained by plasma processing and characterized by HR-TEM. The need for the discovery of such strategies is imposed by the numerous mechanisms developed by pathogenic microorganisms manage to gain resistance to the majority of currently available antibiotics.