Mohamed Abdel Salam

Kinetics and thermodynamic study of aniline adsorption by multi-walled carbon nanotubes from aqueous solution.

Multi-walled carbon nanotubes (MWCNTs) were used in the adsorptive removal of aniline, an organic pollutant, from an aqueous solution. It was found that carbon nanotubes with a higher specific surface area adsorbed and removed more aniline from an aqueous solution. The adsorption was dependent on factors, such as MWCNTs dosage, contact time, aniline concentration, solution pH and temperature. The adsorption study was analyzed kinetically, and the results revealed that the adsorption followed pseudo-second order kinetics with good correlation coefficients. In addition, it was found that the adsorption of aniline occurred in two consecutive steps, including the slow intra-particle diffusion of aniline molecules through the nanotubes. Various thermodynamic parameters, including the Gibbs free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°), were calculated. The results indicated that the spontaneity of the adsorption, exothermic nature of the adsorption and the decrease in the randomness reported as ΔG°, ΔH° and ΔS°, respectively, were all negative.

Novel application of modified multiwalled carbon nanotubes as a solid phase extraction adsorbent for the determination of polyhalogenated organic pollutants in aqueous solution

This paper describes a novel application of pristine and chemically modified multiwalled carbon nanotubes (MWCNTs) as the packing materials for the determination of different polyhalogenated organic pollutants, pentachlorophenol, 2,4,5-trichlorophenol, 3,3′,4,4′-tetrachlorobiphenyl and 2,2′,5,5′-tetrabromobiphenyl, from aqueous solution based on solid phase extraction. The modified MWCNTs were characterized using different techniques and the results revealed the successful modification of the MWCNTs with octadecyl amine and poly(ethylene glycol), separately. Factors that maybe influence the preconcentration efficiency, such as sample flow rate, adsorbent mass, sample pH and sample volume, were studied. Desorption of the target analytes was studied using different solvents and the results showed that acetone was the best solvent for all the analytes compared with methanol and hexane. All the results indicated that the proposed method could be used for the simultaneous determination of different pollutants in environmental water samples at trace levels.

Effect of the N content of Fe/N/graphene catalysts for the oxygen reduction reaction in alkaline media

In this work a series of N–modified graphene composites with different N/C ratios have been synthesised. The incorporation of Fe atoms into the N–modified graphene composites leads to the formation of Fe/N/C ensembles on the outer graphene layers along with Fe3C and metallic Fe phases in the bulk of the graphite nanoplates as revealed by X-ray absorption and XPS analyses. The adequate choice of the N/C atomic ratio of precursors to prepare Fe/N/graphene based materials is crucial to obtain electrocatalysts with an optimal performance for the ORR. The activity for the oxygen reduction reaction (ORR) of the Fe/N–graphene based electrocatalysts increases with increasing amount of accessible nitrogen, that is, with the amount of nitrogen by surface area.

Synthesis of nanocomposites of polypyrrole/carbon nanotubes/silver nano particles and their application in water disinfection

Contamination of drinking or irrigation water with pathogenic bacteria, such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), is a major global health problem. Nanomaterials have been of growing interest owing to their promising properties as antimicrobial agents. In this study, in situ oxidative polymerization of pyrrole with silver nitrate was employed to obtain nanocomposites materials containing different percentages of single wall carbon nanotubes (CNT0–60/PPy/AgNPs). The reaction proceeds smoothly at room temperature and the silver content was about 80 wt% of composite. The morphology of composites was determined by transmission electron microscope (TEM) to indicate the formation of core–shell structure in which AgNPs as core and PPy–CNT as shell with observed homogeneity in the nanocomposites. The samples were also characterized by ATR-FTIR, XRD, and TGA. CNT0–60/PPy/AgNPs materials were used for bacterial removal from water. The bacterial removal was evaluated using the column filter method. The results indicated that the removal percentage of E. coli ranged from 87.5% to 95% using CNT0–20/PPy/AgNPs. The data obtained in this study indicated that CNT60/PPy/AgNPs nanocomposite was found to be effective towards E. coli with 100% removal, whereas PPy/AgNPs obtained in this work was specific for the complete removal of S. aureus (100%).

Multi-walled Carbon Nanotubes/Unsaturated Polyester Composites: Mechanical and Thermal Properties Study

Two types of multi-walled carbon nanotubes (MWCNTs) were used to modify unsaturated polyester (UP) through the formation of composites. The pristine MWCNTs, polyester, and the obtained carbon nanotubess/polyester composites were characterized chemically and physically using scanning electron microscopy, surface area analysis, and infrared spectroscopy. The thermal and mechanical properties of the carbon nanotubes/polyester composites were studied. In general, it was observed that the addition of MWCNTs to the polyester did not change the thermal stability significantly, whereas it changed the mechanical properties greatly. The addition of carbon nanotubes to the polyester enhanced the tensile strength, strain, Youngs modulus, and the maximum force to 4.2%, 86.0%, 12.7%, and 27.9%, respectively, upon the addition of 0.3% Sigma MWCNTs.

Chemical modification of multi-walled carbon nanotubes using different oxidising agents: optimisation and characterisation

Chemical modification of the multi-walled carbon nanotubes (MWCNTs) via oxidation was investigated. MWCNTs were oxidised using different oxidising agents, namely nitric acid/sulphuric acid, acidified potassium permanganate, and hydrogen peroxide. The selection of suitable oxidising agent was optimised depending on the integrity of the CNTs. The oxidised MWCNTs were able to suspend in water; with high stability, for a long period of time. FT-IR measurements showed the presence of carboxylic acid function groups especially for the MWCNTs oxidised with nitric acid and hydrogen peroxide. The texture analysis (specific surface area and pore size distribution) showed that oxidation of the MWCNTs led to a decrease in the specific surface area and as a result of introducing a new function groups at the MWCNTs surface which led to the collapse of the total pore volume. Scanning electron microscope images showed that the pristine MWCNTs are highly tangled tubes with diameters of 80-150 nm.

Electrochemical coating of stainless steel with multi-walled carbon nanotubes/polyaniline composite layer

Doped polyaniline (PANI) in its emeraldine salt form with different quantities of oxidised multi-walled carbon nanotubes (OxMWCNTs) via in situ electro-polymerisation on the stainless steel (SS) has been performed. Presence of OxMWNTs in the composite was confirmed by thermal gravimetric analysis (TGA) and scanning electron microscope (SEM). The OxMWNTs increased significantly the electro-deposition rate on the steel surface. The reinforcing of OxMWNTs in the PANI decreased the porosity of the PANI and forming a network held the polymer. The influences of composite layer on the passivation and corrosion of the SS were studied and compared with pure PANI layer.

Influence of Single-Walled Carbon Nanotubes on the Performance of Poly(Azomethine-Ether) Composite Materials

ABSTRACT The present work is aimed to fabricate a new set of composite materials containing conducting poly(azomethine-ether) reinforced with single-walled carbon nanotubes in the form of single-walled carbon nanotube/poly(azomethine-ether)1–5 for excellent enhanced thermal as well as conducting behavior of poly(azomethine-ether). Single-walled carbon nanotubes of variable loading have been embedded into conducting poly(azomethine-ether) using in situ polymerization technique. Before attempting the polymerization, 1,3-thiazole established poly(azomethine-ether) and its conformable monomers have been prepared and their chemical structures have been correlated by spectral analyses. Furthermore, ηinh and Mw values for poly(azomethine-ether) were found 0.89 dL g−1 and 39723.6, respectively. The fabricated single-walled carbon nanotube/poly(azomethine-ether)1–5 composites were specified and characterized by wide-angle X-ray diffraction patterns, Fourier transform infrared spectroscopy, thermal behavior, scanning electron microscopy, and transmission electron microscopy characterization techniques. A perfect indicative response for this composite material was estimated by Fourier transform infrared spectra and X-ray diffraction as well. Both techniques displayed all intensive characteristic peaks regarding single-walled carbon nanotubes and poly(azomethine-ether) in the spectra or diffraction pattern for single-walled carbon nanotube/poly(azomethine-ether)1–5. The role of single-walled carbon nanotubes on the performance of poly(azomethine-ether) was considerably examined. Single-walled carbon nanotube/poly(azomethine-ether)1–5 showed relatively higher thermal stability. Single-walled carbon nanotube/poly(azomethine-ether)1 displayed the lowest final composite degradation temperature value (552°C), whereas single-walled carbon nanotube/poly(azomethine-ether)5 displayed the highest value (621°C). T10 and T25 values showed a gradual temperature increased while single-walled carbon nanotubes increased. Single-walled carbon nanotube/poly(azomethine-ether)1 showed the lowest thermal stability and single-walled carbon nanotube/poly(azomethine-ether)5 showed the highest thermal stability between all fabricated products. Furthermore, transmission electron microscopy images showed a prominent increase in single-walled carbon nanotubes diameters (40–60 nm). The conductivity values were significantly increased while single-walled carbon nanotubes content was increased and reached to the semiconductors. ε′ values were also increased in both single-walled carbon nanotube/poly(azomethine-ether)4,5 which have higher single-walled carbon nanotubes content. GRAPHICAL ABSTRACT

Fabrication of an L-glutathione sensor based on PEG-conjugated functionalized CNT nanocomposites: a real sample analysis

Three series of polyethylene glycol–carbon nanotube nanocomposites in the form of PEG/CNTa–e, PEG/f-CNT.Oxia–e, and PEG/CNT.C18a–e have been fabricated using a dissolution stirring ultra-sonication method. The compounds were then characterized using different characterization techniques, including FT-IR, XRD, and TEM. The FT-IR and XRD data provided clear evidence of the CNTs functionalization as well as the composite formation. The FT-IR spectral data of the functionalized MWCNTs were slightly changed due to the introduction of PEG groups on their surfaces. The TEM images indicated that the nanotubes were homogenously distributed and embedded within the PEG polymer matrix. A flat glassy carbon electrode was modified with GCE/PEG-f-CNToxd nanocomposites (NCs) to obtain a sensor for L-glutathione (GSH), which was seen to exhibit improved sensitivity, low detection limit, large dynamic range, short response time, and good stability, whereby the calibration plot (at +0.5 V) was linear (r2: 0.9957) in the 0.1 nM to 1.0 mM GSH concentration range, the detection limit was as low as 0.026 nM, and the sensitivity was 17.4 μA μM−1 cm−2. To the best of our knowledge, this is the first report on the determination of GSH using such a modified GCE/PEG-f-CNTs by an I–V approach. The GCE/PEG-f-CNT was applied for the selective determination of GSH in spiked rabbit serum samples and achieved acceptable results.

Adsorptive removal of malachite green and Rhodamine B dyes on Fe3O4/activated carbon composite

ABSTRACT This study demonstrates the adsorption experiments of toxic dyes malachite green (MG) and Rhodamine B (RB) on Fe3O4-loaded activated carbon (AC). AC, which is known to be a high-capacity adsorbent, was aimed to be easily separated from aqueous media by loading it with Fe3O4. Fe3O4-loaded AC was prepared by the coprecipitation method and named magnetic activated carbon (M-AC), and the produced M-AC was characterized by x-ray diffraction (XRD), thermogravimetric analysis (TGA), and pHpzc analyses. MG and RB adsorption by the M-AC was performed separately by batch technique and the effects of adsorbent amount, solution pH, and initial dye concentration on the adsorption were explored. Maximum removal efficiencies were found to be 96.11% for MG and 98.54% for RB, and the Langmuir isotherm model was the most fitted isotherm model for the adsorption. The kinetic and thermodynamic studies showed that the adsorption proceeded via the pseudo-second-order kinetic model and endothermic in-nature for both dyes. GRAPHICAL ABSTRACT