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35 results on '"Al-rashdi, Awad A."'

3. Quinoline derivatives as corrosion inhibitors for mild steel in acid medium: Deeper insights from experimental, ab initio density functional theory modeling, and in silico ecotoxicity investigations

Author

Fernandes, Caio Machado, primary, Palmeira-Mello, Marcos V., additional, Leite, Mylena C., additional, da Silva, Gustavo B., additional, Souza, Alessandra M.T., additional, Velasco, Javier A.C., additional, Al-Rashdi, Awad A., additional, Lgaz, Hassane, additional, and Ponzio, Eduardo A., additional

Published
2024
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9. Green-synthetized β-amino-α-carbethoxy ethyl acrylates as corrosion inhibitors for mild steel in acid media: Experimental performance evaluation and atomic/molecular-level modeling

Author

Machado Fernandes, Caio, primary, Coutinho, Mayra S., additional, Leite, Mylena C., additional, Martins, Vinicius, additional, Batista, Mariana P., additional, Faro, Leticia V., additional, Al-Rashdi, Awad A., additional, Silva, Júlio César M., additional, Batalha, Pedro N., additional, Lgaz, Hassane, additional, and Ponzio, Eduardo A., additional

Published
2023
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10. Improving the measurement of butyltin compounds in environmental samples

Author

Al-Rashdi, Awad and Howard, Alan G.

Subjects
543, QD Chemistry
Abstract

Tributyltin compounds (TBT) are highly toxic pollutants, mainly introduced to the environment as a marine antifouling agent. The main aim of this work was to evaluate the present methods for the measurement of TBT and its breakdown products dibutyltin and monobutyltin in environmental sediments and waters and to improve upon their measurement. For the analysis of sediments, a triple hexane/acetic acid extraction was employed of tropolone complexes of the organotin compounds. Grignard reagent derivatization and measurements by gas chromatography with pulsed flame photometric detection were then employed. The TBT detection limit of 5 μg Sn/ kg in sediment was below the UK environmental quality target (EQS) value for TBT in sediment (1-2 mg Sn/kg). A pilot investigation was carried out on a small dockyard in Southampton to evaluate if the total amount of tin could be used to predict the presence of TBT. Due to different sources of tin contamination in the studied area no clear overall correlation of TBT with total tin was found. As part of the investigation into the determination of butyltin in sediment, the extraction of TBT from paint particles deposited in sediment during boat refurbishment and the removal of sulphur interferences were investigated. For the extraction of TBT in paint, a pre-treatment procedure was developed based on pre-treatment with dichloromethane (DCM). This treatment improved the extraction of TBT from the paint, but TBT losses can occur during DCM removal by evaporation. Sulphur interferences were successfully removed from the sediment extract by improving the clean-up procedure. This procedure was based on treatment of the hexane extract with activated copper and then passing the hexane extract through a C18 solid phase extraction column. For the determination of butyltins in water a doubly functionalized mesoporous silica was synthesized and used to extract butyltin compounds from water based on a solid phase dispersion technique. Butyltin chlorides were collected from the water on the surface of the HOC18-nanoscavenger, hexylated using a Grignard reagent and quantified by GC-PFPD. Another approach was based on ethylation of tributylin chloride using NaEt4B followed by extraction of the ethylated species on the HOC18-nanoscavenger. TBT detection limits of 1.5 and 3 ng Sn/ L were achieved using the Grignard and NaEt4B approaches respectively and were regarded satisfactory, as they were below or near to the UK EQS for water ( 2 ng/ L). The Grignard approach was more efficient than the NaEt4B approach, but the latter was more precise.

Published
2011

30. Free volume properties of the zinc oxide nanoparticles/waterborne polyurethane coating system studied by a slow positron beam.

Author

Awad, Somia, Al-Rashdi, Awad, Abdel-Hady, EE, Jean, YC, and Van Horn, J David

Subjects
*ZINC oxide, *NANOPARTICLES, *POLYURETHANES, *POSITRON beams, *MONOENERGETIC radiation
Abstract

A variable, mono-energetic positron beam was employed to study the free volume characteristics of coating system composed of zinc oxide nanoparticles dispersed in waterborne polyurethane. Positron annihilation lifetime spectroscopy, in tandem with Doppler-broadening energy spectra and derived S parameter is used to quantitatively assess the free volume and interfacial interactions between zinc oxide nanoparticle surface and waterborne polyurethane. It was found that S parameter decreases with increasing ZnO load from 0 to 5%. The decrease of S parameter is explained as a result of strong interfacial interactions between the surface of the ZnO nanoparticles and WBPU chains. Furthermore, the half depth where the change in S parameter is reduced by half from the surface to bulk was found to increase with increasing ZnO concentration. These results are presented in the framework of free volume interactions in which the S parameter is quantitatively used to characterize the free volume in the inorganic/organic nanocomposite matrix. [ABSTRACT FROM AUTHOR]

Published
2019
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31. Improving the measurement of butyltin compounds in environmental samples

Author

Al-Rashdi, Awad. and Al-Rashdi, Awad.

Abstract

Tributyltin compounds (TBT) are highly toxic pollutants, mainly introduced to the environment as a marine antifouling agent. The main aim of this work was to evaluate the present methods for the measurement of TBT and its breakdown products dibutyltin and monobutyltin in environmental sediments and waters and to improve upon their measurement. For the analysis of sediments, a triple hexane/acetic acid extraction was employed of tropolone complexes of the organotin compounds. Grignard reagent derivatization and measurements by gas chromatography with pulsed flame photometric detection were then employed. The TBT detection limit of 5 ?g Sn/ kg in sediment was below the UK environmental quality target (EQS) value for TBT in sediment (1-2 mg Sn/kg). A pilot investigation was carried out on a small dockyard in Southampton to evaluate if the total amount of tin could be used to predict the presence of TBT. Due to different sources of tin contamination in the studied area no clear overall correlation of TBT with total tin was found. As part of the investigation into the determination of butyltin in sediment, the extraction of TBT from paint particles deposited in sediment during boat refurbishment and the removal of sulphur interferences were investigated. For the extraction of TBT in paint, a pre-treatment procedure was developed based on pre-treatment with dichloromethane (DCM). This treatment improved the extraction of TBT from the paint, but TBT losses can occur during DCM removal by evaporation. Sulphur interferences were successfully removed from the sediment extract by improving the clean-up procedure. This procedure was based on treatment of the hexane extract with activated copper and then passing the hexane extract through a C18 solid phase extraction column. For the determination of butyltins in water a doubly functionalized mesoporous silica was synthesized and used to extract butyltin compounds from water based on a solid phase dispersion technique. Butyltin c

Published
2011

34. Effect of N2 Ion Bombardment on Optical and Mechanical Properties of Ultra-High Molecular Weight Polyethylene (UHMWPE)

Author

Abdul-Kader, A.M., El-Gendy, Y.A., Al-Rashdi, Awad A., and Salem, A.M.

Abstract

The effect of ion beam bombardment on the optical and mechanical properties of ultra-high molecular weight polyethylene (UHMWPE) was investigated. UHMWPE polymer samples were bombarded with 150 keV N2 ions under vacuum at room temperature to high fluences ranging from 1x1016 to 2x1017 ions cm-2. The untreated as well as treated samples were investigated by ultraviolet-visible (UV-Vis) spectrophotometer and Vickers micro-hardness techniques. The direct and indirect optical band gap decreased from 2.9 and 1.65 eV for pristine sample to 1.7 and 1 eV for those bombarded with N2 ion beam at the highest fluence, respectively. With increasing ion fluence, an increase in the number of carbon atoms per conjugation length, N and number of carbon atoms per cluster, M in a formed cluster were observed. A significant improvement in surface hardness was obtained by increasing the ion fluence.

Published
2013
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35. Fabrication of Novel Al(OH) 3 /CuMnAl-Layered Double Hydroxide for Detoxification of Organic Contaminants from Aqueous Solution.

Author

Eniola JO, Kumar R, Al-Rashdi AA, Ansari MO, and Barakat MA

Abstract

A novel lamellar Al(OH) 3 /CuMnAl-layered double hydroxide (LDH) nanocomposite was successfully synthesized via the hydrothermal method and tested as a highly efficient adsorbent for the removal of Congo red (CR) dye from aqueous solution. Structural, morphological, and spectroscopic characterization of the Al(OH) 3 /CuMnAl-LDH nanocomposite were studied by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, photoluminescence (PL) analysis, and UV-visible spectroscopy analysis techniques. The CR dye adsorption performance of the prepared materials increased with an increase in functionality. The adsorption capacity of the Al(OH) 3 /CuMnAl-LDH nanocomposite (172 mg/g, pH 7, temp 30 °C) was found to be higher than that of pure Al(OH) 3 (32 mg/g, pH 7, temp 30 °C) and CuMnAl-LDH (102 mg/g, pH 7, temp 30 °C). The results revealed that anion exchange and hydrogen bonding are mainly responsible for the adsorption of CR onto the Al(OH) 3 /CuMnAl-LDH nanocomposite. Moreover, the adsorption of CR in the presence of Cu(II) and NaCl salt showed a synergistic and antagonistic effect while the presence of anionic Cr(VI) ions had no significant effect. The adsorption thermodynamics, isotherm, and kinetics modeling analyses were also conducted to study the interactions between CR molecules and the Al(OH) 3 /CuMnAl-LDH nanocomposite. The adsorption of CR was found to be endothermic and followed by the pseudo-second-order kinetics and the Langmuir adsorption isotherm model. The developed nanocomposite showed excellent potential for treating industrial wastewater., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)

Published
2019
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