Environmentally friendly preparation of exfoliated graphite

H.M.A. Asghar,S.N. Hussain,H. Sattar,N.W. Brown,E.P.L. Roberts 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

Graphite intercalation compounds (GIC) have received global attention in the last decade because of the growing number of applications of these materials. Conventionally, bisulfate intercalated graphite is synthesized by chemical intercalation; which requires concentrated sulfuric acid (98%) and an oxidizing agent such as H2O2 and HNO3. In this study, bisulfate intercalated graphite was prepared by electrochemical intercalation using dilute sulfuric acid with the aim to reduce the sulfur content in the final product. The electrochemical intercalation method required sulfuric acid with half of the concentration of that required for chemical intercalation, and without the need for an oxidizing agent. Chinese natural large flake graphite was used as the raw material for the electrochemical process. The GIC was characterized by the exfoliation volume obtained by thermal shock at a temperature of 850℃. The effect of sulfuric acid concentration, electrochemical treatment time, particle size and temperature on the exfoliation volume was investigated. It was found that the exfoliation volume of the GIC-bisulfate, which is a function of degree of intercalation, can be controlled using the sulfuric acid concentration and treatment time. A sulfuric acid concentration of 50% and an electrochemical treatment time of 60 min were found to produce a GIC with the maximum exfoliation volume for the range of conditions studied.

Magnetic Properties of La3+-ion-doped Polycrystalline Z-type Hexaferrite Powders Synthesized via the Co-precipitation Method

M. M. Rashad,M. Rasly,I. A. Ibrahim,H. M. El-Sayed,A. A. Sattar 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3

Co2Z-type hexagonal ferrite powders doped with La3+ ions (Ba3−XLaxCo2Fe24O41 where x =0.0, 0.05, 0.10 and 0.15) were prepared using a co-precipitation method. The results revealed thatsingle-phase Co2Z-type ferrite was formed from the precipitated precursor in the presence of sodiumdodecyl sulfate (SDS) as an anionic surfactant. The obtained precursor was preheated at 600 ℃ for4 h then post annealed at 1300 ℃ for 6 h. The crystallite size increased with increasing of La3+-ion molar ratio. The microstructure of the formed powders appeared to be a hexagonal-plateletlikestructure. The DC resistivity of the obtained Co2Z decreased with increasing La3+ content. The saturation magnetization (Ms = 53.7 - 55.5 emu/g) was slightly increased with increasingsubstitution of La3+ ion. Moreover, two resonance frequency peaks were observed through theimaginary part of complex magnetic permeability; meanwhile, a decrease in the real part of thecomplex magnetic permeability was observed through the X-band frequencies.

Electrochemically synthesized GIC-based adsorbents for water treatment through adsorption and electrochemical regeneration

H.M.A. Asghar,S.N. Hussain,H. Sattar,N.W. Brown,E.P.L. Roberts 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

The flake GIC material delivered a small adsorptive capacity for a number of organic pollutants, however, underwent quick adsorption and electrochemical regeneration in minutes. In this study, binary and ternary GIC-based adsorbents were prepared using electrochemical intercalation of Chinese large flake graphite (CLFG) and Madagascan medium flake graphite (MMFG) materials. In this context GICbisulphate, GIC-nitrate, GIC-bisulphate-acetate, GIC nitrate-bisulphate, and GIC-nitrate-acetate were developed and characterized in order to evaluate their adsorptive and electrical properties. The adsorption behaviour was studied using an organic dye, acid violet 17, as a model dissolved organic pollutant. The treatment time and acid concentration for electrochemical intercalation were optimized in order to maximize the adsorptive capacity of the GIC based adsorbents. GIC-bisulphate delivered double adsorptive capacity after electrochemical intercalation, whereas, GIC nitrate diminished the adsorptive capacity to one half that of GIC bisulphate. However, no significant effect of ternary intercalated compounds was observed in terms of improved adsorption capacity or electrical conductivity.

Simplified methods of the 3D-SVPWM for four-wire three-leg inverter

Awad, Fathy H.,Mansour, Ahmed A.,Marei, Mostafa I.,El-Sattar, Ahmed A. The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.6

This paper introduces a novel technique for simplification of a three-dimension space vector pulse width modulation (3D-SVPWM). Conventional SVPWM calculations are based on trigonometric functions or several decomposition matrices. Thus, a very fast embedded controller is needed either for two-dimension space vector pulse width modulation (2D-SVPWM) or 3D-SVPWM. The proposed simplified 3D-SVPWM is dedicated to four-wire three-leg inverters. This technique is based on first-order equations of the curve fitting technique to reduce calculation time. Therefore, this method can be implemented with low memory storage and Central Processing Unit (CPU) capability. In addition, high accuracy can be achieved using higher-order equations. Many approaches are introduced for simplifications. The applications of the proposed simplified 3D-SVPWM method are also provided. Simulation results of the proposed simplified 3D-SVPWM and the conventional 3D-SVPWM are discussed. Finally, the results are verified using a real-time simulator based on Typhoon device (402) as Hardware-In-the-Loop. In addition, the controller of the simplified method is implemented and operated on the C2000 LAUNCHXL-F28379D as a low-cost microcontroller kit.

Chlorinated breakdown products formed during oxidation of adsorbed phenol by electrochemical regeneration of a graphite intercalation compound

S.N. Hussain,H.M.A. Asghar,H. Sattar,N.W. Brown,E.P.L. Roberts 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.30 No.-

The process of adsorption using graphite intercalation compound (GIC) adsorbent with electrochemicalregeneration has been investigated for the removal and oxidation of phenol in wastewater. The presentstudy deals with the formation of chlorinated breakdown products released in treated water duringelectrochemical regeneration of GIC adsorbents. The main chlorinated breakdown products observedwere 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol with lower concentrations of 2,4-dichlorophenol than 2-chlorophenol and 4-chlorophenol. Experiments performed at low current density( 10 mA cm 2), low initial phenol concentration (10 mg L 1), and use of a chloride free catholyteminimised the concentration of chlorinated breakdown products. In addition, only a few mg L 1 of 2,4-dichlorphenol and 3,5-dichlorophenol were observed after five adsorption cycles operated in batchrecycle mode for an initial phenol concentration of 50 mg L 1. The formation of chlorinated breakdownproducts was found largely to be associated with the oxidation of phenol from solution as opposed to theadsorbed phenol. These results have important implications in reducing the formation of chlorinatedbreakdown products during wastewater treatment by adsorption and electrochemical regeneration.

Disinfection performance of adsorption using graphite adsorbent coupled with electrochemical regeneration for various microorganisms present in water

S.N. Hussain,A.P. Trzcinski,H.M.A. Asghar,H. Sattar,N.W. Brown,E.P.L. Roberts 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.44 No.-

The disinfection performance of the process of adsorption using a graphitic material combined withelectrochemical regeneration for a range of microorganisms including bacteria, fungi, yeast and protozoain a laboratory scale sequential batch reactor is demonstrated. The bacterial species studied werePseudomonas aeruginosa,Staphylococcus aureus and Legionella pneumophila. A 3.0 log10 reduction in theconcentration of P. aeruginosa cells was achieved with the adsorbent that was regenerated at 30 mA cm 2with 100% regeneration on each adsorption cycle. The process was quite effective in removing S. aureuspresent in water with a significantly higher reduction in the number of cells (ca. 9-log10 reduction) atrelatively low current density (10 mA cm 2). Similarly, L. pneumophila were removed from water with aca. 7.5-log10 reduction in the number of bacterial cells. The SEM images confirmed the adsorption of L. pneumophila onto the adsorbent and its electrochemical regeneration at 20 mA cm 2 that is considered arefractory pathogen against chlorination. The process was also found to be suitable for disinfecting fungalspores, Aspergillus awamori and yeasts including Saccharomyces cerevisiae and Rhodosporidium turoloidesHowever, the removal of Cryptosporidium parvum from water was not demonstrated successfully. Thepreliminary results suggest that using a chloride free environment and a relatively high current densitycould be useful in disinfecting C. parvum.

Toxicological and Pharmacological Studies of New Coumarin and Furocoumarin Derivatives in Albino rats

Osama A. El Shabrawy,Seham Abd El Sattar El Batran,Mohamed Refat H. Mahran,Nabila M. Ibrahim 한국생약학회 2011 Natural Product Sciences Vol.17 No.4

Synthetic coumarin and furocoumarin derivatives were evaluated for anticoagulant activity and the effect on liver and kidney function. It was found that all of the compounds under investigation proved to be neither toxic nor lethal up to 500 mg/100 g body weight as a single dose for 24 hrs. All tested compounds showed a significant increase in prothrombin time (PT) in the acute model but failed to show a significant action in the chronic model. Furthermore, all tested compounds revealed a significant increase in activated partial thromboplastin time (APTT) as compared to control value in both acute and chronic model. Also, all tested compounds did not cause any significant changes on liver and kidney functions in rats.

A review on the properties and applications of chitosan, cellulose and deep eutectic solvent in green chemistry

Xin Xiong Chang,Nabisab Mujawar Mubarak,Shaukat Ali Mazari,Abdul Sattar Jatoi,Awais Ahmad,Mohammad Khalid,Rashmi Walvekar,E.C. Abdullah,Rama Rao Karri,M.T.H Siddiqui,Sabzoi Nizamuddin 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.104 No.-

The concept of green chemistry has attracted attention due to the green synthesis and ecofriendly natureof the compounds leading to the green and sustainable chemical industries and processes. Chitosan is anecofriendly material, which is biodegradable, non-toxic, and biocompatible. It has the potential to bemodified into biofilms for various applications such as biomedical, packaging, and pharmaceutical fields. Nevertheless, some poor properties of chitosan restrict its wide applications. The incorporation ofnanocellulose fillers into chitosan matrix can enhance the mechanical and thermal properties of chitosan. Cellulose nanomaterials can be achieved through chemical and mechanical modifications. The commontype of nanocellulose are cellulose nanofibers (CNFs), cellulose nano-whiskers (CNWs), tunicate CNCs (t-CNCs), algae cellulose particles (AC) and bacterial cellulose particles (BC). Nanocellulose are applied asthe reinforcement fillers in various polymer matrices such as polysaccharides, proteins, lipids, polylacticacid etc. Deep eutectic solvents (DES) are relatively novel green solvents, which can be applied in variousfields. DES are widely applied in metal processing, polymer processing and synthesis. Even though thereare not much studies available on DES for synthesis of nanocomposite films; however they are used aseco-friendly solvents in manufacturing processes. This study reviews the discovery, structure, propertiesof chitosan and cellulose, their derivatives and applications. In addition, the paper also discusses theproperties of DES and their applications.

Role of Natural Killer Cell Subsets in Cardiac Allograft Rejection : <b>NK Cells Promote Alloresponses</b>

McNerney, M. E.,Lee, K.-M.,Zhou, P.,Molinero, L.,Mashayekhi, M.,Guzior, D.,Sattar, H.,Kuppireddi, S.,Wang, C.-R.,Kumar, V.,Alegre, M.-L. Wiley (Blackwell Publishing) 2006 American journal of transplantation Vol.6 No.3

<P>To achieve donor-specific immune tolerance to allogeneic organ transplants, it is imperative to understand the cell types involved in acute allograft rejection. In wild-type mice, CD4(+) T cells are necessary and sufficient for acute rejection of cardiac allografts. However, when T-cell responses are suboptimal, such as in mice treated with costimulation-targeting agents or in CD28-deficient mice, and perhaps in transplanted patients taking immunosuppressive drugs, the participation of other lymphocytes such as CD8(+) T cells and NK1.1(+) cells becomes apparent. We found that host NK but not NKT cells were required for cardiac rejection. Ly49G2(+) NK cells suppressed rejection, whereas a subset of NK cells lacking inhibitory Ly49 receptors for donor MHC class I molecules was sufficient to promote rejection. Notably, rejection was independent of the activating receptors Ly49D and NKG2D. Finally, our experiments supported a mechanism by which NK cells promote expansion and effector function of alloreactive T cells. Thus, therapies aimed at specific subsets of NK cells may facilitate transplantation tolerance in settings of impaired T-cell function.</P>