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- 저자 : H.M.A. Asghar (검색결과 8 건)
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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.
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Comparative adsorption–regeneration performance for newly developed carbonaceous adsorbent
H.M.A. Asghar,S.N. Hussain,N.W. Brown,E.P.L. Roberts 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.69 No.-
A proprietary adsorbent material called Nyex 1000 was developed by the Arvia Technology Ltd. (UK based waste water treatment company). Nyex 1000 was being employed for a number of commercial applications dealing with the removal of organic contaminants from industrial effluents. This adsorbent material had small adsorptive capacity. With the aim to address small adsorptive capacity, a new graphite based adsorbent material was developed. The particle design was accomplished through successive chemical, thermal and mechanical treatments of raw graphite material (natural large flake graphite, to be called here as NLFG). The chemical treatment of the NLFG was carried out through electrochemical intercalation using dilute (50%) sulfuric acid in an electrochemical cell. Chemically treated NLFG then went through thermal treatment at 850 °C and followed by mechanical treatments consisting of compression (4536 kgf cm−2) and chopping at 18,000 rpm for 30 s. The developed adsorbent material, (exfoliated compacted graphite, to be called here as ECG) and NLFG were characterized using state of the art techniques including SEM, BET surface area, XRD, Zeta potential, Boehm surface titration, bed electrical conductivity and laser size analysis. The characterization results showed significant increase in internal specific surface area from 1 to 17 m2 g−1. It was attributed to the development of partially porous particle surface verified by SEM results. The XRD, Boehm surface titration, Zeta potential results endorsed the associated chemical and physical changes appeared in the composition of the NLFG as a result of chemical, thermal and mechanical treatments. Adsorption-regeneration studies were conducted using developed ECG and existing Nyex 1000 materials. The pollutants used for adsorption–regeneration studies were acid violet 17, phenol, humic acid, ethane thiol and methyl propane thiol dissolved in aqueous solution. The results were compared and it was found that ECG showed significantly improved adsorption capacity with many folds. Both adsorbent materials, ECG and Nyex 1000 delivered 100% electrochemical regeneration efficiencies.
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H.M.A. Asghar,S.N. Hussain,E.P.L. Roberts,A.K. Campen,N.W. Brown 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.5
With the aim to address waste water treatment problems, a novel and economic water treatment technology was introduced at the University of Manchester. It comprised of a unique combination of adsorption and electrochemical regeneration in a single unit. This process successfully eliminated a number of organic pollutants by using an electrically conducting adsorbent material called NyexTM which was a modified form of synthetic graphite. To expand the scope of other graphite types in waste water treatment applications, natural vein and recycled vein graphite materials were selected for electrochemical surface treatment (pre-treatment) in order to evaluate their adsorptive and electrical properties. New graphite based adsorbents were developed and characterized using a laser diffraction particle size analyser,BET surface area, SEM analysis, X-ray (EDS) elemental analysis, X-ray powder diffraction, Boehm surface titration, Zeta potential electrical bed conductivity and bulk density measurements. Boehm surface titration and EDS (X-ray) elemental analysis showed a significant increase in oxygen containing surface functional groups. Although, no significant improvement in bed electrical conductivity was found to occur after electrochemical surface treatment, however, natural vein and recycled vein graphite materials presented highest bed electrical conductivity amongst competing graphite materials. Aqueous solution of acid violet 17 as a standard pollutant was used to evaluate the comparative performance of these adsorbents. The investigations revealed that electrochemical surface treatment contributed to an increase in the adsorption capacity by a factor of two only for natural vein graphite. Un-treated recycled vein graphite adsorbent delivered the same adsorptive capacity (3.0 mg g-1) to that of electrochemically treated natural vein graphite. The electrochemical regeneration efficiency at around 100% was obtained using a treatment time of 60 and 30 min, current density of 14 mA cm-2, charge passed of 36 and 18 C g-1 for synthetic graphite, natural and recycled vein graphite materials respectively. Relatively a small consumption of electrical energy, 24 J g-1 for regenerating natural vein graphite adsorbent versus 36 J g-1 for synthetic graphite adsorbent, was found to be required for destruction/oxidation of adsorbed acid violet 17. Multiple adsorption/regeneration cycles presented no loss in adsorptive capacity over 5adsorption/regeneration cycles. The use of natural and recycled vein graphite adsorbents offered some advantages over graphite intercalation based adsorbents with reduced electrical energy consumption during regeneration and simpler separation of particulate adsorbent.
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H.M.A. Asghar,S.N. Hussain,N.W. Brown,E.P.L. Roberts 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.3
Electrically conducting adsorbent materials called NyexTM 1000 & 2000 have already been reported withcomparatively low adsorption capacity for various organic, biologically non-degradable and toxiccompounds. Two composite adsorbents called CA1 & CA2 were synthesized using synthetic graphite-carbon black and expanded graphite-carbon black respectively. The aim of developing the newadsorbents was to increase the adsorption capacity along with good electrical properties. The developedadsorbents were characterized using N2 adsorption for specific surface area, Boehm surface titration forsurface chemistry, bed electrical conductivity, laser size analyzer for average particle size, and scanningelectron microscope (SEM) for particle morphology and shape. Then both the composite adsorbents weretested for the adsorption of acid violet 17 followed by an electrochemical regeneration. The adsorptionstudy revealed that both the adsorbents had almost similar kinetic behavior with a significant increase inadsorption capacity for acid violet 17 (300 & 26 mg g-1 respectively) when compared with theadsorption capacity of previously developed electrically conducting materials called NyexTM 1000 &2000 (3.5 and 9 mg g-1 respectively). The composite adsorbent CA2 was successfully electrochemicallyregenerated by passing an electric charge of 138 C g-1 at a current density of 14 mA cm-2 for a treatmenttime of 60 min, whereas, the composite adsorbent CA1 could not be regenerated successfully. Theregeneration efficiencies of CA2 were obtained at around 120% during five adsorption–regenerationcycles. The amount of actual charge passed of 138 C g-1 for achieving 100% regeneration efficiency wasfound to be similar with stoichiometrically calculated amount of charge. The amount of electrical energyrequired to oxidize each mg of adsorbed acid violet onto CA2 (24 J mg-1) was found to be significantlylower to that of NyexTM 1000 & 2000 adsorbents (52 J mg-1 & 32 J mg-1 respectively).
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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.
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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.
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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.
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