Tawfik A. Saleh

King Fahd University of Petroleum and Minerals, Az̧ Z̧ahrān, Eastern Province, Saudi Arabia

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Publications (68)158.27 Total impact

  • Tawfik A. Saleh · Auwal M. Muhammad · Shaikh A. Ali
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    ABSTRACT: Hydrophobic cross-linked polyzwitterionic acid (HCPZA) containing long chain (C18) hydrophobes and residues of a glutamic acid having unquenched nitrogen valency was synthesized. Exploiting the chelating ability of the amino acid residues to scavenge toxic metals and the hydrophobic surface to scoop up the organic contaminants, the resin HCPZA was evaluated for simultaneous removal of chromium and eriochrome black T (EBT) from wastewaters. The structure and morphology of the polymer before and after sorption were characterized by using FTIR, TGA, EDX and SEM. The effect of various parameters such as contact time, pH and initial concentrations were investigated to arrive at optimum conditions. The adsorption of eriochrome black T and Cr (III) on HCPZA reached equilibrium in 30 min. The mechanism of adsorption was investigated using kinetic, diffusion and isotherm models. The adsorption kinetic data were described well by the pseudo-second order model and by the Freundlich isotherm model. EDX analysis confirmed the adsorption of Cr (III) and EBT on the polymer. The hydrophobic resin exhibited a remarkable simultaneous adsorption capacity for EBT and Cr (III) and thus demonstrated its potential to be a promising adsorbent for removal of dyes and heavy metal ions from wastewaters.
    No preview · Article · Jan 2016 · Journal of Colloid and Interface Science
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    ABSTRACT: Activated carbon derived from the rice straw was used for the rapid removal and fast adsorption of methylene blue (MB) from the solvent phase of the aqueous solution. The developed adsorbent was characterized using various analytical techniques such as scanning electron microscopy and FTIR. The effect of various influential parameters including solution pH, adsorbent dosage, contact time, initial adsorbate concentration, stirring speed, and temperature on MB removal were well investigated and optimized. The experimental optimized data showed that a maximum amount of MB ions can be removed at contact time 25 min, dye ion concentration 40 mg/L, and pH of 7. The obtained results of the isotherm study revealed that adsorption data was in good agreement with Langmuir isotherm model (with R2 value of 0.988 and maximum adsorption capacity of 62.5 mg/g at initial pH of 7 and temperature of 298 K). The negative values of ΔG° and the positive values of ΔH° (22.73 kJ/mol) and ΔS° (104 J/mol K) showed that the adsorption process was a spontaneous physical adsorption process i.e. endothermic and entropy driven.
    Full-text · Article · Jan 2016 · Desalination and water treatment
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    Gaddafi I. Danmaliki · Tawfik A. Saleh
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    ABSTRACT: Activated carbon was prepared from end-of-life tires, and its surface functional groups were enhanced by wet chemical oxidation using nitric acid. The carbonization and activation temperatures were optimized. The obtained material was characterized using a Brunauer-Emmett-Teller surface area analyzer, a Fourier transform infrared spectroscope and a scanning electron microscope coupled with an energy dispersive spectroscope. It was evaluated for adsorptive desulfurization of dibenzothiophene (DBT) in a model fuel. Five factors (dosage, concentration of the sulfur compounds, contact time, column length and flow rate) were varied using a 16 factorial design experiment. The optimum carbonization and activation temperatures that yielded a 473 m2/g surface area of the adsorbent for 5 hours were 500 °C and 900 °C, respectively. The interaction plot revealed that the adsorbent dosage, column length and dosage had the most influence on the percentage removal of DBT. The kinetic data for the adsorption process complied to a pseudo-second-order kinetic model with an R2 of 0.999, and the surface adsorption and intraparticle diffusion were operated concurrently. The equilibrium adsorption is best fitted using the Freundlich isotherm model. The efficiency of the produced carbons is comparable to other studies on adsorptive desulfurization, and the results are promising and should be tested for industrial applications.
    Full-text · Article · Jan 2016 · Journal of Cleaner Production
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    Tawfik A Saleh · Gaddafi I Danmaliki
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    ABSTRACT: This work reports on the influence of treatment conditions on the waste tire-derived activated carbon for adsorptive desulfurization. The rubber tires were carbonized and activated. The obtained activated carbon (AC) was treated with HNO3 or NaOH at a temperature range of 30-90 °C. The morphology and surface properties of AC were characterized by surface pH, Boehm's titration, N2 adsorption-desorption isotherms, Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscope. The AC sample, treated with HNO3 at 90 °C, possess the highest surface oxygen containing functional groups (2.39 mmol/g), surface area (473.35 m2/g) and pore volume (0.70 cm3/g) and the more adsorption capacity to the refractory sulfur compounds. The Boehm's titration experiments indicated that the amount of surface oxygen containing functional groups on the surface of the acid-treated AC increases with treatment temperatures. Acid-treated AC at 90 °C proves to be optimum for adsorptive desulfurization with the order of dibenzothiophene > benzothiophene > thiophene.
    Full-text · Article · Jan 2016 · Journal of the Taiwan Institute of Chemical Engineers
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    ABSTRACT: The study reports the synthesis of a unique cross-linked polymer containing zwitterionic (±) and dianionic (=) moieties in each repeating unit via tert-butyl hydroperoxide-initiated cyclopolymerization of N,N-diallyl-N-sulfopropyl ammonio-propyl phosphonic acid in the presence of a cross-linker to give a cross-linked polyzwitterion (CPZ). The cross-linked polyzwitterion/dianion (CPZDA) was accessed by the treatment of CPZ with NaOH. The structure and morphology of the polymer were characterized by using FTIR, TGA, EDX and SEM. The adsorption performance of the resin was evaluated using Ni(II) as a model under the influence of various parameters such as pH, initial metal ion concentration, contact time and temperature to arrive at the optimum conditions. The mechanism of the adsorption was investigated using kinetic, diffusion, isotherm and thermodynamic models. The maximum adsorption capacity at 296 K was found to be 45.5 mg/g at pH 5.5. The adsorption process fitted well pseudo-second order kinetic model and its mechanism was studied by intraparticle diffusion model. The thermodynamic parameters revealed the adsorption process as endothermic in nature with activation energy of 15.8 KJ/mol. In the context of metal ion removal, resin CPZDA has demonstrated its advantage of good stability, fast uptake, high capacity, and the ease of reusability. The resin's excellent ability to remove nickel (II) ions even from wastewater samples makes it a potential candidate for real sorption applications.
    Full-text · Article · Dec 2015 · Chemical Engineering Research and Design
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    ABSTRACT: A series of novel Polydithiocrabamates (DTCP) series were synthesized via Mannich-type polycondensation where Aniline and a series of diaminoalkanes were linked together with paraformaldehyde. The resultant polymer series were converted to dithiocarbamate (DTC) groups by reaction with carbon disulphide in the presence of potassium hydroxide. The size distribution, morphology, molecular structure, and properties of the DTCP series were analysed by FT-IR, 13C NMR, X-ray diffraction, FESEM, AFM, and TGA. A factorial design was created in order to study the effect of the alkyl chain length, pH, contact time and Hg (II) ions initial concentration on the performance of the DTCP towards the removal of Hg (II) ions from aqueous solution. After DTCP screening, further studies were performed on CS2-buta. The adsorption of Hg (II) ions on CS2-buta was spontaneous and endothermic, giving negative and positive values for δG and δH, respectively. The experimental data fitted the pseudo-second order kinetic model and Langmuir isotherm model (Q m=0.11mmol/g). CS2-buta demonstrated high selectivity for the removal of Hg (II) ions (99.87% removal) from wastewater samples. This suggests that CS2-buta demonstrates high potential towards removal of Hg (II) ions as well as other toxic heavy metals from wastewater.
    Full-text · Article · Nov 2015 · Journal of the Taiwan Institute of Chemical Engineers
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    ABSTRACT: Dune sand is one of the predominant soils in the world, particularly in the Arabian Peninsula and North Africa. In order to use these soils in constructions, pre-treatment of sand is essential. Though the usage of cement for stabilising sand has long been the practice to achieve the required strength, it is not cost effective and its manufacturing consumes a lot of energy. Consequently, it would be noble to use industrial by-products, often considered as waste materials, such as electric arc furnace dust (EAFD), in the stabilisation of sand. This research reports the potentiality of using EAFD for improving the strength of dune sand. Specimens, mixed with 2% cement and mixed with 5, 10, 20 and 30% EAFD plus 2% cement, were evaluated using unconfined compressive strength, soaked CBR and durability tests. Results of this investigation indicated that dune sand stabilised with 20 and 30% EAFD plus 2% cement has been qualified as a construction material for sub-base in rigid and flexible pavements, respectively, as per ACI requirements. Scanning electron microscope, energy dispersive X-ray analysis and backscattered electron images, in addition to, XRD analysis were used to identify the various phases in the sand-2% cement-30% EAFD mixture.
    No preview · Article · Oct 2015 · International Journal of Pavement Engineering
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    ABSTRACT: This work reports on the adsorption efficiency of two classes of adsorbents: nano-adsorbents including carbon nanotubes (CNTs) and carbon nanofibers (CNFs); and micro-adsorbents including activated carbon (AC) and fly ash (FA). The materials were characterized by thermogravimetric analysis, transmission electron microscopy, Brunauer–Emmett–Teller (BET) specific surface area, zeta potential, field emission scanning electron microscopy, and UV spectroscopy. The adsorption experimental conditions such as pH of the solution, agitation speed, contact time, initial concentration of phenol, and adsorbent dosage were optimized for their influence on the phenol. The removal efficiency of the studied adsorbents has the following order: AC > CNTs > FA > CNFs. The capacity obtained from Langmuir isotherm was found to be 1.348, 1.098, 1.007, and 0.842 mg/g of AC, CNTs, FA, and CNFs, respectively, at 2 hours of contact time, pH 7, an adsorbent dosage of 50 mg, and a speed of 150 rpm. The higher adsorption of phenol on AC can be attributed to its high surface area and its dispersion in water. The optimum values of these variables for maximum removal of phenol were also determined. The experimental data were fitted well to Langmuir than Freundlich isotherm models.
    Full-text · Article · Oct 2015 · Toxicological and Environmental Chemistry
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    DESCRIPTION: Expermental research work for treated water from phenol by using Nano and micro carbon based adsorbent materials .
    Full-text · Research · Sep 2015
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    ABSTRACT: The efficiency of Fe2O3, Al2O3 and TiO2 nanoparticles-loaded activated carbon (AC) for the adsorption of phenol from waters, was investigated. The raw and doped ACs were characterized by using Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, Thermogravimetric analysis and Brunauer–Emmett–Teller surface analysis. Batch adsorption experiments were performed to evaluate the effects of solution pH, agitation speed, contact time, adsorbent dosage and ionic strength on the phenol removal efficiency. Activated carbon impregnated with Fe2O3, Al2O3 and TiO2 showed higher adsorption capacity compared to raw AC. The maximum removal of phenol was achieved by iron oxide, aluminum Oxide and titanium oxide doped AC under the optimum conditions of 200 mg dosage, at pH 7, 150 rpm agitation speed, 2 ppm initial phenol concentration and contact time of 2 h. While for raw AC, the maximum removal was achieved for an adsorbent dosage of 300 mg under the same treatment conditions. The Langmuir isotherm model best fitted the data of the adsorption of phenol using AC, AC–TiO2, AC–Fe2O3 and AC–Al2O3, with correlation coefficient of 0.971, 0.96, 0.976 and 0.972. Surface characterization of both the impregnated AC showed an improvement in its surface area of the doped AC. The adsorption capacities, as determined by the Langmuir isotherm model were 1.5106, 3.1530, 3.2875 and 3.5461 mg/g for raw AC, AC–TiO2, AC–Fe2O3 and AC–Al2O3.
    Full-text · Article · Sep 2015 · Journal of Molecular Liquids
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    ABSTRACT: This work aims to evaluate the potential of waste rubber tire as an inexpensive sorbent material for nickel ion removal from aqueous solution. A laboratory scale study carried out on the production of activated carbon (AC) from waste rubber tire by physical activation method. Scanning electron microscope analysis was used to characterize the surface properties of the AC adsorbent. The surface area of AC was measured to be 465 m2/g. This large surface area of the AC could play a vital role in enhancing the removal of Ni(II). Aqueous solutions containing nickel ion in varying concentrations were prepared. Batch adsorption experiments at different operating parameters such as pH, metal concentration, adsorbent dose, contact time and temperature were carried out. These in turn revealed the adsorption capacity and helped in determining the mechanism with respect to thermodynamics, equilibrium and kinetics. The kinetic studies were carried out to determine the kinetics of the adsorption process. The Langmuir isotherm was followed under the present conditions with R2 = 0.938. The overall absolute deviations between experimental and predicted values were found to be 14.4%. The Langmuir model better appears to fit the adsorption of Ni onto AC adsorbent. The characterization and computational studies of the AC adsorbent after adsorption of nickel was also carried out and the results confirmed the positive adsorption process. FTIR analysis of AC before and after Ni adsorption indicated that adsorption of nickel metal on AC took place with the disappearance/diminishing of carbonyl groups. The results of nickel adsorption on AC revealed its potential for pollutant removal and finally its application in water treatment.
    No preview · Article · Sep 2015 · Desalination and water treatment
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    ABSTRACT: Exfoliated polystyrene/layered double hydroxide (PS/LDH) nanocomposites were prepared by direct intercalation of PS into MgAl LDH at 60 C. The MgAl LDH as the nanofiller was modified via the precipitation of the salt mixture of magnesium and aluminum metals by sodium dodecyl sulfate (SDS). Various techniques, Fourier Transformed Infrared Spectroscopy (FTIR), X-Ray-diffraction (XRD), Filed Emission Transmission Electron Microscopy (FETE) and thermo gravimetric analyses (TGA) were employed for structural properties and thermal stability of the nanocomposites. FTIR spectra indicated the presence of both functional groups of SDS–LDH and PS. XRD patterns and TEM images indicated the formation of amorphous dispersed and exfoliated nanocomposites. Increase in thermal stability with SDS–MgAl LDH content was observed by TGA and DTG through the T 0.5 (T 0.5 the degradation temperature at 50%) and T max (T max the maximum rate of change) with a maximum obtained for a loading of 2 and 4 wt%.
    Full-text · Article · Aug 2015 · RSC Advances
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    ABSTRACT: Silver hydroxide nanoparticles (AgOH-NPs) were efficiently festooned onto multiwalled carbon nanotubes (MWCNTs) and characterized by analytical techniques such as SEM, FT-IR and BET analysis. These were used for the removal of radioactive uranium(VI) followed by its complexation with eriochrome cyanine R in the presence of cetyl trimethyl ammonium bromide (CTAB). The adsorption process and its mass transfer were accelerated and assisted using ultrasound waves. The AgOH-NPs–MWCNTs has large surface area that was suitable for qualitative and quantitative removal of UO22+ ion. The effect of several parameters was optimized by central composite design (CCD) and the respective value was set as follows: adsorbent mass (5 mg), contact time (10 min), initial UO22+ ions concentration (2 mg L−1) and initial ECR concentration (8 mg L−1). It was found that UO22+ ion adsorption follow combination of the pseudo-second-order rate equation and intraparticle diffusion model. Equilibrium data well fitted with the Freundlich model and reveal that the small amount (5 mg) of AgOH-NPs–MWCNTs is sufficient for removal of high amount of UO22+ ion (R > 96% and adsorption capacity of 140 mg g−1) in a 10 min contact time.
    No preview · Article · Aug 2015 · The Chemical Engineering Journal
  • Tawfik A Saleh
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    ABSTRACT: Silica combined with 2 % multiwall carbon nanotubes (SiO2-CNT) was synthesized and characterized. Its sorption efficacy was investigated for the Hg(II) removal from an aqueous solution. The effect of pH on the percentage removal by the prepared material was examined in the range from 3 to 7. The adsorption kinetics were well fitted by using a pseudo-second-order model at various initial Hg(II) concentrations with R 2 of >0.99. The experimental data were plotted using the interparticle diffusion model, which indicated that the interparticle diffusion is not the only rate-limiting step. The data is well described by the Freundlich isotherm equation. The activation energy (Ea) for adsorption was 12.7 kJ mol−1, indicating the process is to be physisorption. Consistent with an endothermic process, an increase in the temperature resulted in increasing mercury removal with a ∆Ho of 13.3 kJ/mol and a ∆So 67.5 J/mol K. The experimental results demonstrate that the combining of silica and nanotubes is a promising alternative material, which can be used to remove the mercury from wastewaters.
    No preview · Article · Jun 2015 · Environmental Science and Pollution Research
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    ABSTRACT: In this work, ferric Oxidenanoparticles decoratedcarbon fibers and carbon nanotubes (CNF/Fe2O3 and CNT/Fe2O3) were synthesized and characterizedby Scanning Electron Microscopy (SEM), thermogravimetricanalysis (TGA), Energy Dispersive X-ray Spectroscopy (EDS),Transmission electron microscopy (TEM), X-ray Diffraction (XRD), Zeta Potential and BET surface area analyzer. The prepared nanocomposites were evaluated or the removal of phenol ions from aqueous solution.The effects of experimental parameters, such as shaking speed, pH, contact time, adsorbent dosage and initial concentration,were evaluated for the phenol removal efficiency. The adsorption experimental data were represented by both the Langmuir and Freundlich isotherm models. The Langmuir isotherm model best fitted the data on the adsorption of phenol, with a high correlation coefficient.The adsorption capacities, as determined by the Langmuir isotherm model were 0.842, 1.098, 1.684 and 2.778 mg/g for raw CNFs, raw CNTs, CNF-Fe2O3 and CNT-Fe2O3 respectively.
    Full-text · Article · Jun 2015 · Journal of Saudi Chemical Society
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    ABSTRACT: The present work reports on the efficiency of activated carbon loaded with zinc oxide nanoparticles (AC/ZnO) for removing dichloromethane, trichloromethane and carbon tetrachloride from aqueous solutions. Waste tires were used as a raw material for the production of activated carbon (AC) by thermo-chemical process. Zinc oxide nanoparticles were loaded into AC by using Zn(NO3)2.6H2O. The AC/ZnO composite has been characterized by BET analyzer, scanning electron spectroscope, energy dispersive X-ray spectroscope, FTIR spectrophotometer, and X-ray diffraction. Batch experiments were conducted under various adsorbent dosages, initial concentrations and contact time. Rapid adsorption was observed with adsorption capacity of 6.67 mg/g for dichloromethane, 11.91 mg/g for chloroform and 16.10 mg/g for carbon tetrachloride. The equilibrium was obtained in 20 min of contact time. The adsorption of these pollutants onto AC/ZnO was described well by the pseudo second-order model, and the hydrophilic fraction adsorption fitted the intraparticle diffusion model. Freundlich and Langmuir models were used to evaluate the process, and the Langmuir adsorption isotherm model fitted the data better than other models. The reusability of the composite was proved when no significant decrease in its adsorption capacity was observed even after several times of regeneration.
    Full-text · Article · May 2015 · Journal of the Taiwan Institute of Chemical Engineers
  • Tawfik A. Saleh · Abdulaziz A. Al‐Saadi
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    ABSTRACT: This work focuses on the surface characterization and sorption activity of carbon derived from waste tires. The carbon was prepared by thermal treatment of waste rubber tires, followed by exposure to nitric acid and hydrogen peroxide. The tired-obtained activated carbon (AC) was evaluated using a variety of techniques. Fourier transform infrared spectroscope and Raman spectra reveal existence of hydroxyl and carboxylic groups on AC surface. Scanning electron microscope and Brunauer–Emmett–Teller revealed the porosity of AC is well developed with mesopore structure (mesopore volume of 0.96 cm3/g). AC was tested for Rhodamine B sorption, and the adsorption kinetics well fitted using a pseudo second-order kinetic model. The adsorption isotherm data could be well described by the Langmuir model. Semiempirical calculations using Austin Model 1 were performed to explain the adsorption at molecular level. Binding enthalpies in the range of 0.5–4 kcal/mol of four possible scenarios were computed. We believe the combination between experimental work and semiempirical calculations allows for a better understanding of Rhodamine B molecules adsorption on the AC surface. Copyright © 2015 John Wiley & Sons, Ltd.
    No preview · Article · May 2015 · Surface and Interface Analysis
  • Zakariyah A. Jamiu · Tawfik Abdo Saleh · Shaikh A. Ali
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    ABSTRACT: In this work, a unique cross-linked polyzwitterion/anion having aspartic acid residue was synthesized via butler’s cyclopolymerization protocol involving N,N-diallylaspartic acid hydrochloride, 1,1,4,4-tetraallylpiperazinium dichloride and sulfur dioxide in the presence of azoisobutyronitrile. The structure and morphology of the polymer were characterized by using FTIR, TGA, EDX and SEM. The adsorption performance of the resin was evaluated using lead Pb(II) as model. The effect of various parameters such as contact time, pH, initial concentration and temperature were investigated to arrive at optimum conditions. Optimum pH of 6.0 and dosage of 1.5g L-1 were obtained. The mechanism of adsorption was investigated using kinetic, diffusion, isotherm and thermodynamic models. The adsorption kinetic data were described well by the pseudo-second order model with R2 of 0.999. The activation energy (Ea) of the adsorption process was calculated as 39.29 kJ mol−1. The negative ∆Go values indicate a spontaneous adsorption process while the negative ∆Ho (-43.87 KJ/mol) suggests an exothermic reaction. Adsorption data were described well by the Langmuir and Temkin models. EDX analysis confirmed the adsorption of Pb2+on the polymer. The overall results suggest that the polymer could be employed as an efficient adsorbent for the adsorption of toxic Pb2+ from polluted aqueous solutions.
    No preview · Article · Apr 2015 · RSC Advances
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    ABSTRACT: A film-shear reactor was used to significantly enhance the oxidative desulfurization (ODS) of model fuels using hydrogen peroxide as the oxidant. Significant increases in the amount of sulfur removed were seen in comparison to conventionally stirred ODS reactions. For example, up to 50% desulfurization occurred in a single pass of the model fuel through the film-shear reactor at 10 °C. The desulfurization reactions were very fast in the reactor, occurring on the time scale of seconds to minutes. Desulfurization was studied under a variety of conditions, and a statistical design of experiment (DOE) showed that the fuel to oxidant ratio was the only statistically significant parameter to impact the extent of desulfurization: a larger amount of oxidant led to higher desulfurization. A variety of benzothiophene contaminants (benzothiophene, 2-methylbenzothiophene, 5-methylbenzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene) were examined, and the film-shear reactor was effective in removing all of these contaminants. The film-shear reactor was effective at both low (0.5-2.0 mL/min) and high (100-300 mL/min) flow rates. Experiments showed that oxygen in air was not an effective oxidant for ODS in the film-shear reactor. Experiments using Mo(CO)6 as a molecular thermometer showed that “hot spots” are not forming in the film-shear reactor, and thus the increase in the ODS rate cannot be attributed to intense thermal activation occurring within the film-shear reactor. It is suggested that superb mixing of the aqueous and fuel phases is responsible for the increased rate of ODS in the reactor.
    No preview · Article · Apr 2015 · Fuel
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    ABSTRACT: In the present work, alumina/carbon nanotube nanocomposite was synthesized and characterized using field emission scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface analyzer. The nanocomposite was evaluated for the 4-chlorophenol and phenol removal from aqueous solution with comparison to the pristine carbon nanotubes. Batch adsorption experiments were carried out to evaluate the effect of pH, agitation speed, contact time, adsorbent dosage, and initial concentration on the 4-chlorophenol and phenol removal efficiency. Experimental result showed the adsorption of 4-chlorophenol and phenol by nanocomposite to be pH dependent with the highest removal achieved at pH 6. CNTs showed better adsorption efficiency than CNT–Al2O3 which could be assigned to the increase in the surface area from 155.5 m2/g of CNT to 227.5 m2/g of CNT–Al2O3. Langmuir and Freundlich isotherm models were applied for analyzing adsorption equilibrium data of 4-chlorophenol removal on the as-prepared nanocomposite and pristine carbon nanotubes, which suggested that the Langmuir model provides better correlation of the experimental data with R2 of 0.994 and 0.999 respectively. While for phenol, correlation coefficients of Langmuir adsorption isotherm model were 95% and 99.4% for CNT and CNT–Al2O3 respectively.
    Full-text · Article · Feb 2015 · Journal of Molecular Liquids