Tawfik A. Saleh

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

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Publications (50)120.93 Total impact

  • [Show abstract] [Hide abstract]
    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.
    Chemical Engineering Journal 08/2015; 273. DOI:10.1016/j.cej.2015.03.002 · 4.32 Impact Factor
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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.
    Journal of the Taiwan Institute of Chemical Engineers 05/2015; DOI:10.1016/j.jtice.2015.04.004 · 3.00 Impact Factor
  • 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.
    Surface and Interface Analysis 05/2015; 47(7). DOI:10.1002/sia.5775 · 1.39 Impact Factor
  • 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.
    RSC Advances 04/2015; 5(53). DOI:10.1039/C5RA05447H · 3.71 Impact Factor
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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.
    Fuel 04/2015; 156. DOI:10.1016/j.fuel.2015.04.028 · 3.41 Impact Factor
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    ABSTRACT: In this work, the potential of fly ash impregnated with aluminum oxide (FA-Al2O3) for adsorption of phenol from aqueous solution was studied. Batch adsorption experiments were carried out to evaluate the effects of the experimental parameters pH, agitation speed, contact time, adsorbent dosage, and initial concentration on the phenol removal efficiency. The adsorption of phenol by FA-Al2O3 was found to be pH dependent with the best removal achieved at pH 7. The optimum set of parameters for the removal were, 200 rpm agitation speed, 200 mg adsorbent dosage, 2 h contact time, and 2 ppm initial phenol concentration. Both the Langmuir and Freundlich isotherm models represented the adsorption experimental data. However, the Langmuir isotherm model best fitted the data on the adsorption of phenol using FA and FA-Al2O3, with correlation coefficient of 97.7 and 97.9, respectively. The improvement in the adsorption efficiency of FA-Al2O3 over FA could be attributed to the increase in the surface area, which was found to be 11.889 m2/g and 7.1 m2/g for FA-Al2O3 and FA, respectively.
    Desalination and water treatment 02/2015; DOI:10.1080/19443994.2015.1010238 · 1.17 Impact Factor
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    ABSTRACT: The cross-linked tetrapolymeric anionic polyelectrolyte (CAPE) was synthesized. The sorption activity of CAPE was evaluated for the adsorption of chromium (III). Adsorption process fitted the pseudo-second order kinetic model well. The CAPE is of fast uptake with high capacity and reusability. g r a p h i c a l a b s t r a c t a b s t r a c t A novel cross-linked acidic tetrapolymer (CPZA) was synthesized via the cyclopolymerization of different zwitterionic monomers bearing amino, carboxylate, phosphonate and sulfonate motifs and a cross-linker using ammonium persulfate as the initiator. The cross-linked tetrapolymeric anionic polyelectrolyte (CAPE) was obtained by the treatment of CPZA with NaOH. The sorption activity of CAPE was evaluated for the adsorption of chromium (III) using batch equilibrium technique. The experimental data fitted Langmuir, Freundlich and Temkin isotherm models. The maximum adsorption capacity was found to be 48.5 mg/g at pH 5.5 and temperature of 296 K. The adsorption process fitted pseudo-second order kinetic model well and the mechanism was studied by intraparticle diffusion model. Thermodynamic parameters reveal that the adsorption process was endothermic in nature. The resin has not only the advantages of fast uptake with high capacity but also the ease of reusability and good stability. The resin demonstrates an excellent ability to remove chromium (III) ions even from real wastewater samples, suggesting that the resin could be a good candidate for real sorption applications.
    Chemical Engineering Journal 02/2015; 269:9. DOI:10.1016/j.cej.2015.01.083 · 4.32 Impact Factor
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    ABSTRACT: This work reports a comprehensive study of the adsorption characteristics of cadmium(II) on modified structures of carbon nanotubes (CNTs), carbon nanofibres (CNFs), activated carbon (AC), and fly ash (FA). The characterization was performed using field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface analysis. Several experimental parameters; adsorbent dosage, pH, and agitation speed and contact time, were investigated for their effects on the adsorption of cadmium(II) from water. The optimum conditions of 2 h of contact time, pH 7, 50 mg adsorbent dosage and 150 rpm rotational speed were observed. Models of first-order, second-order and pseudo-second-order were fitted to the experimental data, and pseudo-second-order kinetics were observed to describe the adsorption of cadmium(II) on these adsorbents. The adsorption behaviours of cadmium(II) were evaluated using the Freundlich and Langmuir isotherm models. The maximum adsorption capacities of the modified adsorbents were observed to be 2.02 mg/g, 1.98 mg/g, 1.22 mg/g and 1.58 mg/g, for CNTs, AC, CNFs and FA, as obtained from Langmuir isotherm models. It was determined that surface modification of the CNTs, CNFs, and AC enhanced their adsorption efficiency. The results obtained are promising for the use of these modified materials with respect to water purification applications.
    Journal of Molecular Liquids 01/2015; DOI:10.1016/j.molliq.2015.01.033 · 2.08 Impact Factor
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    ABSTRACT: In this study the electrochemistry of carbidopa (CD) was studied by electrochemical methods at a carbon paste electrode modified by ZnO/CNTs nanocomposite and room-temperature ionic liquid, n-hexyl-3-methylimidazolium hexafluoro phosphate (ZnO/CNTs/ILs/CPE). The oxidation peak potential of the CD at a surface of ZnO/CNTs/ILs/CPE appeared at 570 mV that was about 90 mV lower than the oxidation peak potential at the surface of the unmodified carbon paste electrode (CPE) under similar condition. Under the optimized conditions, the oxidation peak current of CD showed two linear dynamic ranges (in 0.09–450 μmol L−1) with a detection limit of 0.05 μmol L−1, using square wave voltammetry (SWV). The proposed sensor was successfully applied for the determination of CD in real samples such as pharmaceutical serum, water and urine.
    International journal of electrochemical science 12/2014; 10(2). · 1.96 Impact Factor
  • Tawfik A. Saleh, V.K. Gupta
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    ABSTRACT: The remarkable increase in the number of vehicles worldwide; and the lack of both technical and economical mechanisms of disposal make waste tires to be a serious source of pollution. One potential recycling process is pyrolysis followed by chemical activation process to produce porous activated carbons. Many researchers have recently proved the capability of such carbons as adsorbents to remove various types of pollutants including organic and inorganic species. This review attempts to compile relevant knowledge about the production methods of carbon from waste rubber tires. The effects of various process parameters including temperature and heating rate, on the pyrolysis stage; activation temperature and time, activation agent and activating gas are reviewed. This review highlights the use of waste-tires derived carbon to remove various types of pollutants like heavy metals, dye, pesticides and others from aqueous media.
    Advances in Colloid and Interface Science 09/2014; 211. DOI:10.1016/j.cis.2014.06.006 · 8.64 Impact Factor
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    ABSTRACT: This work reports the recycling of waste rubber tires (WRT) to produce a carbonaceous material as adsorbent of an environmental value. The produced material was activated by thermal–chemical process. The WRT-derived carbonaceous adsorbent (CA) was characterized by means of scanning electron microscope, energy-dispersive X-ray spectroscopy and infrared and Raman spectroscopic techniques. The developed CA was tested and evaluated as potential adsorbent for methyl orange (MO) removal. A series of MO stock solutions whose concentrations range from 1 × 10− 6 to 1 × 10− 4 M was prepared to investigate the possible activity of CA. Experimental parameters such as dosage amount, initial concentration and temperature were optimized. A rapid and fast equilibrium has been observed. The maximum adsorption took place in the pH range of 3–5. The temperature-effect study revealed that the process is exothermic. A possible adsorption mechanism has been suggested on the view of calculated frontier molecular orbitals of the methyl orange molecule.
    Journal of Molecular Liquids 03/2014; 191:85–91. DOI:10.1016/j.molliq.2013.11.028 · 2.08 Impact Factor
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    ABSTRACT: Pulsed laser ablation in liquid (PLAL) with 532 nm wavelength laser with 5 ns pulse duration is used to produce the nanostructure copper oxide and the effects of oxidizing media (deionized water and hydrogen peroxide) on the composition, morphology and optical properties of the product materials produced by PLAL were studied. XRD and TEM studies indicate that in the absence of hydrogen peroxide, the product material is in two phases (Cu/Cu2O) with the spherical nanoparticle structure, whereas in the presence of hydrogen peroxide in the liquid medium, the product material revealed other two phases (Cu/CuO) with nanorod-like structure. The optical studies revealed a considerable red shift (3.34-2.5 eV) in the band gap energy in the case of hydrogen peroxide in the liquid medium in PLAL synthesis compared to the one in the absence of it. Also the product material in the presence of hydrogen peroxide in the liquid medium showed a reduced photoluminescence intensity indicating the reduced electron-hole recombination rate. The red shift in the band gap energy and the reduced electron-hole recombination rate make the product material an ideal photocatalyst to harvest solar radiation for various applications. The most relevant signals on the FTIR spectrum for the samples are the absorption bands in the region between 450 and 700 cm-1 which are the characteristics bands of copperoxygen bonds. The reported laser ablation approach for the synthesis of Cu2O and CuO nanoparticles has the advantages of being clean method with controlled particle properties.
    Applied Surface Science 12/2013; 286:149-155. DOI:10.1016/j.apsusc.2013.09.038 · 2.54 Impact Factor
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    ABSTRACT: Pulsed laser ablation in liquids is a simple synthesis process of nano-particles for the production of high purity material with no need for any expensive instrumentation except laser. The 532 nm wavelength laser beam with 5 ns pulse width and 10 Hz repetition rate was an ablating laser source. In order to control the size and stoichiometry of the nano particles, the laser ablation was done in the presence of 9% of H2O2. The optical properties and structure of the prepared samples were studied using different analytical techniques, such as energy dispersive X-ray spectroscope (EDS), X-ray Diffraction, UV-Visible absorption, Photoluminescence, FT-IR. In order to study the morphology of the prepared nano-sized powders, Field Emission Scanning Electron Microscope was used. From the above analytical studies it was found that the particle size was between 13 and 28 nanometer, while the band gap energy was estimated to be 2.46 eV.
    2013 10th International Conference on High Capacity Optical Networks and Enabling Technologies (HONET-CNS); 12/2013
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    ABSTRACT: The aim of this work was to investigate the utilization of waste tire carbons as a low cost adsorbent for removal of cadmium (II) ion from aqueous solution with density functional theory calculations to shed more light on the adsorption process. Thus, activated carbon was prepared from waste rubber tires and characterized by means of field emission scanning electron microscopy, energy-dispersive X-ray and Fourier transform infrared spectroscopies. Effect of various operating parameters like contact time, dosage, agitation speed and pH on the removal of Cd(II) from aqueous solution by the batch adsorption technique was investigated. The adsorption process was relatively fast and the equilibrium was reached after about 60 min of contact. Characterization of activated carbon after adsorption was also conducted. Density functional theory (DFT) calculations were performed to estimate the binding energy of Cd2 + ions towards carboxylic acid, carbonyl and hydroxyl groups. The calculated binding energy of the adsorption process was predicted to be in the range of 190–212 kcal/mol, and the Cd2 + ion tends to approach more conveniently towards the carbonyl's oxygen atom in the carboxylic acid and carbonyl groups. The developed sorbent exhibited the advantages of being inexpensive and of double benefit to the environment.
    Journal of Molecular Liquids 12/2013; 188:136–142. DOI:10.1016/j.molliq.2013.09.036 · 2.08 Impact Factor
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    Preprints-American Chemical Society, Division of Energy Fuels, Indianapolis, Indiana, USA; 09/2013
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    ABSTRACT: Effective activated porous carbon (AC) was prepared by thermal treatment of waste rubber tires and was further activated using oxidizing agents like nitric acid and hydrogen peroxide. The tire-derived porous carbon was characterized by means of FTIR and X-ray diffraction. Careful analysis of the IR spectra of the synthesized AC reveals a number of bands centered at about 3400, 2350, 1710, 1650, and 1300-1000cm, proving the existence of hydroxyl and carboxylic groups on the surface of AC in addition to CC double bonds. The developed AC was tested and evaluated as a potential adsorbent for the removal of lead (II) ions. Experimental parameters, such as contact time, initial concentration, adsorbent dosage, and pH were optimized. AC was effective in a pH range between 4 and 7 with a highest uptake of lead ions at pH 5 and 6. For further understanding of the chemistry behind the process, density functional theory (DFT) calculations were performed at the B3LYP/6-31G(d) level adopting a functionalized pyrene molecule as a model. The binding energy of Pb(II) ion toward carboxylic acid, carbonyl, and hydroxyl groups was calculated. A binding energy in the range of 310-340kcal/mol, which is considered to be high and to be indicative of a chemisorptions process, was predicted. The adsorption of the lead ion toward the CO groups in relatively all cases shows more stable binding compared to the sorption toward the alcohol groups.
    Journal of Colloid and Interface Science 04/2013; 396:264-9. DOI:10.1016/j.jcis.2013.01.037 · 3.55 Impact Factor
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    ABSTRACT: Environmental friendly and clean transportation fuels are very important and worldwide desired fuels. It can be achieved by removing undesirable compounds/elements in fuel oil. Most prominent among these are sulfur compounds and up to a lesser extent nitrogen compounds. Thus removal of sulfur compounds from fuel oils has become very significant and gained maximum attention worldwide to produce better quality fuels without sulfur compounds or a minimum possible limit. We are reporting here results of our ongoing research project being carrying out using novel coated metaloxides for the adsorption and removal of sulphur compounds in model fuel oils. Dimethyl dibenzothiiophene (DMDBT) and Dibenzothiiophene (DBT), were mainly used in model fuel oil. Several reaction conditions were applied and at optimized conditions around 60-80% desulfurization was achieved. The initial results revealed that these coated metal oxides are very effective in adsorbing DMDBT and DBT on the surface of metal oxides. Overall the non-catalytic desulfurization process of adsorption provided very effective results and these metal oxides can further be modified to get more desired results.
    245th ACS National Meeting & Exposition, Preprints, Division of Energy and Fuels; 04/2013
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    ABSTRACT: Adsorption is a widely used technique for the separation and removal of pollutants from wastewaters. Carbon nanotubes (CNTs) are emerging as potential adsorbents because of its well defined cylindrical hollow structure, large surface area, high aspect ratios, hydrophobic wall and easily modified surfaces. In this review, dye adsorption capability of CNTs and CNT based composites from aqueous system has been compiled. This article provides the information about the defect, adsorption sites on CNTs and batch adsorption studies under the influence of various operational parameters such as contact time, solution pH, temperatures etc. and deals with mechanisms involved in adsorption of dyes onto CNTs. From the literature reviewed, it is observed that single walled carbon nanotubes (SWCNTs) show higher adsorption capacity than multi walled carbon nanotubes (MWCNTs) and functionalized and CNT composite have better sorption capacity than as grown CNTs. It is evident from the literature that CNT based nanosorbents have shown good potential for the removal of dyes from aqueous solution. However, still more research work should be focused on the development of cost effective, higher efficient and environmental friendly CNT based nanosorbents for their commercial applications.
    Advances in Colloid and Interface Science 03/2013; DOI:10.1016/j.cis.2013.03.003 · 8.64 Impact Factor
  • Vinod K Gupta, Tawfik A Saleh
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    ABSTRACT: The quality of water is continuously deteriorating due to its increasing toxic threat to humans and the environment. It is imperative to perform treatment of wastewater in order to remove pollutants and to get good quality water. Carbon materials like porous carbon, carbon nanotubes and fullerene have been extensively used for advanced treatment of wastewaters. In recent years, carbon nanomaterials have become promising adsorbents for water treatment. This review attempts to compile relevant knowledge about the adsorption activities of porous carbon, carbon nanotubes and fullerene related to various organic and inorganic pollutants from aqueous solutions. A detailed description of the preparation and treatment methods of porous carbon, carbon nanotubes and fullerene along with relevant applications and regeneration is also included.
    Environmental Science and Pollution Research 02/2013; 20(5). DOI:10.1007/s11356-013-1524-1 · 2.76 Impact Factor
  • ChemInform 11/2012; 43(45). DOI:10.1002/chin.201245270