Showing papers by "Tawfik A. Saleh published in 2016"

Nanocomposite of carbon nanotubes/silica nanoparticles and their use for adsorption of Pb(II): from surface properties to sorption mechanism

Abstract: This paper demonstrates the synthesis of multi-wall carbon nanotubes and silica nanocomposite (CNT/SiO2). Successful realization of MWCNT/SiO2 nanostructure was observed by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and high-resolution transmission electron microscopy studies. The as-prepared nanocomposite was evaluated as an adsorbent to remove lead, Pb(II), from aqueous solutions. The resulting MWCNT/SiO2 manifests propitious adsorption performance (~95%) over silica nanoparticles (~50%) and CNTs (~45%). Lagergren’s pseudo-first order, pseudo-second order and intraparticle diffusion models were used to analyse the kinetic data obtained at different initial Pb(II) concentrations. The adsorption kinetic data were described well by the pseudo-second order model with R2 of 0.99. The activation energy (Ea) of the adsorption process was calculated as 15.8 kJ mol−1. Adsorption data were described well by the Langmuir and Temkin models. Th...

Graphene Dendrimer-stabilized silver nanoparticles for detection of methimazole using Surface-enhanced Raman scattering with computational assignment

Abstract: Graphene functionalized with polyamidoamine dendrimer, decorated with silver nanoparticles (G-D-Ag), was synthesized and evaluated as a substrate with surface-enhanced Raman scattering (SERS) for methimazole (MTZ) detection. Sodium borohydride was used as a reducing agent to cultivate silver nanoparticles on the dendrimer. The obtained G-D-Ag was characterized by using UV-vis spectroscopy, scanning electron microscope (SEM), high-resolution transmission electron microscope (TEM), Fourier-transformed infrared (FT-IR) and Raman spectroscopy. The SEM image indicated the successful formation of the G-D-Ag. The behavior of MTZ on the G-D-Ag as a reliable and robust substrate was investigated by SERS, which indicated mostly a chemical interaction between G-D-Ag and MTZ. The bands of the MTZ normal spectra at 1538, 1463, 1342, 1278, 1156, 1092, 1016, 600, 525 and 410 cm−1 were enhanced due to the SERS effect. Correlations between the logarithmical scale of MTZ concentrations and SERS signal intensities were established, and a low detection limit of 1.43 × 10−12 M was successfully obtained. The density functional theory (DFT) approach was utilized to provide reliable assignment of the key Raman bands.

Influence of acidic and basic treatments of activated carbon derived from waste rubber tires on adsorptive desulfurization of thiophenes

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.

Synthesis of zinc oxide/talc nanocomposite for enhanced lead adsorption from aqueous solutions

Abstract: In this study, talc was modified with zinc oxide nanoparticles to form a ZnO/talc nanocomposite. The nanocomposite was characterized using X-ray powder diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption/desorption, field emission scanning electron microscopy. The characterization revealed that ZnO nanoparticles were well incorporated with the talc. The adsorption efficiency of the prepared nanocomposite was evaluated for Pb(II) removal from aqueous solution. The related parameters such as agitating time, dosage and pH, were optimized. Adsorption characteristics of the talc, and ZnO/talc nanocomposite were compared and the results showed that ZnO/talc nanocomposite had the highest adsorption capacity. The kinetic sorption data were found to fit the pseudo-second-order kinetic model. The experimental isotherm data of lead adsorption were examined using the Freundlich and the Langmuir models. The maximum lead adsorption capacity of the adsorbent was determined as 48.3 mg g−1. The mechanism of adsorption was found to be controlled by electrostatic attraction on the nanocomposite. The overall results indicated the prepared nanocomposite can be employed as an alternative for Pb(II) removal from wastewater.

Synthesis of hydrophobic cross-linked polyzwitterionic acid for simultaneous sorption of Eriochrome black T and chromium ions from binary hazardous waters.

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.

An Overview of Membrane Science and Technology

Abstract: In this chapter, the reader can find extensive and useful information regarding membranes, including membrane definition, history, and the major contributions in membrane science and technology. The contributions before 1900 and the contributions made up to the present date are highlighted in this chapter. Membrane separation processes and methods for membrane evaluation are also highlighted in separate sections. The parameters used to evaluate the performance of the membrane are discussed. Some of these measures are directly related to materials selection and membrane preparation methods. Useful information about nanomaterials with the history of their development is also introduced. The chapter is supported by several illustrative figures and tables and many references.

Silver colloid and film substrates in surface-enhanced Raman scattering for 2-thiouracil detection

Abstract: Surface-enhanced Raman scattering-based silver substrates were designed and fabricated for the detection of 2-thiouracil (2-TU). Two types of silver nanoparticles (Ag/NPs) were prepared using reducing agents: sodium borohydride (type I) and trisodium citrate dehydrate (type II) on a substrate. Their morphology and structure were characterized using Fourier transformed infrared spectroscopy, Raman spectroscopy, and high-resolution transmission electron microscopy. The average size of the Ag/NPs (type I), and Ag/NPs (type II) was about 15 nm and 60 nm, respectively. The UV spectrum showed a maximum absorbance of silver nanoparticles at about 400–430 nm. Raman and Surface-Enhanced Raman Scattering (SERS) spectra of 2-TU were recorded, and the vibrational bands were assigned by means of Density Functional Theory (DFT) based calculations. The 2-TU molecules are adsorbed through the sulfur and nitrogen atoms to the silver surface, due to a high affinity. SERS spectra showed that the interaction between 2-TU and Ag/NPs led to enhanced SERS bands at 1164 cm−1 for ν (CS), 1052 cm−1 assigned to ν (N4–C7), 921 cm−1 for ν (N4–C5), 649 cm−1 related to γ (N–H), and 572 attributed to γ (S–C5–N). The correlation between the concentrations of 2-thiouracil and the SERS signal intensity was investigated with silver colloid and film substrates. The film mode showed better correlation coefficients and improved detection limits due to the protection against agglomeration.

Zeolite modified with copper oxide and iron oxide for lead and arsenic adsorption from aqueous solutions

Abstract: How to completely remove toxic metals from water is still a serious challenge, and is the mission that faces researchers and scientists today. In this work, zeolite/copper oxide (CuO) and zeolite/iron oxide (Fe3O4) nanocomposites (NCs) were prepared via a co-precipitation method. Several techniques were used for characterization of the prepared NCs including UV-visible, powder X-ray diffraction, N2 adsorption for determining the specific surface areas (Brunauer–Emmett–Teller (BET)) and pore volumes. The morphology was investigated by field emission scanning electron microscopy. The batch adsorption experiment process was used to study the applicability of the prepared NCs to removing lead (Pb) and arsenic (As) from aqueous solutions. The effects of the adsorbent dosage, pH, initial metal concentration and contact time on the adsorption process were investigated. The obtained results revealed that in 40 minutes 0.15 g of prepared zeolite/Fe3O4 (NCs) was able to remove 97.2% of Pb and 96.8% of As from 100 mg/L aqua solutions at a pH of between 4 and 6. The Langmuir isotherm model showed higher correlation coefficients and provided better agreement with the experimental data. The adsorption kinetic is a chemi-physisorption process that follows the pseudo second-order kinetic model.

Microwave-induced H2SO4 activation of activated carbon derived from rice agricultural wastes for sorption of methylene blue from aqueous solution

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 th...

Adsorption of phenol on aluminum oxide impregnated fly ash

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, whi...

Removal of mercury (II) via a novel series of cross-linked polydithiocarbamates

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 (Qm = 0.11 mmol/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.

Kinetic and intraparticle diffusion studies of carbon nanotubes-titania for desulfurization of fuels

Abstract: The authors report on the kinetics, pseudo first-order model, pseudo second-order model, and intraparticle diffusion mechanism. Thus, the experimental data of the adsorption of thiophene, benzothiophene, and dibenzothiophene on a material of carbon nanotubes-titania were fitted to the kinetics and intraparticle diffusion models. The kinetics parameters of qe and correlation coefficient indicated that the data are not fitted with the pseudo first-order model while they are well fitted to the pseudo second-order model with R2 of more than 0.99 and the maximum adsorption capacities qe calculated from the pseudo second order model are in accordance with the experimental values for the three sulfur compounds in a model fuel. The results indicated that the adsorbent has a higher adsorption efficiency toward DBT over the other two sulfur compounds. Fitting the data to the intraparticle diffusion model indicated the intraparticle diffusion was not only rate-controlling step and hence it can be suggested t...

Synthesis, Classification, and Properties of Nanomaterials

Abstract: Nanomaterials are materials with at least one external dimension measuring approximately 1 to 100 nm. They play an important role in the fabrication of many devices and modified materials because of their unique physical and chemical properties, such as a large surface-area-to-volume ratio, and their high mechanical strength. This chapter discusses the synthesis, classification, and characterization of nanomaterials. Zero-dimensional, one-dimensional, two-dimensional, and three-dimensional nanostructured materials are discussed. The synthesis of nanomaterials, including top-down and bottom-up approaches, and various chemical, physical, and mechanical methods are addressed. The applications of nanomaterials and nanoparticles incorporated into polymeric nanomaterials in adsorption and membrane processes are also discussed.

Electrochemical Investigation of Gold Nanoparticle-Modified Glassy Carbon Electrode and its Application in Ketoconazole Determination

Abstract: Ketoconazole (KCZ) is an extensively used antifungal compound and is an active ingredient of anti-scaling shampoos, pomades, and skin ointments. In this work, the cyclic voltammetric behaviour of KCZ was studied with a gold nanoparticle (AuNP)-modified glassy carbon (GC) electrode. The conditions for KCZ determination with GC/AuNP were optimised to achieve the best possible response. A pre-adsorption voltage of –1.6 V, a deposition time of 120 s, pH 4.0, and stirring of the KCZ solution during deposition were chosen as the optimum conditions for KCZ determination. The anodic peak at 0.697 V was used for KCZ determination. A linear concentration range of 20–100 μM (R2 = 0.9986) and a detection limit of 2.3 μM (3σ) was achieved for KCZ using the GC/AuNP electrode.

Aminomethylphosphonate Chelating Ligand and Octadecyl Alkyl Chain in a Resin for Simultaneous Removal of Co(II) Ions and Organic Contaminants

Abstract: The efficiency of a hydrophobic cross-linked polyzwitterionic acid for the simultaneous removal of Co(II) and organic dyes from water was examined. The synthesis of the resin was conducted via cyclotetrapolymerization of N,N-diallyl-N-aminomethylphosphonic acid as a hydrophilic monomer, N,N-diallyl-N-octadecylammonium chloride as a hydrophobic monomer, and SO2 in the presence of a cross-linker using the initiator α,α′-azoisobutyronitrile. The efficiency of the resin for the removal of Co(II) was evaluated under the effects of metal ion concentration, temperature, adsorption contact time, and medium pH. The results show the adsorption data fitted a pseudo-second-order model. The standard enthalpy change ΔHo was 23.2 kJ/mol, suggesting an endothermic adsorption process. The adsorption from the mixture of the binary systems of Co(II) with eriochrome Black T, methyl orange, phenol, or methylene blue exhibited a distinct bimodal behavior that could be ascribed to the chelating and hydrophobic nature of the pre...

Nanocomposites and Hybrid Materials for Adsorptive Desulfurization

Abstract: Desulfurization (removal of S compounds) of fuels is an important research topic in recent years. Several techniques have been reported to remove the sulfur-containing compounds in fuels. One of these techniques is adsorptive desulfurization (ADS) (removal based on chemisorption and physisorption) which has received much attention because of low energy consumption and facile operation condition. This chapter discusses the methods employed under this technique and the types of nanocomposites and hybrid materials (adsorbents) that have been investigated as potential adsorbents. The strategies to enhance sulfur adsorption capacity and main challenges will be discussed.

Selective photocatalytic oxidation of aromatic alcohols into aldehydes by tungsten blue oxide (TBO) anchored with Pt nanoparticles

Abstract: Achieving selective transformation of organic functional groups in an energy efficient and environmentally benign way is an important yet challenging endeavour in the field of chemical science. Utilization of heterogeneous photocatalysis for selective conversion holds great potential from cost, energy, and environment viewpoints. In this work, we report the fabrication of nanocomposites comprising hypostoichiometric tungsten oxide (WO3−x) modified with platinum nanoparticles and/or reduced graphene oxide (RGO) and their deployment in highly selective (>99%) and efficient (>80%) conversion of aromatic alcohols into corresponding aldehydes under simulated sunlight and ambient conditions. Efficacy of the nanocomposites was investigated by studying the oxidation of benzyl alcohol (BA), 4-methoxybenzyl alcohol (4-MBA) and cinnamyl alcohol (CA) into corresponding aldehyde, in terms of alcohol concentration, RGO and/or Pt loading, and the amount of photocatalyst employed. Systematic investigations on the chemical stability, recyclability, photocatalytic and photoelectrocatalytic aspects helped to shed light on the role of excitons towards the observed selectivity. A plausible mechanism to explain the observed attributes of the photocatalyst is proposed that provides impetus to design future photocatalysts with anticipated attributes for selective oxidation reactions.

Carbon-Based Nanomaterials for Desulfurization: Classification, Preparation, and Evaluation

Abstract: The special interest in ultra-low sulfur diesel (ULSD) is informed by the need to comply with the strict government policy on low sulfur content of transportation fuels. Better knowledge of different factors that concern deep desulfurization of fuels is important to achieve ultra-low sulfur fuels and cheaper way of producing ULSD. Both the capital and operating cost of the adsorptive desulfurization process is cheaper compare to the conventional hydroprocessing. The need to produce more volume of fuel such as diesel with very low sulfur content from low grade feed stocks like heavy oil and light cycle oil (LCO) in order to meet up with the global demand for sulfur-free fuels is pertinent. Several on-going researches are pointing to the use of adsorbents for removal of sulfur compounds from the hydrocarbon refining stream. In this chapter, varieties of carbon nanomaterials suitable for adsorptive desulfurization are discussed. The approach is feasible for commercial applications with any adsorbent of an adequate lifetime of activity as well as high capacity.

Membrane Fouling and Strategies for Cleaning and Fouling Control

Abstract: Fouling presents the most difficult challenge to the design and operation of membrane processes. In this chapter, the reader can find extensive and useful information regarding membrane fouling and types of foulants. Fouling classification, including colloidal fouling, organic fouling, inorganic fouling, and biofouling is discussed. Factors influencing fouling are categorized under factors related to the feed, such as processing variables and those related to the membrane materials. Some fouling mechanisms are also discussed. The chapter discusses the strategies for membrane cleaning, including chemical (acids, bases, chelating agents, oxidants, disinfectants, and surfactants), physical, and mechanical means (backflushing, backpulsing, ultrasound, electric field, and magnetic field treatment), with emphasis on the cleaning temperature and time. Finally, fouling reduction by modification and coating methods is addressed.