Mazen Khaled

Removal of mercury from water by multi-walled carbon nanotubes

The removal of mercury (Hg(2+)) ions from contaminated water using multiwalled carbon nanotubes (MWCNTs) was investigated in this study. Results of the study showed that MWCNTs slurry was very efficient in removing as high as 1.0 mg/L of Hg(2+) from aqueous solutions via the adsorption mechanism. This removal efficiency was found to be a function of the aqueous pH level, dosage of CNTs, mixing rate, and contact time. The study showed that the Hg uptake by MWCNTs increased to 100% with an increase in pH from pH 4 to 8. The results also showed that higher dosage of MWCNTs, showed higher removal of Hg(2+). In a 50 mL water sample, 10 mg of MWCNTs was needed to remove all of the 0.1 mg/L of Hg(2+) ions. On the other hand, increasing the mixing rate from 50 to 150 rpm improved the removal efficiency. The experimental results also showed that mercury adsorption by MWCNTs follow a pseudo second-order reaction with a rate (k) of 0.018 and it is well described by the Langmuir isotherm model with maximum adsorptive capacity (q(max)) of 13.16.

Novel EPR characterization of the antioxidant activity of tea leaves

Electron paramagnetic resonance (EPR) spectroscopy is utilized to investigate several categories of green and black tea: Twining green tea (TGT), Chinese green tea (CGT), Red-labels black tea (RBT). Basically, two EPR signals from all the studied samples are observed: One of them is a very weak sharp EPR signal with deltaHpp approximately 10 G and g-factor = 2.00023 superimposed on the other broad signal with deltaHpp approximately 550 G and g-factor = 2.02489. The broad signal is a characteristic one of manganese(II) complex, while the sharp signal is related to a stable radical of aromatic origin exist in a powder condition. The feature of the manganese EPR signal is attributed to manganese(II) complex and reflected the molecular behavior of Mn(II) in the protein system of the natural leaves. The sharp signal, which is most probably due to a semiquinones radicals, is observed at room temperature and its intensity is remarkably affected by photo degradation of the studied samples. The intensity of manganese(II) EPR signal is found to be related to ageing and disintegration of the tea leaves. Moreover, direct relation between the relative intensity of the semiquinones radical signal and antioxidant activity of the studied samples was also correlated.

Removal of Chromium (III) from water by using modified and nonmodified carbon nanotubes

This study was carried out to evaluate the environmental application of modified and nonmodified carbon nanotubes through the experiment removal of chromium trivalent (III) from water. The aim was to find the optimal condition of the chromium (III) removal from water under different treatment conditions of pH, adsorbent dosage, contact time and agitation speed. Multi wall carbon nanotubes (MW-CNTs) were characterized by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The diameter of the carbon nanotubes produced varied from 20-40 nm with average diameter of 24nm and 10 micrometer in length. Adsorption isotherms were used to model the adsorption behavior and to calculate the adsorption capacity of the absorbents. The results showed that, 18% of chromium (III) removal was achieved using modified carbon nanotubes (M-CNTs) at pH 7, 150 rpm, and 2 hours for a dosage of 150 mg of CNTs. The removal of Cr (III) is mainly attributed to the affinity of chromium (III) to the physical and chemical properties of the CNTs. The adsorption isotherms plots were well fitted with experimental data.

Electrochemical study of laser nitrided and PVD TiN coated Ti–6Al–4V alloy: the observation of selective dissolution

Abstract Several techniques are considered to improve the tribological and corrosion properties of the Ti–6Al–4V alloy. One of the promising techniques is the duplex treatment. In the present study, electrochemical testing of a duplex treated Ti–6Al–4V alloy is considered. The duplex treatment is carried out in two steps. In the first step, the alloy surface is laser nitrided while in the second step, the nitrided alloy surface is PVD TiN coated. Corrosion rates and electrochemical properties of the treated surfaces are investigated using polarization techniques. A comparison of the electrochemical response of the duplex treated, PVD TiN coated, and untreated workpieces is made. X-Ray diffraction spectroscopy (XRD), energy dispersive spectrometry (EDS) and scanning electron microscopy (SEM) are carried out to examine the coating layer, pit morphology and elemental structures due to duplex treatment and controlled electro-oxidation. It is found that the duplex treated workpiece surface is more resistant to corrosion as compared to TiN coated and untreated surfaces. Among the three metals contained in the alloy, aluminum is found to selectively dissolve in large proportion in solution during oxidation.

Influence of dust and mud on the optical, chemical, and mechanical properties of a pv protective glass.

Recent developments in climate change have increased the frequency of dust storms in the Middle East. Dust storms significantly influence the performances of solar energy harvesting systems, particularly (photovoltaic) PV systems. The characteristics of the dust and the mud formed from this dust are examined using various analytical tools, including optical, scanning electron, and atomic force microscopies, X-ray diffraction, energy spectroscopy, and Fourier transform infrared spectroscopy. The adhesion, cohesion and frictional forces present during the removal of dry mud from the glass surface are determined using a microtribometer. Alkali and alkaline earth metal compounds in the dust dissolve in water to form a chemically active solution at the glass surface. This solution modifies the texture of the glass surface, thereby increasing the microhardness and decreasing the transmittance of the incident optical radiation. The force required to remove the dry mud from the glass surface is high due to the cohesive forces that result from the dried mud solution at the interface between the mud and the glass. The ability altering the characteristics of the glass surface could address the dust/mud-related limitations of protective surfaces and has implications for efficiency enhancements in solar energy systems.

Laser induced photocatalytic degradation of hazardous dye (Safranin-O) using self synthesized nanocrystalline WO3

The photocatalytic degradation of Safranin-O (known as Basic Red 2) in water using locally synthesized nanocrystalline WO(3) as a photocatalyst was investigated under UV laser irradiation. The photo-oxidation removal of the dye was monitored by UV-vis spectrophotometer. The blank experiments for either laser irradiated only Safranin-O solution or the suspension containing WO(3) and Safranin-O in the dark showed that both laser illumination and the photocatalyst were essential for the removal of Safranin-O. The effect of experimental parameters including laser energy, catalyst loading, solution pH and the initial dye concentration on photocatalytic degradation of Basic Red 2 were also investigated. Results indicate that the rate of reaction is strongly influenced by the adsorption of an azo dye into the surface of the photocatalyst materials and suggests an optimum catalyst loading and dye concentration for the degradation reaction. It was investigated that the adsorption of the dye decreases at higher alkaline pH because both catalyst and substrate are negatively charged, developing repulsive forces between them. Kinetic data obtained reveals that the rate of the reaction obeys the first-order kinetics.

Removal of arsenic from water by iron oxide nanoparticles impregnated on carbon nanotubes

The removal of Arsenic (As (III)) ions from water using modified multi-walled carbon nanotubes (MCNTs) was demonstrated in this study. Results of the study showed that raw (non-modified) MCNTs have very poor efficiency in removing As (III) from water by conventional adsorption mechanisms. However, when MCNTs were modified with iron oxide (Fe-MCNTs), a significant improvement in the As (III) removal efficiency was observed. Results of the study also showed that Fe-MCNTs have much higher efficiency in removing As (III) than MCNTs modified with carboxyl group (COOH-MCNTs). Under the experimental conditions used in the study, about 77.5% of As (III) removal was achieved by the Fe-MCNTs, while COOH-MCNTs removed only 11% at pH 5. In addition, the adsorption kinetics of MCNTs indicated that there is a strong affinity of As (III) ions to the surface of the Fe-MCNTs.

Simultaneous electrochemical and electron paramagnetic resonance studies of keto and hydroxy carotenoids

Cyclic voltammogram (CV) and simultaneous electrochemical and electron paramagnetic resonance (SEEPR) measurements have been carried out on the oxygenated carotenoids: echinenone, canthaxanthin, isozeaxanthin and rhodoxanthin in dichloromethane. The CV displays are markedly different from that of β-carotene. Comproportionation constants, deduced from EPR spin concentration measurements of electrochemically oxidized dihydroxy β-carotene and several keto carotenoids vary by four orders of magnitude. ΔHpp values deduced from the SEEPR spectra of the cation radicals are in the range 13.2 to 14.5 G and the g-factors are 2.0027 ± 0.0002. These EPR parameters are in accordance with a polyene π-cation radical structure. Theoretical CVs are calculated using DigiSim, a CV simulation program, and the proposed mechanism involves three electrode and two homogeneous reactions.

Kinetic study of laser-induced photocatalytic degradation of dye (alizarin yellow) from wastewater using nanostructured ZnO

Nanoparticles of zinc oxide semiconductor were applied for removal of toxic organic pollutants such as dyes (alizarin yellow GG) from wastewater using laser induced photocatalytic process. A special photoreactor was designed for this purpose using local resources. Laser enhanced photo degradation of alizarin yellow GG (AYGG) was carried out by irradiating the contaminated aqueous solution with a 355 nm radiation generated from third harmonic of Nd:YAG laser. The effect of different operational parameters such as the initial dyes concentration, the concentration of photocatalyst, laser irradiation time, laser energy and pH on photocatalytic degradation of the dyes was investigated. It was observed that pH and the initial dyes concentration has a significant role in the dyes removal process. Using the optimum conditions (parameters), almost 90% degradation was achieved by nano ZnO in a short span of time. The efficiency achieved in this work using nano ZnO was much higher than micro ZnO catalyst and using conventional custom made setups. This is a first study of its kind where laser and nano ZnO particles have been employed for removal of dyes from wastewater.

Comparison of the INDO to the RHF-INDO/SP derived EPR proton hyperfine couplings for the carotenoid cation radical: experimental evidence

Abstract Austin model 1 (AMI) geometry-optimized coordinates were used as input to an INDO and an RHF-INDO/SP molecular orbital calculation. Comparison to ENDOR-derived methyl proton hyperfine coupling of the carotenoid cation radical formed photolytically on Nafion film and the second-moment-deduced EPR linewidth of the electrochemically prepared carotene cation in solution showed excellent agreement with the RHF-INDO/SP-derived proton hyperfine couplings. The INDO-derived solution linewidth was calculated to be 60% larger than that found experimentally due to the calculated INDO methyl protons being larger by 64%.