Bassam S. Tawabini

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.

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.

Levels of arsenic in fish from the Arabian Gulf

Abstract Levels of total arsenic were determined in muscle tissues of 13 species of finfish and 3 species of crustaceans from the Arabian Gulf. The range was 0.16–32.3 μg g −1 wet wt for finfish. Averages found for prawn, crab and lobster were 15.8, 6.28, and 12.7 μg g −1 wet wt, respecitively. The levels ranked among the highest reported in the literature.

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.

Thermal stability of a platinum aluminide coating on nickel-based superalloys

An investigation was carried out to determine the thermal stability of a platinum aluminide coating on the directionally solidified alloy MAR M 002 and its single-crystal version alloy, SRR 99, at 800, 1000 and 1100°C. The morphology, structure and microchemical composition of the coating were characterized using scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. In the as-deposited condition, the coating was found to consist of two layers. Most of the platinum was concentrated in the outer coating layer which consisted of a fine dispersion of PtAl2 in a matrix of β-(Ni, Pt)Al containing other elements in solid solution, such as cobalt and chromium. The inner coating layer was relatively free of platinum and consisted essentially of β-NiAl. Exposure at 800°C was found to have no significant effect on the structure and composition of the coating on each alloy. At temperatures ⩾1000°C, however, PtAl2 became thermodynamically unstable and significant interdiffusion occurred between the coating and alloy substrate. After exposure at 1000°C, the components of the outer coating layer were NiAl and Ni3Al. However, after exposure at 1100°C, the outer coating layer consisted only of Ni3Al. Also, after exposure at both temperatures, the composition of the outer coating layer approached that of the inner layer due to interdiffusion. Although the coating on both alloys exhibited similar structural stability at all temperatures investigated, the coating on alloy MAR M 002 was found to develop a more protective scale. This behaviour was correlated with differences in alloy substrate composition particularly rare-earth elements such as hafnium.

Prediction of reformate research octane number by FT-i.r. spectroscopy

Abstract Fourier transform infrared (FT-i.r.) spectroscopy was used to calculate the research octane number (RON) of naphtha feed and reformate during the course of performance evaluation of reforming catalysts. Five absorption regions that correspond to aliphatic and aromatic bands within the mid-infrared region were utilized for developing the correlation for RON estimation. Statistical methods were used to derive third degree polynomial equations which could give a better estimate of engine RON. The technique was found to give excellent correlation (R2 = 0.95) with the engine RON data.

Simultaneous Removal of MTBE and Benzene from Contaminated Groundwater Using Ultraviolet-Based Ozone and Hydrogen Peroxide

Efficiency of ultraviolet-ozone (UV/O3) and ultraviolet-hydrogen peroxide (UV/H2O2) processes was investigated for simultaneous removal of methyl tertiary butyl ether (MTBE) and benzene from contaminated ground water. The photoreactor employed housed 15-watt low pressure (LP) and 150-watt medium pressure (MP) mercury UV lamps. Oxidation of contaminants was studied at two different levels of ozone and hydrogen peroxide. Brackish groundwater samples were spiked with MTBE and benzene up to a concentration of 500 μg L−1. Removal potential was evaluated at different parameters such as UV type and intensity and peroxide and ozone dosages, as well as contact time. Results indicated that no removal of the contaminants was attained when treated with hydrogen peroxide or ozone alone. However, about 50% and 30% removal of MTBE were achieved in 30 minutes when irradiated with MP-UV and LP-UV lamps, respectively. On the other hand, UV/H2O2 process was found to be superior in removal of MTBE (90% in 10 min.) and benzene (95% in 5 min.) compared to UV/O3 process. Furthermore, removal of benzene was comparatively easier than MTBE in both approaches. It is hence concluded that higher UV intensities and elevated doses of H2O2 accelerate simultaneous removal of MTBE and benzene from water.

Hydrocarbon group (PONA) analysis of reformate by FT-i.r. spectroscopy

Multicolumn valve-switching gas chromatography is commonly used in refineries for determining paraffins, olefins, naphthenes and aromatics (PONA) contents of reformate and naphtha samples. A simplified and fast alternative method, Fourier transform infrared (FT-i.r.) spectroscopy, for the same purpose was successfully used in the present work. In this method, a calibration technique which took both spectral and concentration data into consideration was developed by using the instrument manufacturers software utilizing partial least-squares (PLS) regression analysis. For this, the mid-i.r. range (4000-400 cm−1) was subdivided into four regions that are usually attributed to different functional groups. An excellent correlation between the FT-i.r. and g.c. results was found, particularly for paraffins and aromatics (R2 = 0.97 and 0.96 respectively). The average absolute differences between the results obtained from FT-i.r. and g.c. were 1.3, 0.5, 0.2 and 0.9 vol.% for paraffins, olefins, naphthenes and aromatics respectively.

Removal of methyl tertiary butyl ether (MTBE) from contaminated water using UV-assisted nano composite materials

This study was designed to examine the efficacy of UV-assisted nano material treatments to remove methyl tertiary butyl ether (MTBE) from contaminated water. The focus was to investigate the applicability of combining the degradation potential of nano TiO2 photocatalysis and adsorption power of carbon nano tubes (CNTs). Effect of different combinations of two ultraviolet radiations (UVA and UVC) and three types of nano materials: TiO2, CNTs, and TiO2/CNTs on MTBE remediation was studied. Removal efficiency of different combinations varied significantly with highest removal (95%) achieved by UVC-TiO2, followed by UVC-CNTs (75%) and UVA-TiO2/CNTS (60%). However, additive effect of UV/TiO2/CNTs on MTBE removal from water was not observed. Major degradation byproducts formed were acetone, tertiary butyl formate, and tertiary butyl alcohol.

Simultaneous determination of benzotriazole copper inhibitor and microbiocidal isothiazolinenones by high-performance liquid chromatography

Abstract A high-performance liquid chromatographic (HPLC) procedure for the separation and determination of the components of a formulation that contained sodium benzotriazole (copper inhibitor), 2-methyl-4-isothiazoline-3-one and 5-chloro-2-methyl-4-isothiazoline-3-one (microbiocide mixture) was developed. This mixture is used to protect and maintain a large water-chilling plant in Saudi Arabia. A UV spectrophotometric method was tried unsuccessfully as both sodium benzotriazole and the isothiazolinones had λmax at 275 nm, so an HPLC method was sought. Optimum conditions were established using a Hewlett-Packard RP C8 column to be methanol-water (40:60) containing 0.05 M KH2PO4 as the eluent at a flow-rate of 1 ml/min. The relative standard deviation of the method at the 95% confidence level was found to be 0.8, 0.7 and 2.4% for the respective components at concentration levels of 35, 115 and 50 mg/l, respectively.