Z.H. Yamani

Detection of heavy metals in Arabian crude oil residue using laser induced breakdown spectroscopy

Laser induced breakdown spectroscopy (LIBS) was applied for the elemental analysis of Arabian crude oil residue samples. The spectra due to trace elements such as Ca, Fe, Mg, Cu, Zn, Na, Ni, K and Mo were recorded using this technique. The dependence of time delay and laser beam energy on the elemental spectra was also investigated. Prior to quantitative analysis, the LIBS system was calibrated using standard samples containing these trace elements. The results achieved through this method were compared with conventional technique like inductively coupled plasma.

The role of various binding materials for trace elemental analysis of powder samples using laser-induced breakdown spectroscopy.

Study of various binding materials like potassium bromide, poly(vinyl alcohol), starch, silver and aluminum has been carried out using laser-induced breakdown spectroscopy (LIBS). The role of matrix effects using these five binders on LIBS signal intensity was investigated for better performance of LIBS technique as a quantitative analytical tool. For comparative study of different binders, the signal intensity of different Mg lines at 518.3, 517.2, 383.8 and 279.5nm wavelengths were recorded for pellets prepared with known concentrations of Mg in these binders. The influence of laser energy on ablated mass under different binding materials and its correlation with LIBS signal intensity has been explored. Optical scanning microscopy images of the ablated crater were studied to understand the laser ablation process. The study revealed that the binding material plays an important role in the generation of LIBS signal. The relative signal intensity measured for a standard Mg line (at 518.3nm) were 735, 538, 387, 227 and 130 for potassium bromide, starch, poly(vinyl alcohol), silver and aluminum as binders, respectively. This indicates clearly that potassium bromide is better as a binder for LIBS studies of powder samples.

On-line monitoring of remediation process of chromium polluted soil using LIBS.

Due to large growth in leather and textile industries to cater for the needs of a growing world population, contamination of soil and water resources by chromium has become a great threat for humans and animals. In this work, Laser Induced Breakdown Spectroscopy (LIBS) was applied to monitor the remediation process of soil contaminated with Chromium metal. This study was conducted at a laboratory scale by setting up an experiment in a container holding soil contaminated with chromium. This setup represents actual field conditions where remediation process could be applied and monitored for the removal of toxic metals like Cr. For generation of LIBS spectrum, the plasma was produced by focusing a pulsed Nd: YAG laser at 1064 nm on the soil contaminated with chromium under remediation process. The evaluation of the potential and capabilities of LIBS as a rapid tool for remediation process of contaminated sites is discussed in detail. Optimal experimental conditions were evaluated for improving the sensitivity of our LIBS system for monitoring of remediation process through parametric dependence study. The minimum detection limit of our spectrometer for chromium in soil matrix was 2 mg Kg(-1).

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.

Laser-induced efficient reduction of Cr(VI) catalyzed by ZnO nanoparticles

The present study demonstrates the complete removal of Cr(VI) in aqueous suspensions of zinc oxide nanoparticles using a novel laser-induced photocatalytic process without the use of any additive. The study showed that ∼95% Cr(VI) was removed within short time (60 min) of laser exposure in the presence of ZnO. However, the removal of chromium using conventional setup under identical conditions was found to be negligible. Effect of critical parameters, such as laser energy, catalyst concentration, chromium concentration, and added electron donor and acceptor on the photocatalytic reduction process was also investigated. The data regarding temporal behavior of metal removal was fitted to first-order kinetic and reaction rate was computed.

Optimization of the LIBS Parameters for Detection of Trace Metals in Petroleum Products

Abstract Parametric dependence of laser-induced breakdown spectroscopy (LIBS) for detection of trace elements has been studied. LIBS was applied for quantitative measurements of environmentally important trace metals such as magnesium, lead, copper, and calcium in oil samples. This work incorporates investigations of LIBS experimental parameters such as the distance between the plasma and optical fiber, sample rotation speed, laser pulse energy, gate delay, and position of the focal spot on the pellets. The optimized parameters are tested for the preparation of the calibration curves for Mg, Pb, Cu, and Ca. Limits of detection (LOD) of our LIBS system were also estimated for these elements. The system was applied for trace metals detection in Arabian crude oil residue samples which is not trivial to detect with conventional techniques.

Laser Induced Photocatalytic Splitting of Water Over WO3 Catalyst

The photocatalytic activity of WO 3 semiconductor powder for water splitting into H 2 and O 2 was studied. Instead of conventional broad spectrum light sources like lamps, monochromatic laser radiations in the UV region (γ = 355 nm) were used as the light source for the study of photocatalytic water splitting over WO 3 . An alternate route based upon the photo-chromic properties of WO 3 for the production of hydrogen was suggested. The effect of dissolved metal ions on H 2 and O 2 yield in the presence of various metal ions was also investigated. The effect of the hole-capture agent on H 2 and O 2 yield was also studied by using methanol as a hole-capture agent. The data on pH measurements during the course of reaction was found very useful in explaining the reaction mechanism in general, and metal ions action in particular.

Preparation of WO3/g-C3N4 composites and their enhanced photodegradation of contaminants in aqueous solution under visible light irradiation

A series of WO3/g-C3N4 composite photocatalysts with different mass ratios were prepared by a simple pyrolysis method, using tungstic acid and melamine as the starting materials. The microstructure and optical properties of as-synthesized WO3/g-C3N4 composite photocatalysts were investigated by X-ray diffraction, UV–Vis diffuse reflection spectroscopy and photoluminescence spectroscopy. Compared with WO3, g-C3N4 and well-known commercial photocatalysts, an improved visible-light-induced photodegradation of Rhodamine B and methyl tertiary butyl ether in aqueous solution was observed on WO3/g-C3N4 composite, due to the high carrier separation efficiency at the interface between WO3 and g-C3N4. Moreover,xa0the photoactivity and photostability of catalyst after many runs was also evaluated.

Study of hazardous metals in iron slag waste using laser induced breakdown spectroscopy

Laser Induced Breakdown Spectroscopy (LIBS) was applied for quantitative elemental analysis of slag samples collected from a local steel plant using an Nd: YAG laser emitting radiation at 1064 nm wavelength. The concentration of different elements of environmental significance such as cadmium, calcium, sulfur, magnesium, chromium, manganese, titanium, barium, phosphorus and silicon were 44, 2193, 1724,78578, 217260, 22220, 5178, 568, 2805, 77871 were mg Kg− 1, respectively. Optimal experimental conditions for analysis were investigated. The calibration curves were drawn for different elements. The concentrations determined with our Laser-Induced Breakdown Spectrometers were compared with the results obtained using Inductively Coupled Plasma (ICP) emission spectroscopy. Our study demonstrates that LIBS could be highly appropriate for rapid online analysis of iron slag waste. The relative accuracy of our LIBS system for various elements as compared with ICP method is in the range of 0.001 - 0.049 at 2.5% error confidence. Limits of detection (LOD) of our LIBS system were also estimated for the elements noted here. The hazardous effects of some of the trace elements present in iron slag exceeding permissible safe limits are also discussed.

450 nm visible light-induced photosensitized degradation of Rhodamine B molecules over BiOBr in aqueous solution

BiOBr was investigated as an efficient catalyst for the photosensitized degradation of Rhodamine B (RhB) dye using 450xa0nm monochromatic light as a source of excitation. It was found that RhB molecules can be decomposed via a photosensitized process more efficiently on the un-excited BiOBr semiconductor (Egxa0=xa02.8xa0eV) and the reaction follows apparent zeroth order kinetics. The effects of catalyst dosage and reaction temperature on the photodegradation efficiency as well as the photostability of as-prepared BiOBr have been investigated. Around 85xa0% removal efficiency was achieved using 0.4xa0mg/mL of BiOBr at room temperature (300xa0K). A possible photodegradation mechanism has been also proposed and discussed based on the experimental results achieved in this study.