Zain H. Yamani

Laser-induced removal of a dye C.I. Acid Red 87 using n-type WO3 semiconductor catalyst

Water contamination by organic substances such as dyes is of great concern worldwide due to their utilization in many industrial processes and environmental concerns. To cater the needs for waste water treatment polluted with organic dyes, laser-induced photocatalytic process was investigated for removal of a dye derivative namely Acid Red 87 using n-type WO3 semiconductor catalyst. The degradation was investigated in aqueous suspensions of tungsten oxide under different experimental conditions using laser instead of conventional UV lamp as an irradiation source. The degradation process was monitored by measuring the change in dye concentration as a function of laser irradiation time by employing UV spectroscopic analysis. The degradation of dye was studied by varying different parameters such as laser energy, reaction pH, substrate concentration, catalyst concentration, and in the presence of electron acceptors such as hydrogen peroxide (H2O2), and potassium bromate (KBrO3). The degradation rates were found to be strongly dependent on all the above-mentioned parameters. Our experimental results revealed that the dye degradation process was very fast (within few minutes) under laser irradiation as compared to conventional setups using broad spectral lamps (hours or days) and this laser-induced photocatalytic degradation method could be an effective means to eliminate the pollutants present in liquid phase. The experience gained through this study could be beneficial for treatment of waste water contaminated with organic dyes and other organic pollutants.

Determination of trace elements in volcanic rock samples collected from cenozoic lava eruption sites using LIBS.

Trace elements of environmental significance present in the volcanic rock samples collected from sites of the Cenozoic era flood basalt flows and eruptions were detected using locally developed laser-induced breakdown spectrometer. For spectro-chemical analysis of these samples, the plasma was generated by focusing a pulsed Nd: YAG laser radiation at 1064 nm wavelength on the target rock samples. These samples were collected from four widely separated locations surrounding the volcanic eruption sites belonging to the Harrat Hutaymah volcanic field in the vicinity of Taba town, situated to the east of Hail city of northern Saudi Arabia. These samples represent the scoria basalt lava flows as well as a large tuff-ring crater and it contains xenoliths. These flows occur widespread over the Earths surface in this region, and their contained xenoliths are brought up from depths of a few tens of kilometers. This volcanic field has received much less attention in the previous geological studies; and consequently, its effects on the environment are not well defined. The concentration of different elements of environmental significance like Cr, Pb, Mn, Cd, Sr and other trace metals like Cu, Al, Ca, Mg, Zn, Ti and Fe in these rock samples were determined by spectral analysis. Parametric dependence for improvement of LIBS sensitivity for detection of these elements was also carried out. The highest concentration detected of environmentally significant elements like Cr, Mn, Pb, Sr and Ni are 1910, 1399, 90.5, 12412 and 461.5 ppm, respectively in four different lava samples which are considered to be much higher than the safe permissible limits. The LIBS results were compared with the results obtained using other analytical techniques such as the inductively coupled plasma atomic emission spectroscopy (ICP-AES).

Enhanced photoactivity on Ag/Ag3PO4 composites by plasmonic effect

The work presented here deals with the photoreduction in metallic silver nanoparticles onto the surface of Ag(3)PO(4) and resulting photocatalytic activity enhancement toward degradation of dye molecules, namely Rhodamine B (Rh. B) as a model compound, from aqueous solution under UV or visible light irradiation. Our results clearly indicated that the photoactivity of Ag(3)PO(4) was significantly enhanced by depositing an optimum amount of silver nanoparticles, even though the adsorption kinetics rate and capacity decreased after the silver nanoparticles agglomerate extensively. The surface plasmon resonance (SPR) excited between the silver nanoparticles and Rh. B interface is a physical origin and responsible for the boosted photoactivity, which strongly depends on the specific wavelength of the incident light. This work provides and suggests a novel scheme for Ag/Ag(3)PO(4) composites having plasmonic effect on the interface with detailed experimental and theoretical study.

Sonochemical-driven ultrafast facile synthesis of SnO2 nanoparticles: Growth mechanism structural electrical and hydrogen gas sensing properties

Synthesis of SnO2 nanoparticles have been successfully accomplished moderately at lower temperature by facile, rapid, efficient and mild ultrasonic irradiation method. The as-grown SnO2 nanoparticles are investigated by various characterization techniques in terms of structural, optical, electrical and gas sensing properties. XRD investigation has shown that the SnO2 nanoparticles materials exhibit single rutile crystal phase with high crystallinity. FESEM studies showed uniform and monodisperse morphology of SnO2 nanoparticles. The chemical composition of SnO2 was systematically studied by EDX measurements. Additional confirmation of three Raman shifts (432, 630, 772cm-1) indicated the characteristic properties of the rutile phase of the as-grown SnO2 nanoparticles. The optical properties of SnO2 nanoparticles were examined by DRS, and the electronic band gap of SnO2 nanoparticles were around 3.6eV. Electrical properties of the SnO2 nanoparticles measured at various temperatures have shown the semiconducting properties. Surface area and pore size of synthesized nanoparticles were analyzed from BET. It has been revealed that SnO2 nanoparticles have surface area is 47.8574m2/g and the pore size is 10.5nm. Moreover, hydrogen gas sensor made of SnO2 nanoparticles showed good sensitivity and faster response for the hydrogen gas. This method is template-less and surfactant-free which circumvents rigorous reaction work-up for the former removal, reaction temperature and reaction time compared to hydrothermal synthesis and pertinent to many other oxide materials.

Sonochemical Assisted Solvothermal Synthesis of Gallium Oxynitride Nanosheets and their Solar-Driven Photoelectrochemical Water-Splitting Applications.

Gallium oxynitride (GaON) nanosheets for photoelectrochemical (PEC) analysis are synthesized via direct solvothermal approach. Their FE-SEM revealed nanosheets morphology of GaON prepared at a reaction time of 24 hours at 180 °C. The elemental composition and mapping of Ga, O and N are carried out through electron dispersive X-ray spectroscopy (EDX). The cubic structure of GaON nanosheets is elucidated by X-ray diffraction (XRD)analysis. The X-ray Photoelectron Spectroscopy (XPS) further confirms Ga, O and N in their respective ratios and states. The optical properties of GaON nanosheets are evaluated via UV-Visible, Photoluminescence (PL) and Raman spectroscopy’s. The band gap energy of ~1.9 eV is calculated from both absorption and diffused reflectance spectroscopy’s which showed stronger p-d repulsions in the Ga (3d) and N (2p) orbitals. This effect and chemical nitridation caused upward shift of valence band and band gap reduction. The GaON nanosheets are investigated for PEC studies in a standard three electrode system under 1 Sun irradiation in 0.5 M Na2SO4. The photocurrent generation, oxidation and reduction reactions during the measurements are observed by Chronoampereometry, linear sweep Voltametry (LSV) and Cyclic Voltametry (CV) respectively. Henceforward, these GaON nanosheets can be used as potential photocatalyts for solar water splitting.

Pulsed laser-induced photocatalytic reduction of greenhouse gas CO2 into methanol: A value-added hydrocarbon product over SiC

CO2 was converted into value-added hydrocarbons (methanol) by laser-induced photocatalytic reduction of CO2 over commercially available silicon-carbide (SiC) granules as catalyst. The conversion of CO2 was carried out in a glass reactor having quartz window and equipped with stirring system and was provided with continuous CO2 flow at ambient conditions. Laser radiations of 355 nm, which were generated by third harmonics of Nd:YAG laser (1060 nm) were applied as an excitation source. The methanol yield as a function of irradiation time and catalysts dosage were monitored by the gas chromatographic analysis (GD-FID) of water samples collected at prescribed intervals. A specific GC column was used which separated hydrocarbons efficiently without any interference from water present in the sample. The study indicated that the commercially available SiC granular material is an excellent catalyst in laser-induced photocatalytic conversion of CO2 into high value hydrocarbons.

Detection of lead in paint samples synthesized locally using-laser-induced breakdown spectroscopy

A laser-induced breakdown spectroscopy (LIBS) setup was developed to detect lead and other toxic contaminants such as chromium in paint emulsion samples manufactured in Saudi Arabia. The lead concentration detected in these samples was in the 327.2–755.3 ppm range, which is much higher than the safe permissible limit set by Saudi regulatory agencies. Similarly, chromium concentration (98.1–149.5 ppm) was found in high concentrations as well. The results obtained with our LIBS setup are comparable with the sample analysis utilizing a standard technique such as ICP, and our LIBS results are comparable to ICP with in an accuracy limit of 2–4 %.

Efficient removal of phenol from water using Fe2O3 semiconductor catalyst under UV laser irradiation.

Efficient removal of phenol was carried out using laser induced photocatalyis process in the presence of Fe2O3 semiconductor catalysts, and under UV laser irradiation. Parametric dependence of the removal process was investigated carefully by variation of laser irradiation time, laser energy, and concentration of the catalysts. pH measurements were also carried out to understand the photocatalytic process for removal of phenol. Maximum phenol removal achieved in this process was more than 90% during 1 hour of laser irradiation. This is considered highly efficient as compared to conventional setups using lamps. Reaction kinetics for the removal of phenol was also studied, and a reaction rate of 0.017 min− 1 was estimated, following first order kinetics.

Facile preparation of magnetic C/TiO2/Ni composites and their photocatalytic performance for removal of a dye from water under UV light irradiation.

Development of a photocatalyst with high efficiency and separability is still a challenging task in the field of wastewater treatment. In this study, new magnetic separable C/TiO2/Ni composite as a photocatalyst was prepared by a facile pyrolysis reaction, using powdered activated carbon (PAC), TiO2 and Ni(Ac)2 as precursors. The results proved that the photocatalyst (C/TiO2/Ni) synthesized in this work exhibited greater removal activity for Methyl Orange (MO) dye from water as compared with the commercially available well reported TiO2 nanoparticles (P25). This significant enhancement in the photocatalytic activity for wastewater treatment due to the combination of PAC and TiO2 could be presumed as the synergetic effect on the contacting interface of TiO2 and PAC, and such effect was initially demonstrated by electrochemical impedance measurements. Furthermore, the trait that it consists of magnetic properties and therefore is easy to be recycled, which could be harnessed by an external magnet and may have many advantages over pure metal oxides (like TiO2) especially in the industrial procedures.

BiOCl-assisted photodegradation of Rhodamine B under white light and monochromatic green pulsed laser irradiation

BiOCl-assisted photodegradation of Rhodamine B (Rh. B) molecules was investigated by using white light and green pulsed laser as sources of irradiation in the visible region for the first time. The dependences of removal efficiencies on catalyst dosage, incident pulsed laser energy were investigated and discussed. The dissolved oxygen was found to play an important role during the photochemical reaction. In addition the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) levels of Rh. B molecular were calculated using a Gaussian 03 program. These calculations were valuable to identify the possible photo-catalytic excitation process involved in degradation of Rh.B.