Search results for: zinc sulfate or Zn

Authors: Ratna Siti Khodijah, Mirzam Abdurrachman

Abstract:

Gold is recovered from gold ores. Within the ores, there are not only gold but also several types of precious metals. Copper, silver, and platinum group elements (ruthenium, rhodium, palladium, rhenium, osmium, and iridium) are metals commonly found in the ores. These metals combine to form an ore because they have the same properties. It is due to their position in periodic-system-of-elements are near to gold. However, the presence of mercury in every gold ore has not been mentioned, even though it is located right next to gold in the periodic-system-of-elements and they are located in the same block, d-block. Thus, it is possible that mercury is contained in the ores. Moreover, the elements of the same group with mercury—zinc and cadmium—sometimes can be found in the ores. It is suspected that mercury can not be detected because the processing of gold ores usually using fire assay method. Before the ores melting, mercury would evaporate because it has the lowest boiling point of all precious metal in the ores. Therefore, it suggested doing research on the presence of mercury in gold ores by CVAAS method. The results of this study would obtain the amount of mercury in gold ores that should be purified. So it can be produced economically if possible.

Keywords: boiling point, d-block, fire assay, precious metal

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Authors: Pavel Baroch, Jiri Rezek, Michal Prochazka, Tomas Kozak, Jiri Houska

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Transparent semiconducting amorphous IGZO films have attracted great attention due to their excellent electrical properties and possible utilization in thin film transistors or in photovoltaic applications as they show 20-50 times higher mobility than that of amorphous silicon. It is also known that the properties of IGZO films are highly sensitive to process parameters, especially to oxygen partial pressure. In this study we have focused on the comparison of properties of transparent semiconducting amorphous indium gallium zinc oxide (IGZO) thin films prepared by conventional sputtering methods and those prepared by high power impulse magnetron sputtering (HiPIMS) method. Furthermore we tried to optimize electrical and optical properties of the IGZO thin films and to investigate possibility to apply these coatings on thermally sensitive flexible substrates. We employed dc, pulsed dc, mid frequency sine wave and HiPIMS power supplies for magnetron deposition. Magnetrons were equipped with sintered ceramic InGaZnO targets. As oxygen vacancies are considered to be the main source of the carriers in IGZO films, it is expected that with the increase of oxygen partial pressure number of oxygen vacancies decreases which results in the increase of film resistivity. Therefore in all experiments we focused on the effect of oxygen partial pressure, discharge power and pulsed power mode on the electrical, optical and mechanical properties of IGZO thin films and also on the thermal load deposited to the substrate. As expected, we have observed a very fast transition between low- and high-resistivity films depending on oxygen partial pressure when deposition using conventional sputtering methods/power supplies have been utilized. Therefore we established and utilized HiPIMS sputtering system for enlargement of operation window for better control of IGZO thin film properties. It is shown that with this system we are able to effectively eliminate steep transition between low and high resistivity films exhibited by DC mode of sputtering and the electrical resistivity can be effectively controlled in the wide resistivity range of 10-² to 10⁵ Ω.cm. The highest mobility of charge carriers (up to 50 cm2/V.s) was obtained at very low oxygen partial pressures. Utilization of HiPIMS also led to significant decrease in thermal load deposited to the substrate which is beneficial for deposition on the thermally sensitive and flexible polymer substrates. Deposition rate as a function of discharge power and oxygen partial pressure was also systematically investigated and the results from optical, electrical and structure analysis will be discussed in detail. Most important result which we have obtained demonstrates almost linear control of IGZO thin films resistivity with increasing of oxygen partial pressure utilizing HiPIMS mode of sputtering and highly transparent films with low resistivity were prepared already at low pO2. It was also found that utilization of HiPIMS technique resulted in significant improvement of surface smoothness in reactive mode of sputtering (with increasing of oxygen partial pressure).

Keywords: charge carrier mobility, HiPIMS, IGZO, resistivity

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Authors: S. F. H. Tasfy, N. A. M. Zabidi, M. S. Shaharun

Abstract:

Carbon dioxide is highly thermochemical stable molecules where it is very difficult to activate the molecule and achieve higher catalytic conversion into alcohols or other hydrocarbon compounds. In this paper, series of the bimetallic Cu/ZnO-based catalyst supported by SBA-15 were systematically prepared via impregnation technique with different Cu: Zn ratio for hydrogenation of CO₂ to methanol. The synthesized catalysts were characterized by transmission electron microscopy (TEM), temperature programmed desorption, reduction, oxidation and pulse chemisorption (TPDRO), and surface area determination was also performed. All catalysts were tested with respect to the hydrogenation of CO₂ to methanol in microactivity fixed-bed reactor at 250^oC, 2.25 MPa, and H₂/CO₂ ratio of 3. The results demonstrate that the catalytic structure, activity, and methanol selectivity was strongly affected by the ratio between Cu: Zn, Where higher catalytic activity of 14 % and methanol selectivity of 92 % was obtained over Cu/ZnO-SBA-15 catalyst with Cu:Zn ratio of 7:3 wt. %. Comparing with the single catalyst, the synergetic between Cu and Zn provides additional active sites to adsorb more H₂ and CO₂ and accelerate the CO₂ conversion, resulting in higher methanol production under mild reaction conditions.

Keywords: hydrogenation of carbon dioxide, methanol synthesis, Cu/ZnO-based catalyst, mesoporous silica (SBA-15), metal ratio

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Authors: Derradji Chebli, Abdallah Bouguettoucha, Zoubir Manaa, Amrane Abdeltif

Abstract:

Pharmaceutical products, such as sulfamethoxazole (SMX) are rejected in the environment at trace level by human and animals (ng/L to mg/L), in their original form or as byproducts. Antibiotics are toxic contaminants for the aquatic environment, owing to their adverse effects on the aquatic life and humans. Even at low concentrations, they can negatively impact biological water treatment leading to the proliferation of antibiotics-resistant pathogens. It is therefore of major importance to develop efficient methods to limit their presence in the aquatic environment. In this aim, advanced oxidation processes (AOP) appear relevant compared to other methods, since they are based on the production of highly reactive free radicals, and especially ●OH. The objective of this work was to evaluate the degradation of SMX by microwave-assisted Fenton reaction (MW/Fe/H2O2). Hydrogen peroxide and ferrous ions concentrations, as well as the microwave power were optimized. The results showed that the SMX degradation by MW/Fe/H2O2 followed a pseudo-first order kinetic. The treatment of 20 mg/L initial SMX by the Fenton reaction in the presence of microwave showed the positive impact of this latter owing to the higher degradation yields observed in a reduced reaction time if compared to the conventional Fenton reaction, less than 5 min for a total degradation. In addition, increasing microwave power increased the degradation kinetics. Irrespective of the application of microwave, the optimal pH for the Fenton reaction remained 3. Examination of the impact of the ionic strength showed that carbonate and sulfate anions increased the rate of SMX degradation.

Keywords: antibiotic, degradation, elimination, fenton, microwave, polluant

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Authors: Arjun Dakuri, J. Hayavadana

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The study includes selection of 100 % bamboo fabric and cotton fabric for the study. The 100% bamboo fabrics were of 127 g/m², and 112 g/m² and 100% cotton grey fabric were of 104 g/m². The cotton fabric was desized, scoured, bleached and then treated with ZnO (as antimicrobial agent) with 1%, 2% and 3% using pad-dry cure method, whereas the bamboo fabrics were only desized. The antimicrobial activity of bamboo and ZnO treated cotton fabrics were evaluated and compared against E. coli and S. aureus as per the standard AATCC - 147. Moisture management properties of selected fabrics were also analyzed. Further, the selected fabric samples were tested for comfort properties like bending length, tearing strength, drape-ability, and specific handle force and air permeability. It was observed that bamboo fabrics show significant antibacterial activity and the same was shown by 3% ZnO treated cotton fabric. Both cotton and bamboo fabrics show improved moisture management properties than the cotton fabric. The comfort properties of bamboo fabrics are found to be superior to cotton fabrics making it more suitable for applications in place of cotton.

Keywords: antimicrobial activity, bamboo, cotton, comfort properties, moisture management, zinc oxide

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Authors: Kiurski S. Jelena, Oros B. Ivana, Kecić S. Vesna, Kovačević M. Ilija, Aksentijević M. Snežana

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The adsorption efficiency of various adsorbents for the removal of Zn(II) ions from the waste printing developer was studied in laboratory batch mode. The maximum adsorption efficiency of 94.1% was achieved with unfired clay pellets size (d≈15 mm). The obtained values of adsorption efficiency was subjected to the independent samples t-test in order to investigate the statistically significant differences of the investigated adsorbents for the effective removal of Zn(II) ions from the waste printing developer. The most statistically significant differences of adsorption efficiencies for Zn(II) ions removal were obtained between unfired clay pellets size (d≈15 mm) and activated carbon (|t|= 6.909), natural zeolite (|t|= 10.380), mixture of activated carbon and natural zeolite (|t|= 9.865), bentonite (|t|= 6.159), fired clay (|t|= 6.641), fired clay pellets size (d≈5 mm) (|t|= 6.678), fired clay pellets size (d≈8 mm) (|t|= 3.422), respectively.

Keywords: Adsorption efficiency, adsorbent, statistical analysis, zinc ion.

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Authors: Min Wu, Shuming Shen, Xuhong Yang, Rencheng Tang

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Every year, numerous organic wastes from fiber byproducts of the wool textile industry, poor quality raw wools not fit for spinning, horns, nails and feathers from butchery are disposed. These wastes are abundant in keratin which is a renewable material. Wool fiber/keratin/PVA composites with different proportions were prepared in this study, and the influence of the proportions on their structure and properties were studied, aiming to understand the potential application of keratin in the field of biomedicine, degradable wrapper, and cosmetics film, and provide a new way to reuse keratin wastes. The urea / sodium sulfide / sodium dodecyl sulfate (SDS) method was used to dissolve the wool. After filtration and dialysis, the wool keratin solution was achieved. Then the keratin solution and polyvinal (PVA) solution were blended in different proportions, and the wool fibers cut into a certain length were cast into the blended solution. Thereby, various wool fiber/keratin/PVA composite films with different proportions were formed through pouring the solution into a flat box and drying at room temperature. The surface morphology, molecular structure, and mechanical property of the composite films were studied. The results showed that, there are α-helix structure, β-sheet and random coil conformations in the pure keratin film, as well as in the wool fiber. Compared with wool fiber, the crystallinity of keratin decreased. PVA can obviously improve the mechanical property of the blended film. When the blended ratio of keratin and PVA is 20:80, the mechanical property of the blended film is greatly improved. The composite films with 8%-16% of wool fibers have better flexibility than those without wool fibers.

Keywords: composite film, keratin, mechanical property, morphological structure, PVA, wool fiber

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Authors: Piyaporn Buaklang, Narisa Kengtrong Bordeerat

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The use of nanoparticles is increasing worldwide and there are many nanotech-based daily products available in the market. The toxicity of nanoparticles results from their extremely small size which can be transported easily into the blood stream and other organs. We aimed to study the genotoxicity of two nanoparticles, Titanium dioxide (TiO2-NPs) and Zinc oxide (ZnO-NPs), in TK6 cells by micronucleus assay. The cells were tested at 8, 24, and 48 hours after exposed to 0.10, 0.25, 0.50 and 1.00 µg/mL of TiO2-NPs particles size < 25 nm and < 100 nm and to ZnO-NPs at 1, 10, 50, and 100 µg/mL, particles size < 50 nm and < 100 nm. At 24 hours of incubation transmission electron microscope (TEM) revealed that the nanoparticles TiO2-NPs at 1.00 µg/mL and ZnO-NPs at 10 µg/mL were able to be taken into the cells and induced the production of increasing amount of micronucleus in dose-dependent manner. The effect of the two nanoparticles on chromosome aberration indicated that TiO2-NPs and ZnO-NPs are genotoxic. In addition, the toxicity of TiO2-NPs was found to be 10 times more toxic than ZnO-NPs after 24 hours exposure. Analysis showed that the TiO2-NPs induced formation of micronucleus was both time and dose dependent, whereas the genotoxicity of ZnO-NPs was only dose dependent. In conclusion, TiO2-NPs and ZnO-NPs were able to transport through the cells membrane and directly genotoxic to TK6 cells in dose-dependent manner.

Keywords: nanoparticles, genotoxicity, human lymphoblast cells (TK6), micronucleus

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Authors: C. Akpagu Francis, V. Nnamani Emmanuel

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Drinking and use of polluted water from ponds, rivers, lakes, etc. for other domestic activities especially by the larger population in the rural areas has been a major source of health problems to man. A study was carried out in two different ponds in Oji River, Enugu State of Nigeria to determine the extent of total dissolved solid (TDS), metals (lead, cadmium, iron, zinc, manganese, calcium), biochemical oxygen demand (BOD). Samples of water were collected from two different ponds at a distance of 510, and 15 metres from the point of entry into the ponds to fetch water. From the results obtained, TDS (751.6Mg/l), turbidity (24ftu), conductivity (1193µs/cm), cadmium (0.008Mg/l) and lead (0.03mg/t) in pond A (PA) were found to have exceeded the WHO standard. Also in pond B (PB) the results shows that TDS (760.30Mg/l), turbidity (26ftu), conductivity (1195µs/cm), cadmium (0.008mg/l) and lead (0.03Mg/l) were also found to have exceeded the WHO standard which makes the two ponds. Water very unsafe for drinking and use in other domestic activities.

Keywords: physicochemical, groundwater, Oji River, Nigeria

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Authors: Delele Worku Ayele, Bing-Joe Hwang

Abstract:

A method that does not employ hot injection techniques has been developed for the size-tunable synthesis of high-quality CdSe quantum dots (QDs) with a zinc blende structure. In this environmentally benign synthetic route, which uses relatively less toxic precursors, solvents, and capping ligands, CdSe QDs that absorb visible light are obtained. The size of the as-prepared CdSe QDs and, thus, their optical properties can be manipulated by changing the microwave reaction conditions. The QDs are characterized by XRD, TEM, UV-vis, FTIR, time-resolved fluorescence spectroscopy, and fluorescence spectrophotometry. In this approach, the reaction is conducted in open air and at a much lower temperature than in hot injection techniques. The use of microwaves in this process allows for a highly reproducible and effective synthesis protocol that is fully adaptable for mass production and can be easily employed to synthesize a variety of semiconductor QDs with the desired properties. The possible application of the as-prepared CdSe QDs has been also assessed using deposition on TiO2 films.

Keywords: average life time, CdSe QDs, microwave (MW), mass production oleic acid, Na2SeSO3

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Authors: Abderrahmane Hamdi, Julie Chalon, Benoit Dodin, Philippe Champagne

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This research work concerns the synthesis of hydrophobic and self-cleaning coatings as an alternative to fluorine-based coatings used on glass. The developed, highly transparent coatings are produced by a chemical route (sol-gel method) using two silica-based precursors, hexamethyldisilazane and tetraethoxysilane (HMDS/TEOS). The addition of zinc oxide nanoparticles (ZnO NPs) within the gel provides a photocatalytic property to the final coating. The prepared gels were deposited on glass slides using different methods. The properties of the coatings were characterized by optical microscopy, scanning electron microscopy, UV-VIS-NIR spectrophotometer, and water contact angle method. The results show that the obtained coatings are homogeneous and have a hydrophobic character. In particular, after thermal treatment, the HMDS/TEOS@ZnO charged gel deposited on glass constitutes a coating capable of degrading methylene blue (MB) under UV irradiation. Optical transmission reaches more than 90% in most of the visible light spectrum. Synthetized coatings have also demonstrated their mechanical durability and self-cleaning ability.

Keywords: coating, durability, hydrophobicity, sol-gel, self-cleaning, transparence

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Authors: Farida Kaouah, Wassila Hachi, Lamia Brahmi, Chahida Ousselah, Salim Boumaza, Mohamed Trari

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The feasibility of using solar irradiation instead of UV light in photocatalysis is a promising approach for water treatment. In this study, photocatalytic degradation of a widely used textile dye, Acid Blue 25 (AB25), with noble metal loaded ZnO photocatalyst (Ag/ZnO), was investigated in aqueous suspension under solar light. The results showed that the deposition of Ag as a noble metal onto the ZnO surface, improved the photodegradation of AB25. . The effect of different parameters such as catalyst dose, initial dye concentration, and contact time was optimized and the optimal degradation of AB25 (97%) was achieved for initial AB25 concentration of 24 mg L−1 an catalyst dose of 1 g L−1 at natural pH (5.42) after 180 min. The kinetic studies were achieved and revealed that the photocatalytic degradation process obeyed to Langmuir–Hinshelwood model and followed a pseudo-first order rate expression. This work envisages the great potential that sunlight photocatalysis has in the degradation of dyes from wastewater

Keywords: acid dye, photocatalytic degradation, sunlight, zinc oxide, noble metal, Langmuir–Hinshelwood model

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Authors: Benjamin Kaufmann, Michael Hofstätter, Nadine Raidl, Peter Supancic

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ZnO varistors are the leading overvoltage protection elements in today’s electronic industry. Their highly non-linear current-voltage characteristics, very fast response times, good reliability and attractive cost of production are unique in this field. There are challenges and questions unsolved. Especially, the urge to create even smaller, versatile and reliable parts, that fit industry’s demands, brings manufacturers to the limits of their abilities. Although, the varistor effect of sintered ZnO is known since the 1960’s, and a lot of work was done on this field to explain the sudden exponential increase of conductivity, the strict dependency on sinter parameters, as well as the influence of the complex microstructure, is not sufficiently understood. For further enhancement and down-scaling of varistors, a better understanding of the microscopic processes is needed. This work attempts a microscopic approach to investigate ZnO varistor performance. In order to cope with the polycrystalline varistor ceramic and in order to account for all possible current paths through the material, a preferably realistic model of the microstructure was set up in the form of three-dimensional networks where every grain has a constant electric potential, and voltage drop occurs only at the grain boundaries. The electro-thermal workload, depending on different grain size distributions, was investigated as well as the influence of the metal-semiconductor contact between the electrodes and the ZnO grains. A number of experimental methods are used, firstly, to feed the simulations with realistic parameters and, secondly, to verify the obtained results. These methods are: a micro 4-point probes method system (M4PPS) to investigate the current-voltage characteristics between single ZnO grains and between ZnO grains and the metal electrode inside the varistor, micro lock-in infrared thermography (MLIRT) to detect current paths, electron back scattering diffraction and piezoresponse force microscopy to determine grain orientations, atom probe to determine atomic substituents, Kelvin probe force microscopy for investigating grain surface potentials. The simulations showed that, within a critical voltage range, the current flow is localized along paths which represent only a tiny part of the available volume. This effect could be observed via MLIRT. Furthermore, the simulations exhibit that the electric power density, which is inversely proportional to the number of active current paths, since this number determines the electrical active volume, is dependent on the grain size distribution. M4PPS measurements showed that the electrode-grain contacts behave like Schottky diodes and are crucial for asymmetric current path development. Furthermore, evaluation of actual data suggests that current flow is influenced by grain orientations. The present results deepen the knowledge of influencing microscopic factors on ZnO varistor performance and can give some recommendations on fabrication for obtaining more reliable ZnO varistors.

Keywords: metal-semiconductor contact, Schottky diode, varistor, zinc oxide

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Authors: Khamael M. Abualnaja, Lidija Šiller, Ben R. Horrocks

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Surface enhanced Raman spectroscopy (SERS) of Silicon nano crystals (SiNCs) were obtained using two different laser excitations: 488 nm and 514.5 nm. Silver nano particles were used as plasmonics metal nano particles due to a robust SERS effect that observed when they mixed with SiNCs. SiNCs have been characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It is found that the SiNCs are crystalline with an average diameter of 65 nm and FCC lattice. Silver nano particles (AgNPs) of two different sizes were synthesized using photo chemical reduction of AgNO3 with sodium dodecyl sulfate (SDS). The synthesized AgNPs have a polycrystalline structure with an average particle diameter of 100 nm and 30 nm, respectively. A significant enhancement in the SERS intensity was observed for AgNPs100/SiNCs and AgNPs30/SiNCs mixtures increasing up to 9 and 3 times respectively using 488 nm intensity; whereas the intensity of the SERS signal increased up to 7 and 2 times respectively, using 514.5 nm excitation source. The enhancement in SERS intensities occurs as a result of the coupling between the excitation laser light and the plasmon bands of AgNPs; thus this intense field at AgNPs surface couples strongly to SiNCs. The results provide good consensus between the wavelength of the laser excitation source and surface plasmon resonance absorption band of silver nano particles consider to be an important requirement in SERS experiments.

Keywords: silicon nanocrystals (SiNCs), silver nanoparticles (AgNPs), surface enhanced raman spectroscopy (SERS)

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Authors: Alaa M. Younis, Ismail S. Ismail, Lamiaa I. Mohamedein, Shimaa F. Ahmed

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Sandy surface sediments collected from fourteen sites along the gulfs of Suez and Aqaba coasts, Egypt were analyzed for heavy metals including Iron, Manganese, Zinc, Chromium, Nickel, Lead, Copper and Cadmium in order to evaluate the pollution status and environmental risk assessment of the study area. The obtained results showed that the concentrations of investigated metals are represented in the following sequence; For Gulf of Aqaba sediments Fe > Mn > Zn > Pb > Cr > Ni > Cu > Cd. While for Gulf of Suez Sediments Fe > Mn > Pb > Zn > Cu > Cr > Ni > Cd. The degree of surface sediment contamination using Geo-accumulation index (I geo) and Metal Pollution Index (MPI) was computed. Higher MPI values were observed at the sites III (Nama Bay) and VIII (Rex Beach). According to Sediment quality guidelines (SQGs) approach, Pb and Cu in the gulf of Suez at station IX (Kabanon Beach) had probably adverse ecological effects to marine organisms.

Keywords: heavy metal, environmental risk, Suez gulf, Aqaba gulf

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Authors: Murtada Ahmed Oshi, Jin-Wook Yoo

Abstract:

Layer-by-layer (LBL) coating has gained popularity for drug delivery of therapeutic drugs. Herein we described a novel approach for enhancing the therapeutic efficiency of the locally administered dexamethasone (Dex) for inflammatory bowel disease (IBD). We utilized a LBL-coating technique on Dex microcrystals (DexMCs) with multiple layers of polyelectrolytes composed of poly (allylamine hydrochloride) (PAH), poly (sodium 4-styrene sulfonate) (PSS) and Eudragit® S100 (ES). The successful deposition of the layers onto DexMCs surfaces were confirmed through zeta potential measurement and confocal laser scanning microscopy. The surface morphology was investigated through scanning electron microscopy. The drug encapsulation efficiency was 95% with a mean particle size of 2 µm and negative surface charge (-40 mV). Moreover, in vitro drug release study showed a minimum release of the drug ( 15%) at an acidic condition during initial first 5 h, followed by sustained-release at an alkaline condition. For in vivo study, LBL-DxMCs were administered orally to ICR mice suffering from dextran sulfate sodium-induced colitis. LBL-DxMCs substantially enhanced anti-IBD activities as compared to DxMCs. Macroscopic, histological and biochemical (tumor necrosis factor-α, interleukin-6 and myeloperoxidase) examinations revealed marked improvements of colitis signs in the mice treated with LBL-DxMCs compared with those treated with DxMCs. Overall, LBL-DxMCs could be a suitable candidate for the treatment of IBD.

Keywords: dexamethasone, inflammatory bowel disease, LBL-coating, polyelectrolytes

Procedia PDF Downloads 177

Authors: Udayakumar Vee, Franck Quero

Abstract:

Zwitterionic polymers generally have been viewed as a new class of antimicrobial and non-fouling materials. They offer a broad versatility for chemical modification and hence great freedom for accurate molecular design, which bear an equimolar number of homogenously distributed anionic and cationic groups along their polymer chains. This study explores the effectiveness of the auxetic zwitterion carboxylate/sulfonate hydrogel in the diabetic-induced mouse model. A series of silver metal-doped auxetic zwitterion carboxylate/sulfonate/vinylaniline copolymer hydrogels is designed via a 3D printer. Zwitterion monomers have been characterized by FT-IR and NMR techniques. The effect of changing the monomers and different loading ratios of Ag over zwitterion on the final hydrogel materials' antimicrobial properties and biocompatibility will be investigated in detail. The synthesized auxetic hydrogel has been characterized using a wide range of techniques to help establish the relationship between molecular level and macroscopic properties of these materials, including mechanical and antibacterial and biocompatibility and wound healing ability. This work's comparative studies and results provide new insights and guide us in choosing a better auxetic structured material for a broad spectrum of wound healing applications in the animal model. We expect this approach to provide a versatile and robust platform for biomaterial design that could lead to promising treatments for wound healing applications.

Keywords: auxetic, zwitterion, carboxylate, sulfonate, polymer, wound healing

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Authors: Delele Worku Ayele, Bing-Joe Hwang

Abstract:

A method that does not employ hot injection techniques has been developed for the size-tunable synthesis of high-quality CdSe quantum dots (QDs) with a zinc blende structure. In this environmentally benign synthetic route, which uses relatively less toxic precursors, solvents, and capping ligands, CdSe QDs that absorb visible light are obtained. The size of the as-prepared CdSe QDs and, thus, their optical properties can be manipulated by changing the microwave reaction conditions. The QDs are characterized by XRD, TEM, UV-vis, FTIR, time-resolved fluorescence spectroscopy, and fluorescence spectrophotometry. In this approach, the reaction is conducted in open air and at a much lower temperature than in hot injection techniques. The use of microwaves in this process allows for a highly reproducible and effective synthesis protocol that is fully adaptable for mass production and can be easily employed to synthesize a variety of semiconductor QDs with the desired properties. The possible application of the as-prepared CdSe QDs has been also assessed using deposition on TiO2 films.

Keywords: CdSe QDs, Na2SeSO3, microwave (MW), oleic acid, mass production, average life time

Procedia PDF Downloads 681

Authors: Christy Rosaline, Rathankar Roa, Waheeta Hopper

Abstract:

Persistence of tuberculosis, emergence of multidrug-resistance and extensively drug-resistant forms of the disease, has increased the interest in developing new antitubercular drugs. Developing inhibitors for 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase from Mycobacterium tuberculosis (MtbDAH7Ps), an enzyme involved in shikimate pathway, gives a selective target for antitubercular agents. MtbDAH7Ps was screened against ZINC database, and shortlisted compounds were subjected to induce fit docking. Prime/Molecular Mechanics Generalized Born Surface Area calculation was used to validate the binding energy of ligand-protein complex. Molecular Dynamics analysis for of the lead compounds–MtbDAH7Ps complexes showed that the backbone of MtbDAH7Ps in their complexes were stable. These results suggest that the shortlisted lead compounds ZINC04097114, ZINC15163225, ZINC16857013, ZINC06275603, and ZINC05331260 could be developed into novel drug leads to inhibit DAH7Ps in Mycobacterium tuberculosis.

Keywords: MtbDAH7Ps, Mycobacterium tuberculosis, HTVS, molecular dynamics

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Authors: Chundong Li, V. V. Neshchimenko, M. M. Mikhailov

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The effect of the modification of ZnO powders by ZrO2, Al2O3, TiO2, SiO2, CeO2 and Y2O3 nanoparticles with a concentration of 1-30 wt % is investigated by diffuse reflectance spectra within the wavelength range 200 to 2500 nm before and after 100 keV proton and electron irradiation. It has been established that the introduction of nanoparticles ZrO2, Al2O3 enhances the optical stability of the pigments under proton irradiation, but reduces it under electron irradiation. Modifying with TiO2, SiO2, CeO2, Y2O3 nanopowders leads to decrease radiation stability in both types of irradiation. Samples modified by 5 wt. % of ZrO2 nanoparticles have the highest stability of optical properties after proton exposure. The degradation of optical properties under electron irradiation is not high for this concentration of nanoparticles. A decrease in the absorption of pigments modified with nanoparticles proton exposure is determined by a decrease in the intensity of bands located in the UV and visible regions. After electron exposure the absorption bands have in the whole spectrum range.

Keywords: irradiation, nanopowders, radiation stability, zinc oxide

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Authors: Shefaa Mansour, Hassan Arafat, Shadi Hasan

Abstract:

Management of reverse osmosis (RO) brine has become a major area of research due to the environmental concerns associated with it. This study worked on studying the feasibility of the direct contact membrane distillation (DCMD) system in the treatment of this RO brine. The system displayed great potential in terms of its flux and salt rejection, where different operating conditions such as the feed temperature, feed salinity, feed and permeate flow rates were varied. The highest flux of 16.7 LMH was reported with a salt rejection of 99.5%. Although the DCMD has displayed potential of enhanced water recovery from highly saline solutions, one of the major drawbacks associated with the operation is the fouling of the membranes which impairs the system performance. An operational run of 77 hours for the treatment of RO brine of 56,500 ppm salinity was performed in order to investigate the impact of fouling of the membrane on the overall operation of the system over long time operations. Over this time period, the flux was observed to have reduced by four times its initial flux. The fouled membrane was characterized through different techniques for the identification of the organic and inorganic foulants that have deposited on the membrane surface. The Infrared Spectroscopy method (IR) was used to identify the organic foulants where SEM images displayed the surface characteristics of the membrane. As for the inorganic foulants, they were identified using X-ray Diffraction (XRD), Ion Chromatography (IC) and Energy Dispersive Spectroscopy (EDS). The major foulants found on the surface of the membrane were inorganic salts such as sodium chloride and calcium sulfate.

Keywords: brine treatment, membrane distillation, fouling, characterization

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Authors: S. K. Pyne, M. Mondal, G. Samanta

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A survey was carried out in red lateritic zone of West Bengal to compare the mineral status in plasma of livestock grazing over red lateritic region. Sufficient number of samples of soil, feeds, fodder and blood were collected from four districts of red lateritic zone namely, West Midnapore, Birbhum, Bankura and Purulia respectively. The samples were analysed for Calcium (Ca), Phosphorus (P), Copper (Cu), Zinc (Zn), Manganese (Mn) and Iron (Fe). Concentration of Cu, Mn and Fe in soil were above the minimum critical level, whereas, Zn deficiency is wide spread in red lateritic soil. Paddy straw is deficient in Ca, P, Zn and Mn in the region. Green fodders are also deficient in P, Cu, Zn. The richness of iron (Fe) in soil, feeds, fodder and tree leaves is the characteristics of this region. Phosphorus is deficient in plasma of all categories of livestock with the exception of bullock. Cu is deficient in plasma of calf. Plasma Mn and Fe were higher (p<0.01) in the animals of red lateritic zone. The study reveals that the overall deficiency of phosphorus in different categories of livestock and there is need of dietary supplementation.

Keywords: mineral, red lateritic zone, grazing livestock, plasma

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Authors: Larbi Belagraa, Miloud Beddar, Abderrazak Bouzid

Abstract:

The needs of the construction sector still increasing for concrete. However, the shortage of natural resources of aggregate could be a problem for the concrete industry, in addition to the negative impact on the environment due to the demolition wastes. Recycling aggregate from construction and demolition (C&D) waste presents a major interest for users and researchers of concrete since this constituent can occupies more than 70% of concrete volume. The aim of the study here in is to assess the effect of sulfate resistant cement combined with the local mineral addition of marble waste fillers on the mechanical behavior of a recycled aggregate concrete (RAC). Physical and mechanical properties of RAC including the density, the flexural and the compressive strength were studied. The non destructive test methods (pulse-velocity, rebound hammer) were performed . The results obtained were compared to crushed aggregate concrete (CAC) using the normal compressive testing machine test method. The optimal content of 5% marble fillers showed an improvement for both used test methods (compression, flexion and NDT). Non-destructive methods (ultrasonic and rebound hammer test) can be used to assess the strength of RAC, but a correction coefficient is required to obtain a similar value to the compressive strength given by the compression tests. The study emphasizes that these waste materials can be successfully and economically utilized as additional inert filler in RAC formulation within similar performances compared to a conventional concrete.

Keywords: marble waste fillers, mechanical strength, natural aggregate, non-destructive testing (NDT), recycled aggregate concrete

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Authors: M. Rose Ntsewa, P. E. Dlamini, V. E. Mbanjwa, R. Chauke

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Land-use change from undisturbed forest to tea plantation may lead to accumulation or loss of soil organic carbon (SOC). So far, the factors controlling the vertical distribution of SOC under the long-term establishment of tea plantation remain poorly understood, especially in oxisols. In this study, we quantified the vertical distribution of SOC under tea plantation compared to adjacent undisturbed forest Oxisols sited at different topographic positions and also determined controlling edaphic factors. SOC was greater in the 30-year-old tea plantation compared to undisturbed forest oxisols and declined with depth across all topographic positions. Most of the SOC was found in the downslope position due to erosion and deposition. In the topsoil, SOC was positively correlated with heavy metals; manganese (r=0.62-0.83; P<0.05) and copper (r=0.45-0.69), effective cation exchange capacity (ECEC) (r=0.72) and mean weight diameter (MWD) (r=0.72-0.73), while in the subsoil SOC was positively correlated with copper (r=0.89-0.92) and zinc (r=0.86), ECEC (r=0.56-0.69) and MWD (r=0.48). These relationships suggest that SOC in the tea plantation, oxisols is chemically stabilized via complexation with heavy metals, and physically stabilized by soil aggregates.

Keywords: oxisols, tea plantation, topography, undisturbed forest

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Authors: Imen Harabi, Hanae Toura, Safa Jemai, Bernabe Mari Soucase

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A promising alternative to traditional Quantum Dots QD materials, which contain toxic heavy elements such as lead and cadmium, sheds light on indium phosphide quantum dots (InP QDs) Owing to improve the quantum yields of photoluminescence and other properties. InP, InP/ZnS core/shell and InP/ZnS/ZnS core/shell/shell Quantum Dots (QDs) were synthetized by the hot injection method. The optical and structural properties of the core InP QDs, InP/ZnS QDs, and InP/ZnS/ZnS QDs have being considered by several techniques such as X-ray diffraction, transmission electron microscopy, optical spectroscopy, and photoluminescence. The average diameter of InP, InP/ZnS, and InP/ZnS/ZnS Quantum Dots (QDs) was varying between 10 nm, 5.4 nm, and 4.10 nm. This experience revealed that the surface morphology of the Quantum Dots has a more regular spherical form with color variation of the QDs in solution. The emission peak of colloidal InP Quantum Dots was around 530 nm, while in InP/ZnS, the emission peak is displayed and located at 598 nm. whilst for InP/ZnS/ZnS is placed at 610 nm. Furthermore, an enhanced PL emission due to a passivation effect in the ZnS-covered InP QDs was obtained. Add the XRD information FWHM of the principal peak of InP QDs was 63 nm, while for InP/ZnS was 41 nm and InP/ZnS/ZnS was 33 nm. The effect of the Zinc stearate precursor concentration on the optical, structural, surface chemical of InP and InP/ZnS and InP/ZnS/ZnS QDs will be discussed.

Keywords: indium phosphide, quantum dot, nanoparticle, core-shell, multishell, luminescence

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Authors: Garima, S. Pushpavanam

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In this work, analysis of an Aqueous two-phase (polymer-salt) system for extraction of sunset yellow dye is carried out. A polymer-salt ATPS i.e.; Polyethylene glycol-600 and anhydrous sodium sulfate is used for the extraction. Conditions are chosen to ensure that the extraction results in a concentration of the dye in one of the phases. The dye has a propensity to come to the Polyethylene glycol-600 phase. This extracted sunset yellow dye is degraded photo catalytically into less harmful components. The cloud point method was used to obtain the binodal curve of ATPS. From the binodal curve, the composition of salt and Polyethylene glycol -600 was chosen such that the volume of Polyethylene glycol-600 rich phase is low. This was selected to concentrate the dye from a dilute solution in a large volume of contaminated solution into a small volume. This pre-concentration step provides a high reaction rate for photo catalytic degradation reaction. Experimentally the dye is extracted from the salt phase to Polyethylene glycol -600 phase in batch extraction. This was found to be very fast and all dye was extracted. The concentration of sunset yellow dye in salt and polymer phase is measured at 482nm by ultraviolet-visible spectrophotometry. The extraction experiment in micro channels under stratified flow is analyzed to determine factors which affect the dye extraction. Focus will be on obtaining slug flow by adding nanoparticles in micro channel. The primary aim is to exploit the fact that slug flow will help improve mass transfer rate from one phase to another through internal circulation in dispersed phase induced by shear.

Keywords: aqueous two phase system, binodal curve, extraction, sunset yellow dye

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Authors: Z. O. Apotiola, J. F. Fashakin

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A study was conducted to investigate the storage stability of Mr Chef and Annapurna salts. The salts were bought from Mile 12 market in Lagos State and were stored for a period of six months. The stability of the iodine content was then investigated by storing some at ambient temperature (24-30oC) and some at atmospheric temperature (21-35 oC), and from each storage condition, a sample each was taken every month to analyze for the iodine and moisture contents. The result shows that there was a significant difference between Mr Chef and the standard and Annapurna and the standard. The iodine content of Mr Chef stored at ambient and atmospheric temperature decreases progressively from 48.70±0.00-37.00±0.00 and 47.60±0.00-11.60±0.00 respectively. And that of Annapurna at both ambient and atmospheric temperature also decreases progressively from 47.60±0.00-36.60±0.00 and 47.60±0.00-10.60±0.00 respectively. Also, the moisture content of both salts at the zero month to the sixth month both at room temperature and atmospheric temperature increases from 1.11±0.00-1.70±0.00 and 1.11±0.00-2.40±0.00 respectively. The results of the heavy metals shows that only Copper, Zinc and Cobalt were detected at the first and the sixth month in both Mr Chef and Annapurna which ranges from 0.15±0.00-0.38±0.00 and 0.18±0.00 - 3.50±0.00 respectively. Hence, the stability of iodine in salt is influenced by the storage conditions it is subjected to and the length of time it is been stored.

Keywords: salt, iodine, stability, ambient, atmospheric temperature

Procedia PDF Downloads 546

Authors: Celia Marilia Martins, Sonia I. V. Guilundo, Iris M. Victorino, Antonio O. Quilambo

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In Mozambique rapid industrialization (mining, aluminium and cement activities) and urbanization processes has led to the incorporation of heavy metals on soil, thus degrading not only the quality of the environment, but also affecting plants, animals and human healthy. Several methods have been used to remediate contaminated soils, but most of them are costly and difficult to get optimum results. Currently, phytoremediation is an effective and affordable technological solution used to extract or remove inactive metals from contaminated soil. Phytoremediation is the use of plants to clean up a contamination from soils, sediments, and water. This technology is environmental friendly and potentially cost effective. The present investigation summarised the potential of edible vegetable to grow under the high level of heavy metals such as lead and zinc. The plants used in these studies include Tomatoes, lettuce and Soya beans. The studies have shown that edible plants can be grown under the high level of heavy metals on the soil. Further investigations are identifying mechanisms used by plants to ensure a safe and sustainable use for remediation of contaminated soils by heavy metals.

Keywords: contaminated soil, edible plants, heavy metals, phytoremediation

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Authors: Jin-Woo Park, Sung-Soo Lee, Nong-Moon Hwang

Abstract:

The generation of charged nanoparticles in the gas phase during the Chemical Vapor Deposition (CVD) process has been frequently reported with their subsequent deposition into films and nanostructures in many systems such as carbon, silicon and zinc oxide. The microstructure evolution of films and nanostructures is closely related with the size distribution of charged nanoparticles. To confirm the generation of charged nanoparticles during GaN, the generation of GaN charged nanoparticles was examined in an atmospheric pressure CVD process using a Differential Mobility Analyser (DMA) combined with a Faraday Cup Electrometer (FCE). It was confirmed that GaN charged nanoparticles were generated under the condition where GaN nanostructures were synthesized on the bare and Au-coated Si substrates. In addition, the deposition behaviour depends strongly on the charge transfer rate of metal substrates. On the metal substrates of a lower CTR such as Mo, the deposition rate of GaN was much lower than on those of a higher CTR such as Fe. GaN nanowires tend to grow on the substrates of a lower CTR whereas GaN thin films tend to be deposited on the substrates of a higher CTR.

Keywords: chemical vapour deposition, charged cluster model, generation of charged nanoparticles, deposition behaviour, nanostructures, gan, charged transfer rate

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Authors: Preeti Pal, Anjali Pal

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Chitosan is an effective sorbent for removal of contaminants from wastewater. However, the ability of pure chitosan is specific because of its cationic charge. It causes repulsion in the removal process of various cationic charged molecules. The present study has been carried out for the successful removal of Pb²⁺ ions from aqueous solution by modified chitosan beads. Surface modification of chitosan (CS) beads was performed by using the anionic surfactant (AS), sodium dodecyl sulfate (SDS). Micelle aggregation property of SDS has been utilized for the formation of bilayer over the CS beads to produce surfactant modified chitosan (SMCS) beads. Prepared adsorbents were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) in order to find out their composition and surface morphology. SMCS beads, when compared to the pure CS beads, showed three times higher adsorption. This higher adsorption is believed to be due to the adsolubilization of Pb²⁺ ions on SDS bilayer. This bilayer provides more adsorption sites for quick and effective removal of Pb²⁺ ions from the aqueous phase. Moreover, the kinetic and adsorption isotherm models were employed to the obtained data for the description of the lead adsorption processes. It was found that the removal kinetics follows pseudo-second order model. Adsorption isotherm data fits well to the Langmuir model. The maximum adsorption capacity obtained is 100 mg/g at the dosage of 0.675 g/L for 50 mg/L of Pb²⁺. The adsorption capacity is subject to increase with increasing the Pb²⁺ ions concentration in the solution. The results indicated that the prepared hydrogel beads are efficient adsorbent for removal of Pb²⁺ ions from the aqueous medium.

Keywords: adsolubilisation, anionic surfactant, bilayer, chitosan, Pb²⁺

Procedia PDF Downloads 211