Search results for: metal complexes

Authors: M. A. Lawal, A. Uzairu, M. S. Sallau

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The presence and bioaccumulation of lead (Pb), cadmium (Cd), and chromium (Cr) in blood, urine, nail, and hair samples of electronic repair technicians in Kaduna-Nigeria were assessed using Fast Sequential Atomic Absorption Spectrophotometry. 10 electronic repair technicians from within Kaduna Metropolis volunteered for the pilot study. The mean blood concentrations of Pb, Cd, and Cr in the subjects were 29.33 ± 4.80, 7.78 ± 10.57, and 24.78 ± 21.77 µg/dL, respectively. The mean urine concentrations of Pb, Cd, and Cr were 24.18 ± 2.98, 6.81 ± 10.05, and 14.78 ± 14.20 µg/dL, respectively. Mean nail metal values of 37.13 ± 4.08, 1.00 ± 1.21, and 18.49 ± 12.71 µg/g were obtained for Pb, Cd, and Cr, respectively while mean hair metal values of 39.41 ± 5.63, 1.09 ± 1.14, and 19.13 ± 11.61 µg/g for Pb, Cd, and Cr, respectively. Positive Pearson correlation coefficients were observed between Pb/Cd, Pb/Cr, and Cd/Cr in all samples and they indicate the metals are likely from the same pollution source. The mean concentrations of the metals in all samples were higher than the WHO, ILO, and ACGIH standards, implying the repairers are likely occupationally exposed and are subject to serious health concerns. Social habits like smoking were found to significantly affect the concentrations of these metals. The level of education, use of safety devices, period of exposure, the nature of electronics and the age of the repairers were also found to remarkably affect the concentrations of the metals.

Keywords: bioaccumulation, electronic repair technicians, heavy metals, occupational hazard

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Authors: O. O. Olawusi-Peters, K. I. Adejugbagbe

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The concentration of heavy metal (Cd, Pb, Fe, Zn, Cu) in Clarias gariepinus collected from fish markets; Fanibi (Station I) and Fiwasaye (Station II) in Akure metropolis, Ondo state, Nigeria were investigated to ascertain the safety for the consumers. 60 samples were collected from the two markets in three batches (I, II, III) for a period of six months and analyzed for heavy metals in the gills and muscles of the fish. Also, the Health Risk Index (HRI) was used to determine the health risk of these metals to the consumer. The results showed that the investigated metal concentration was higher in station I than station II, except Pb having higher concentration in station II than station I. In both stations, the highest concentration of Fe was recorded in the gills (12.60 ± 1.51; 6.94 ± 1.38) and muscles (3.72 ± 0.09; 3.86 ± 0.33) of samples in batch I. Also, the HRI revealed that consumption of Clarias gariepinus from these study areas did not pose any health risk (HRI < 1). In addition, concentrations of the heavy metals were all below the permissible limits recommended by FAO/WHO.

Keywords: health risk index, heavy metals, clarias gariepinus, akure metropolis, fish monger

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Authors: Anjali Sidhu, Anju Bala, Amit Kumar

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Metal nanoparticles have the potential to revolutionize the agriculture owing to sizzling interdisciplinary nano-technological application domain. Numerous patents and products incorporating engineered nanoparticles (NPs) entered into agro-applications with the collective goal to promote proficiency as well as sustainability with lower input and generating meager waste than conventional products and approaches. Loose smut of wheat caused by Ustilago segetum tritici is an internally seed-borne pathogen. It is dormant in the seed unless the seed germinates and its symptoms are expressed at the reproductive stage of the plant only. Various seed treatment agents are recommended for this disease but due to the inappropriate methods of seed treatments used by farmers, each and every seed may not get treated, and the infected seeds escape the fungicidal action. The antimicrobial potential and small size of nanoparticles made them the material of choice as they could enter each seed and restrict the pathogen inside the seed due to the availability of more number of nanoparticles per unit volume of the nanoformulations. Nanoparticles of diverse nature known for their in vitro antimicrobial activity viz. ZnO, MgO, CuS and AgNPs were synthesized, surface modified and characterized by traditional methods. They were applied on infected wheat seeds which were then grown in pot conditions, and their mycelium was tracked in the shoot and leaf region of the seedlings by microscopic staining techniques. Mixed responses of inhibition of this internal mycelium were observed. The time and method of application concluded to be critical for application, which was optimised in the present work. The results implicated that there should be field trails to get final fate of these pot trails up to commercial level. The success of their field trials could be interpreted as a revolution to replace high dose organic fungicides of high residue behaviour.

Keywords: metal nanoparticles, nanopriming, seed borne pathogen, Ustilago segetum tritici

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Authors: Mohammed M. Algaradah

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A chelating mercapto- nanoscavenger has been developed exploiting the high surface area of monodisperse nano-sized mesoporous silica. The nanoscavenger acts as a solid phase trace metal extractant whilst suspended as a quasi-stable sol in aqueous samples. This mode of extraction requires no external agitation as the particles move naturally through the sample by Brownian motion, convection and slow sedimentation. Careful size selection enables the nanoscavenger to be easily recovered together with the extracted analyte by conventional filtration or centrifugation. The research describes the successful attachment of chelator mercapto to ca. 136 ± 15 nm high surface area (BET surface area = 1006 m2 g-1) mesoporous silica particles. The resulting material had a copper capacity of ca. 1.34 ± 0.10 mmol g-1 and was successfully applied to the collection of a trace element from water. Essentially complete recovery of Cu (II) has been achieved from freshwater samples giving typical preconcentration factors of 100 from 50 µg/l samples. Data obtained from a nanoscavenger-based extraction of copper from samples were not significantly different from those obtained by using a conventional colorimetric procedure employing complexation/solvent extraction.

Keywords: nano scavenger, mesoporous silica, trace metal, preconcentration

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Authors: Lowanika Victor Tibane, David Mamba

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Human body, animals, and plants depend on certain essential metals in permissible quantities for their survival. Excessive metal concentration may cause severe malfunctioning of the organisms and even fatal in extreme cases. Because of gold mining in the Witwatersrand basin in South Africa, enormous untreated mine dumps comprise elevated concentration of essential trace elements. Elevated quantities of trace metal have direct negative impact on the quality of soil for different land use types, reduce soil efficiency for plant growth, and affect the health human and animals. A total of 21 subsoil samples were examined using inductively coupled plasma optical emission spectrometry and X-ray fluorescence methods and the results elevated men concentration of Fe (36,433.39) > S (5,071.83) > Cu (1,717,28) > Mn (612.81) > Cr (74.52) > Zn (68.67) > Ni (40.44) > Co (9.63) > P (3.49) > Mo > (2.74), reported in mg/kg. Using various contamination indices, it was discovered that the sites surveyed are on average moderately contaminated with Co, Cr, Cu, Mn, Ni, S, and Zn. The ecological risk assessment revealed a low ecological risk for Cr, Ni and Zn, whereas Cu poses a very high ecological risk.

Keywords: essential trace elements, soil contamination, contamination indices, toxicity, descriptive statistics, ecological risk evaluation

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Authors: Otuwose E. Agyeno, Adeniyi A. Jayeola, Bashir A. Ajala

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P. esculentus is indigenous to Nigeria yet no wild relation has been encountered or reported. This has made it difficult to establish proper lineages between the varieties and landraces under cultivation. The present work is the first to determine the apormophy of 135 morphoanatomical characters in organs of 46 accessions drawn from 23 populations of this species based on dicta. The character states were coded in accession x character-state matrices and only 83 were informative and utilised for neighbour joining clustering based on euclidean values, and heuristic search in parsimony analysis using PAST ver. 3.15 software. Compatibility and evolutionary trends between accessions were then explored from values and diagrams produced. The low consistency indices (CI) recorded support monophyly and low homoplasy in this taxon. Agglomerative schedules based on character type and source data sets divided the accessions into mainly 3 clades, each of complexes of accessions. Solenostemon rotundifolius (Poir) J.K Morton was the outgroup (OG) used, and it occurred within the largest clades except when the characters were combined in a data set. The OG showed better compatibility with accessions of populations of landrace Isci, and varieties Riyum and Long’at. Otherwise, its aerial parts are more consistent with those of accessions of variety Bebot. The highly polytomous clades produced due to anatomical data set may be an indication of how stable such characters are in this species. Strict consensus trees with more than 60 nodes outputted showed that the basal nodes were strongly supported by 3 to 17 characters across the data sets, suggesting that populations of this species are more alike. The OG was clearly the first diverging lineage and closely related to accessions of landrace Gwe and variety Bebot morphologically, but different from them anatomically. It was also distantly related to landrace Fina and variety Long’at in terms of root, stem and leaf structural attributes. There were at least 5 other clades with each comprising of complexes of accessions from different localities and terrains within the study area. Spherical stem in cross section, size of vascular bundles at the stem corners as well as the alternate and whorl phyllotaxy are attributes which may have facilitated each other’s evolution in all accessions of the landrace Gwe, and they may be innovative since such states are not characteristic of the larger Lamiaceae, and Plectranthus L’Her in particular. In conclusion, this study has provided valuable information about infraspecific diversity in this taxon. It supports recognition of the varietal statuses accorded to populations of P. esculentus, as well as the hypothesis that the wild gene might have been distributed on the Jos Plateau. However, molecular characterisation of accessions of populations of this species would resolve this problem better.

Keywords: clustering, lineage, morphoanatomical characters, Nigeria, phylogenetics, Plectranthus esculentus, population

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Authors: Rasha Al-Saedi, Anthony Meijer

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The progress of new porous materials has increased rapidly over the past decade for use in applications such as catalysis, gas storage and removal of environmentally unfriendly species due to their high surface area and high thermal stability. In this work, a theoretical study of the zirconium-based metal organic framework (MOFs) were examined in order to determine their potential for gas adsorption of various guest molecules: CO2, N2, CH4 and H2. The zirconium cluster consists of an inner Zr6O4(OH)4 core in which the triangular faces of the Zr6- octahedron are alternatively capped by O and OH groups which bound to nine formate groups and three benzoate groups linkers. General formula is [Zr(μ-O)4(μ-OH)4(HCOO)9((phyO2C)3X))] where X= CH2OH, CH2NH2, CH2CONH2, n(NH2); (n = 1-3). Three types of adsorption sites on the Zr metal center have been studied, named according to capped chemical groups as the ‘−O site’; the H of (μ-OH) site removed and added to (μ-O) site, ‘–OH site’; (μ-OH) site removed, the ‘void site’ where H2O molecule removed; (μ-OH) from one site and H from other (μ-OH) site, in addition to no defect versions. A series of investigations have been performed aiming to address this important issue. First, density functional theory DFT-B3LYP method with 6-311G(d,p) basis set was employed using Gaussian 09 package in order to evaluate the gas adsorption performance of missing-linker defects in zirconium cluster. Next, study the gas adsorption behaviour on different functionalised zirconium clusters. Those functional groups as mentioned above include: amines, alcohol, amide, in comparison with non-substitution clusters. Then, dispersion-corrected density functional theory (DFT-D) calculations were performed to further understand the enhanced gas binding on zirconium clusters. Finally, study the water effect on CO2 and N2 adsorption. The small functionalized Zr clusters were found to result in good CO2 adsorption over N2, CH4, and H2 due to the quadrupole moment of CO2 while N2, CH4 and H2 weakly polar or non-polar. The adsorption efficiency was determined using the dispersion method where the adsorption binding improved as most of the interactions, for example, van der Waals interactions are missing with the conventional DFT method. The calculated gas binding strengths on the no defect site are higher than those on the −O site, −OH site and the void site, this difference is especially notable for CO2. It has been stated that the enhanced affinity of CO2 of no defect versions is most likely due to the electrostatic interactions between the negatively charged O of CO2 and the positively charged H of (μ-OH) metal site. The uptake of the gas molecule does not enhance in presence of water as the latter binds to Zr clusters more strongly than gas species which attributed to the competition on adsorption sites.

Keywords: density functional theory, gas adsorption, metal- organic frameworks, molecular simulation, porous materials, theoretical chemistry

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Authors: Shohreh Azizi, Wag Nel

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The rapid population growth in South Africa has increased the requirement of waste water treatment facilities. The aim of this study is to assess the potential use of Fluidized bed Bio Reactor for Mmabatho sewage treatment plant. The samples were collected from the Inlet and Outlet of reactor daily to analysis the pH, Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Suspended Solid (TSS) as per standard method APHA 2005. The studies were undertaken on a continue laboratory scale, and analytical data was collected before and after treatment. The reduction of 87.22 % COD, 89.80 BOD % was achieved. Fluidized Bed Bio Reactor remove Bod/COD removal as well as nutrient removal. The efforts also made to study the impact of the biological system if the domestic wastewater gets contaminated with any industrial contamination and the result shows that the biological system can tolerate high Total dissolved solids up to 6000 mg/L as well as high heavy metal concentration up to 4 mg/L. The data obtained through the experimental research are demonstrated that the FBBR may be used (<3 h total Hydraulic Retention Time) for secondary treatment in Mmabatho wastewater treatment plant.

Keywords: fluidized bed bioreactor, wastewater treatment plant, biological system, high TDS, heavy metal

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Authors: Darshna Sharma, Suban K. Sahoo

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The detection of intracellular fluoride in human cancer cell HeLa was achieved by chemosensors derived from vitamin B6 cofactors using fluorescence imaging technique. These sensors were first synthesized by condensation of pyridoxal/pyridoxal phosphate with 2-amino(thio)phenol. The anion recognition ability was explored by experimental (UV-VIS, fluorescence and 1H NMR) and theoretical DFT [(B3LYP/6-31G(d,p)] methods in DMSO and mixed DMSO-H2O system. All the developed sensors showed both naked-eye detectable color change and remarkable fluorescence enhancement in the presence of F- and AcO-. The anion recognition was occurred through the formation of hydrogen bonded complexes between these anions and sensor, followed by the partial deprotonation of sensor. The detection limit of these sensors were down to micro(nano) molar level of F- and AcO-.

Keywords: chemosensors, fluoride, acetate, turn-on, live cells imaging, DFT

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Authors: Verena M. Moock, Darien E. Arce Chávez, Mariana M. Espejel González, Leopoldo Ruíz-Huerta, Crescencio García-Segundo

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Uncertainty analysis in industrial computed tomography is commonly related to metrological trace tools, which offer precision measurements of external part features. Unfortunately, there is no such reference tool for internal measurements to profit from the unique imaging potential of X-rays. Uncertainty approximations for computed tomography are still based on general aspects of the industrial machine and do not adapt to acquisition parameters or part characteristics. The present study investigates the impact of the acquisition time on the dimensional uncertainty measuring a stainless steel cylinder with a circular tomography scan. The authors develop the figure difference method for X-ray radiography to evaluate the volumetric differences introduced within the projected absorption maps of the metal workpiece. The dimensional uncertainty is dominantly influenced by photon energy dissipated as heat causing the thermal expansion of the metal, as monitored by an infrared camera within the industrial tomograph. With the proposed methodology, we are able to show evolving temperature differences throughout the tomography acquisition. This is an early study showing that the number of projections in computer tomography induces dimensional error due to energy absorption. The error magnitude would depend on the thermal properties of the sample and the acquisition parameters by placing apparent non-uniform unwanted volumetric expansion. We introduce infrared imaging for the experimental display of metrological uncertainty in a particular metal part of symmetric geometry. We assess that the current results are of fundamental value to reach the balance between the number of projections and uncertainty tolerance when performing analysis with X-ray dimensional exploration in precision measurements with industrial tomography.

Keywords: computed tomography, digital metrology, infrared imaging, thermal expansion

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Authors: V. D. Povolockiy, V. E. Roshchin, Y. Kapelyushin

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Smelting of copper matte is followed by production of a large amount of slag. This slag mostly contains silicates and can be utilized in a construction industry. In addition to silicates it also contains Fe; if the Fe content is high, the density of the silicate phases increases and such a slag cannot be used as an additive for the concrete. Furthermore, slags obtained during copper matte production contain copper, sulphur, zinc and some other elements. Fe is the element with the highest price in these slags. An extraction of Fe is possible even using the conventional methods, e.g., the addition of slag to the charge materials during production of sinter for the blast furnace smelting. However, in this case, the blast furnace hot metal would accumulate sulphur and copper which is very harmful impurity for the steelmaking. An accumulation of copper by the blast furnace hot metal is unacceptable, as copper cannot be removed during further steelmaking operations having a critical effect on the properties of steel. In present work, the technological scheme for non-waste utilization of the copper smelting slags has been suggested and experimentally confirmed. This scheme includes a solid state reduction of Fe and smelting for the separation of cast iron and slag. During solid state reduction, the zinc vapor was trapped. After the reduction and smelting operations, the cast iron containing copper was used for the production of metal balls with increased mechanical properties allowing their utilization for milling of ore minerals. Such a cast iron could also be applied in the production of special types of steel with copper. The silicate slag freed from Fe might be used as a propping agent in the oil industry, or granulated for application as an additive for concrete in a construction industry. Thereby, the suggested products for a Mini Mill plant with non-waste utilization of the copper smelting slags are cast iron grinding balls for the ore minerals, special types of steel with copper, silicate slag utilized as an additive for the concrete and propping agents for the oil industry.

Keywords: utilization of copper slag, cast iron, grinding balls, propping agents

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Authors: Pradeep Lamichhane, Nima Pourali, E. V. Rebrov, Volker Hessel

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Nitrogen fixation is critical for plants for the biosynthesis of protein and nucleic acid. Most of our atmosphere is nitrogen, yet plants cannot directly absorb it from the air, and natural nitrogen fixation is insufficient to meet the demands. This experiment used a fast-modulated surface-confined atmospheric pressure plasma created by a 6 kV (peak-peak) sinusoidal power source with a repetition frequency of 68 kHz to fix nitrogen. Plasmas have been proposed for excitation of nitrogen gas, which quickly oxidised to NOX. With different N2/O2 input ratios, the rate of NOX generation was investigated. The rate of NOX production was shown to be optimal for mixtures of 60–70% O2 with N2. To boost NOX production in plasma, metal oxide catalysts based on TiO2 were coated over the dielectric layer of a reactor. These results demonstrate that nitrogen activation was more advantageous in surface-confined plasma sources because micro-discharges formed on the sharp edges of the electrodes, which is a primary function attributed to NOX synthesis and is further enhanced by metal oxide catalysts. The energy-efficient and sustainable NOX synthesis described in this study will offer a fresh perspective for ongoing research on green nitrogen fixation techniques.

Keywords: nitrogen fixation, fast-modulated, surface-confined, sustainable

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Authors: Chatkaew Tansakul, Saovajit Nanruksa, Surasak Chonchirdsin

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Heavy metals in the environment can be occurred by both natural weathering process and human activity, which may present significant risks to human health and the wider environment. A number of heavy metals, i.e. Arsenic (As) and Manganese (Mn), are found with a relatively high concentration in the northern part of Thailand that was assumptively from natural parent rocks and materials. However, scarce literature is challenging to identify the accurate root cause and best available explanation. This study is, therefore, aim to gather heavy metals data in 5 provinces of the North of Thailand where PTT Exploration and Production (PTTEP) public company limited has operated for more than 20 years. A thousand heavy metal analysis is collected and interpreted in term of Enrichment Factor (EF). The trend and distribution of heavy metals in soil and sediment are analyzed by considering altogether the geochemistry of the regional soil and rock. . In addition, the relationship between land use and heavy metals distribution is investigated. In the first conclusion, heavy metal concentrations of (As) and (Mn) in the studied areas are equal to 7.0 and 588.6 ppm, respectively, which are comparable to those in regional parent materials (1 – 12 and 850 – 1,000 ppm for As and Mn respectively). Moreover, there is an insignificant escalation of the heavy metals in these studied areas over two decades.

Keywords: contaminated soil, enrichment factor, heavy metals, parent materials in North of Thailand

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Authors: Nayab Kanwal, Noor Us Saher

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The management and utilization of food resources is becoming a big issue due to rapid urbanization, wastage and non-sustainable use of food, especially in developing countries. Therefore, the use of seafood as alternative sources is strongly promoted worldwide. Marine pollution strongly affects marine organisms, which ultimately decreases their export quality. The monitoring of contamination in marine organisms is a good indicator of the environmental quality as well as seafood quality. Monitoring the accumulation of chemical elements within various tissues of organisms has become a useful tool to survey current or chronic levels of heavy metal exposure within an environment. In this perspective, this study was carried out to compare the previous and current levels (Year 2012 and 2014) of heavy metals (Cd, Pb, Cr, Cu and Zn) in crabs marketed in Karachi and to estimate the toxicological risk associated with their intake. The accumulation of metals in marine organisms, both essential (Cu and Zn) and toxic (Pb, Cd and Cr), natural and anthropogenic, is an actual food safety issue. Significant (p>0.05) variations in metal concentrations were found in all crab species between the two years, with most of the metals showing high accumulation in 2012. For toxicological risk assessment, EWI (Estimated weekly intake), Target Hazard quotient (THQ) and cancer risk (CR) were also assessed and high EWI, Non- cancer risk (THQ < 1) showed that there is no serious threat associated with the consumption of shellfish species on Karachi coast. The Cancer risk showed the highest risk from Cd and Pb pollution if consumed in excess. We summarize key environmental health research on health effects associated with exposure to contaminated seafood. It could be concluded that considering the Pakistan coast, these edible species may be sensitive and vulnerable to the adverse effects of environmental contaminants; more attention should be paid to the Pb and Cd metal bioaccumulation and to toxicological risks to seafood and consumers.

Keywords: cancer risk, edible crabs, heavy metals pollution, risk assessment

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Authors: S. A. Kondratyev, O. I. Ibragimova

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The authors discuss the collecting abilities of desorbable species (DS) of saturated fatty acids. The DS species of the reagent are understood as species capable of moving from the surface of the mineral particle to the bubble at the moment of the rupture of the interlayer of liquid separating these objects of interaction. DS species of carboxylic acids (molecules and ionic-molecular complexes) have the ability to spread over the surface of the bubble. The rate of their spreading at pH 7 and 10 over the water surface is determined. The collectibility criterion of saturated fatty acids is proposed. The values of forces exerted by the spreading DS species of reagents on liquid in the interlayer and the liquid flow rate from the interlayer are determined.

Keywords: criterion of action of physically adsorbed reagent, flotation, saturated fatty acids, surface pressure

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Authors: Michael A. Sprayberry, Vincent C. Paquit

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Process parameter optimization in metal powder bed electron beam melting (MPBEBM) is crucial to ensure the technology's repeatability, control, and industry-continued adoption. Despite continued efforts to address the challenges via the traditional design of experiments and process mapping techniques, there needs to be more successful in an on-the-fly optimization framework that can be adapted to MPBEBM systems. Additionally, data-intensive physics-based modeling and simulation methods are difficult to support by a metal AM alloy or system due to cost restrictions. To mitigate the challenge of resource-intensive experiments and models, this paper introduces a Multi-Objective Reinforcement Learning (MORL) methodology defined as an optimization problem for MPBEBM. An off-policy MORL framework based on policy gradient is proposed to discover optimal sets of beam power (P) – beam velocity (v) combinations to maintain a steady-state melt pool depth and phase transformation. For this, an experimentally validated Eagar-Tsai melt pool model is used to simulate the MPBEBM environment, where the beam acts as the agent across the P – v space to maximize returns for the uncertain powder bed environment producing a melt pool and phase transformation closer to the optimum. The culmination of the training process yields a set of process parameters {power, speed, hatch spacing, layer depth, and preheat} where the state (P,v) with the highest returns corresponds to a refined process parameter mapping. The resultant objects and mapping of returns to the P-v space show convergence with experimental observations. The framework, therefore, provides a model-free multi-objective approach to discovery without the need for trial-and-error experiments.

Keywords: additive manufacturing, metal powder bed fusion, reinforcement learning, process parameter optimization

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Authors: Doo W. Lee, Soo J. Lee, Bye R. Yoon, Jae Y. Jho, Kyehan Rhee

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Hand exoskeletons have been developed in order to assist daily activities for disabled and elder people. A figure exoskeleton was developed using ionic polymer metal composite (IPMC) actuators, and the performance of it was evaluated in this study. In order to study dynamic performance of a finger dummy performing pinching motion, force generating characteristics of an IPMC actuator and pinching motion of a thumb and index finger dummy actuated by IMPC actuators were analyzed. The blocking force of 1.54 N was achieved under 4 V of DC. A thumb and index finger dummy, which has one degree of freedom at the proximal joint of each figure, was manufactured by a three dimensional rapid prototyping. Each figure was actuated by an IPMC actuator, and the maximum fingertip force was 1.18 N. Pinching motion of a dummy was analyzed by two video cameras in vertical top and horizontal left end view planes. A figure dummy powered by IPMC actuators could perform flexion and extension motion of an index figure and a thumb.

Keywords: finger exoskeleton, ionic polymer metal composite, flexion and extension, motion analysis

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Authors: Y. A. R. Oliveira, M. A. Couto dos Santos, N. B. C. Júnior, S. J. L. Ribeiro, L. D. Carlos

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The Eu(TTA)3(H2O)2 complex (TTA = thenoyltrifluoroacetone) pure (EuTTA) and incorporated in an organicinorganic hybrid material (EuTTA-hyb) are revisited, this time from the crystal field parameters (CFP) and Judd-Ofelt intensity parameters (Ωλ) point of view. A detailed analysis of the emission spectra revealed that the EuTTA phase still remains in the hybrid phase. Sparkle Model calculations of the EuTTA ground state geometry have been performed and satisfactorily compared to the X-ray structure. The observed weaker crystal field strength of the phase generated by the incorporation is promptly interpreted through the existing EXAFS results of the EuTTA-hyb structure. Satisfactory predictions of the CFP, of the 7F1 level splitting and of the Ωλ in all cases were obtained by using the charge factors and polarizabilities as degrees of freedom of non-parametric models.

Keywords: crystal field parameters, europium complexes, Judd-Ofelt intensity parameters

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Authors: Kiurski S. Jelena, Ranogajec G. Jonjaua, Oros B. Ivana, Kecić S. Vesna

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The adsorption efficiency of fired clayey pellets of 5 and 8 mm diameter size for Cu(II) and Zn(II) ions removal from a waste printing developer was studied. In order to investigate the influence of contact time, adsorbent mass and pellet size on the adsorption efficiency the batch mode was carried out. Faster uptake of copper ions was obtained with the fired clay pellets of 5 mm diameter size within 30 minutes. The pellets of 8 mm diameter size showed the higher equilibrium time (60 to 75 minutes) for copper and zinc ions. The results pointed out that adsorption efficiency increases with the increase of adsorbent mass. The maximal efficiency is different for Cu(II) and Zn(II) ions due to the pellet size. Therefore, the fired clay pellets of 5 mm diameter size present an effective adsorbent for Cu(II) ions removal (adsorption efficiency is 63.6%), whereas the fired clay pellets of 8 mm diameter size are the best alternative for Zn(II) ions removal (adsorption efficiency is 92.8%) from a waste printing developer.

Keywords: adsorption efficiency, clayey pellet, metal ions, waste printing developer

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Authors: Navven Desai, Veena Soraganvi

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Heavy metals such as lead, cadmium and mercury do not have biological significance hence they are known to be extremely toxic heavy metals. Water contains various heavy metals like Cadmium (Cd), Chromium (Cr), Copper (Cu), Nickel (Ni), Arsenic (As), Lead (Pb), and Zinc (Zn) etc., when it gets polluted with industrial waste water. These heavy metals cause various health effects even at low concentration when consumed by humans. Most of the heavy metals are poisonous to living organisms. Heavy metals are non-degradable and are preserved in the environment through bioaccumulation. Therefore removal of heavy metals from water is necessary. In recent years, a great deal of attentions has been focused on to the application of nanosized metal oxides to treat heavy metals, especially titanium oxides, ferric oxides, manganese oxides, aluminium oxides and magnesium oxides as adsorbent and photocatalyst. TiO2 based photocatalysts have attracted continuously increasing attention because of the excellent properties such as high light -conversion efficiency, chemical stability, nontoxic nature, low cost. The catalyst displays high photocatalytic activity because of its large surface area. In this study, the photocatalytic degradation of Lead (Pb) from aqueous solution was investigated in natural sunlight by using TiO2 as Nanomaterial. This study was performed at laboratory scale. All the experiments were carried out in the batch process. The concentration of lead was constant (25mg/lit) in the experiment and effect of titanium dioxide dose and pH were varied to study the removal efficiency of the lead by adsorption. Further study was performed on the dependence of photocatalytic reaction on the reaction temperature. The aqueous solution was prepared by Lead metal powder. TiO2 photo catalyst nanopowder used was Sisco-74629 grade. The heavy metal is analyzed with VARIAN AA 240 atomic adsorption spectrophotometer. The study shows, with increasing TiO2 dose and pH the lead removal increases. According to study, it can be concluded that the utilization of titanium dioxide accounted for higher efficiency in the removal of lead from aqueous solution.

Keywords: adsorption, heavy metals, nanomaterial, photocatalysis

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Authors: Kageeporn Wongpreedee, Bongkot Phichaikamjornwut, Duangkhae Bootkul

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The technique of stone in place casting had been established in jewelry production for two decades. However, the process were not widely used since it was limited to precious stones with high hardness and high stabililty at high temperature. This experiment were tested on tourmaline which is semi-precious gemstone having less hardness and less stability comparing to precious stones. The experiment were designed into two parts. The first part is to understand the phenomena of tourmaline under the heating conditions. Natural tourmaline stones were investigated and compared inclusions inside stones tested at temperature of 500 °C, 600 °C, and 700 °C. The second part is to cast the treated tourmaline with ion-implanation under the stones in place casting conditions. The results showed that stones were able to tolerate as much as at 700 °C showing the growths of inclusions inside the stones. The second part of this experiment were compared tourmaline with ion-implantation and natural tourmaline using on stones in place casting process at different stone setting types. The results showed that the cracks and inclustions of both treat and natural tourmaline with stones in place casting were propagate due to high stress of metal contractions. The stones with ion-implatation were more likely tolerate to cracks and inclusion propagations inside the stones.

Keywords: stone in place casting, tourmaline, ion implantation, metal contraction

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Authors: Heba M. Gobara, Ahmed A. M. El-Naggar, Rasha S. El-Sayed, Amal A. AlKahlawy

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In this study, metal organic framework (Cr-MIL-101) and TiO₂ nanoparticles were utilized as two semiconductors for water splitting process. The coupling of both semiconductors in order to improve the photocatalytic reactivity for the hydrogen production in presence of methanol as a hole scavenger under visible light (sunlight) has been performed. The forementioned semiconductors and the collected samples after water splitting application are characterized by several techniques viz., XRD, N₂ adsorption-desorption, TEM, ED, EDX, Raman spectroscopy and the total content of carbon. The results revealed an efficient yield of H₂ production with maximum purity 99.3% with the in-situ formation of graphene oxide nanosheets and multiwalled carbon nanotubes coated over the surface of the physically mixed Cr-MIL-101–TiO₂ system. The amount of H₂ gas produced was stored when using Cr-MIL-101 catalyst individually. The obtained data in this work provides promising candidate materials for pure hydrogen production as a clean fuel acquired from the water splitting process. In addition, the in-situ production of graphene nanosheets and carbon nanotubes is counted as promising advances for the presented process.

Keywords: hydrogen production, water splitting, photocatalysts, Graphene

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Authors: Oluwasanmi Teniola, Abraham Adeleke, Ademola Ibitoye, Moshood Shitu

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To establish an economical and efficient process for the recovery of gold metal from refractory gold ore obtained from Esperando axis of Osun state Nigeria, the adsorption of gold (III) from aqua reqia leached solution of the ore using bagasse nanoparticles has been studied under various experimental variables using batch technique. The extraction percentage of gold (III) on the prepared bagasse nanoparticles was determined from its distribution coefficients as a function of solution pH, contact time, adsorbent, adsorbate concentrations, and temperature. The rate of adsorption of gold (III) on the prepared bagasse nanoparticles is dependent on pH, metal concentration, amount of adsorbate, stirring rate, and temperature. The adsorption data obtained fit into the Langmuir and Freundlich equations. Three different temperatures were used to determine the thermodynamic parameters of the adsorption of gold (III) on bagasse nanoparticles. The heat of adsorption was measured to be a positive value ΔHo = +51.23kJ/mol, which serves as an indication that the adsorption of gold (III) on bagasse nanoparticles is endothermic. Also, the negative value of ΔGo = -0.6205 kJ/mol at 318K shows the spontaneity of the process. As the temperature was increased, the value of ΔGo becomes more negative, indicating that an increase in temperature favors the adsorption process. With the application of optimal adsorption variables, the adsorption capacity of gold was 0.78 mg/g of the adsorbent, out of which 0.70 mg of gold was desorbed with 0.1 % thiourea solution.

Keywords: adsorption, bagasse, extraction, nanoparticles, recovery

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Authors: Efe Gumuslu, Guclu Insel, Gülten Yuksek, Nilay Sayi Ucar, Emine Ubay Cokgor, Tuğba Olmez Hanci, Didem Okutman Tas, Fatoş Germirli Babuna, Derya Firat Ertem, Ökmen Yildirim, Özge Erturan, Betül Kirci

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Although water reclamation and reuse are inseparable parts of sustainable production concept all around the world, current levels of reuse constitute only a small fraction of the total volume of industrial effluents. Nowadays, within the perspective of serious climate change, wastewater reclamation and reuse practices should be considered as a requirement. Industrial sector is one of the largest users of water sources. The OECD Environmental Outlook to 2050 predicts that global water demand for manufacturing will increase by 400% from 2000 to 2050 which is much larger than any other sector. Metal finishing industry is one of the industries that requires high amount of water during the manufacturing. Therefore, actions regarding the improvement of wastewater treatment and reuse should be undertaken on both economic and environmental sustainability grounds. Process wastewater can be reused for more purposes if the appropriate treatment systems are installed to treat the wastewater to the required quality level. Recent studies showed that membrane separation techniques may help in solving the problem of attaining a suitable quality of water that allows being recycled back to the process. The metal finishing factory where this study is conducted is one of the biggest white-goods manufacturers in Turkey. The sheet metal parts used in the cookers production have to be exposed to surface pre-treatment processes composed of degreasing, rinsing, nanoceramics coating and deionization rinsing processes, consecutively. The wastewater generating processes in the factory are enamel coating, painting and styrofoam processes. In the factory, the main source of water is the well water. While some part of the well water is directly used in the processes after passing through resin treatment, some portion of it is directed to the reverse osmosis treatment to obtain required water quality for enamel coating and painting processes. In addition to these processes another important source of water that can be considered as a potential water source is rainwater (3660 tons/year). In this study, process profiles as well as pollution profiles were assessed by a detailed quantitative and qualitative characterization of the wastewater sources generated in the factory. Based on the preliminary results the main water sources that can be considered for reuse in the processes were determined as painting and styrofoam processes.

Keywords: enamel coating, painting, reuse, wastewater

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Authors: Silviya Todorova, Anton Naydenov, Ralitsa Velinova, Alexander Larin

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Catalytic combustion of methane has been extensively investigated for emission control and power generation during the last decades. The alumina-supported palladium catalyst is widely accepted as the most active catalysts for catalytic combustion of methane. The activity of Pd/Al₂O₃ decreases during the time on stream, especially underwater vapor. The following order of activity in the reaction of complete oxidation of methane was established: Co₃O₄> CuO>NiO> Mn₂O₃> Cr₂O₃. It may be expected that the combination between Pd and these oxides could lead to the promising catalysts in the reaction of complete methane. In the present work, we investigate the activity of Pd/Al₂O₃ catalysts promoted with other metal oxides (MOx; M= Ni, Co, Ce). The Pd-based catalysts modified by metal oxide were prepared by sequential impregnation of Al₂O₃ with aqueous solutions of Me(NO₃)₂.6H₂O and Pd(NO₃)₂H₂O. All samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). An improvement of activity was observed after modification with different oxides. The results demonstrate that the Pd/Al₂O₃ catalysts modified with Co and Ce by impregnation with a common solution of respective salts, exhibit the most promising catalytic activity for methane oxidation. Most probably, the presence of Co₃O₄ and CeO₂ on catalytic surface increases surface oxygen and therefore leads to the better reactivity in methane combustion.

Keywords: methane combustion, palladium, Co-Ce, Ni-Ce

Procedia PDF Downloads 186

Authors: Sunil Kumar, Sandip Dhole, Deepak Salunke, Chung-ming Sun

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Heterocycles bearing nitrogen, oxygen, and selenium are present in innumerable biologically active compounds. For instance, coumarin containing dicoumarol acts as naturally occurring anticoagulant. 2-Acylamido selenazole works as Store-Operated Calcium (SOC) channel regulator. Therefore, due to biologically significance of selenazole and coumarin and our quest to develop efficient methodologies for the synthesis of complex heterocycles, the trisubstituted angular isocoumarinoselenazole synthesis was proposed and achieved by starting from nitrobenzoic acid derivative, available commercially. Synthetic procedure involves three steps: i) the construction of 2-aminobenzoselenazoles, ii) their regioselective N-alkylation at position-2 and iii) alkyne insertion via Ru catalyzed C-H activation. Transition metal free synthesis of benzoselenazoles was successfully brought about by the addition/elimination reaction via intramolecular C-Se bond formation. In the next step, N-alkylation of selenazole furnished two regioisomers. Both the isomers exhibited different reactivity towards [4+2] alkyne annulation reaction. The fusion of α-pyrone ring on the benzo[1,3-d]selenazole skeleton was achieved via Ru(II)-catalyzed C-H activation and alkyne insertion. As evident from mechanism, the selenazole 'N' plays an important role for the experiential selectivity.

Keywords: alkylation, alkyne insertion, coumarin, selenazole

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Authors: Yukinori Taniguchi, Kazuyoshi Kurita, Kohei Mizuta, Keigo Nishitani, Ryuichi Fukuda

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Tungsten carbide is widely used as a tool material in metal manufacturing process. Since tungsten is typical rare metal, establishment of recycle process of tungsten carbide tools and restore into cemented carbide material bring great impact to metal manufacturing industry. Recently, recycle process of tungsten carbide has been developed and established gradually. However, the demands for quality of cemented carbide tool are quite severe because hardness, toughness, anti-wear ability, heat resistance, fatigue strength and so on should be guaranteed for precision machining and tool life. Currently, it is hard to restore the recycled tungsten carbide powder entirely as raw material for new processed cemented carbide tool. In this study, to suggest positive use of recycled tungsten carbide powder, we have tried to fabricate a carbon based sintered steel which shows reinforced mechanical properties with recycled tungsten carbide powder. We have made set of newly designed sintered steels. Compression test of sintered specimen in density ratio of 0.85 (which means 15% porosity inside) has been conducted. As results, at least 1.7 times higher in nominal strength in the amount of 7.0 wt.% was shown in recycled WC powder. The strength reached to over 600 MPa for the Fe-WC-Co-Cu sintered alloy. Wear test has been conducted by using ball-on-disk type friction tester using 5 mm diameter ball with normal force of 2 N in the dry conditions. Wear amount after 1,000 m running distance shows that about 1.5 times longer life was shown in designed sintered alloy. Since results of tensile test showed that same tendency in previous testing, it is concluded that designed sintered alloy can be used for several mechanical parts with special strength and anti-wear ability in relatively low cost due to recycled tungsten carbide powder.

Keywords: tungsten carbide, recycle process, compression test, powder metallurgy, anti-wear ability

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Authors: Sushil Kumar Saraswat, K. K. Pant

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Co metal supported on SiO2 and Al2O3 catalysts with a metal loading varied from 30 of 70 wt.% were evaluated for decomposition of methane to CO/CO2 free hydrogen and carbon nano materials. The catalytic runs were carried out from 550-800 oC under atmospheric pressure using fixed bed vertical flow reactor. The fresh and spent catalysts were characterized by BET surface area analyzer, TPR, XRD, SEM, TEM, and TG analysis. The data showed that 50% Co/Al2O3 catalyst exhibited remarkable higher activity and stability up to 10 h time-on-stream at 750 oC with respect to H2 production compared to rest of the catalysts. However, the catalytic activity and durability was greatly declined at a higher temperature. The main reason for the catalytic inhibition of Co containing SiO2 catalysts is the higher reduction temperature of Co2SiO4. TEM images illustrate that the carbon materials with various morphologies, carbon nanofibers (CNFs), helical-shaped CNFs, and branched CNFs depending on the catalyst composition and reaction temperature, were obtained. The TG data showed that a higher yield of MWCNTs was achieved over 50% Co/Al2O3 catalyst compared to other catalysts.

Keywords: carbon nanotubes, cobalt, hydrogen production, methane decomposition

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Authors: Muammer Kaya

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The main purpose of this article is to provide a comprehensive review of various physical and chemical processes for electronic waste (e-waste) recycling, their advantages and shortfalls towards achieving a cleaner process of waste utilization, with especial attention towards extraction of metallic values. Current status and future perspectives of waste printed circuit boards (PCBs) recycling are described. E-waste characterization, dismantling/ disassembly methods, liberation and classification processes, composition determination techniques are covered. Manual selective dismantling and metal-nonmetal liberation at – 150 µm at two step crushing are found to be the best. After size reduction, mainly physical separation/concentration processes employing gravity, electrostatic, magnetic separators, froth floatation etc., which are commonly used in mineral processing, have been critically reviewed here for separation of metals and non-metals, along with useful utilizations of the non-metallic materials. The recovery of metals from e-waste material after physical separation through pyrometallurgical, hydrometallurgical or biohydrometallurgical routes is also discussed along with purification and refining and some suitable flowsheets are also given. It seems that hydrometallurgical route will be a key player in the base and precious metals recoveries from e-waste. E-waste recycling will be a very important sector in the near future from economic and environmental perspectives.

Keywords: e-waste, WEEE, recycling, metal recovery, hydrometallurgy, pirometallurgy, biometallurgy

Procedia PDF Downloads 356

Authors: Nouacer Imane, Benalia Mokhtar, Djedid Mabrouk

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The adsorption ability of a powdered activated carbons (PAC) derived from Luffa cylindrica investigated in an attempt to produce more economic and effective sorbents for the control of Cu(II) ion from industrial liquid streams. Carbonaceous sorbents derived from local luffa cylindrica, were prepared by chemical activation methods using ZnCl2 as activating reagents. Adsorption of Cu (II) from aqueous solutions was investigated. The effects of pH, initial adsorbent concentration, the effect of particle size, initial metal ion concentration and temperature were studied in batch experiments. The maximum adsorption capacity of copper onto grafted Luffa cylindrica fiber was found to be 14.23 mg/g with best fit for Langmuir adsorption isotherm. The values of thermodynamic parameters such as enthalpy change, ∆H (-0.823 kJ/mol), entropy change, ∆S (-9.35 J/molK) and free energy change, ∆G (−1.56 kJ/mol) were also calculated. Adsorption process was found spontaneous and exothermic in nature. Finally, the luffa cylindrica has been evaluated by FTIR, MO and x-ray diffraction in order to determine if the biosorption process modifies its chemical structure and morphology, respectively. Luffa cylindrica has been proven to be an efficient biomaterial useful for heavy metal separation purposes that is not altered by the process.

Keywords: adsorption, cadmium, isotherms, thermodynamic, luffa sponge

Procedia PDF Downloads 249