Enhancing Chromium (VI) removal from synthetic and real tannery effluents by using diatomite-embedded nanopyroxene

A commercial filter aid material of Diatomite was modified via loading it with a low mass fraction of polyethylenimine-functionalized pyroxene nanoparticles (PEI-PNs) to enhance its adsorption activities. The modified Diatomite was then used for Cr(VI) removal from dichromate solution and from real tannery wastewater. For the synthetic wastewater, batch adsorption experiments were first performed at various pH and Cr(VI) initial concentrations. Then, the obtained kinetic parameters were used to investigate the continuous adsorption inside the fixed-bed column. The continuous removal of the Cr(VI) was performed inside a fixed-bed column under various influent flow rates, Cr(VI) initial concentrations, and bed-heights. In the column experiments, high adsorption of Cr(VI) was observed at low flow rates, high bed heights, and low influent initial concentrations. A dimensionless form of the advection-axial dispersion model, featuring Peclet number as a fitting parameter, was then used to study the breakthrough behavior under various dynamic parameters. Afterward, the modified Diatomite was used to remediate well characterized real tannery wastewater. For the treatment of the tannery wastewater, our modified filter aid, compared with the non-modified one, showed an outstanding performance and a higher removal efficiency.The authors are grateful to the Natural Sciences and Engineering Research Council of Canada (NSERC) (Grant No. RGPIN-2015- 05222). A special acknowledgement to Dr. Tobias Fürstenhaupt for access to the Microscopy and Imaging Facility of the Health Science Center at the University of Calgary and Dr. Christopher Debuhr for providing access to the Instrumentation Facility for Analytical Electron Microscopy at the University of Calgary and Dr. Gerardo Vitale for drawing the CPK representation of nanopyroxene and diatomite surface

Density functional theory study on the catalytic dehydrogenation of methane on MoO3 (010) surface

Methane conversion offers hydrocarbon building blocks of high market value, which are easier to transport than natural gas. Under non-oxidative conditions, the process can also produce clean hydrogen fuel. In this study, we explored the catalytic dehydrogenation of methane on molybdenum oxide (MoO3) surface. Periodic density functional theory calculations were performed to study the adsorption of CH4 on two different supercells of the MoO3 (010) surface. It was found that CH4 adsorption was more favorable on a smooth surface constructed of Mo and O network, rather than a surface made with dangling O atoms as thought before. A reaction mechanism for hydrogen formation was then proposed. The first energy barrier for the H-abstraction step was calculated to be 66.4 kJ/mol, which is lower than previously reported values obtained for simple MoxOy clusters. The reactions were discussed using the two-state reactivity approach, where different electronic states can play a role in the H-abstraction step. The mechanism also showed the formation of methyl radicals and ethylene, in addition to molecular hydrogen.This research is funded by Qatar University’s grant number QUCG-CAS-21221

Treatment of olive mill based wastewater by means of magnetic nanoparticles: Decolourization, dephenolization and COD removal

AbstractOlive mill wastewater (OMW) is an environmental concern that has been highlighted as a serious environmental problem in the Mediterranean basin countries because of its high organic load and phytotoxic and antibacterial phenolic compounds, which resist biological degradation. Consequently, this type of wastewater represents a huge challenge for the conventional wastewater treatment techniques as it can impact the lifetime of bacteria needed for the treatment. Iron-oxide nanoparticles are attractive for wastewater treatment for two important reasons. First, nanoparticles can remove pollutants from wastewater rapidly. Second, this magnetic type of nanoparticles could be separated easily using a magnet after finishing treatment process. In this study, we aimed at investigating the effectiveness of the magnetic iron oxide nanoparticles in the removal of large organic contaminants from OMW. Batch and continuous mode processes were applied on OMW treatment to determine the effect of contact time, solution pH, coexisting contaminants and the adsorption isotherm.The results showed that the adsorption was fast and the adsorption reached equilibrium within less than 30min. The adsorption equilibrium data fit very well to the Brunauer–Emmett–Teller (BET) Model, indicating multi-layers adsorption. The adsorption of major pollutants was associated to an efficient removal of coexisting contaminants such as heavy metals and free ions. The adsorption of OMW pollutants was dependent on pH of the solution. Finally, continuous-mode process was tested successfully using a packed bed column that combined sand filtration with magnetic nanoparticles to decolourize OMW effluent. This study will provide valuable insight on the effect of nanoparticles toward the treatment and recyclability of olive mill wastewater, which is crucial for the local olive mill industry. After seeing the successful achievement of integrating nanoparticles with fixed bed filtration, a preliminary process description and cost estimation of stand-alone plant (with a capacity of 4m3/h) for OMW treatment were considered in this study. Process capital and annual operating costs were estimated to be $12,306 and$476/year, respectively

Kinetic study of the thermo-oxidative decomposition of metformin by isoconversional and theoretical methods

The drug metformin is the most prescribed drug to treat type II diabetes and has been recently reported to have anticancer activities. Because of its wide use, its potential risk on the environment is extremely concerning. In this study, the mechanism and the thermodynamics of the thermo-oxidative decomposition of the metformin were investigated as part of a new solution for the pharmaceutical contamination of water bodies. Thermogravimetry and mass spectrometry were used to demonstrate the metformin thermo-oxidative decomposition under air in the temperature range 25–800 °C. The isoconversional methods of Kissinger-Akahira Sunose (KAS) and Friedman (FR) were implemented to deduce the trends of effective activation energies. As expected, the effective activation energy (Eα) of the reaction was dependent on the reaction temperature, suggesting multi-step reactions. The Eα ranged from 100 to 145 kJ/mol and 200–300 kJ/mol for the KAS and FR methods, respectively. The kinetic triplet, Aα, ΔS‡, and ΔG‡ were also determined by finding the appropriate reaction model. Theoretical calculations were implemented to propose a full reaction mechanism. The oxidation of metformin was investigated with both molecular O2(t) and atomic O(t) oxygen. The experimental results were then explained under the light of the computational data to explain the variation of Eα with temperature, and the competition between the O2(t)/O(t) species

Enhanced thermal conductivity and reduced viscosity of aegirine-based VR/VGO nanofluids for enhanced thermal oil recovery application

The depleting of the available conventional energy supplies together with an industrial shift towards unconventional resources like heavy oil/bitumen has become more pronounced. The steam-based heating methods are primarily used by the oil industry for the heavy oil/bitumen recovery. However, the thermal recovery methods are energy-intensive and have limited applications, especially for both thin and deep reservoirs. Therefore, there is a high priority need to investigate alternative approaches. To date, the most progressive alternative technique that has proven its potential during pilot-plant tests is nanocatalytic in-situ heavy oil/bitumen upgrading via hot-fluid injection. Hence, the continual improvement of this technique is of utmost importance. This study aims to propose a new injecting nanofluid system suitable for high-temperature injection into the reservoir with consecutive heavy oil/bitumen upgrading and recovery. Here we report a new type of copper-based nanofluid using a blend of vacuum gas oil (VGO) and vacuum residue (VR) as the mother solvent. The nanoparticles were prepared by low-temperature hydrothermal synthesis route. Their detailed surface, morphology and size characterizations were achieved by X-ray diffraction, dynamic light scattering and scanning electron microscopy. The stable nanofluids were prepared by dispersing copper-based nanoparticles in a mixture of VGO and VR, at different ratios and temperatures. A set of measurements to determine the thermal conductivity and viscosity of the nanofluid with different loading of nanoparticle were performed. The thermal conductivity values of nanofluid systems are substantially higher than that of the base fluids. The nanofluid for 2 wt% of copper-doped aegirine nanoparticles dispersed in VGO and VGO/VR mixture exhibits a maximum thermal conductivity of 20% and 24%, respectively. It was found that the thermal conductivity of nanofluids increases with decreasing the hydrodynamic particle size. Moreover, the presence of chemo-physical interactions between nanoparticles and base fluid further enhances the thermal conductivity. Also, the temperature augmentation in a range from 80 to 110 °C exhibited a positive effect on thermal conductivity enhancement of vacuum residue-based nanofluid system. This particular nanofluid may find potential applications in enhancing heavy oil upgrading and recovery

Pyrolysis and Oxidation of Asphaltene-Born Coke-like Residue Formed onto in Situ Prepared NiO Nanoparticles toward Advanced in Situ Combustion Enhanced Oil Recovery Processes

Pyrolysis and oxidation of asphaltene-born coke-like residue formed onto ex situ and in situ prepared NiO nanoparticles as initial steps toward developing advanced in situ combustion enhanced oil recovery (EOR) processes were studied. The in situ synthesized NiO nanoparticles in heavy oil matrix, containing coke-like residue, were characterized by X-ray diffraction, Brunauer–Emmett–Teller, field-emission scanning electron microscopy, and energy-dispersive X-ray mapping techniques. The pyrolysis and postpyrolysis oxidation of the coke residue were investigated by temperature-programmed pyrolysis (TPP) and temperature-programmed oxidation (TPO) methods, respectively. Oxidation kinetics of the coke residue was described by the Kissinger–Akahira–Sunose isoconversional method. The results showed a higher percentage of coke residue on the in situ prepared nanoparticles than the ex situ employed ones. Eventually, during the TPP of the coke residue, the amount of carbon oxides released per total amount of the coke is 18.6% higher for the in situ NiO as compared to the ex situ NiO nanoparticles. This may be attributed to the uniform dispersion of the in situ NiO in the coke residue. Furthermore, compared to the ex situ NiO, the in situ NiO nanoparticles shift the oxidation temperature of the coke residue by about 100 °C to lower temperature. Multistep kinetics was predicted with a significant drop of the activation energy of the oxidation of the coke residue in the presence of in situ and ex situ NiO nanoparticles, confirming their catalytic effect. However, the pre-exponential factor, as a representation of the collision efficiency, is significantly higher over the in situ NiO compared to the ex situ NiO, leading to the enhanced oxidation of the coke residue. This may be attributed to the loss of surface area due to particle aggregation for the case of ex situ preparation, as well as the orientation of asphaltene molecules during the adsorption onto the surface. The asphaltenes could be aligned mostly vertically over the in situ NiO surface; thus the vertical alignment provides good channels for diffusion of gas-phase oxygen onto the surface leading to high collision efficiency and catalytic activity

<i>In Situ</i> Upgrading of Athabasca Bitumen Using Multimetallic Ultradispersed Nanocatalysts in an Oil Sands Packed-Bed Column: Part 2. Solid Analysis and Gaseous Product Distribution

Thermal cracking of Athabasca bitumen was carried out in an oilsand packed-bed column, in the presence and absence of <i>in situ</i> prepared trimetallic nanocatalysts at a pressure of 3.5 MPa, residence time of 36 h, and temperatures of 320 and 340 °C. In this part of the study, the effects of reaction severity (time and temperature) as well as the presence of nanocatalysts in packed media on solid and gaseous products were investigated. Results showed that the presence of trimetallic nanocatalysts enhanced the hydrogenation reactions and, consequently, led to significant reduction of coke formation (51.3%) and CO₂ emission reduction. Further, the analysis of the gaseous products and deposited solids confirmed the previous findings reported in part 1 (10.1021/ef401716h) of this study. The accumulative volume of coke precursor gases, such as ethylene and propylene, increased with the reaction severity. However, reaction severity has no significant effect on the atomic metallic ratios (metal/total metal) of the employed trimetallic nanocatalysts, which clearly demonstrates the stability of injected ultradispersed (UD) nanocatalysts (metal/total metal: Mo, 0.6267; Ni, 0.1808; and W, 0.1924) in the porous media at high pressure and temperature. Nonetheless, aggregation of nanocatalysts inside the porous media was observed and graphically demonstrated by environmental scanning electron microscopy (ESEM) images. Overall, the presence of trimetallic nanocatalysts in porous media not just enhanced bitumen upgrading but also improved the produced liquid quality and reduced the coke content as well as CO₂ emission by 50%