Search

This work describes the synthesis and evaluation of nanocomposite membranes based on calcium phosphate (CP)/ionic liquids (ILs) for high-temperature proton exchange membrane (PEM) fuel cells. Several composite membranes were synthesized by varying the mass ratios of ILs with respect to the CP and all supported on porous polytetrafluoroethylene (PTFE). The membranes exhibit high proton conductivities. Two ionic liquids were investigated in this study, namely, 1-Hexyl-3- methylimidazolium tricyanomethanide, [HMIM][C4N3−], and 1-Ethyl-3-methylimidazolium methanesulfonate, [EMIM][CH3O3S−]. At room temperature, the CP/PTFE/[HMIM][C4N3−] composite membrane possessed a high proton conductivity of 0.1 S cm−1. When processed at 200 °C, and fully anhydrous conditions, the membrane showed a conductivity of 3.14 × 10−3 S cm−1. Membranes based on CP/PTFE/[EMIM][CH3O3S−] on the other hand, had a maximum proton conductivity of 2.06 × 10−3 S cm−1 at room temperature. The proton conductivities reported in this work appear promising for the application in high-temperature PEMFCs operated above the boiling point of water.

Biological plants such as algae have a great potential of fixating CO2 from flue gases or atmospheric air and converting it into useful biomass. This is because CO2 is part of their photosynthesis ...

Dust accumulation on photovoltaic (PV) modules is responsible for the reduction in solar radiation received and/or transmitted, hence, decreases the efficiency of the PV cells. To enhance the performance of PV modules, the nature and the structure of dust should be evaluated. This paper investigates the seasonal variability of dust and PV soiling losses over 4 months (15 weeks, over the summer of 2018) in a soiling station deployed at the American University of Sharjah, UAE. A custom-made setup was employed to collect the dust samples on glass sheets. This will provide a better understanding of the soil deposition rates and composition. The accumulated dust was characterized for its morphological and elemental properties. The dust samples were directly collected from the panels mounted outdoor in the desert environment. Various characterization techniques were performed to determine the dust samples’ composition. The results showed that the dust particles are mostly rich in carbon, oxygen, calcium, silicon, thus indicating the presence of silica and calcite. UV–Vis results showed a decrease in transmittance of 30% after 15 weeks of soiling. This results of this work are essential for the development of proper self-cleaning techniques for PV modules deployed in Sharjah.

The decarbonization of hydrocarbons is explored in this work as a method to produce hydrogen and mitigate carbon dioxide (CO2) emissions. An integrated process for power generation and carbon capture based on a hydrocarbon fueled-decarbonization unit was proposed and simulated. Ethane and propane were used as fuels and subjected to the thermal decomposition (decarbonization) process. The system is also composed of a carbon fuel cell (CFC) and hydrogen fuel cell (HFC) for the production of power and a pure CO2 stream that is ready for sequestration. The HFC is a high-temperature proton exchange membrane fuel cell operating at 200 °C. Simulations were performed using ASPEN HYSYS V.10 for the entire process including the CFC and HFC being operated at various operating temperatures (200–800 °C). The power output from the CFC and the HFC as well as the overall process efficiency were calculated. The model incorporates an energy recovery system by adopting a counter-current shell and tube heat exchangers and a turbine. The water produced from the fuel cell system can be utilized in the plant to recover the heat from the furnace. The results showed a 100% carbon capture with a nominal plant capacity of 108 MWe produced when propane fuel was fed to the decarbonizer. The CFC theoretical efficiency is 100% and the practical efficiency was taken as 70% when all internal polarizations were considered. The results showed that, in the case of propane, the CFC power output was 89 MWe when the CFC operated at 650 °C, and the HFC power output was around 45 MWe at 200 °C with an overall actual plant efficiency of 35% and 100% carbon capture. Sensitivity analysis recommends a hydrocarbon fuel cost of 0.011 $/kW as the most feasible option. The results reported here on the decarbonization of hydrocarbon fuels are promising toward the direct production of hydrogen with full carbon dioxide sequestration at a potentially lower cost especially in rural areas. The overall actual efficiencies are very competitive to those of conventional power plants operated without carbon capture.

Paper and pulp mills generate substantial quantities of cellulose-rich sludge materials that are disposed in landfills at a large scale. For sustainability purposes, sludge materials can be bioprocessed to produce renewable fuels and useful chemicals. The enzymatic hydrolysis of cellulose is the process bottleneck that affects the conversion economics directly by using zero-cost raw materials. In order to study and optimize the process, the characteristics of the sludge raw materials should be first evaluated. In this work, sludge samples were obtained from paper mills located at different locations in Wisconsin and Minnesota. Part of the sludge samples was washed (de-ashed) with hydrochloric acid while the other part remained unwashed. The samples were subjected to multiple spectroscopic analyses techniques to evaluate the morphological properties of cellulose fibers and to estimate the total structural carbohydrate content. The results showed that the de-ashing process changed some fiber characteristics and cellulose crystallinity structure in all sludge samples. Sludge sample A (obtained from Kraft pulp and recycled paper mill region) showed a high percentage of fiber, with crystalline cellulose, compared to the other two sludge samples suggesting that sludge A is a valuable source to make value-added products. Aspen Plus mass and energy calculations performed in view of the ‘zero’ cost and the reliable supply of sludge raw materials producing 2 mol H2/mol glucose. Moreover, the results showed that extracting crystalline cellulose from these sludge samples is more profitable than crystalline cellulose made from the other lignocellulosic feedstocks. The results reported here showed that the utilization of these sludge materials would be an economically attractive and promising alternative for the production of hydrogen.

Composite membranes composed of zirconium phosphate (ZrP) and imidazolium-based ionic liquids (IL), supported on polytetrafluoroethylene (PTFE) were prepared and evaluated for their application in proton exchange membrane fuel cells (PEM) operating at 200 °C. The experimental results reported here demonstrate that the synthesized membrane has a high proton conductivity of 0.07 S cm−1, i.e, 70% of that reported for Nafion. Furthermore, the composite membranes possess a very high proton conductivity of 0.06 S cm−1 when processed at 200 °C under completely anhydrous conditions. Scanning electron microscopy (SEM) images indicate the formation of very small particles, with diameters in the range of 100–300 nm, within the confined pores of PTFE. Thermogravimetric analysis (TGA) reveals a maximum of 20% weight loss up to 500 °C for the synthesized membrane. The increase in proton conductivity is attributed to the creation of multiple proton conducting paths within the membrane matrix. The IL component is acting as a proton bridge. Therefore, these membranes have potential for use in PEM fuel cells operating at temperatures around 200 °C.

The modern development of (PEMFCs) is still faced by several obstacles such as membrane cost and performance. Perfluorosulfonic acid membranes (e.g. Nafion of DuPont) are currently the most successful in PEMFCs. PEMFCs usually operate at temperatures around 80°C and at atmospheric pressure. Higher temperature operation (T >100°C) is preferred and has several advantages including enhanced fuel cell kinetics, improved catalysts tolerance for contaminants and recovery of useful heat. However, the high-temperature operation is not permitted using Nafion membranes as they dehydrate and their proton conductivity dramatically decreases, thus, lowering the fuel cell efficiency. Therefore, this work aims at developing a Nafion-free membrane that would successfully operate at higher temperatures and with reasonable proton conductivity (preferably higher than 10-3 S/cm). In this study, novel solid proton conductors based on polyaniline (PANI) and ionic liquids (ILs) are proposed as membranes in PEMFCs. PANI-IL composite membranes are fabricated using porous polytetrafluoroethylene (PTFE) as support. The composite membrane was evaluated for its proton conductivity. The results showed a high proton conductivity range of 0.01 to 0.02 S/cm when a 3.7 wt % of the ionic liquid (IL)[1-Hexyl-3-Methylimidazolium Tricyanomethanide] was used.

During the electrolytic reduction of magnesium, it is very important to understand the mechanism of the digestion of the magnesium chloride dihydrate granules in the molten electrolyte throughout the chlorination process. This work aimed to investigate the kinetics of this digestion process. The results showed that the granules digestion is happening in two stages. The first stage is very fast, hence, results in the formation of MgOHCl during the dehydration and the hydrolysis of magnesium chloride dihydrate in the interior of the granules. The kinetic results for the first stage was best modeled using shrinking core model where the surface reaction was the rate controlling step. The second stage was best modeled as a first-order homogenous reaction. The kinetic parameters for the two stages were determined along with the Arrhenius plots. The results of this kinetics study are essential for the mathematical modeling of the chlorination process of the magnesium chloride dihydrate granules.

In this study, a new efficient resin-based material has been synthesized through the surface modification of silica by functionalized calix[4]arene and applied for the adsorption of metal ions from aqueous media. The synthesis of functionalized calix[4]arene modified silica (FCMS) resin was characterized by FTIR, CHNS, BET surface area, SEM analyses. The FCMS resin has high thermal and chemical stabilities that were checked by the thermogravimetric analysis and various acidic/basic conditions. The efficiency of the FCMS resin was checked by performing a set of batch experiments under optimized parameters such as concentration of the metal solution, pH, resin dosage, time, temperature, and competitive adsorption in mixed solutions. The results showed that better adsorption has been achieved at pH 7, with 25 mg adsorbent dosage and 10 min contact time. The equilibrium kinetic study showed that the metal adsorption follows the pseudo 2nd order kinetic model with quite high coefficients of determination values (R-2 > 0.99). The experimental data have been validated by applying three adsorption isotherm models and the results revealed that the Freundlich isotherm model (R-2 > 0.99) was the best fit for the adsorption of Cu2+, Pb2+, and Cd2+ ions. However, the sorption energy calculated from the D-R isotherm model for Cu2+, Pb2+, and Cd2+ ions suggested that an ion-exchange mechanism is involved on the surface of the FCMS resin. The thermodynamic data demonstrated that the reaction is spontaneous and endothermic. The FCMS resin was also applied on real wastewater samples and the results demonstrated that the resin has a good ability to treat metal-contaminated wastewater. (C) 2021 Elsevier B.V. All rights reserved.

Cu-TiO2 nano-catalysis were successfully prepared using sol-gel method and used for solar photo-reduction of CO2 in gas and liquid phase. Adding Cu to TiO2 matrix modify its crystalline structure, improved its optical property and increased the photo-catalytic activity toward CO2 reduction. Incorporating Cu at an oxidation state of 2+ into TiO2 matrix generated a mixture of Anatase and Rutile structure with high surface area, increased oxygen vacancies and enhanced atomic mobility which improved CO2 photo-reduction in both phases. The highest CO2 photoreduction rate was observed to occur for Cu-TiO2 nano-catalyst with Cu loading of 1.5 wt%. Methanol was the most produced hydrocarbon amongst the products with a production rate of 4.0 μmol·g-cat−1·h−1, followed by methane. Gas phase solar CO2 photo-reduction was effective and dependent on the gas relative humidity. CO2 and H2O mixture with relative humidity (%RH) ≤ 30% generated CH4 and CO as the main products. At higher %RH, the main products were methane, hydrogen, methanol, ethanol, and acetaldehyde. Gas phase solar CO2 photoreduction is more effective than liquid phase in terms of hydrocarbons production rate, space yield, and quantum efficiencies. Results showed that solar photo-catalytic reduction can be successfully applied to reduce CO2 from the atmosphere.

The world's first fuel cell described in the early 1800's was fueled with hydrogen. While hydrogen is still the most common fuel, hydrocarbon fuels offer several advantages including availability at a lower cost, higher storage density and existing infrastructure. This paper provides an overview for the significant potential benefits of using hydrocarbon fuels directly in a fuel cell system. Their use leads to a reduction in the capital cost due to the elimination of the fuel processor unit. The fundamentals, advantages, types of direct hydrocarbon fuel cells (DHFC), challenges and applications are discussed in this paper. The past and current status of research and development activities are addressed with emphasis on efficiency and exergy analyses. In spite of their high theoretical energy efficiency, technical challenges remain unsolved in DHFC systems. In high temperature hydrocarbon fueled operation, the deposition of carbon-based material leads to fuel cell degradation. In lower temperature fuel cells, electrode (mainly the anode) over-potentials and fuel crossover are still challenging. Therefore, the improvement and commercialization of these types of fuel cells will probably require the development of less or non-noble catalysts and reasonably functioning membranes.

Endocrine-disrupting chemicals (EDCs) target the endocrine system by interfering with the natural hormones in the body leading to adverse effects on human and animal health. These chemicals have been identified as major polluting agents in wastewater effluents. Pharmaceuticals, personal care products, industrial compounds, pesticides, dyes, and heavy metals are examples of substances that could be considered endocrine active chemicals. In humans, these chemicals could cause obesity, cancer, Alzheimer's disease, autism, reproductive abnormalities, and thyroid problems. While in wildlife, dysfunctional gene expression could lead to the feminization of some aquatic organisms, metabolic diseases, cardiovascular risk, and problems in the reproductive system as well as its levels of hatchability and vitellogenin. EDCs could be effectively removed from wastewater using advanced technologies such as reverse osmosis, membrane treatment, ozonation, advanced oxidation, filtration, and biodegradation. However, adsorption has been proposed as a more promising and sustainable method for water treatment than any other reported technique. Increased attention has been paid to biodegradable polymers and their nano-composites as promising adsorbents for the removal of EDCs from wastewater. These polymers could be either natural, synthetic, or a combination of both. This review presents a summary of the most relevant cases where natural and synthetic biodegradable polymers have been used for the successful removal of EDCs from wastewater. It demonstrates the effectiveness of these polymers as favorable adsorbents for novel wastewater treatment technologies. Hitherto, very limited work has been published on the use of both natural and synthetic biodegradable polymers to remove EDCs from wastewater, as most of the studies focused on the utilization of only one type, either natural or synthetic. Therefore, this review could pave the way for future exploration of biodegradable polymers as promising and sustainable adsorbents for the removal of various types of pollutants from wastewater.

A new process for the production of bioethanol from paper mill sludge (PMS) is described in this work. PMS biomass feedstock was processed via the simultaneous saccharification and fermentation (SSF) with and without accelerants. The enzymatic hydrolysis and fermentation were first evaluated, and the energy demand was 2.2 MJ/L of produced ethanol. When the enzymatic hydrolysis and fermentation were combined, the energy demand was reduced to 1.0 MJ/L ethanol, the sugars production increased, and the overall capital cost of the process decreased. The sugar yield was improved by adding accelerant and selecting the optimal fiber recovery method. The accelerant improved the enzymatic hydrolysis via a pathing/bridging mechanism. The SSF with the chemical fiber recovery method coupled with accelerant addition would be the best process configuration. Upon this combination, the glucose profile was enhanced from 9.8 g/L to 17.0 g/L. The sludge fiber conversion by SSF was improved by selecting an efficient fiber recovery method combined with the accelerant addition. SSF in chemical fiber recovery with accelerant addition was the best process by a 10% improvement of ethanol yield. The proposed process configuration offers a lower cost and sustainable process and contributes to the circular economy of zero waste discharges.

Flexible and Implantable electrodes are proposed in neural sensing and muscle stimulation, particularly for peripheral nerve injuries. Functional stimulation have been used for decades in restoring muscle functions after injuries, and assist the nerve recovery process, which is often slow. Conventional electrodes are fabricated from precious metals such as platinum and gold. They are functional, but these materials also suffer from various drawbacks including the high cost, poor mechanical mismatch at the interface between the electrode tip and the soft human tissue, thus, leading to a high inter-facial impedance. This high impedance affects the quality of the signal to noise ratio (SNR) resulting in a poor recording for the neural activity. On the long term, these electrode materials can possibly damage the soft tissues due to their stiff nature. Therefore, several research activities were triggered to develop less expensive, easy to fabricate, biocompatible and flexible electrode materials that would offer solutions to the preceding problems. This work describes the synthesis of flexible and low-cost bio-electrodes based on Poly(methyl methacrylate) (PMMA) supported on silicone. The objective is to investigate their potential as candidates for sensing and recording peripheral neural signals. The synthesized electrodes were evaluated for their electrochemical properties when various mass ratios were used during the preparation process. The initial experimental results showed an impedance of 0.99 k□ for the bio-electrode sample. The impedance of these electrodes at 1 kHz was equal to 1.6 MΩ. Upon evaluation and comparison with the literature, the results appear to be very promising specifically when compared with polypyrrole (PPy)-conductive polymer and Iridium -based electrodes

This work presents the synthesis and deposition of CuI and FeCu materials on copper substrates for dye-sensitized solar cell applications. FeCu is a metastable alloy of iron and copper powders and possesses good optical and intrinsic magnetic properties. Coupled with copper iodide as tandem layers, the deposition of these two materials was permutated over a pure copper substrate, characterized and then tested within a solar cell. The cell was sensitized with a natural dye extracted from a local desert plant (Calotropis gigantea) and operated with an iodine/triiodide electrolyte. The results show that the best layer arrangement was Cu/FeCu/CuI, which gave an efficiency of around 0.763% (compared to 0.196% from reported cells in the literature using a natural sensitizer).

We present some facile routes to synthesize copper iodide (CuI) thin crystalline films and crystals. Using both hydrothermal and solvothermal techniques, particles at the nano/micro size are intrinsically produced on copper sheets by controlling the reaction between the sheet and iodine material under various parameters. The results are then characterized using scanning electron microscopy SEM, Xrays diffraction XRD and ellipsometry to obtain microstructural and optical properties, respectively. The thickness of the resulting film can be controlled by tuning working parameters such as temperature, concentrations of solvents, as well as time. The produced films/Crystals of CuI and can be used for different energy applications such as solar thermal collectors or photovoltaic cells, as the resulting microstructures possessed optical bandgaps ranging from 2.6-2.9 eV.

Photovoltaic (PV) solar panels are one of the most important sources of renewable energy. The life cycle analysis is a tool used to evaluate components or systems in terms of cost and environmental impact. This paper discusses the life cycle analysis for PV solar panels technology. Two distinct technologies of cells based on single crystalline silicon (reference) and polycrystalline gallium were studied. The reference cell material, manufacturing process, maintenance, transport, disposal and end of life (EOL) potential were analyzed during the lifetime of the solar panel. The analysis focused on three main elements: the energy consumption, the CO 2 footprint and the cost for all phases of the life cycle process. The materials used, maintenance, transportation, manufacturing processes, disposal, EOL potential were also discussed in detail for both technologies. The results showed that a change in the material has a massive influence on the total energy consumption, CO 2 footprint, and cost. These values were 7.35 × 1010 J, 0.510 metric ton of CO 2 and the US $ 584, respectively, for reference cell (silicon) whereas for Gallium the values were 7.7 × 1010J, 0.717 metric ton CO 2 and US $ 986, respectively.

Maize ( Zea mays L.) is one of the main crops, which is easily susceptable to Aspergillus flavus infection resulting in huge losses worldwide. This study was carried out to investigate the effect of combining heat and irradiation treatments in controlling the fungal growth in maize grains. Surface disinfected maize grains were artificially contaminated with spores of Aspergillus flavus Link NRRL 5906, and then exposed to gamma radiation with doses of 3.0, 4.0 and 5.0 kGy. The samples were additionally heat treated at 60 °C for 30 min. The heat and irradiation treatments showed a synergistic effect on controlling Aspergillus flavus growth. The heat treatment reduced the required radiation dose of about 0.5–1.0 kGy when 4.0 kGy or 5.0 kGy irradiation was used. The combined heat and irradiation treatment of moisture reduced the average CFU by 8 log cycles when 4 kGy or 5 kGy irradiation was used and by 7 log cycles when 3 kGy irradiation was used. The heat treatment of moisture alone reduced the average CFU by only by 0.8 log cycles. Combining irradiation with heat treatment to reduce the required radiation dose is very useful especially when there is a concern over biological side effects of irradiation.

This work investigates the performance of a single-effect absorption chiller utilizing an aqueous lithium bromide solution as the working fluid and driven by hot fluid rejected from either a geothermal power plant or the outlet of a thermal solar collector. This relatively low enthalpy return fluid, which will otherwise be reinjected back into the earth, will be utilized as the thermal energy source of the chiller. Although such chillers are considered low-grade energy refrigeration cycles, the one proposed here has an advantage in terms of economy and efficiency. A parametric analysis is performed using Engineering Equation Solver software and is used to highlight the effect of the heat exchanger size on the coefficient of performance of the chiller. The analysis proved that the proposed device can operate with excellent cooling capacity, reaching 16 kW, and a relatively high coefficient of performance (~ 0.7) while being driven by the low-grade energy. The heat source temperature, solution heat exchanger effectiveness and the size of the absorber were shown to be key parameters for the design and operation of absorption chillers. Moreover, increasing the heat source mass flow rate has a significant impact on both cooling capacity and coefficient of performance at low values (< 10 kg/s) and unnoticeable impact at higher values (> 10 kg/s).

Olive mills wastewater (OMW) causes a serious environmental problem in the olive oil producing countries. This is due to its high organic matter content (COD), acidic pH values, suspended solids and high content of phytotoxic and antibacterial phenolic compounds. In this study, titanium dioxide (TiO2) as an adsorbent to reduce the COD value of the olive mill wastewater was investigated. Several variables were studied including the removal efficiency, effect of the initial COD value, amount of TiO2, temperature and pH value. The results revealed that the adsorption reached equilibrium within

This study investigates the impact of bio-carriers' surface area and shape, wastewater chemistry and operating temperature on ammonia removal from real wastewater effluents using Moving bed biofilm reactors (MBBRs) operated with three different AnoxKaldness bio-carriers (K3, K5, and M). The study concludes the surface area loading rate, specific surface area, and shape of bio-carrier affect ammonia removal under real conditions. MBBR kinetics and sensitivity for temperature changes were affected by bio-carrier type. High surface area bio-carriers resulted in low ammonia removal and bio-carrier clogging. Significant ammonia removals of 1.420 ± 0.06 and 1.103 ± 0.06 g − N/m2. d were achieved by K3(As = 500 m2/m3) at 35 and 20 °C, respectively. Lower removals were obtained by high surface area bio-carrier K5 (1.123 ± 0.06 and 0.920 ± 0.06 g − N/m2. d) and M (0.456 ± 0.05 and 0.295 ± 0.05 g − N/m2. d) at 35 and 20 °C, respectively. Theta model successfully represents ammonia removal kinetics with θ values of 1.12, 1.06 and 1.13 for bio-carrier K3, K5 and M respectively. MBBR technology is a feasible choice for treatment of real wastewater effluents containing high ammonia concentrations. The authors gratefully acknowledge the financial support provided by the Qatar University Internal Grant ( QUUG-CENG-CHE-14\15-11 ). Scopus

Industrial processes generate toxic organic molecules that pollute environment water. Phenol and its derivative are classified among the major pollutant compounds found in water. They are naturally found in some industrial wastewater effluents. The removal of phenol compounds is therefore essential because they are responsible for severe organ damage if they exist above certain limits. In this study, ground Ziziphus leaves were utilized as adsorbents for phenolic compounds from synthetic wastewater samples. Several experiments were performed to study the effect of several conditions on the capacity of the Ziziphus leaves adsorbent, namely: the initial phenol concentration, the adsorbent concentration, temperature, pH value, and the presence of foreign salts (NaCl and KCl). The experimental results indicated that the adsorption process reached equilibrium in about 4 h. A drop in the amount of phenol removal, especially at higher initial concentration, was noticed upon increasing the temperature from 25 to 45 °C. This reflects the exothermic nature of the adsorption process. This was also confirmed by the calculated negative enthalpy of adsorption (−64.8 kJ/mol). A pH of 6 was found to be the optimum value at which the highest phenol removal occurred with around 15 mg/g at 25 °C for an initial concentration of 200 ppm. The presence of foreign salts has negatively affected the phenol adsorption process. The fitting of the experimental data, using different adsorption isotherms, indicated that the Harkins-Jura isotherm model was the best fit, evident by the high square of the correlation coefficient (R2) values greater than 0.96. The kinetic study revealed that the adsorption was represented by a pseudo-second-order reaction. The results of this study offer a basis to use Ziziphus leaves as promising adsorbents for efficient phenol removal from wastewater.

The effect of Phosphotungstic acid (PWA) on the proton conductivity and morphology of zirconium phosphate (ZrP), porous polytetrafluoethylene (PTFE), glycerol (GLY) composite membrane was investigated in this work. The composite membranes were synthesized using two approaches: (1) Phosphotungstic acid (PWA) added to phosphoric acid and, (2) PWA + silicic acid were added to phosphoric acid. ZrP was formed inside the pores of PTFE via the in situ precipitation. The membranes were evaluated for their morphology and proton conductivity. The proton conductivity of PWA–ZrP/PTFE/GLY membrane was 0.003 S cm−1. When PWA was combined with silicic acid, the proton conductivity increased from 0.003 to 0.059 S cm−1 (became about 60% of Nafion’s). This conductivity is higher than the proton conductivity of Nafion–silica–PWA membranes reported in the literature. The SEM results showed a porous structure for the modified membranes. The porous structure combined with this reasonable proton conductivity would make these membranes suitable as the electrolyte component in the catalyst layer for direct hydrocarbon fuel cell applications.

The increase in atmospheric CO2 concentration and the release of nutrients from wastewater treatment plants (WWTPs) are environmental issues linked to several impacts on ecosystems. Numerous technologies have been employed to resolves these issues, nonetheless, the cost and sustainability are still a concern. Recently, the use of microalgae appears as a cost-effective and sustainable solution because they can effectively uptake CO2 and nutrients resulting in biomass production that can be processed into valuable products. In this study single (Spirulina platensis (SP.PL) and mixed indigenous microalgae (MIMA) strains were employed, over a 20-month period, for simultaneous removal of CO2 from flue gases and nutrient from wastewater under ambient conditions of solar irradiation and temperature. The study was performed at a pilot scale photo-bioreactor and the effect of feed CO2 gas concentration in the range (2.5–20%) on microalgae growth and biomass production, carbon dioxide bio-fixation rate, and the removal of nutrients and organic matters from wastewater was assessed. The MIMA culture performed significantly better than the monoculture, especially with respect to growth and CO2 bio-fixation, during the mild season; against this, the performance was comparable during the hot season. Optimum performance was observed at 10% CO2 feed gas concentration, though MIMA was more temperature and CO2 concentration sensitive. MIMA also provided greater removal of COD and nutrients (~83% and >99%) than SP.PL under all conditions studied. The high biomass productivities and carbon bio-fixation rates (0.796–0.950 gdw·L−1·d−1 and 0.542–1.075 gC·L−1·d−1 contribute to the economic sustainability of microalgae as CO2 removal process. Consideration of operational energy revealed that there is a significant energy benefit from cooling to sustain the highest productivities on the basis of operating energy alone, particularly if the indigenous culture is used. This work was made possible by the support of a National Priorities Research Program (NPRP) grant from the Qatar National Research Fund (QNRF), grant reference number NPRP 6-1436-2-581 Scopus

NiO and NiOTiO2 nano-catalysts were synthetized using solution combustion synthesis (SCS) method and tested toward ammonia oxidation in synthetic and real wastewater. As-synthesized NiO nano-catalyst showed a tightly agglomerated nano-porous spherical structure with sizes ranging from 10 to 50 nm. NiO TiO2 nano powders have homogenous structure with an average size of 19.5 n 0.03 nm and a lattice spacing of 0.22 n 0.03 nm corresponding to cubic planes of NiO and 0.25 n 0.01 nm corresponding to TiO2. Cyclic voltammetry under alkaline condition at low potential ranging from 0.95 to 1.35 V vs. HgO/Hg improved the electro-chemical activity of the nano-catalysts by the formation of Ni(OH)2 film on the surface of catalyst as confirmed by XPS measurements. Ammonia electro-oxidation on nano-catalysts occurred at approximately 1.28 V vs. HgO/Hg and was highly pH-dependent. Ammonia removals up to 92.9 and 96.4% were achieved by NiO and NiO TiO2, respectively. Total nitrogen material balance showed that the electro-chemical oxidation of ammonia produce small amounts of NO2 and NO3 and the balance N2. Ammonia oxidation at concentration less than 150 mM followed direct electron transfer mechanism, whereas at higher concentrations, the oxidation mechanism shifted to the indirect oxidation regime. Ammonia electro-oxidation kinetics followed zero order reaction at ammonia concentration 100 mM and first order kinetics at higher concentrations. More than 93% of ammonia, 35% of organic matter and 40% phosphorous were removed from real wastewater samples using electro-oxidation process confirming the suitability of this technology as advanced wastewater treatment. The authors acknowledge the support of Qatar University to carry out and present this work. The statements made herein are solely the responsibility of the authors. Scopus

Direct methanol fuel cells (DMFC) are promising candidates for small-scale portable applications. They are characterized by their high energy density that is ten times higher than that of the lithium ion batteries. Hence, they have the potential to be prosperous alternatives to replace secondary batteries. However, their performance is limited by the Methanol crossover (MCO) through the electrolyte membranes especially at high methanol concentration. Consequently, the development of a new membrane to minimize MCO is considered to be a crucial improvement toward commercialization of DMFC. In this study, a composite membrane of graphene oxide (GO)/Nafion 117 was synthesized. The performance of this composite membrane in a DMFC was studied. This composite membrane was prepared by depositing a thin film of GO on Nafion 117 membrane. GO was synthesized in the laboratory from graphite using modified Hummer's method. The composite membrane was characterized using X-ray diffraction (XRD), Energy Dispersive Spectroscopy (EDS) and Electrochemical Impedance Spectroscopy (EIS). The Nafion-GO membranes were tested in a direct methanol fuel cell with 2 M and 5 M methanol concentrations. Preliminary results showed an improvement in the fuel cell performance and a decrease in methanol crossover when GO-Nafion membranes were used.

The treatment of olive mill wastewater (OMW) in Jordan was investigated in this work using ultrasound oxidation (sonolysis) combined with other advanced oxidation processes such as ultraviolet radiation, hydrogen peroxide (H2O2) and titanium oxide (TiO2) catalyst. The efficiency of the combined oxidation process was evaluated based on the changes in the chemical oxygen demand (COD). The results showed that 59% COD removal was achieved within 90 min in the ultrasound /UV/TiO2 system. A more significant synergistic effect was observed on the COD removal efficiency when a combination of US/UV/TiO2 (sonophotocatalytic) processes was used at low ultrasound frequency. The results were then compared with the COD values obtained when each of these processes was used individually. The effects of different operating conditions such as, ultrasound power, initial COD concentration, the concentration of TiO2, frequency of ultrasound, and temperature on the OMW oxidation efficiency were studied and evaluated. The effect of adding a radical scavenger (sodium carbonate) on the OMW oxidation efficiency was investigated. The results showed that the sonophotocatalytic oxidation of OMW was affected by the initial COD, acoustic power, temperature and TiO2 concentration. The sonophotocatalytic oxidation of OMW increased with increasing the ultrasound power, temperature and H2O2 concentration. Sonolysis at frequency of 40 kHz combined with photocatalysis was not observed to have a significant effect on the OMW oxidation compared to sonication at frequency of 20 kHz. It was also found that the OMW oxidation was suppressed by the presence of the radical scavenger. The COD removal efficiency increased slightly with the increase of TiO2 concentration up to certain point due to the formation of oxidizing species. At ultrasound frequency of 20 kHz, considerable COD reduction of OMW was reported, indicating the effectiveness of the combined US/UV/TiO2 process for the OMW treatment.

This paper reports on the properties of an MFI-type zeolite (silicalite-1) membrane synthesized on a novel tubular support with a 0.45 µm-pore size active layer consisting of zirconium and titanium oxides. Even though the membrane was synthesized by a pore plugging method, apart from penetrating into the support, the silicalite-1 crystals formed a 1.5 µm layer on top of the support. After the zeolite synthesis, the Si constituted more than 35% of the active layer of the support, which implies small size and close packing of the silicalite-1 crystals in the pores of the active layer. Single gas permeation tests with N2 and CO2 revealed comparable N2 and CO2 permeances. On the other hand, CO2/N2 gas separation tests performed at different total feed pressures and feed compositions lead to CO2/N2 permselectivities as high as 26.0, with the corresponding CO2 permeance of 6 × 10−8 mol/m2 Pa s. The effects of changing the partial pressure gradient of CO2 across the membrane by means of varying the total feed pr...