Comparative Analytical Study on Crack Width of Reinforced Concrete Structures

This paper presents a comparative study for the cracking limit state according to design codes. It aims mainly to connect research findings with design code equations. Appropriate recommendations are reached and the various factors and parameters influencing crack width investigated. The most appropriate equation for crack width calculation can be found. This is done by creating an analytical and numerical program studied various factors and parameters affecting on the crack width. The Analytical study includes some variables affecting the crack width such as steel stress, concrete cover, flexural reinforcement ratio and rebar arrangement. A 3-D finite element analysis by ABAQUS were used to model and idealize the problem. The numerical results were compared with the analytical results. It was concluded that some codes did not take into account the impact of some major variables and cases on the crack width. Also, it was found that some codes are not clear in the region concerning the position of the crack width calculation and the values obtained for the crack width. For calculating crack width values, JSCE (2007) equation is the most appropriate equation as it takes into account the main parameters that affect crack width. Doi: 10.28991/cej-2021-03091720 Full Text: PD

Metal-oxide nanotubes functional material tailored for membrane water/wastewater treatment

Titanium Dioxide Nano-Tubes (TNTs) synthesized by hydrothermal method were used to prepare new polysulfone thin film nanocomposite (TFN) membranes. The TFN membranes contained different TNTs proportions (0.1, 0.3 and 0.5 wt. %). A polyamide selective layer was formed on top of the TFN membrane surface using interfacial polymerization (IP). Nanofiltration experiments were performed using NaCl and MgSO4 salts solutions. The water flux was found to increase with increased TNT loading in the membrane due to high porosity of embedded nanoparticles and the formation of enlarged pores. The antifouling behaviour of the membrane was tested by bovine serum albumin (BSA) solution and found to improve with increased TNT content in the membrane. - 2019 IOP Publishing Ltd. All rights reserved.This paper was made possible by an NPRP10-0127-170270 and NPRP8-1115-2-473 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

Reaction kinetics of carbon dioxide in aqueous blends of N-methyldiethanolamine and L-arginine using the stopped-flow technique

Reduction of carbon dioxide emission from natural and industrial flue gases is paramount to help mitigate its effect on global warming. Efforts are continuously deployed worldwide to develop efficient technologies for CO 2 capture. The use of environment friendly amino acids as rate promoters in the present amine systems has attracted the attention of many researchers recently. In this work, the reaction kinetics of carbon dioxide with blends of N-methyldiethanolamine and L-Arginine was investigated using stopped flow technique. The experiments were performed over a temperature range of 293 to 313 K and solution concentration up to one molar of different amino acid/amine ratios. The overall reaction rate constant (k ov ) was found to increase with increasing temperature and amine concentration as well as with increased proportion of L-Arginine concentration in the mixture. The experimental data were fitted to the zwitterion and termolecular mechanisms using a nonlinear regression technique with an average absolute deviation (AAD) of 7.6% and 8.0%, respectively. A comparative study of the promoting effect of L-Arginine with that of the effect of Glycine and DEA in MDEA blends showed that MDEA-Arginine blend exhibits faster reaction rate with CO 2 with respect to MDEA-DEA blend, while the case was converse when compared to the MDEA-Glycine blend.The authors thank Ahmed Soliman and Dan Jerry Cortes for providing laboratory support This paper was made possible by an NPRP Grant # 7-1154-2-433 from the Qatar National Research Fund (a member of Qatar Foundation)

Adsorption of organic water pollutants by clays and clay minerals composites: A comprehensive review

Clays and clay minerals are inexpensive, non-toxic, and naturally occurring minerals that have been utilized in water remediation as adsorbents. However, clays and clay minerals and those modified with heat, surfactants, acids, or organic-inorganic modifiers exhibit low adsorption capacity and re-generation ability towards organic water pollutants. The development of clays and clay minerals composites has gained considerable attention in recent years due to their enhanced adsorption capacity, ease of recovery from aqueous solution and improved physiochemical properties relative to raw and modified clays and clay minerals. This review aims to assess recent literature on clays and clay minerals composites including bentonite, montmorillonite and kaolinite intercalated with carbonaceous, metals, metal oxides, chitosan and polymeric materials and appraise their adsorption performance towards organic water pollutants. The review examines the effect of the composites' physicochemical properties on the adsorption performance and evaluates the adsorption mechanism as well as regeneration methods. The review also attempts to highlight the current progress in this area by assessing the outcomes of recently published articles and outline the research gaps for future research.This publication was made possible by an Award [GSRA6-2-0516-19029] from Qatar National Research Fund (a member of Qatar Foundation). The contents herein are solely the responsibility of the author[s]. Open access funding is provided by the Qatar National Library.Scopu

Chromium removal from tannery wastewater by electrocoagulation: Optimization and sludge characterization

The treatment of tannery effluent is of great interest as it contains a complexmixture ofpollutants, primarily chromium. The disposal of this wastewater can have adverse effects on the environment and aquatic life, which is an emerging problemfor the environment. In this work, electrocoagulation is used to remove chromium from real tannery wastewater, focusing on performance optimization and sludge characterization. Electrocoagulation experiments were conducted using an electrochemical cell with iron electrodes immersed in a specific volume of tannery wastewater. Operating parameters, such as the initial chromium concentration, pH and current density as well as power consumption were evaluated to determine optimum chromium removal. The optimizationwas performed using Response Surface Methodology combined with central composite design. Analysis of variance (ANOVA) was used to determine the response, residual, probability, 3D surface and contour plots. The maximum chromium removal was 100% at the optimum values of 13 mA/cm2, 7 and 750 ppm for current density, pH and concentration, respectively.This research received no external funding. The authors are grateful to the staffof the Gas Processing Center (GPC) for their help with the experimental work, especially Ahmed Soliman and Dan Cortes. They would also like to thank the Environmental Research Centre, the Chemical Engineering Department, and the Central Laboratory Unit at Qatar University for their support.Scopu

Adsorption of 4-Nitrophenol onto Iron Oxide Bentonite Nanocomposite: Process Optimization, Kinetics, Isotherms and Mechanism

Despite its importance in chemical industry, 4-Nitrophenol (4-NP) is a persistent organic pollutant that has serious effects on the ecosystem. In the present study, Box–Behnken design in response surface methodology was used to optimize the adsorption process parameters for the maximum 4-NP removal at 30 ℃ using Fe3O4/Bt NC. The regression model results suggested that the optimum adsorbent dosage, initial concentration, pH and contact time were 0.3182 g, 85 mg/L, 11 and 137.2 min, respectively. The regression model showed an optimum removal of 100%, while 99.5% removal was obtained from batch experiments at the optimum conditions suggested by the regression model, which confirm the model validity. The adsorption data best fitted to Freundlich isotherm model and Pseudo second-order kinetic model suggesting the existence of physical and chemical interaction between the fabricated composite and 4-NP. FTIR analysis suggested that the adsorption mechanism included an electrostatic attraction and the formation of new chemical bonds. Obtained results suggest that Fe3O4/Bt NC can be an effective adsorbent for complete 4-NP removal at the indicated optimum conditions.This research was made possible by an NPRP Grant # 10-0127-170270 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. The author Dina Ewis acknowledged the financial support of QNRF through the Graduate Sponsorship Research Award (GSRA) number GSRA#6-2-0516-19029.Scopu

Effective Heterogeneous Fenton-Like degradation of Malachite Green Dye Using the Core-Shell Fe3O4@SiO2 Nano-Catalyst

In this study, the application of the core-shell Fe3O4@SiO2 nano-catalysts for fenton-like degradation of malachite green dye has been presented. The nano-catalysts were prepared using a combination of solvothermal and sol-gel techniques and characterized using XRD, FTIR, SEM/EDX, TEM and VSM techniques. The effects of various reaction parameters on the degradation of malachite green dye using the prepared nano-catalysts were investigated. The optimal condition for pH, catalyst dosage and H2O2 amount were found to be at 6.7, 15 mg and 50 μL, respectively. Under the optimized conditions, a degradation efficiency of 96.18 % for malachite green dye was achieved using the catalyst within 30 minutes at 303 K with a pseudo first order rate constant of 0.1102 min−1. The plausible mechanism for MG degradation was determined to be the combination of adsorption and simultaneous decomposition via formation of hydroxyl radicals. The performance of the nano-catalyst was compared with other fenton-like catalysts reported in the literature. Finally, the magnetic properties of the Fe3O4@SiO2 catalysts was utilized for its successful recovery and application in multiple degradation cycles.This research was made possible by an NPRP Grant#10-0127-170270 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. The authors would like to acknowledge the help Centre for Advanced Materials (CAM) at Qatar University and Mr. Abdullah Al Ashraf for providing XRD test data. SEM/EDX tests was accomplished in the Central Laboratories unit, Qatar University.Scopu

Electrochemical reduction of CO2 into formate/formic acid: A review of cell design and operation

The release of carbon dioxide (CO2) into the atmosphere is threatening the environment and ecosystems, resulting in major challenges to sustainable development for modern industry. In this context, CO2 electrochemical reduction (CO2 ECR) is one of the most promising technologies to mitigate the effects of high CO2 content in the atmosphere. Electrochemical technology can convert CO2 into value-added chemicals including methanol, ethanol and formate. In this review, different mechanisms of CO2 electrochemical reduction into formate/formic acid are reviewed, highlighting the different cell designs. Also, the effect of cell design and operating parameters on the electrochemical reduction process are discussed. The review aims to highlight recent developments in the CO2 electrochemical cell design for formate production and provide guidelines for future advancements. Challenges of large-scale production and research gaps are also provided. 2023 The AuthorsThe authors would like to acknowledge the support of Qatar National Research Fund (a member of Qatar Foundation) through Grant # NPRP 12 C-33923-SP-102 (NPRP12 C-0821-190017). The findings achieved herein are solely the responsibility of the authors. Open Access funding provided by the Qatar National Library.Scopu

CFD and statistical approach to optimize the average air velocity and air volume fraction in an inert-particles spouted-bed reactor (IPSBR) system

Inert-particles spouted bed reactor (IPSBR) is characterized by intense mixing generated by the circular motion of the inert particles. The operating parameters play an important role in the performance of the IPSBR system, and therefore, parameter optimization is critical for the design and scale-up of this gas-liquid contact system. Computational fluid dynamics (CFD) provides detailed modeling of the system hydrodynamics, enabling the determination of the operating conditions that optimize the performance of this contact system. The present work optimizes the main IPSBR operating parameters, which include a feed-gas velocity in the range 0.5-1.5 m/s, orifice diameter in the range 0.001-0.005 m, gas head in the range 0.15-0.35 m, mixing-particle diameter in the range 0.009-0.0225 m, and mixing-particle to reactor volume fraction in the range 2.0-10.0 vol % (which represents 0.01-0.1 kg of mixing particles loading). The effects of these parameters on the average air velocity and average air volume fraction in the upper, middle, and conical regions of the reactor were studied. The specific distance for each region has been measured from the orifice point to be 50 mm for the conical region, 350 mm for the middle region and 550 mm for the upper rejoin. The selected factors were optimized to obtain the minimum air velocity distribution (maximum gas residence time) and the maximum air volume fraction (maximum interfacial area concentration) because these conditions will increase the gas holdup, the gas-liquid contact area, and the mass transfer coefficient among phases. Response surface methodology (RSM) was used to determine the optimum operating conditions. The regression analysis showed an excellent fit of the experimental data to a second-order polynomial model. The interaction between the process variables was evaluated using the obtained three-dimensional surface plots. The analysis revealed that under the optimized parameters of a feed-gas velocity of 1.5 m/s, orifice diameter of 0.001 m, gas head of 0.164 m, mixing-particle diameter of 0.0225 m, and mixing-particle loading of 0.02 kg, the minimum average air velocity and highest air volume fraction were observed throughout the reactor.This work was supported by the ADNOC Refining Research Center , Abu Dhabi, UAE.Scopu

The influence of the accessory genome on bacterial pathogen evolution

Bacterial pathogens exhibit significant variation in their genomic content of virulence factors. This reflects the abundance of strategies pathogens evolved to infect host organisms by suppressing host immunity. Molecular arms-races have been a strong driving force for the evolution of pathogenicity, with pathogens often encoding overlapping or redundant functions, such as type III protein secretion effectors and hosts encoding ever more sophisticated immune systems. The pathogens’ frequent exposure to other microbes, either in their host or in the environment, provides opportunities for the acquisition or interchange of mobile genetic elements. These DNA elements accessorise the core genome and can play major roles in shaping genome structure and altering the complement of virulence factors. Here, we review the different mobile genetic elements focusing on the more recent discoveries and highlighting their role in shaping bacterial pathogen evolution