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Decreasing the concentration of pollutants in wastewater is a necessary issue particularly in the third-world countries. Mercury is known as one of the most important metal contaminants with harmful impacts on the environment. The present work is based on the lab-scale Hg elimination from synthetic wastewater. For this purpose, adsorption application in continuous mode has been chosen and a modified activated carbon which is sulphurised via dimethyl-disulphide was applied as adsorbent. Thus, the original activated carbon performance in Hg2+ adsorption was compared with the sulphurised sorbent. Investigation of the dynamic behaviour of adsorption fixed bed system which is highly demanded prior to industrialisation, was studied in the present work to predict the mass transfer coefficients and diffusional properties of adsorbent-adsorbate system. Therefore, a diffusional model namely Axial-dispersion Film Pore-Surface Diffusion model including all the main mass transfer mechanisms in porous beds was implemented. Apart from the mathematical model, one of the most common shortcut approaches (Thomas model) was applied to describe the adsorption behaviour in fixed beds for comparison with the mathematical model results. Based on the Thomas model and experimental results, several important properties of both adsorbate/adsorbent system such as equilibrium adsorption capacity and exhaustion rate were calculated and explained. According to the results of mathematical modelling, the factors and mechanisms with the lowest degree of importance were determined in each system, and the more appropriate/simpler mathematical models were suggested. [ABSTRACT FROM AUTHOR]

The current study deals with the removal of mercury ions from aqueous solutions by sulfurized and original activated carbons (ACs) in the batch and fixed bed modes. The modified sample containing sulfur groups showed higher uptake capacities and larger breakpoints. The XPS and EDS analyses confirmed the introduction of carbon–sulfur bonds onto the AC's surface after impregnation with dimethyl-disulfide. In the work, the diffusional models named, "Film Pore Concentration-Dependent Surface Diffusion (FPCDSD)" and "Axial dispersion Film Pore Concentration-Dependent Surface Diffusion (AFPCDSD)" were respectively applied to explain the batch and bed-mode kinetic data to clarify the rate-controlling mechanisms and estimate the diffusional/mass transfer properties of adsorbate–adsorbent systems. In all cases, the sulfurized AC showed greater Ds (surface diffusivity) values attributed to the higher mercury loading on this sorbent which facilitates ion hopping on the surface sites. The internal and film diffusions both played notable roles in mercury adsorption mechanism. [ABSTRACT FROM AUTHOR]

This work aims at analyzing the transient behavior of a photovoltaic-Polymer Electrolyte Membrane (PV-PEM) water electrolyser system based on regional weather data. The goal of a dynamic modeling is to check how the system works against the load variations. In this study, the PV array is used for power supply then, a controller and power conditioning to provide clean energy for electrolyser. The electrolyser model is developed in MATLAB and it is used in a TRNSYS environment. The performance of a PEM electrolyser can be illustrated by the polarization curve which is voltage–load current (V–I) characteristics. Moreover, a mathematical modeling for computing dynamic voltage based on current and all operation parameters in electrolyser stacks have been developed. Then the transient behavior of the PV-PEM system is analyzed over the seasonal condition base on Vienna average weather information. [ABSTRACT FROM AUTHOR]

In order to improve the performance coefficients of the classic Savonius rotor, a newly-designed blade was proposed and numerically analyzed via CFD tools. For this purpose, a comprehensive-validated numerical analysis was carried out to take into account all aerodynamic aspects of the new design. The blade geometry was optimized by determining the best overlap ratio (0.47) which led to the highest performance at different tip speed ratios. The better performance of the optimal advanced Savonius rotor compared to the classic rotor was demonstrated by comparing its torque and power coefficients at different tip speed ratios. It is shown that working at relatively low tip speed ratios results in higher torque coefficients with more superiority over the corresponding classical rotor; however, to achieve more stable and regular blade rotation with less noise and fluctuations, tip speed ratios around 0.75 and smaller are proposed. In order to demonstrate the separation points, the wake phenomenon, and vortices behind the rotating blades, the pressure, velocity, and vorticity contours were prepared and analyzed. [ABSTRACT FROM AUTHOR]