Chemical Engineering @ChemengFiles.Com

The phenomenon of concrete carbonation is a very worrying given the serious consequences that may result, resulting from corrosion of reinforcement responsible for sustaining the structures of buildings. While there are various factors that influence the corrosion of reinforcing steel (oxygen, moisture, pH, etc.) Massive release of CO2 into the atmosphere plays a dominant role in the electrolytic connection for the activation of destructive process.

While calcium hydroxide, sodium and potassium, dissolved in the aqueous component of concrete, are responsible for the high pH which acts as a shield of steel, when the CO2 enters the concrete is a reaction between the liquid phase hydroxides interstitial hydrated cement compounds, so that when all the Ca (OH) 2, Na (OH) and K (OH) present in the pores have been carbonate, the pH begins to decrease, resulting in an acidic environment that produces a steady and progressive corrosive effect on steel.

While many times have you wanted to label as a process of osmosis filtration on a molecular scale is easy to understand and realize that reverse osmosis is a process clearly differentiated from the micro filtration or filtration.

There are three aspects which indicate clearly that this difference:
1. In the process of filtering the entire flow passes through the separator element. This only prevents the passage of solid particles of a predetermined size.
2. By contrast, reverse osmosis, only a portion of the feed rate through the membrane and constitutes the product. The remaining flow is discharged without passing through the membrane and becomes the rejection.
3. In reverse osmosis, never separated material accumulates on the surface of the membrane, as occurs in other processes, as is the rejection which is responsible for the drag of the material.
4. While the osmosis seawater flow is parallel to the membrane, filtration is perpendicular.

For aerosol Brownian coagulation in the transition regime of Knudsen number in the presence of an interparticle potential, the Fokker-Planck equation is solved by using the Grad's 13-moment method. The mass and energy accommodation coefficients that are used to describe the results of collisional processes are appropriately defined and interfaced with the Fokker-Planck moment equations. Analytical and numerical solutions of the number and energy flux profiles for the potential-free, power-law potential, van der Waals potential, and Coulombic potential situations are obtained. The results are in good agreement with those predicted by the flux-matching method of Fuchs. The present fundamental approach, therefore, provides theoretical support of the coagulation coefficient expression obtained by the empirical flux-matching method.