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Desalination Lab Report

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Aim

The aim of this experiment is to test the effect of selected variables on the osmotic pressure during desalination. The variables being researched include: the size of the cation, different salinities and the solubility of a number of salts normally found in seawater.

Background Information

I have for a number of years been interested in environmental issues such as water consumption and the carbon footprint that characterizes our modern societies. In a previous experiment I created an organic geyser, designed to use compost to provide a source of energy to heat water. In the present experiment, I will be exploring the potential for utilizing desalination to increase the quantity of potable water for human consumption.

Water is a …show more content…

The force, which drives reverse osmosis (water leaving the solution side of semipermeable membrane), is the pressure of a solution combined with external added pressure. In the presence of additional pressure solvent molecules can move out of the solution at a higher rate than the rate of solvent molecules flowing into the solution. Under these circumstances the solute will eventually be concentrated on one side of the semipermeable barrier. This process of reverse osmosis (separating the water from the solutes) underlies desalination. However, reverse osmosis desalination, although practical, is a costly method of water purification, due to the relatively high concentration of dissolved salts (3.5%) in seawater or brackish water. In spite of the high cost, the method is effective, making it the most common form of desalination today. This process serves not only to remove the salt, but also the organic matter commonly found in …show more content…

This strength thus makes it more durable than the current polymer membranes that are in use. Its thinness results in less resistance during the process of pushing solvent molecules across the semipermeable membrane. Consequently, less pressure needs to be generated, cutting the energy costs of desalination by between 15-46% . In order for the graphene to work as a semipermeable membrane, it must contain pores, created to accommodate the exact size of a solvent particle but small enough to prevent the solute from flowing through. For desalination, the ideal size of the pores is one nanometer . In order to create the pores of an adequate size, there are three possible methods : helium-ion bombardment, chemical etching and self-assembling systems. The use of graphene for desalination is still being developed. At present the main barrier to progress is creating graphene semipermeable membranes with pores of the right size on a large enough

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