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Danielle has taught middle school science and has a doctorate degree in Environmental Health
Even if you don't know the definition for the chemical process of leaching, you've probably witnessed it take place. If you've ever brewed a cup of tea or made instant coffee, for instance, you've seen leaching in action. Leaching is just the process of extracting a substance from a solid material that has come into contact with a liquid.
In leaching, the liquid is very important, as it facilitates the ability to remove, or extract, a given substance from a solid matrix (i.e. material). Let's break this definition down by using the example of brewing tea.
You go into your kitchen and decide you would like to make a hot cup of green tea. Of course you know that a green tea bag, hot water, and a cup is needed to make the tea. Shown in this diagram, we can relate each of these components to the definition of leaching: (1) The tea bag would be our solid matrix, (2) the green tea would be the substance extracted, and (3) the hot water would be our liquid source.
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Going back to our story on making tea, you proceed with boiling water and add it to a cup. As you steep your green tea bag in the hot water, what do you notice? The water not only changes colors, but more importantly, green tea is extracting from the tea bag into the water. After steeping for a few minutes, you sip from your mug and taste not just hot water, but delicious green tea, too.
Although making tea is a very well known process, it's also an ideal example of how leaching works. You took a solid matrix, like the tea bag, introduced it to a liquid, in this instance the hot water, and extracted green tea, or a substance, to make a cup of tea. Now that we understand what leaching is, let's look at the process in more detail, specifically regarding commercial applications.
Within the chemical industry, the process of leaching is commonly referred to as extraction. Let's look at this diagram of how the leaching, or extraction, process works.
First, the solvent comes into contact with the solid matrix. A solvent is usually a liquid that functions to dissolve a substance or solute. A solute is the substance being dissolved by a solvent. Thus, the solvent would be the liquid and the solute would be the substance you would like to extract from the solid matrix. Again, referring to our tea example, the solute would be your green tea extracted while the solvent would be the hot water.
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Next, the solvent travels through the solid matrix, separating the substance, or solute, from this matrix so that it can be collected. This step is commonly referred to as percolation, which is really just a fancy word for filtering. You are essentially filtering out, or separating, the solute you desire from the solid matrix, using a solvent.
Both steps lead to the end result, which is extraction of the desired substance (i.e. a solute). If we do a quick overview, there are three main parts to leaching you should remember: contact, separate, extract. You let your solvent come into contact with the solid matrix, separate the desired substance from the solid matrix using the solvent, and extract the desired substance for collection.
Sometimes nasty contaminants can leach out from soils and make their way into our groundwater, directly affecting our drinking supply. Water-soluble contaminants such as fertilizers or pesticides, often used in agriculture, can be carried by water directly into our soils. The soil often contains precious groundwater used as a water supply source. Leaching of these nasty contaminants into our ground water, from the soil, can cause environmental concerns.
With estimates at roughly 50% of ground water used for drinking water, it makes perfect sense why leaching of contaminants into this source is worthy of consideration. Although the levels of contaminants are not present at a concentration high enough to be detrimental to our health, scientists (and environmental health professionals) remain proactive at protecting our ground water and drinking water supply.
Leaching is a process of extracting a substance from a solid material that is dissolved in a liquid. This process is commonly referred to as extraction, particularly in the chemical industry. Three basic steps are involved in the leaching process: contact, separation, and extraction. A liquid must come into contact with a solid matrix containing the substance that needs to be extracted. Following contact, the liquid will separate this desired substance from the solid matrix. Extraction of this substance can follow after separation is complete. Leaching of contaminants from soil into groundwater is an environmental concern. Examples of the leaching process range from extracting tea from a tea bag to commercial applications.
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College Earth Science: Help and Review23 chapters | 247 lessons | 1 flashcard set
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