Solvent extraction is the process mostly used by the government bodies or the industries for pollution clean up. It is also a very innovative and yet extremely cheap and quick method. The major function of solvent extraction is to determine various components of substances generated from industry, agriculture or prevalent in environmental samples. One of the most used extraction process in this genre is Soxhlet extraction which is a type of analytical technique. Over the years it has undergone lot of changes; mostly the changes have been made by raising temperature of solvent which is in contact with the component from which the extraction is made so that the extraction time is reduced. The latest modifications have been presented by an American chemist Edward L. Randall which has been found to be very effective.
Simply speaking Solvent extraction is a process which is used to clean or extract harmful materials or chemical pollutants. PCBs, grease or oil are the chemicals which do not dissolve in water. But they stick or remain absorbed to the soil, sludge or sediment which pollutes the surface. The chemicals used in solvent extraction dissolve these chemical pollutants and clean the site.
The first step of solvent extraction starts with observation of the soil where the chemical pollutants are absorbed. This soil is then picked up and sieved to remove the unwanted debris and large particles like rocks. This soil is then put in the extractor with the solvent for extraction. The solvent used depends upon the type of chemical pollutants in the soil. The soil thus cleaned is then tested for the presence of chemical pollutants if any. If the soil still has some traces of harmful chemicals, it is once again processed through the extraction process or otherwise returned back to ground from where it was picked up.
The pollutants thus separated are poured in the separator. Now the process is done to separate the pollutants from the solvent. The solvent thus separated is then recycled for reusing again in the process of solvent extraction. If the solvent cannot be reused then they are disposed off or destroyed. Many times, the solvent remains absorbed in the extracted soil. The soil is heated due to which the liquid solvent turns into gas which is removed from the soil. When the gas cools down it again change into liquid state and is recycled.
Solvent extraction is a perfectly safe process when performed as per the regular guidelines. Most often it is performed in a covered place due to which it is easier to capture any traces of harmful components if they are released during the process. The soil is too tasted of any tasted of solvent as well as the pollutant before it is released back. So this process is very safe, takes less time than other cleaning methods, and is cheaper as well. 125 tons of soil can be extracted by this process in a day in general case. But the rate of extraction also depends upon:
Many times the industrial wastes and other agricultural wastes stuff the soil with sediments and other types of pollutants which are difficult to remove. In case of agricultural land, the soil needs to be free from the pollutants to give good yield. Solvent extraction is carried out to clean up such chemically polluted soils. Many times the process is carried out at the work site so as to reduce the transportation cost and also the time taken.