Many will remember their high school chemistry classes and their attempts to analyse the composition of a solution. The process often begins by adding a reagent to form an insoluble compound on which to perform further tests. Separating the solid and liquid phases involves filtration through a porous paper disk held in place by a funnel. The clear fluid or filtrate trickles through into a test tube while the precipitated solids remain trapped on the surface of the filter paper. In this case, the objective is to retain the solids for further study. However, filters of various kinds are most often used to purify a liquid or gas, in which case it is the filtrate that will be the portion to retain.
The Early Days
While chemistry lessons are a comparatively modern development, liquid filtration can be traced to around 500 BC and a Greek scientist and physician named Hippocrates. Rather than neat little paper discs, he filtered the boiled water he used to bathe feverish patients through a piece of cloth. Around 900 years later, the Egyptians adopted various practices to purify their drinking water. After first boiling it, they then left it to percolate through layers of sand and gravel to remove insects and other particulate matter.
During the early 17th century, Sir Robert Bacon experimented with a new use for liquid filtration. He passed seawater through the sand to remove its salt content. However, the invention of the microscope and the alarming discovery of the innumerable microorganisms invariably present in water sparked the quest to develop new and improved ways to remove these and other impurities. Soon after, several countries began to use alternative materials, such as wool, charcoal, and sponge to remove these newly-discovered germs from their drinking water.
By the early 20th century, the development of new liquid filtration technology intensified, spurred by legislation introduced in many countries, setting acceptable water purity standards. Progress in other industries, such as pharmaceuticals, food and beverages, and petrochemicals also created many new applications for filter media and a need for alternative technologies.
Sand filters are still a common feature in water treatment plants, and charcoal filters are a popular means to treat tap water in many homes. However, the need for increasingly higher degrees of purity has led to new options, including synthetic membranes, ion-exchange resins, and reverse osmosis (RO). These liquid filtration techniques operate in the nano range to provide levels of purity once considered impossible. Flow Clear Filtration is a specialist in this crucially important field, offering world-class products for domestic, commercial and industrial use.