Vacuum filtration, also known as suction filtration, is a chemistry laboratory technique that allows for accelerating and streamlining filtration processes with the help of a pressure differential. The method is commonly used for separating solids from liquids (for example, for recovering a product of synthesis when the product is a solid in suspension) and purifying solvents, and plays a major role in sample preparation in research and analyses carried out in the food and beverage, pharmaceutical and water and wastewater treatment industries, among others.
In a traditional filtration procedure, it is gravity
that provides the force which draws the liquid
through the filter medium. Thanks to the
complex multi-layer structure of the filter, only
the liquid and small particles can pass through
it becoming the so-called filtrate, whereas
larger solid particles (the so-called oversize) are
retained on the filter paper’s surface. High (hot
filtration) or low (cold filtration) temperatures
are sometimes applied to deal with solutions
which can only be effectively filtered in a special
thermal environment.
The application of vacuum enables the achievement of much higher process rates than are
possible in gravity-assisted filtration, with the vacuum source creating a difference (maximum one
atmosphere) in pressure on both sides of the filter and thus helping increase the speed with which
the solution is forced through it.
Selecting the Equipment
Depending on the application, the right type of filter paper has to be selected, with qualitative paper letting more material through and filtering faster, and quantitative paper filtering finer particles but lowering the filtration speed.
The glassware needs to be vacuum rated so that it can withstand one atmosphere to which it is subjected. When it comes to the vacuum source itself, a number of important considerations have to be taken into account to make sure that the filtration procedure is performed in an effective and efficient manner to bring the desired process results.
Vacuum Level
Modest vacuum levels of between 40 Torr (53 mbar) and 200 Torr (266 mbar) are normally sufficient to meet the needs of most vacuum filtration applications. Too deep a vacuum can lead the filter paper to tear or the filtrate to boil in the vacuum flask.
Free Air Displacement
The requirement depends on the size of the filter and the number of filter holders, the leak rate of the system, and the condition of the solid particles collected on the filter’s surface (the so-called filter cake).
Vacuum Pump Type
The substance to be filtered determines the choice, with economical standard-duty dry vacuum pumps typically handling aqueous solutions and chemical-duty diaphragm pumps with corrosion-resistant construction able to deal with aggressive vapors being used for filtering organic solvents and acid solutions
WOB-L® Pump Efficiency
Welch, a brand of Ingersoll Rand, a leading provider of pressure and vacuum solutions for numerous industries, offers a wide range of state-of-the-art vacuum pumps configured for vacuum filtration of liquid mixtures. Our portfolio includes WOB-L® piston models 2522, 2534, and 2546 which:
Features:
The WOB-L is perfect for aqueous vapors for filtration solvent/media. It also includes the technology designed for suspended solids samples as well as food slurry analysis.
Gas Pump Technology Capabilities are listed below for the WOB-L:
Sources:
Starting at from $455.50 Sale $432.73
