The Role, Properties, and Classifications of Filter Paper
Here HAWACH brings together the basic concepts and terminology of filter paper to help you make the right choice. The main component of filter paper is cotton fiber, which has good affinity for water, it can absorb nearly one quarter of water, of which 6%-7% is combined with cellulose in the form of hydrogen bond. And in general is very difficult to remove, relative to the affinity with water. When the mobile phase of organic solvent passes through the sample, it will distribute the water and the organic phase continuously, and then as the mobile phase keeps moving, the substances of various components are continuously redistributed, further making the substances separated and purified. Analytical laboratories commonly use filter paper as a filtration medium to separate solutions from solids.
Ash content of filter paper
The ash content of cellulose filter paper is determined by weighing the residue of combustion under air at 900°C. The minimum ash content is essential for the weight method and is a valid measure of general purity levels. The cotton fiber in the filter paper has a weaker affinity with organic solvents, so in most cases paper chromatography is the bound water in the filter paper fiber as the stationary phase, while the mobile phase is based on organic solvents.
Properties of filter paper
In the selection of suitable filter paper must be decided after the following four factors, the first is the hardness, the filter paper will be wet when filtering. A tougher filter paper should be chosen if the filtration process takes long time. Next is its filtration efficiency, the filtration efficiency is mainly determined by the tightness of the water permeable pores on the filter paper and the size of the pores. Next is the capacity, the capacity is mainly determined by the density of water permeation pores, the more dense the pores, the higher its capacity. The last is the applicability. Some filter papers are made in very special steps, so care must be taken when applying them. The filter paper cannot filter zinc chloride because it will corrode and break the filter paper.
Chemical compatibility of filter paper
It is important to ensure that the structure of the filter media is not damaged by exposure to certain chemicals. In addition, exposure to these chemicals should not cause the filter to shed fibres or particles, or have substances precipitated. Time, temperature, concentration and length of applied pressure will all affect compatibility. A chemical compatibility chart is provided to assist you in making your choice.
Load capacity of filter paper
This refers to the ability of fibre-based products to carry particles while maintaining the operating filtration rate and pressure differential. In general, glass fibre filter papers have a higher carrying capacity and a relatively lower membrane loading capacity than cellulose filter papers with the same particle retention and thickness.
Main classifications of filter paper
In general filter paper can be divided into two kinds, one is qualitative and the other is quantitative. HAWACH’s qualitative and quantitative filter papers are made from high purity cotton staple, which is specially treated to have a minimum alpha cellulose content of 98%. Qualitative filter paper generally refers to the generation of cotton fibers on its surface after filtration, generally with more residual ash, it is generally only suitable for doing qualitative analysis and for filtering precipitation or suspension in solution, and cannot be used for quality analysis. Qualitative filter paper is generally used for filtering solutions and doing qualitative tests such as chloride and sulfate that do not require calculation of values. Quantitative filter papers are available in high purity for analytical and gravimetric testing.
And quantitative filter paper is commonly used in quantitative analysis, in the process of use must go through a special treatment process, to a certain extent it can resist some chemical reactions effectively, resulting in much less impurities generated on its surface. In addition to the application of filter paper in chemical experiments, we also have the application of filter paper in our life, for example, coffee filter paper is one of the widely used, in general, this filter paper has a high degree of softness, and in industry filter paper is generally used to adsorb suspended particles in the air.
Further more, HAWACH’s cotton fibre filter papers can be used for general filtration down to 2.5 μm particle size and are available in a wide range of combinations of retention rates and flow rates to suit your filtration needs. In addition, HAWACH also offers wet strength, ashless and rigid ashless filter papers. The qualitative filter paper can be sub divided into seven types, BIO-1 Grade Qualitative Filter Paper Disc(Particle Retention: 11μm), BIO-2 Grade Qualitative Laboratory Filtration Filter Paper(Particle Retention: 8μm), BIO-4(Particle Retention: 20μm), BIO-5 Grade Qualitative Chromatography Filter Paper(Particle Retention: 2.5μm), BIO-6(Particle Retention: 3.0μm), BIO-91(pore size: 10μm, wet strengthened) and BIO-113(pore size: 30μm, wet strengthened) .
Quantitative filter paper can be sub divided into five types BIO-40 Grade Quantitative Medium Flow Filter Paper(Particle Retention: 8μm), BIO-41(Particle Retention: 20μm), BIO-42 Grade Quantitative Laboratory Filter Paper(Particle Retention: 2.5μm), BIO-43(Particle Retention: 16μm), and BIO-44 Grade Quantitative Cellulose Filter Paper(Particle Retention: 3μm).
Filtration speed of filter paper
Both the quantitative and qualitative filter paper are divided into three categories based on the speed: fast, medium speed and slow speed, and there are two kinds of round and square, based on the shapes. Three different flow rates to suit different applications, with different physical and chemical specifications. The range of sizes and specifications offers a good balance between filtration speed and particle interception and is mainly used for. Qualitative filter paper is a type of filter paper often used in chemical laboratories to filter precipitates and suspensions. It has a higher silica content than qualitative filter paper and has a certain amount of ash after firing. Quantitative filter papers are mainly used for the determination of cement grades in industrial production, environmental monitoring and quantitative laboratory analysis. Qualitative filter papers are used for analytical pretreatment; precipitation and solid-liquid phase separation and purification; qualitative chemical analysis in many fields such as chemical, metallurgical, pharmaceutical, mining, etc.