Filter media paper

Control Filtration Analytical chemistry Activated carbon Diatomaceous earth Filter media--paper, polypropylene, cotton Low or high pH Organic compounds Dissolved metals Compl exed metals Solid metals SIudge Waste chemicals Waste filter media... 

Filtration is the separation of a fluid-solids mixture involving passage of most of the fluidthrough a porous barrier which retains most of the solid particulates contained in the mixture. This subsec tion deals only with the filtration of solids from liquids gas filtration is treated in Sec. 17. Filtration is the term for the unit operation. A filter is a piece of unit-operations equipment by which filtration is performed. The filter medium or septum is the barrier that lets the liquid pass while retaining most of the solids it may be a screen, cloth, paper, or bed of solids. The hquid that passes through the filter medium is called the filtrate. 

The filter medium can be fibrous, such as cloth granular, such as sand a rigid solid, such as a screen or a mat, such as a felt pad. It can be in the shape of a tube, sheet, bed, fluidized bed, or any other desired form. The material can be natural or man-made fibers, granules, cloth, felt, paper, metal, ceramic, glass, or plastic. It is not surprising that filters are manufactured in an infinite variety of types, sizes, shapes, and materials. 

Used directly in lubricating clarification in a "blotter press", it acts much the same manner as the paper pads, but is much thinner and is not reused. As a precoat, paper protects the filter medium from slimy fines it may be peeled off and discarded after clogging, leaving the medium underneath clean. 

This operation is the separation of the precipitate from the mother liquor, the object being to get the precipitate and the filtering medium quantitatively free from the solution. The media employed for filtration are (1) filter paper (2) porous fritted plates of resistance glass, e.g. Pyrex (sintered-glass filtering crucibles), of silica (Vitreosil filtering crucibles), or of porcelain (porcelain filtering crucibles) see Section 3.24. 

The choice of the filtering medium will be controlled by the nature of the precipitate (filter paper is especially suitable for gelatinous precipitates) and also by the question of cost. The limitations of the various filtering media are given in the account which follows. 

The filters used for gas cleaning separate the solid particles by a combination of impingement and filtration the pore sizes in the filter media used are too large simply to filter out the particles. The separating action relies on the precoating of the filter medium by the first particles separated which are separated by impingement on the filter medium fibres. Woven or felted cloths of cotton and various synthetic fibres are commonly used as the filter media. Glass-fibre mats and paper filter elements are also used. 

Filter Mediums are materials used for filtering, such as filter paper, filter pulps, cotton fabrics, cotton ducks, cotton twills, cotton chain, cotton batting, wool cloths... 

Filtration of Hot Solution (see also Filtration).—This operation is usually necessary in order to remove insoluble impurities, filter fibres, etc. When the substance does not separate rapidly from the hot solution, and the liquid filters quickly, the solution may be filtered through an ordinary funnel with a short stem, fitted with a folded filter paper (Pig. 1). Both funnel and paper should previously be warmed in a steam bath. Or, the solution may be filtered with suction, using suitable types of apparatus (Pigs. 27,28). The funnel and filtering medium should be previously warmed. When the filtrate is collected in a thick glass suction flask,... 

The flask is heated on a steam bath for four hours and then in an oil bath at 145° until all the crystals are dissolved. A mush of crystals separates when the mixture is cooled to room temperature. These are filtered on a Buchner funnel without any filtering medium. After the crystals are pressed dry, they are placed in 1.5 1. of cold water, washed thoroughly, filtered through paper, and dried in the air. The yield is 200-213 g. (60 per cent of the theoretical amount), and the product melts at 205-207° (corr.) (Note 4). 

Use Dyeing mordant, water purification, waterproofing fabrics, manufacture of lakes, filtering medium, chemicals (aluminum salts), lubricating compositions, manufacture of glass, sizing paper, ceramic glaze, antacid. 

Use Rubber filler ceramics, glass, refractories absorbent for crude oil spills manufacture of permanently dry resins and resinous compositions paints, varnishes, and paper (filler) animal and vegetable oils (bleaching agent) odor absorbent filter medium catalyst and catalyst carrier anticaking agent in foods. 

Paper is an important filtering medium. Ashless paper is manufactured from cellulose fibers that have been treated with hydrochloric and hydrofluoric acids to remove metallic impurities and silica ammonia is then used to neutralize the acids. The residual ammonium salts in many filter papers may be sufficient to affect the analysis for nitrogen by the Kjeldahl method (see Section 37C-11). 

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