What is a filter? Chemical Experimental Instruments .

1. Chemical filters are used to remove chemical gas pollutants in the air to meet the needs of microelectronics, nuclear industry, pharmaceutical, chemical, environmental protection, laboratory animals, light industry and other industries. Most of the current chemical filters are activated carbon filters.

Second, the principle of adsorption:

Activated carbon selectively adsorbs gases instead of mechanically "filtering" impurities. There are a large number of micropores on the surface of activated carbon, most of which are smaller than <> pore size

The total internal surface area of micropores per unit of material is called "specific surface area", and the specific surface area can be as high as 700 2300 m2 g. When adsorption is involved, the harmful gases in the air are called "adsorbents", and activated carbon is the "adsorbent". Due to the gravitational pull between molecules, the adsorbate sticks to the inner surface of the pores.

If it is accompanied by a chemical reaction, it is called chemical adsorption, otherwise it is physical adsorption. At the same time that the adsorbate is adsorbed by the adsorbent, some of the adsorbate will be detached from the adsorbent, which is called "desorption". In use, the adsorption capacity will continue to weaken, the desorption will increase, and the activated carbon will be scrapped to a certain extent.

Sometimes, heating or steam fumigation detachs the adsorbate from the adsorbent and regenerates the activated carbon.

3. Activated carbon materials:

Activated carbon materials are divided into granular carbon and fiber carbon. Traditional granular activated carbon includes coal charcoal, wood charcoal, coconut shell charcoal, and bone charcoal. Sometimes, granular charcoal is made into a powder, adhered to other porous materials, and then processed into shape.

Fiber activated carbon is made from organic fibers containing carbon. It has a small pore size, large adsorption capacity, fast adsorption and fast regeneration. Commonly used fiber substrates are phenolic, plant fiber, polyacrylonitrile, and asphalt.

4. Activated carbon adsorption performance:

Adsorption capacity For a certain gas, the maximum amount that can be adsorbed per unit of activated carbon is called "adsorption capacity". Different materials, or adsorption of different gases, have different adsorption capacities. Residence time The time it takes for the air flow to pass through the activated carbon layer is called the "residence time".

The longer the residence time, the more adequate the adsorption. In order to maintain sufficient residence time, the carbon layer should be thick enough and the filtration air speed should not be too high. Service life The new activated carbon has high adsorption efficiency, the efficiency is constantly attenuating in use, and the filter is scrapped when the concentration of harmful substances downstream of the filter is close to the allowable range.

The service life before scrapping is the service life, also known as the "penetration time".

It refers to the filtration device. Instruments include: funnels, beakers, filter paper, funnel racks (or iron frames with iron rings).

For example, funnel: put the filter paper into the filter funnel, and the fold angle of the filter paper should be consistent with the funnel angle; The edge of the filter paper should be lower than the mouth of the funnel (about 5 mm), and at the same time moisten the filter paper with water so that it fits snugly against the funnel, and the liquid level poured into the funnel should be lower than the edge of the filter paper, so that the filter can be pulled.

Filtration [this paragraph] Definition Filtration refers to the screening of eligible solubles from an existing batch of substances and the removal of another part of the insoluble substances that do not meet the criteria. Filtration cannot remove the solubles, and the solubles can only be evaporated.

Passes the fluid through filter paper or other porous materials to separate the solid particles or harmful components it contains. Principle A method of separating liquids from liquid-insoluble solids by taking advantage of differences in the solubility of substances. For example, a small amount of sediment in crude salt is removed by filtration [this paragraph] Experimental instruments funnels, beakers, glass rods, iron frames, and filter paper.

This paragraph] operation essentials to achieve "one stick, two low, three leaning". (See photo).

One sticker: That is, the filter paper is close to the inner wall of the funnel.

Two low 1The edge of the filter paper is lower than the edge of the funnel.

2.The liquid level is lower than the edge of the filter paper.

Three by 1The beaker of the mixture is placed next to the glass rod.

2.The lower end of the glass rod is close to the third layer of filter paper.

3.The lower end of the funnel is close to the inner wall of the beaker. [this paragraph] note 1The mixture in the beaker is stirred with a glass rod before filtration and then filtered.

2.If the solution is still turbid after filtration, it should be filtered again until the solution becomes transparent.

3.Washing method of precipitation in the filter: add distilled water to the filter with a flask or dropper to make the water surface cover without sediment, and after the solution is all filtered out, repeat 2 3 times.

4.When doing purification experiments, it is necessary to extinguish the water before it evaporates, otherwise the crystals will scatter and harm the human body.

Filter media for industrial use.

Gehuajing: the use of imported polymer raw materials production, is the latest environmental protection products, it is widely used in the steady decline of large factories and mining enterprises, disinfection, filtration, etc., for breeding, sugar, papermaking, tap water purification, oil drilling, chemical refining, large oil depots, new chemical textile dust and other units to use, it uses imported equipment production, with acid resistance, alkali resistance, high temperature resistance, corrosion resistance, wear resistance and other advantages, to avoid the disadvantages of poor effect of domestic raw materials, short life.

Reasons for failure 1. The filter paper function fails.

1.The filter paper is broken.

Causes:1The lower end of the glass rod rests against a layer of filter paper. (The filter paper is punctured) 2The beaker containing the mixture is not pressed against the glass rod. (The filter paper is broken by the mixture).

2.The mixture is not filtered.

Cause: The liquid level is higher than the edge of the filter paper. (The mixture runs directly down from the filter paper and funnel).

Two. The instrument is not clean.

1.The lower end of the funnel is not clean.

2.The beaker below where the filtrate is collected is not clean.

In both cases, the filtrate is cloudy.

1. Original: funnel (main material glass), beaker, glass rod, iron frame (including iron ring), filter paper or filter membrane.

2. Passage silver is used: filter flask, beaker, glass rod, filter membrane.

3. Vacuum: more vacuum pumps than atmospheric pressure filtration, and at the same time, it has high requirements for filter bottles and good sealing. Pressurization: The equipment required for multi-pressure filtration is more than normal pressure, and the materials required for corresponding changes are not glass products.

The filter theory is a theory proposed by Broadband in 1958 to explain the role of attentional selection, arguing that the nervous system has a limit in terms of its capacity to process information.

Rationale: The experimental study of the selective effects of attention was initiated by Cherry. In one experiment, Cherry presented two materials to both ears at the same time, and asked the subjects to follow aloud the material they heard in one ear, and Edari checked the information obtained from the other ear.

The former is called Mengshi rough follow-up manuscript follow-ear, and the latter is called non-follow-up ear. It was found that the participants received very little information from the non-following ear. This shows that information that enters from the following ear is further processed and processed because it is noticed, while information that enters from the non-following ear is not accepted by people because it is not noticed.

Experimental instruments: funnel, beaker, glass rod, iron frame (including iron ring), filter paper.

Filtration is the operation of separating the liquid (or gas) in the suspension (or the hot gas containing solid particles) under the action of pushing force or other external forces, and the solid particles and other substances are intercepted by the filter medium, so that the solid and other substances are separated from the liquid (or gas).

Manufacture of filters.

Take a round filter paper, fold it in half and fold it in half, open it 1:3, put it in the funnel to make it close to the funnel wall, press the index finger on the three-layer filter paper, and take the waste liquid tank and put it under the funnel to receive water. Wet the filter paper with a rubber tip dropper, put the dropper back, take the glass rod to drive out the bubbles, put the glass rod back, and put the waste liquid tank back.

Take the iron frame in front of you, put the filtrate beaker on the iron frame, put the funnel on the iron ring, and the lower end of the funnel has a long pointed mouth against the wall of the beaker.

Beakers, funnels, ironclad platforms, glass rods, filter paper, etc

Beakers, funnels, iron stands, glass rods, filter paper, iron rings.

Cups, funnels, iron stands, glass rods, filter paper.

Beakers, funnels, iron stands, stirring rods, filter paper.

Iron stand, glass rod, funnel, beaker, filter paper.

Beakers, stirring rods, iron racks, funnels, filter paper.

When you talk about filter theory, you mean the filter theory of cognitive processing in psychology.

The filter theory, developed by Broadbent, states that our attention is a filter that selects one part of the information for cognitive processing and blocks the other.

Broadbent used a binaural hearing division task to prove the filter theory. The participants were asked to listen to different content with their left and right ears, and then the participants were divided into two groups, and each group repeated what they heard with both ears. But the first group has no chronological order, that is, the left ear hears 123, the right ear hears 456, then the result is 123456, any arrangement is correct.

The second group has a chronological order, that is, the number heard first is written first.

ResultsThe accuracy rate of the first group was much higher than that of the second group. Broadbent's explanation for this is that the first group has a high accuracy rate because there is no order requirement, which only requires a shift of attention, listening to the left ear first and then the right ear. In the second group, because of the order requirement, the attention had to be shifted every time a number was heard.

For example, if the left ear hears 1, the right ear hears 2, and the left ear hears 3, that is 123. So the accuracy rate is relatively low.

However, Murray's "cocktail effect" proves that the filter theory is seriously flawed. However, as an early theory of psychological cognition, it still has a great contribution to the field of psychological cognition.

Filtration is a commonly used method of separating mixtures, and there are various filtration methods, commonly used in laboratories (filter paper) as the filter layer, and (activated carbon) (fine sand) can also be used as the filter layer in actual production and life

In addition to this, the laboratory separates the mixture, as well as crystallization, recrystallization, distillation and extraction.

1.Filtration. Filtration is a method of separating insoluble solids from liquids. Depending on the nature of the components in the mixture, different methods such as atmospheric filtration, vacuum filtration or thermal filtration can be used. The commonly used method of atmospheric pressure filtration in middle schools is to use an ordinary glass funnel as a filter and filter paper as a filter medium.

When the mixture is filtered, the resulting clear liquid is the filtrate, and the solid particles left on the filter medium are the filter residue;

2.Crystallized. The principle of precipitation of crystals from solution of solid substances is often used in production or scientific research to separate soluble mixtures or remove some soluble impurities. The method of separating this mixture is called the crystallization method. The crystallization method can be divided into crystallization, recrystallization (or recrystallization) and step-by-step crystallization.

For example, the main components of bittern are MgCl2 and NaCl, followed by MgSO4, and the less content is KCL.

3.Fractionation, distillation separates mixtures with relatively large differences in boiling points;

4.Extraction.

This is a method of extracting solutes from other solvents by using one solvent to take advantage of the difference in solubility of solutes in immiscible solvents. For example, carbon tetrachloride is used to extract iodine from iodine water.

There are ordinary filtration, thermal filtration, and vacuum filtration.