The development of ion exchange method, the principle of ion exchange

Due to the rapid development of ultrafiltration membranes and reverse osmosis membranes, ion exchange methods are gradually withdrawing from the market in many fields.

Especially in industries with large water treatment, such as power plants and water plants, because the membrane treatment covers a small area (as far as we have seen so far, the same produced water occupies at least half of the area) and is easy to maintain, even if the initial investment is larger than the ion exchange method, many new water treatment projects still use the membrane treatment.

However, some technologies of ion exchange method are not yet able to be achieved by membrane method, and the purity of effluent is lower than that of mixed bed, so it is necessary to prepare high purity water grades.

Membrane + ion exchange is often used as a mixture, or EDI is added. There are also some equipment that cannot be replaced by ion exchange equipment for the time being, such as high-speed mixed beds.

The development direction of ion exchange is that the resin exchange speed is faster, and the structure is more stable and durable. Switching capacity is greater in these aspects.

To be honest, I am not optimistic about the future of ion exchange, I just learned this, and after graduation, I have also used ion exchange and membrane method in power plants, the advantages of membrane method are too great, small footprint, simple maintenance, and maintenance generally does not involve acid and alkali (except for chemical cleaning). Only the mixed bed is a good thing, and the membrane method can only use EDI to achieve the same effect, which is higher than the investment and operation cost of the mixed bed, although the land occupation and maintenance are still disadvantages, but the cost is much higher than that of the mixed bed.

The above is what I know about the situation of ion exchange in the water treatment industry, as for other ion exchange methods, such as chromatography, extraction and other laboratory uses, I don't know (

Looking at the type of resin and the history of development, you can look for Rohm and Haas resin in the United States, which is the world's largest resin manufacturer, and the quality is also the best batch.

It is a way forward for chemical reactions from experiment to production!

Ion exchange principleIon exchange is the process of separating liquid mixtures containing electrolytes using ion exchangers, most commonly ion exchange resins.

The ion exchange process is a process of mass transfer (including external diffusion and internal diffusion) and chemical reaction (ion exchange reaction) between liquid and solid phases.

The ion exchange reaction is generally reversible, and the exchanged ions can be desorbed (reverse exchange) under certain conditions, so that the ion exchanger can be restored to its original state, that is, the ion exchanger can be used repeatedly through exchange and regeneration. At the same time, the ion exchange reaction is carried out quantitatively.

How EDI works:

EDI is a pure water manufacturing technology that combines ion exchange technology, ion exchange membrane technology, and ion electromigration technology (electrodialysis technology).

This technology uses ion exchange energy for deep desalination to overcome electrodialysis polarization and incomplete desalination, and uses electrodialysis polarization to generate H and OH ions to achieve resin self-regeneration to overcome the defects of chemical regeneration after resin failure.

Since the 80s of the 20th century, new technologies have gradually emerged, and after more than ten years of development, EDI technology has occupied a considerable part of the ultrapure water market in North America and Europe.

The principle of ion exchange, you can read the manual or search for this knowledge on the Internet.

The ion exchange process can be summarized as follows: 1Ions in water diffuse to the surface of the resin in an aqueous solution2Ions in water enter the cross-network pores of the resin particles and diffuse3

The ions in the water come into contact with the resin exchange group, and the metathesis reaction occurs, and the ion exchange is carried out4The ions that are exchanged diffuse to the surface of the resin in the cross-network pores of the resin5The main factors affecting the exchange of the exchanged ions to the aqueous solution are flow rate, concentration of raw material solution, temperature, etc.

Flow rateThe flow rate of the raw solution actually reflects the time to reach the equilibrium of the reaction, and in the exchange process, the ions undergo a series of steps of diffusion-exchange-diffusion, and it is important to effectively control the flow rate. In general, the higher the flow rate of the exchange solution, the higher the dialysis volume of ions, and the greater the amount of ions lost through the resin layer during future exchange. Therefore, it is necessary to select the appropriate flow rate according to the exchange capacity, etc.

The exchangeable ions in the raw material concentration resin and the isosexual ions in the solution may be exchanged, and may also be repulsive, the liquid phase ion concentration is high, the resin has many contact opportunities, and it is easier to enter the resin mesh, and the liquid phase concentration is low, and the resin exchange capacity is large, the opposite is true. However, if the concentration of liquid phase ions is too high, it will cause the shrinkage of the cross-network pores on the surface and inside of the resin, and will also affect the ion entering the mesh. Experiments show that when the flow rate is constant, the higher the concentration of the solution, the greater the loss of solute.

The higher the temperature, the more intense the thermal motion of the ions. The number of collisions per unit time increases, resulting in a faster reaction rate. However, if the temperature is too high, the adsorption strength of ions will be reduced, and even the thermal stability of the resin will be affected, which is economically unfavorable.

The anisosexual attraction of the negatively charged group passes through the membrane and enters the concentrator chamber on the right. The negatively charged anions, moving towards the anode, to the anisotropic membrane, are attracted by the anisotropic phase of the positively charged groups on the membrane and pass through the membrane and enter the concentrator chamber on the left. 3. Reverse osmosis method to prepare pure water, principle osmosis:

The phenomenon of solvent entering a solution through a semi-permeable membrane (a membrane that allows solvent molecules to pass through but does not allow solute molecules to pass through) or the natural penetration of solvent from a dilute solution to a relatively concentrated solution. Osmolality: The pressure at which the penetration of a dilute solution into a concentrated solution stops.

Definition of reverse osmosis: add a higher pressure than the natural osmotic pressure on one side of the concentrated liquid, twist the direction of osmosis, and press the solvent in the concentrated solution into the dilute solution on the other side of the semi-permeable membrane, which is contrary to the normal osmosis process in nature. If reverse osmosis exerts a pressure that exceeds the natural osmotic pressure of the solution, the solvent will flow through the semi-permeable membrane, forming a dilute solution on the opposite side and a more concentrated solution on the pressurized side.

Ion exchange is an important method for isolating, purifying, and treating ions. The basic principle of hand counting is to use some specific solid material (called Phi Shou ion exchange resin) to react with ions in solution, adsorb one ion from the solution to the resin surface, and release the other ion into the solution grip.

Ion exchange resins are typically made of polymeric materials with functional groups that can adsorb or release ions. These functional groups can be cationic groups (e.g., -NH3+, -SO3-, etc.) or anionic groups (e.g., -COO-、- PO4-, etc.). The choice of ion exchange resin depends on the type and nature of the ions that need to be purified or separated.

There are two main types of ion exchange methods: cation exchange and anion exchange. In cation exchange, the cationic groups on the resin are able to adsorb and exchange anions in solution; In anion exchange, the anionic group on the resin adsorbs and exchanges the cations in the solution.

1. Ion exchange is the use of ion exchangers (the most common is ion exchange resins) to separate electrolytes.

The process of liquid mixtures. The ion exchange process is a chemical reaction of mass transfer (including external diffusion and internal diffusion) between liquid and solid phases.

Ion exchange reaction) process, usually the ion exchange reaction proceeds quickly, and the process rate is mainly determined by the mass transfer rate.

2. The ion exchange reaction is generally reversible, and the ions that are exchanged under a certain number of pieces can be desorbed (reverse exchange) to restore the ion exchanger to its original state, that is, the ion exchanger can be used repeatedly through exchange and regeneration. At the same time, the ion exchange reaction is carried out quantitatively, so the exchange capacity of the ion exchanger (the equivalent of the ions that can be exchanged per unit mass of the ion exchanger.

number or moles) is limited.

Ion exchange is the process of separating liquid mixtures containing electrolytes using ion exchangers, most commonly ion hand-holding exchange resins. The ion exchange process is a process of mass transfer (including external diffusion and internal diffusion) and chemical reaction (ion exchange reaction) between liquid and solid phases.

Ion exchange is a reversible equivalent intersectional stool exchange reaction. Ion exchange resins are sandwiched between anion and cation exchange membranes to form a single processing unit and form a freshwater chamber. The ion exchange rate decreases with the increase of resin cross-linking degree and increases with the decrease of particles.

Ion exchange is a liquid-solid reaction process, which necessarily involves the diffusion process of substances in the liquid phase and the solid phase.

Some cations in the aqueous solution enter the counterion layer, and the cations that were originally in the counterion layer enter the aqueous solution, and this homogeneous ion exchange between the counterion layer and the aqueous solution at normal concentrations is called ion exchange. Ion exchange mainly occurs between the diffusion layer and the normal aqueous solution, because the surface of clay particles usually carries a negative charge, so the ion exchange is mainly cation exchange, so it is also called cation exchange. Ion exchange strictly obeys the law of equivalence, which states that the cations entering the counterion layer are equal to the equivalents of the cations being displaced out of the counterion layer.

Ion exchange is the exchange of ions in a solid ion exchanger with ions in a dilute solution to achieve the purpose of extracting or removing certain ions in the solution. It is a unit operation that belongs to the mass transfer separation process.

Ion exchange method.

I. Introduction. Ion exchange process is a reversible chemical reaction between ions in the liquid phase and ions in the solid phase, when some ions in the liquid phase are more preferred by ion exchange solids, they will be adsorbed by ion exchange solids, in order to maintain the electric neutrality of the aqueous solution, so the ion exchange solids must release equivalent ions back into the solution.

Ion exchange resins are generally porous or granular, and their size is about, and their ion exchange capacity can be divided according to their exchange capacity characteristics

Strong acid cation exchange resin: mainly contains strong acidic reaction groups such as sulfonic acid group (SO3H), this ion exchange resin can exchange all cations.

Weak acid cation exchange resin: with weak reaction groups such as carboxyl groups (COOH groups), this ion exchange resin can only exchange cations in weak bases, such as Kinlu-resistant Ca2+, Mg2+, and cannot exchange ions in strong bases, such as Ca2+, K+, etc.

Strong alkali anion exchange resin: mainly contains strong reactive groups such as N+(CH3)3 with tetrahedral ammonium salt functional group, in the form of hydroxide, the hydroxide ions in N+(CH3)3OH- can be quickly released for exchange, and the strong alkaline anion exchange resin can be exchanged with all anions for removal.

Weak basic anion exchange resin: with weak reaction groups such as amino groups, it can only remove anions in strong acids such as SO42-, Cl or NO3, and cannot be removed for HCO3, CO32 or SiO42.

Whether it is ion exchange resin or zeolite, it has a certain concentration of exchangeable groups in Mingchun, which is called ion exchange capacityFor cation exchange resins, it's about 200 500 meq 100 gBecause cation exchange is a chemical reaction, the law of mass balance must be observed.

The general equation for ion exchange resins can be expressed as follows:

For the full article, please see: Ion Exchange Basics.

In order to remove ionic impurities from water, the most common method is ion exchange. This method can completely remove ionic impurities in the water, so that it can make very pure water. Therefore, it is a necessary step in the preparation process of boiler water for thermal power plants.

Ion exchange treatment must be carried out with a substance called an ion exchanger. When this substance encounters water, it can exchange a certain ion with the same symbol in the water, and there are many types of ion exchangers, including natural and artificial, organic and inorganic, cationic and anionic, etc., as shown in the table. In addition, according to the structural characteristics, there are macroporous type and gel type.

Please see the full text:

1. Selection and treatment of resin; Column loading process; the exchange process; Elution process.

2. Ion exchange separation method is a method of separating the exchange agent from the ion generation in the solution, and it is a solid-liquid separation method. It is widely used in water treatment, medicine, metallurgy, chemical industry and other fields.

3. The ion exchange separation method is a method of separating the exchange agent from the ion exchange in the solution, which is a method of solid-liquid separation. Natural ion exchangers contain clay, zeolite, starch, cellulose, protein, etc., but the most important categories in practical applications are ion exchange resins, ion exchange membranes, etc. Ion exchange resins are further divided into acid ion exchange resins, alkaline ion exchange resins, neutral ion exchange resins, etc.

The process of ion exchange is that the ions in the exchanger and the ions in the solution realize the equal charge exchange on the total amount, so as to achieve the effect of separating the target ions in the solution. For details, please refer to the ion exchange resin entry.