What is ion exchange resin?
Ion exchange resin is a kind of synthetic functional polymer material containing active groups, which is made of cross-linked polymer copolymer by introducing different nature of ion exchange groups. In its molecular structure, one part is the matrix skeleton of the resin, which has a net-like structure and is chemically stable and insoluble in acids, bases and general solvents; the other part is the active group composed of fixed ions and exchangeable ions, and there are dissociable ions in the active group, and the ion exchange reaction actually takes place in the active group.
How do ion exchange resins work?
The ion exchange resin is mainly used to produce pure water by "ion exchange method": the cations (calcium, magnesium, copper, sodium and other metal ions) and anions (carbonate, nitrate, sulfate and other non-metal ions) generated by the ionization of various inorganic salts in the raw water, after the cation and anion resin layer (ion exchange agent in the ion exchange column), and the resin Hydrogen ions and hydroxide ions are adsorbed by the resin, and the hydrogen ions and hydroxide ions replaced from the resin are combined into water molecules (H2O), thus achieving the effect of removing inorganic salts from the water and achieving the purpose of making desalinated pure water.
Since ion exchange is reversible, used ion exchange resins are generally washed with an appropriate concentration of inorganic acid or alkali to restore them to their original state and reuse them, a process called regeneration. Cation exchange resin can be washed with dilute hydrochloric acid, dilute sulfuric acid and other solutions; anion exchange resin can be treated with sodium hydroxide and other solutions for regeneration.
The main production processes of ion exchange resins.
There are many varieties of ion exchange resins, and most of the ion exchange resins currently in use are based on styrene - diethylene-benzene copolymer and copolymer of acrylic acid and its derivatives with diethylene-benzene. The upstream industry of ion exchange resins is the petrochemical industry. The main raw materials for the production of ion exchange resins include styrene, divinylbenzene, methyl acrylate, sulfuric acid, etc. In addition, dozens of chemical raw materials such as methanol, chloromethyl ether, methylal, etc. are involved.
What are ion exchange resins used for?
(1) Sewage treatment: The demand for ion exchange resins in the sewage treatment industry is large, accounting for about 90% of the production of ion exchange resins for the removal of various anions and cations in water. At present, the large use of ion exchange resin is used in the pure water treatment of thermal power stations, followed by atomic energy, semiconductor materials, electronics industry, etc.
(2) food industry: ion exchange resin can be used in sugar, chicken essence, wine special, biological products and other industrial equipment. For example: fructose syrup is manufactured by extracting starch from bracted rice, then by hydrolysis reaction to produce fructose and glucose, and then by ion exchange method, it can be transformed into fructose syrup. The use of ion exchange resin in the food industry is in the position after sewage treatment.
(3) Pharmaceutical industry industry: pharmaceutical industry ion exchange resin has an important role in the development of new antibacterial drugs and the quality improvement of the original antibacterial drugs. The successful development and design of streptomycin is a prominent example. In recent years, we have also conducted research on the extraction of herbal medicines.
(4) Generation of chemical and crude oil chemicals: In organic chemistry, acids and bases are commonly used as metal catalysts for esterification reactions, hydrolysis reactions, ester exchange, hydration and other reactions. Using ion exchange resin instead of strong oxidant and alkali, the above reactions can also be carried out, and the advantages are more. For example, the resin can be used continuously, the product can be separated out easily, the tubular reactor will not be leached and will not pollute the environment, the reaction can be controlled easily, and other advantages.
The production of methyl tert-butyl ether (MTBE) is made by reacting isobutylene with ethanol using large-plate pore ion exchange resin as catalyst, which replaces the original tetraethyl lead that can cause pollution to the environment.
(5) Eco-environmental protection: ion exchange resins have been applied in many very concerned eco-environmental protection issues. At present, many solutions or non-solutions with toxic positive or non-positive ions can be recycled with the resin. Such as the removal of positive metal ions in electroplating process wastewater, the acquisition of effective substances in film production wastewater, etc.
(6) Wet metallurgy and other industries: Ion exchange resins can be used to separate, extract and purify uranium from depleted uranium ores and to acquire rare earth elements and precious metals.
What is ion exchange resin method?
1. Pre-selection. The particle size of ion exchange resin is generally controlled at 20-35 mesh, some can reach 50 mesh, so it should be dried, crushed and sieved before use, usually dried in an oven, or in a drier with phosphorus pentoxide, calcium oxide or concentrated sulfuric acid, and not divided too fine when crushed, otherwise it will affect the experimental yield.
2、Pre-treatment. Strongly basic ion exchange resin should first be treated with 20 times the volume of resin 4% sodium hydroxide aqueous solution (is the resin into OH type), then washed with 10 times the volume of water, then treated with 10 times the amount of 4% hydrochloric acid (is the resin into chlorine type), and finally washed with distilled water to neutral, then the chlorine type into OH type, and then into chlorine type, and finally treated with 10 times 4% sodium hydroxide aqueous solution. Weakly alkaline ion exchange resin treatment only needs to be washed with 10 times the amount of distilled water, without washing to neutral.
3、Load the column. The treated resin to the beaker, add water and stir fully to remove air bubbles, stand for a few minutes to wait for most of the resin to settle, pour away the upper layer of muddy particles; repeated operations until the upper layer of liquid clarified, you can load the column. Note to put 1cm of glass wire at the bottom of the column, flatten it with a glass rod, pour the resin into the column, and also pay attention to prevent air bubbles.
4、Resin exchange. The sample is prepared into a certain concentration of aqueous solution and passed through the column at an appropriate flow rate, or the sample solution can be repeatedly passed through the column until the components are completely exchanged. Use the colorimetric method to test whether the components are exchanged completely.
5、Resin elution. Note that the components with weak affinity are washed down first. Commonly used ion exchange resin eluents are strong acids, strong bases, salts, different pH buffer solutions, organic solutions, etc. Gradient elution or single concentration elution can be selected.
6、Resin regeneration.
The impact of COVID-19 on the ion exchange resin ultrapure water industry
2020 due to the impact of the new crown pneumonia epidemic, the market demand for laboratory and medical ultrapure water machine is also forecast to increase. Laboratory ultrapure water machines and medical ultrapure water machines are essential equipment needs for both medical and research industries. The polishing resin, an important consumable for ultrapure water machines, will also see an increase in market share demand.
