1. Decontamination and purification of river water The aluminum hydroxide particles often adsorb cationic colloidal particles and are positively charged. These positively charged AI(OH) 3 particles, when encountering negatively charged sio 2 -based mud colloidal particles in water, aggregate into larger particles by means of isoelectric attraction, by means of gravity The sedimentation is removed and the purpose of purifying the water is achieved. Soak it in 5% HCI solution (5% NaOH solution) for 2 h, rinse with pure water to pH 5 (8). Its reaction formula is as follows: Industrial products can be used for both hydrochloric acid and sodium hydroxide. The cation-removed water enters the cathode tower, and the anion exchange resin in the cathode tower adsorbs anions such as SO 4 2- and CI - in the water, and then desorbs the exchangeable group OH - on the exchange group, thus, the anion The hydroxide ions on the exchange resin exchange positions with the anion impurities contained in the water, and the anion impurities are adsorbed and removed by the resin. The ion exchange equation is as follows: The H+ ions exchanged by the yang tower and the OH - ions exchanged by the negative tower combine to form water. It can be seen from the regenerative reaction formula that after regeneration of the spent resin, the resin regains the exchangeable H + and OH - groups, thereby restoring the ability to exchange ions. However, in fact, regeneration can only replace the cation, anion or most of the resin adsorption. Therefore, after regeneration, the exchange capacity is lower than the original, and it can only be improved by continuous improvement to maximize the degree of regeneration. The relationship between the concentration of salt solution and freezing point Freezing point of brine / °C Saline concentration /% Relative density (10 ° C) -7 10 1.0742 -10.8 15 1.1127 -16.3 20 1.1525 -21.33 23.5 1.1797 Api 602 Gate Valve is samll forging shut off valve which widely used in all type system of thermal power plant. API 602 Gate Valve with solid wedge, bolt bonnet or welding bonnet type as well as full port or reduce port. Valve size from 1/2"(PN15) to 2"(PN50) matching pressure class 150(PN16) to class 2500(PN420). Valve connection can be NPT, BW, SW, RF. API 602 Gate Valve Api 602 Gate Valve,Alloy Steel Gate Valve,Api602 Gate Valve,Slab Gate Valve Yongjia South Trading Co.,Ltd , https://www.n-lvalve.com
Titanium white powder production, water consumption, manufacturers are often self-extraction purification treatment of river water, the water only to meet the requirements to become a regular use. River water has more impurities, mainly mud suspensions and other solid suspended matter mainly composed of sio 2 . After the suspension is passed through the sand filter, the coarse particle portion can be removed, but the fine particle portion needs to be treated with an iron- based or aluminum- based water purifying agent to be removed.
Suspensions based on sio 2 are often adsorbed with anionic colloidal particles and are negatively charged. The particles with the same negative charge are relatively stable due to the action of the electric repulsive repulsion, and can be maintained for a long period of time without sedimentation, so that it is difficult to remove.
In the tap water treatment, when an iron-based water purifying agent is added, the iron-based water purifying agent is hydrolyzed in water to form a flocculent iron hydroxide precipitate, and the ferric hydroxide is often adsorbed with cationic particles and is positively charged when it encounters a negative charge. The sediment suspended by sio 2 is the purpose of achieving water purification due to co-precipitation due to mutual attraction. However, there are often a small amount of iron hydroxide particles floating in the water. When washed with metatitanic acid, these particles accumulate on the surface of the filter cake and cover a layer of brown-yellow iron. These irons will eventually affect the finished titanium dioxide. The whiteness, therefore, the iron-based water purifying agent can only be applied to the removal of tap water, and can not be applied to the removal of titanium dioxide production water.
In the removal of titanium dioxide production water, it is necessary to use an aluminum-based (as an example of aluminum sulfate) water purifying agent. Hydrolysis of aluminum sulfate in water produces a precipitate of aluminum hydroxide with the following reaction formula: 
2. Ion exchange water should be used for water washing after bleaching of metatitanic acid, water treatment after post-treatment and water washing after coating.
The surface characteristics of the titanium dioxide particles themselves are hydrophilic and oleophobic, so water can be used as a dispersion medium for post-treatment water selection. However, ordinary tap water or purified river water contains various electrolytes, and ions in the water cause electrical neutralization of the surface of the titanium dioxide particles to cause agglomeration, especially in hard water. Therefore, the dispersion of iron white powder cannot use these waters, and it is necessary to use ion-exchanged deionized pure water.
There are certain water-soluble salts in the slurry after coating. The presence of these water-soluble salts will affect the paint performance of titanium dioxide, mainly affecting the grinding and dispersibility of the pigment, the storage stability of the paint, and the film. Water resistance and weather resistance. If it is washed with tap water or purified river water, it contains impurities such as Ca 2+ , Mg 2+ , Na + , SO 4 2+ , C1 -, etc., so washing with tap water does not achieve the purpose of removing water-soluble salts. Therefore, it must also be washed with ion-exchanged deionized water.
In the bleaching process, the reduced metatitanic acid is also required to be washed with water by deionized water.
Because the pure water prepared by the ion exchange method has the following advantages compared with the pure water obtained by the distillation method: 1 the purity of the water produced is high, which is equivalent to the purity of the secondary distilled water; 2 no fuel; 3 low cost; 4 equipment Simple, easy to assemble, easy to operate; 5 can be mass produced, suitable for industrial production needs, the above advantages are unmatched for the distillation method. Therefore, industrially, pure water produced by ion exchange has gradually replaced the pure water produced by distillation. [next]
Third, the composition and classification of ion exchange resins
The ion exchange resin is a polymer compound having exchangeable ion properties and is composed of the following two parts.
1 The exchanger body is a copolymer composed of a polymer compound and a crosslinking agent, and is a skeleton of an ion exchanger;
2 The exchange group is composed of a positive (anionic) ion capable of exchange and some ions of the linked skeleton.
The resin can be classified into two types: a cation exchange resin containing a cation exchange group (such as a 732 type resin) and an anion exchange resin containing an anion exchange group (such as a 711 type resin).
Fourth, the new resin before the pretreatment method
The newly purchased resins often contain impurities and low molecular organics, which affect the exchange capacity of the resin. Therefore, the new resin must be pretreated before use. The pretreatment methods are dynamic (both in the column) and static (soaked in the container). Practice has proved that the dynamic method is superior to the static method both in economic and effect.
The steps of resin pretreatment are as follows: a male (yin) ion exchange resin is placed in a male (female) column, and water is immersed for more than 12 hours to fully expand the resin, emptied, and rinsed with water to remove pigment, water-soluble and insoluble impurities. Wash until the water is colorless and transparent, soak it in ethanol solution containing 1% NaCl for 24h to remove the aromatic and alcohol-soluble substances, rinse with water until there is no ethanol smell, add 5% HCI solution (5% NaOH solution) soak 12h, rinse with water to pH 4-5 (8-9), soak for 4h with 5% NaOH solution (5% HCl solution), rinse with water to pH 8-9 (4-5), then yang ( The resin has been transformed into a sodium type (chlorine type). Its transformation reaction is as follows:
Five, the principle of the production of ion exchange water
The ion exchange of water is carried out in an exchange column, and the column in which the cation exchange resin is placed is called a yang tower or a male bed; the column in which the anion exchange resin is placed is called a negative column or an anion bed. Because the cation and anion impurities in the water are removed, the yang tower and the cathode tower are generally used in series. The water tower is required to increase the water quality. In order to remove the suspended solids in the water, a sand filter tower is arranged in front of the yang tower. Or pool), in order to reduce the burden of the tower, add a degassing tower in front of the tower to rush to the carbon dioxide in the water.
The ordinary water is passed through the sand filter tower, that is, into the yang tower, and the cation exchange resin in the yang tower first adsorbs cations such as Ca 2+ , Mg 2+ , Na + in the water, and then exchanges the groups on the exchange group. H+ is desorbed, so that the hydrogen ions on the cation exchange resin exchange positions with the cation impurities contained in the water, and the cationic impurities are adsorbed and removed by the cation exchange resin. The ion exchange equation is as follows: [next]
Finally, the water was passed through the mixing tower and reacted again to obtain pure water.
The principle of pure water by ion exchange method is to remove or reduce various ions in water to a certain extent by the exchange of ion exchange resin according to the above equation of ion exchange reaction.
6. Method for producing pure water by the inspection institute
The method of producing pure water by the inspection is as follows.
1Ca 2+ , Mg 2+ ion test Take 10 mL of water, add ammonia - chlorination buffer 1 mL, add a trace of chrome black T indicator, if not blue is qualified.
2S0 4 2- ion test Take 10 mL of water and add a few drops of cesium chloride reagent. If there is no white precipitate, it means no S0 4 2- ion.
3 Chloride (Cl - ) test Take 10 mL of water, add 1 drop of acid acid, add 2-3 drops of silver nitrate test solution, if it does not appear white turbidity, it is qualified.
4 pH test water lOmL, add methyl red indicator 2-3 drops, if not red, it means not acidic; another water lOmL, add 2-3 thymol blue indicator 2-3 drops, if not blue Color means no basicity.
5 Determination of resistivity 1 (1: Some water units do not require high water quality, resistivity and acidity, alkalinity can be exempted from inspection) Check with micro-ampere meter, if the resistivity is greater than 300kΩ is qualified.
Seven, the reason for the resin to be regenerated
In the process of preparing pure water, water and a female, respectively cation anion and cation exchange resin on the OH - or H + exchange groups. When the ion exchange resin in the OH - and H + groups are exchanged after "finished", the resin in water will lose the female, the ability to continue cation exchange resin adsorbing impurity ions i.e. has reached saturation, at this time is called invalid. When the failure of the ion exchange resin, then adsorbed on ion exchange resins of anion and cation removal, exchange new OH - or H + groups, so as to regain the female-exchanged water, the cation capacity, which is referred to as resin regeneration.
Eight, resin regeneration method
The regeneration of the resin includes three processes of backwashing, regeneration, and washing.
1. Backwashing The purpose of backwashing is mainly to flush out bubbles, suspended impurities and agglomerates in the resin layer to ensure that the regenerant is free to pass through the resin layer, thereby improving the regeneration efficiency. The backwashed water passes through the resin layer from bottom to top, and the resin layer is shaken by water. The influent flow rate is increased from small to large until no bubbles remain in the resin layer as an end point.
2. Regeneration (reduction)
The regenerant hydrochloric acid can be diluted with water at a concentration of about 5%. Must use water or dilute sodium cation bed water to avoid precipitation of magnesium hydroxide and pollution ion exchange resin concentration of approximately 2%.
The flow direction of the regenerant can be from top to bottom (referred to as downstream regeneration) or from bottom to top (referred to as countercurrent regeneration). Countercurrent regeneration has many advantages compared to the two methods. When countercurrent regeneration is used, the regenerant consumes less and the effluent quality is good, which is a relatively new regeneration process. The regeneration time is generally considered to be 30-60 min for the yang tower and 60-90 min for the yin tower. [next]
If a mixing tower is used, the resin in the tower is made up of a mixture of male and female resins. The method for regeneration can be prepared by using a commercially available clean salt to form a 10% NaCl solution, and immersed in a mixing tower for 2 hours, so that the cation exchange resin will sink to the bottom, the anion exchange resin will float, and then the layered resin will be separately taken out. Then, add acid or alkali according to the above method, and after processing, mix and then re-install the tower.
3. Washing After the resin is regenerated, the regenerant remaining in the exchange column must be rinsed clean. The initial wash is the continuation of regeneration and the speed cannot exceed the speed of regeneration. When the regenerant is washed, the flow rate can be increased until the operating flow rate is approached. In the process of washing, the quality of the discharged water will continue to increase, and when the quality of the product reaches the requirement, it means that the end of the washing has arrived.
For the water source being washed, tap water can be used for the cation exchange resin; for the anion exchange resin, at least the positive water is used for the positive wash. If tap water is used, it is easy to form precipitates of calcium carbonate and magnesium hydroxide to contaminate the resin.
Regeneration is an exchange resin that is rendered ineffective by dilute acid or dilute alkali, and the adsorbed cations and anions are replaced by H + and OH - ions in the acid and alkali, respectively. The regeneration process is actually the reverse of the exchange reaction. Its reaction formula is as follows:
Nine, storage resin needs to pay attention to matters
When the resin is stored for a long period of time, it should be made into a neutral salt type and washed with pure water. In order to prevent cracking of the resin when it is dried, the resin is preferably immersed in the cooked water. If the resin is dehydrated for some reason during storage, do not use water to soak it. This will cause the sudden and rapid expansion of the resin to break. Generally, it should be soaked in a saturated sodium chloride solution, and then gradually diluted with a salt solution to restore the resin to the cooked water.
The storage temperature of the resin should not be too high and should not exceed 40 °C.
When the resin is stored below 0 ° C, it is necessary to prevent freezing and cracking of the resin. The resin can be stored in a salt solution, and the concentration of the salt solution can be determined according to specific temperature conditions (see table below).