E 200, Polyaluminium Chloride, Aluminum hydroxychloride, PAC, PALC, OCAL, Locron, Astringen 10,1327-41-9, 101707-17-9, 11097-68-0, 114442-10-3

E 200, Polyaluminium Chloride, Aluminum hydroxychloride, PAC, PALC, OCAL, Locron, Astringen 10,1327-41-9, 101707-17-9, 11097-68-0, 114442-10-3

CAS: 1327-41-9;101707-17-9;11097-68-0;114442-10-3

Molecular Formula: AlClHO

Names and Identifiers

Physico-chemical Properties

Upstream Downstream Industry

Introduction

Poly aluminum chloride is a water purification material, inorganic polymer coagulant, also referred to as Poly aluminum, abbreviated as PAC, an inorganic polymer water treatment agent having a relatively large molecular weight and a relatively high charge is produced due to bridging action of hydroxide ions and polymerization of polyvalent anions. In the form can be divided into two kinds of solid and liquid. Solid according to different colors are divided into Tan, beige, golden yellow and white, liquid can appear as colorless transparent, yellowish, light yellow to yellow brown. Different colors of Poly aluminum chloride in the application and production technology are also quite different.

Poly aluminum chloride is an inorganic polymer coagulant, also referred to as Poly aluminum, abbreviated as PAC, an inorganic polymer water treatment agent having a relatively large molecular weight and a relatively high charge is produced due to bridging action of hydroxide ions and polymerization of polyvalent anions. In the form can be divided into two kinds of solid and liquid, and solid according to different colors are divided into brown, yellow and white, different colors of Poly aluminum chloride in the application and production technology are also quite different.

White polymeric aluminum chloride is also known as a polymer coagulant. Is by aluminum hydroxide powder and high purity hydrochloric acid by spray drying processing of a white or milky white milk powder like fine powder, exposed in the air is very easy to melt. White polyaluminum chloride has replaced aluminum sulfate as a neutral sizing precipitant in the paper industry.

Technical indicators

Nature

The liquid product of polyaluminum chloride is a light yellow to brown yellow suspension, and the solid product is a light yellow or orange yellow crystalline powder. It is composed of a series of inorganic polymer compounds with different degrees of polymerization, and has the best morphological distribution. The content of alumina in the transition product is more than 8%, and the content of alumina in the solid product is 20% ~ 40%. Strong removal of organic toxicants and heavy metal ions, stable traits. Soluble in water, the hydrolysis process is accompanied by electrochemical, coagulation, adsorption and precipitation and other physical and chemical processes.

Preparation Method

using industrial aluminum chips to make water purification agent polyaluminum chloride is a simple and economical method, because the main components of industrial aluminum chips are aluminum (94%), aluminum oxide (0.5%), impurities (5.5%), the purity of the water purifying agent after polymerization is relatively high, the production process is relatively simple, and the product after reaction can be cured. Polyaluminum chloride can also be obtained by acid dissolution of aluminum ash.

Preparation Method

using industrial aluminum chips to make water purification agent polyaluminum chloride is a simple and economical method, because the main components of industrial aluminum chips are aluminum (94%), aluminum oxide (0.5%), impurities (5.5%), the purity of the water purifying agent after polymerization is relatively high, the production process is relatively simple, and the product after reaction can be cured. Polyaluminum chloride can also be obtained by acid dissolution of aluminum ash.

Advantages

PAC polyaluminum chloride has good spray drying stability, wide adaptability to water area, fast hydrolysis speed, strong adsorption ability, large alum flower formation, dense precipitation and low effluent turbidity, dehydration performance and other advantages, in the case of the same water quality, spray drying polyaluminum chloride dosage is reduced, especially in the case of poor water quality, spray drying product dosage compared with drum drying polyaluminum chloride, can be reduced by half, not only reduce the labor intensity of workers, and more important is to reduce the cost of water production.

In addition, the use of spray drying products can ensure safety, reduce water accidents, and is very safe and reliable for drinking water. Polymeric aluminum chloride, referred to as high-efficiency poly aluminum chloride, or high-efficiency PAC. The use of the most advanced production technology, the use of high-efficiency reaction polymerization of high-quality raw materials. Zhuqing all quality indicators have reached or even more than the national standard GB15892-2009 requirements. Poly aluminum chloride is processed by spray drying process. Therefore, it can also be called high efficiency spray drying Poly aluminum chloride. Poly aluminum chloride PAC product characteristics: kaibiyuan brand PAC products with fine powder, uniform particles, soluble in water, flocculation effect is good, high efficiency and stability, less dosage, low cost. Suitable for drinking water purification, urban water purification and industrial water purification and other aspects; Suitable for all kinds of turbidity of the source water, PH wide range of application, alum flower formation, fast, fast settling speed.

PAC Poly aluminum chloride water insoluble: the use of plate and frame filter technology, the solid water insoluble mass fraction of 0.3% or less, liquid water insoluble mass fraction of 0.1% or less, to ensure the smooth flow of the user's pipeline, while improving the use of drugs, and the natural sedimentation method is not up to. Polyaluminium chloride PAC-01 (light yellow powder, spray-dried): used for drinking water treatment and wastewater treatment. Poly aluminum chloride-is one of the star products in the water treatment medicament series. Poly aluminum chloride combines the advantages of ordinary Poly aluminum chloride, spray type Poly aluminum chloride, paper-making special high efficiency poly aluminum chloride and many other advantages. All water treatment pharmaceutical products to the latest national standard for the inspection standard, water treatment agents to GB15892-2009 for the detection standard.

Water treatment agent-efficient polymeric aluminum chloride is the best inorganic polymer water treatment agent in China, the treatment of various concentrations of water effect is quite good, and the dosage is small, its dosage is 50% less than the same concentration of ferrous sulfate, 10% less than the same concentration of polymeric aluminum chloride. High effect, low energy is mainly the high degree of polymerization of PAFC, because the general Iron Salt, aluminum salt water treatment agent in the hydrolysis process can only produce AL(OH)2 +, AL(OH)+2, fe (OH)2 +, Fe(OH)+2 and other simple hydrolysis of hydroxyl ions, and PAEC itself is AL3 +, Fe3 + Pre-aqueous intermediate product, it in the hydrolysis process in addition to the formation of the above hydroxyl ions, it can mainly generate a large number of degree of polymerization, positive charge from: AL4(OH)4+8, Fe4(OH)4+8...... Isopolyhydroxy cations are used to neutralize the charge of colloidal particles in water and compress the electric double layer, and a series of reactions such as hydroxyl bridging, cross-linking and surface adsorption occur at the same time. Under the corresponding collision, large alum flowers are condensed, rapid precipitation.

Use

basic aluminum chloride is a new type of inorganic polymer flocculant, which is an efficient, fast and low consumption water treatment agent. In the water and the negative charge of the colloidal particles with the instant neutralization, so that the colloidal de-stable, colloidal particles quickly flocculate, and further bridge the formation of large flocs and rapid precipitation. The turbidity removal effect is 1. 5~3 times of aluminum sulfate according to the comparison of effective components. The flocculation effect of low temperature turbidity water and high turbidity water is incomparable to ordinary inorganic coagulant. Widely used in urban water treatment, water reuse treatment, urban sewage treatment, oilfield reinjection water treatment, circulating cooling water treatment, industrial water treatment and papermaking, printing and dyeing, leather, ceramics, metallurgy, mining, oil, fluoride, coal washing and other industrial wastewater treatment. The effective dosage of the product is 20~50mg/L. The liquid product can be directly metered and added, and the solid product needs to be prepared into 10% ~ 15% solution in the dissolution tank before it is metered and added according to the required concentration. Polyaluminum chloride can also be used in papermaking sizing, casting molding, pharmaceutical refining, cosmetics manufacturing, Catalyst Carrier, sludge dewatering, cement quick setting, fabric wrinkle prevention, sugar liquid, glycerin refining and so on.

Proportioning method

According to the daily use of solid polymeric aluminum chloride PAC, diluted into liquid, summarizes and shares several commonly used polymeric aluminum chloride PAC concentration ratio method, I hope to help you!

In the first step, according to the raw water condition, a small test is made before use to obtain the optimal dosage. Test Solution Configuration according to the weight ratio (W/W), generally with 2 ~ 5%. For example, prepare 3% solution: weigh 3g of polyaluminum chloride PAC solid, put it in a 200ml measuring cylinder, add about 50ml of clear water, dilute it to 100ml scale after it is dissolved, and shake it well.

In the second step, when the polyaluminum chloride PAC is used for production, the polyaluminum chloride PAC solid: Water = 1:9 to 1:15 weight ratio may be mixed and dissolved. Alumina content of less than 1% of the solution is easy to hydrolysis, will reduce the use effect, the concentration is too high to add uniform.

In the third step, the dosage is added according to the optimal dosage obtained by small-scale test. If the amount of alum in the sedimentation tank is small and the remaining turbidity is large, the dosage is too small; If the amount of alum in the sedimentation tank is large and turned up and the remaining turbidity is high, the dosage is too large and should be adjusted appropriately.

Safety

if it is corrosive, it should be immediately rinsed with water if it is accidentally spattered on the skin. Production personnel to do a good job of protection, production equipment to be sealed, found that the leakage should be promptly washed with a large amount of water. The polyaluminum chloride liquid product may be stored in a cement tank. Solid products are easy to absorb moisture, but the use effect is not affected by moisture absorption. It shall not be stored in combination with a mixture of toxic and hazardous substances. There is no risk of explosion and combustion.

Degree of basicity

The basicity of Poly aluminum chloride is a relatively important indicator of Poly aluminum, especially for drinking water grade poly aluminum products, this standard is one of the important indicators of Poly aluminum production line control production. The lower the salt base degree, the higher the price, the purchaser can operate according to the actual situation of the factory. In addition, different raw materials, different processes for the production of polymeric aluminum chloride products are also different, which requires the manufacturer to adjust. Increasing the basicity of polyaluminum chloride products can greatly improve the economic benefits of production and use. When the basicity is increased from 65% to 92%, the cost of raw materials can be reduced by 20% and the cost of use can be reduced by 40%.
Poly aluminum chloride features:

1. The floc has fast forming, good activity and good filterability.
2. no need to add alkaline additives, in case of deliquescence, the effect is unchanged.
3. adapt to wide pH value, strong adaptability, wide range of uses.
4. the treated water was low in salt.
5. can remove heavy metals and radioactive substances on water pollution.
6. the active ingredient is high, easy to store and transport.

Color

There are several kinds of colors, the market sales of Poly aluminum chloride is more mixed, because each manufacturer's production process and raw materials are different, the color of the production is also somewhat different, generally white, yellow, yellow brown these three colors of Poly aluminum chloride, the following to illustrate the use of three different colors under the difference.

within the scope of the national standard of aluminum dioxide content between 27-30 poly aluminum chloride is mostly yellow to yellow light yellow solid powder. These types of Poly aluminum chloride water soluble better, in the dissolution process accompanied by electrochemical, coagulation, adsorption and precipitation and other physical and chemical changes in the final formation of [Al2(OH)3(OH)3]& prop;↓, so as to achieve the purpose of purification. Therefore, in the use of Poly aluminum chloride, without the addition of other additives, floc formation is fast and coarse, high activity, rapid precipitation, the purification effect of high turbidity water is obvious

• White polyaluminum chloride is called high-purity iron-free white polyaluminum chloride, or food grade white polyaluminum chloride. Compared with other polyaluminum chloride, it is the highest quality product, hydrochloric acid, the use of the production process is the most advanced technology spray drying method. White polyaluminum chloride is used in many fields such as papermaking sizing agent, sugar decolorizing and clarifying agent, tanning, medicine, cosmetics, precision casting and water treatment.
• the raw materials of yellow polyaluminum chloride are calcium aluminate powder, hydrochloric acid and bauxite, which are mainly used in sewage treatment and drinking water treatment. If the raw materials for drinking water treatment are aluminum hydroxide powder, hydrochloric acid and slightly calcium aluminate powder, to take the process is the plate and frame pressure filtration process or spray drying process, due to the treatment of drinking water in the country has strict requirements on heavy metals, therefore, both the raw materials and the production process are better than the brown poly aluminum chloride. Yellow polymeric aluminum chloride is generally produced by drum drying or spray tower drying, and there are two solid forms of flaky and powdery.
• Brown polymeric aluminum chloride raw materials are calcium aluminate powder, hydrochloric acid, bauxite and iron powder. The production process is the use of drum drying method, generally used for sewage treatment, because the inside added iron powder so the color is brown, iron powder added more color, iron powder if more than a certain amount in some times also known as poly aluminum ferric chloride, in the sewage treatment has excellent effect.

reparation Method

There are many synthetic methods of Poly aluminum chloride, which can be divided into metal aluminum method, active aluminum hydroxide method, aluminum oxide method, aluminum chloride method and so on according to different raw materials.

metal aluminum method

The raw materials for the synthesis of Poly aluminum chloride by metal aluminum method are mainly the waste materials of aluminum processing, such as aluminum dust, aluminum ash and aluminum slag. The aluminum ash is reacted by slowly adding hydrochloric acid at a certain ratio under stirring, and the liquid polymeric aluminum chloride is prepared by aging polymerization and sedimentation, and then diluted, filtered, concentrated and dried. In the process can be divided into acid method, alkali method, neutralization method 3. The acid method mainly uses HCl, the product quality is not easy to control; The production process of alkali method is difficult, the equipment investment is large, the amount of alkali is large, the pH control cost of raw materials, the cost is high; the most used is the neutralization method, as long as the control ratio, generally can reach the national standard.

aluminum hydroxide method

The purity of aluminum hydroxide powder is relatively high, and the content of toxic substances such as heavy metals in the synthesized polyaluminum chloride is low. The production process of heating and pressure acid dissolution is generally adopted. This process is relatively simple, but the production of polymeric aluminum chloride base degree is low, so the general use of aluminum hydroxide heating pressure acid dissolution plus calcium aluminate ore powder neutralization two steps.

three alumina method

The raw materials containing aluminum oxide mainly include gibbsite, alumina clay, kaolin, coal gangue and so on. The production process can be divided into two steps: the first step is to obtain crystalline aluminum chloride, the second step is to obtain polymeric aluminum chloride by pyrolysis or neutralization method;

aluminum chloride method

using aluminum chloride powder as raw material, the processing of Poly aluminum chloride. This method is most commonly used. Can be used for boiling pyrolysis of crystalline aluminum chloride at 170 deg C, add water aging polymerization, and then cured, dried.

alkali dissolution method

first, the aluminum ash is reacted with sodium hydroxide to obtain a sodium aluminate solution, and then the pH value is adjusted by hydrochloric acid to prepare a polymeric aluminum chloride solution. The product prepared by this method has good color appearance, less water insoluble matter, but high sodium chloride content, high consumption of raw materials, low alumina content in solution, and high industrial production cost.

Effect

The flocculation effect of poly (aluminum chloride) is as follows:

• Strong electro-neutralization of colloidal substances in water.
• hydrolysis products of suspended solids in water excellent bridging adsorption.
• selective adsorption of soluble substances.

Poly aluminum chloride is a kind of inorganic polymer coagulant, due to the bridging effect of hydroxide ions and the polymerization of polyvalent anions and the production of large molecular weight, high charge inorganic polymer water treatment agent) the characteristics are mainly determined by the working principle of the pressure atomizer.

Performance

1. the purified water quality is better than that of aluminum sulfate flocculant, and the cost of water purification is 15-30% lower than that.
2. The floc formation is fast and the settling speed is fast, which is larger than that of traditional products such as aluminum sulfate.
3. the alkalinity of the consumed water is lower than that of various inorganic flocculants, and thus no or less alkali agent may be administered.
4. to adapt to the source water PH5.0-9.0 range can be condensed.
5. the corrosion is small and the operating conditions are good.
6. The solubility is better than that of aluminum sulfate.
7. the increase of salt in the treated water is less, which is beneficial to ion exchange treatment and high purity water preparation.
8. has better adaptability to source water temperature than inorganic flocculants such as aluminum sulfate.

Classification

morphological classification

polyaluminum chloride forms are divided into two types

1. liquid polyaluminum chloride is an undried form, which has the advantages of no dilution, convenient handling and use, and relatively cheap price. The disadvantage is that the transportation requires a tank truck, unit transport costs increase (per ton of solid equivalent to 2-3 tons of liquid), more suitable for users within 100.
2. solid polymeric aluminum chloride is the form of liquid polymeric aluminum chloride after drying. It has the advantages of convenient transportation and does not need a tank truck.

Process Classification

1. roller Poly (aluminum chloride) aluminum content in general, high water insoluble, mostly used for sewage treatment.
2. plate-and-frame Poly (aluminum) chloride has high aluminum content and low water-insoluble content, and is used for sewage treatment and drinking water treatment.
3. spray dried Poly (aluminum) chloride aluminum content is high, water insoluble matter is low, dissolution speed is fast, used for drinking water and higher standard water treatment.

Use

1. urban water supply and drainage purification: river water, reservoir water, groundwater.
2. Industrial water purification.
3. municipal wastewater treatment.
4. the recovery of useful substances in industrial waste water and waste residue, the promotion of coal dust sedimentation in coal washing wastewater, and the recovery of starch in starch manufacturing industry.
5. various industrial wastewater treatment: printing and dyeing wastewater, leather wastewater, fluoride wastewater, heavy metal wastewater, oily wastewater, paper wastewater, coal washing wastewater, mine wastewater, brewing wastewater, metallurgical wastewater, meat processing wastewater, sewage treatment.
6. paper sizing.
7. refined sugar solution.
8. casting molding.
9. fabric anti-wrinkle.
10. catalyst support.
11. pharmaceutical refining
12. rapid setting of cement.
13. cosmetic raw materials.

Method of use

The solid product is dissolved into liquid by adding water at 1:3, and then diluted with 10-30 times of clear water to the required concentration before use. The optimal pH value is 3.5-5.0, and the maximum benefit of coagulation can be obtained by selecting the optimal pH value. The dosage can be determined according to the different turbidity of raw water, the best dosage, the general raw water turbidity in 100-500mg/L, the dosage of 10-20kg per thousand tons. When the turbidity of raw water is high, the dosage is appropriately increased, and when the turbidity is low, the dosage can be appropriately decreased.

for use in rural areas, the medicament can be put into a water tank, stirred evenly, and allowed to stand. The supernatant can be used, and about 1g of the medicament is added per 50kg. If this medicine is used in combination with the high molecular flocculant produced by the company, the effect will be better. Dosing can be the company's production of anionic polyacrylamide or cationic polyacrylamide with PAC dissolved into a composite flocculant after use or the PAC is added to the treated water to form aggregates, after the addition of the company's production of anionic polyacrylamide adsorption bridging into large flocs.

The dosage of Poly aluminum chloride in different water quality:

1. In low turbidity water, dilute the solid polyaluminum chloride product with tap water at a ratio of 1:3 (weight ratio) and stir until completely dissolved
Second, in the life, production of sewage, with reference to each ton of sewage to add about 30g of polymeric aluminum chloride products. Then add the diluted polyacrylamide product, (if the effect is not obvious, please reduce or increase the dosage of the product as appropriate.)
Third, in the paper mill sewage treatment, the proportion of low turbidity water is used, if the effect is not obvious, it can be added at discretion.
Four, the raw water turbidity in 100-500mg/L, the dosage of 5-10mg per thousand tons of water dosage of 5-10kg, before use is best according to the water quality characteristics of small test, select the best value, and then put into use.

The proportion of commonly used sewage:

Packaging

Poly aluminum chloride packaging and precautions

1. plastic woven bag for external use, with plastic film set, each net weight 25kg, can also be modified according to user requirements, and other liquid polymeric aluminum chloride sales.
2. the product shall not be mixed with toxic substances, transported and stored. The product shall be stored in a dry, ventilated and cool place indoors, and shall not be affected by moisture.
3. when loading and unloading should be handled with care, solid product storage period of one year.

Precautions

Poly aluminum chloride Use note:

1. should be used according to the water quality of small test, select the effect of water purification is good, the best point of small volume. The solution should be used with, non drinking water should be selected according to the actual situation.
2. when a solid is used, water is first added to dissolve and prepare a 10-25% solution, and then diluted with water to a desired concentration. When dissolved, water is first added and slowly charged, and stirring is continued.
3. water treatment chemicals from different manufacturers or different grades shall not be mixed, and shall not be mixed with other chemicals.
4. the stock solution and diluent are slightly corrosive, but lower than other inorganic flocculants.
5. Product effective storage period: liquid half year, solid two years. Solid products can still be used after tide.
6. after reasonable dosing, the purified water quality meets the hygienic standard of drinking water.

Coagulation process

1. Coagulation stage: it is a process in which the liquid medicine is injected into the coagulation tank and the raw water is rapidly coagulated to form fine alum flowers in a very short time. At this time, the water body becomes more turbid, it requires the flow of water to produce intense turbulence. Beaker experiment should be rapid (250-300 r/min) stirring 10-30s, generally not more than 2min.
2. flocculation stage: it is the process of alum flower growth and coarsening, which requires appropriate turbulence degree and sufficient residence time (10-15min), and a large number of alum flowers can be observed in the late stage, A clear surface layer was formed. The Beaker experiment was stirred at 150 r/min for about 6 minutes and then at 60 r/min for about 4 minutes until it was in suspension.
3. sedimentation stage: it is the sedimentation process of floc in the sedimentation tank, which requires slow water flow. In order to improve the efficiency, the Inclined Tube (plate) is generally used. Sedimentation Tank (it is best to use the air flotation method to separate the floc), a large number of coarse alum flower is blocked by the Inclined Tube (plate) wall and deposited at the bottom of the tank, the upper layer of water is clear water, the remaining particle size is small, the Alum with small density decreased slowly, and continued to collide with each other. The remaining turbidity remained unchanged in the later period. Beaker experiment should be 20-30 r/min slow mixing 5 minutes, and then 10 minutes of static sedimentation, measurement of turbidity.
4. enhanced filtration, mainly is the reasonable selection of filter layer structure and filter aid, in order to improve the removal rate of filter, it is an important measure to improve water quality.
5. This product is applied to the treatment of environmental protection and industrial wastewater, and the use method is basically the same as that of the water plant. For the raw water treatment with high chroma, high COD and BOD, the effect of auxiliary agent is very good.
6. the use of chemical coagulation method of enterprises, the original equipment does not need to make a large transformation, only the addition of dissolved alum pool can use this product.
7. This product must be kept in a dry, moisture-proof, heat-proof place (<80oC, do not damage the packaging, the product can be stored for a long time).
8. This product must be dissolved to use, dissolution equipment and dosing facilities should use corrosion-resistant materials.

Water purification principle

compressed electric double layer

The structure of the electric double layer of the micelle determines that the concentration of the counter ion at the surface of the colloidal particle is the largest, and the higher the distance from the surface of the colloidal particle is, the lower the counter ion concentration is, and the final ion concentration is equal to that in the solution. When an electrolyte is added to the solution to increase the concentration of ions in the solution, the thickness of the diffusion layer decreases.

when the two colloidal particles are close to each other, the zeta potential decreases due to the decrease of the thickness of the diffusion layer, so the force of their mutual exclusion is reduced, that is, the Inter-gel repulsion of a high ion concentration in the solution is smaller than that of a low ion concentration. The suction between the colloidal particles is not affected by the composition of the aqueous phase, but due to the diffusion thinning, the distance when they collide is reduced, so that the mutual suction is large. It can be seen that the resultant force of repulsion and attraction changes from the repulsive force to the suction force (the repulsive potential energy disappears), and the colloidal particles are rapidly condensed. This mechanism can better explain the deposition phenomenon in the harbor. When fresh water enters the seawater, the salt increases, the ion concentration increases, and the stability of the fresh water entrained colloidal particles decreases, therefore, clay and other colloidal particles are easily deposited in the harbor.

According to this mechanism, when the added electrolyte in the solution exceeds the critical concentration of condensation, there will be no more excess counterions entering the diffusion layer, it is not possible to change the symbol of the colloidal particles and re-stabilize the colloidal particles. This mechanism is to explain the effect of electrolyte on the de-stabilization of colloidal particles by simple electrostatic phenomenon, but it does not consider the role of other properties (such as adsorption) in the process of de-stabilization, therefore, other complicated destabilization phenomena can not be explained. For example, if the dosage of trivalent aluminum salt and iron salt as coagulant is too large, the coagulation effect will decrease and even stabilize again; another example with the colloidal particles with the same number of polymer or polymer organic matter may have a good coagulation effect: isoelectric state should have the best coagulation effect, but often in production practice, when the potential is greater than zero, the coagulation effect is the least.
In fact, the addition of coagulant in aqueous solution to destabilize colloidal particles involves the interaction of colloidal particles and coagulant, colloidal particles and aqueous solution, coagulant and aqueous solution, which is a comprehensive phenomenon.

adsorption neutralization

adsorption electric neutralization means that the particle surface has a strong adsorption effect on the different-sign ions, the different-sign colloidal particles or the chain-like charged parts of the molecule, since this adsorption neutralizes part of its charge and reduces the electrostatic repulsion, it is easy to get close to other particles and adsorb each other. Electrostatic attraction is often the main aspect of these effects at this time, but in many cases, other effects outweigh electrostatic attraction.

For example, the turbidity caused by the removal of negatively charged silver iodide solution with Na and dodecyl ammonium ions (C12H25NH3), it is found that the same monovalent organic amine ions are much more unstable than Na, and the excessive addition of Na will not cause the colloidal particles to stabilize, while the organic amine ions are not, more than a certain dosage can make the colloidal particle re-stable phenomenon, indicating that the colloidal particle adsorbed too much counter ion, so that the original negative charge into a positive charge. When the dosage of aluminum salt and iron salt is high, the phenomenon of re-stabilization and the change of charge will also occur. The above phenomena are suitably explained by the mechanism of adsorption electro-neutralization.

adsorption bridging

The mechanism of adsorption and bridging mainly refers to the adsorption and bridging of polymeric substances and colloidal particles. It is also understood that two large colloidal particles of the same number are linked together due to the presence of one distinct colloidal particle. Polymeric flocculants have a linear structure, and they have chemical groups that can act on some parts of the surface of the colloidal particles. When the high polymer is in contact with the colloidal particles, the groups can react with the surface of the colloidal particles and adsorb each other, the rest of the polymer molecule is extended in solution and can be adsorbed with the colloidal particles with vacancies on the other surface, so that the polymer plays the role of bridging. If the amount of colloidal particles is small, the extended part of the above polymer does not adhere to the second colloidal particles, the extended part will be adsorbed on other parts of the original colloidal particles sooner or later, this polymer can not play a bridging role, and the colloidal particles are in a stable state. When the dosage of polymer flocculant is too large, the surface of the rubber particles will be saturated and the re stable phenomenon will occur. If the colloidal particles that have been bridged and flocculated are subjected to severe stirring for a long time, the bridging polymer may be detached from the surface of another colloidal particle and rewound back to the surface of the original colloidal particle, resulting in a re-stable state.

The adsorption of polymer on the surface of colloidal particles comes from various physical and chemical effects, such as Van der Waals attraction, electrostatic attraction, hydrogen bond, coordination bond, etc., depending on the characteristics of the chemical structure of polymer and colloidal particle surface. This mechanism can explain the phenomenon that non-ionic or ionic polymer flocculants with the same number can obtain good flocculation effect.

mechanism of sediment net capture

when metal salts (such as aluminum sulfate or ferric chloride) or metal oxides and hydroxides (such as lime) are used as the coagulant, when the dosage is large enough to rapidly precipitate metal hydroxides (e. G., Al(OH)3, Fe(OH)3, Mg(OH)2, or metal carbonates (e. G., CaCO3), colloidal particles in water can be captured by these precipitates as they form. When the precipitate is positively charged (Al(OH)3 and Fe(OH)3 in the neutral and acidic pH range), the precipitation rate can be accelerated by the presence of anions in the solution, for example, Silver sulfate ion. In addition, the colloidal particles in the water can be used as the core of the formation of these metal oxide precipitates, so the optimal dosage of the coagulant is inversely proportional to the concentration of the removed substances, that is, the more colloidal particles, the less the dosage of metal coagulant.

Sewage treatment

1: colloidal particles in sewage

in order to determine the process parameters of the water flocculation process, such as the type of flocculant, dosage, pH value of water, temperature and the dosing sequence of various agents, etc., the simulation experiment is generally done. Under the conditions of a certain water temperature and controlling the appropriate stirring intensity and time, the pH value of different color water is adjusted with different flocculants and dosages to see the flocculation effect.
The standard of American Society for Experimental materials ASTM2035-1980 (revised and confirmed in 1990) "flocculation of water, experimental method of flocculation Cup tank" is an advanced method. China and 1997 equivalent to the use of ASTM standard method, issued a national standard method.
The method includes three steps of rapid stirring, slow stirring and static settling. The added livestock coagulant is rapidly dispersed by rapid stirring and contacted with colloidal particles in the water, and the colloidal particles begin to aggregate to produce flocs. By slow stirring, the microflocs were further contacted with each other to grow into larger particles. After the stirring was stopped, the formed colloidal aggregates settled naturally to the bottom by gravity.
The method is suitable for determining the process parameters of the flocculation process of water, including: the type and dosage of flocculant, the pH value of water, the temperature, and the dosing sequence of various chemicals.
By measuring the turbidity and chroma of the water sample in the beaker experiment, the degree of colloid dehydration and aggregation can be known.

2: Procedure

1) the speed of the multi-position mixer can be adjusted from 20-150R/min. The mixing slurry is made of a light-weight corrosion-resistant material, and the size of the slurry is 60mm * 40mm * 2mm, and the shape is rectangular. A lighting device should be provided on the base or inside of the multi-position mixer, through which the formation of the floc can be observed. The size of the multi-position mixer and the mixing sheet should be 3/4 of the beaker.
2) beaker
The size of the beaker, the same shape, the volume of not less than 1500ml.

3, procedure

1) According to the number of beakers set by the multi-position stirrer, 100ml of each water sample was charged into the beaker, and the beaker was positioned. The stirred slurry was then placed in water. The axis of the pulp should be offset from the center of the beaker, and a gap of at least 6.4mm should be left between the pulp and the wall of the beaker. The temperature at the beginning of the experiment was recorded.
2) the flocculant is loaded into the test tube of the reagent rack. For administration, the agent in each tube was diluted to 10ml with water. If the dosage of one of the agents is greater than 10ml. Other tubes should also be hydrated until the volume and dosage are the same. When adding the suspension agent, the agent should be shaken before adding.
3) start the multi-position stirrer, stir rapidly at the speed of 120r/min, add the reagent to each beaker at the same time according to the predetermined dosage of reagent, and stir for 1min .
4) reduce the speed to 20-40R/min speed to keep the beaker particles evenly suspended. Slow stirring for about 20min. The time of initial floc generation was recorded.
5) after the slow stirring is completed, the stirring slurry is extracted from the water, the sedimentation of the floc is observed, and the time taken for most of the floc to settle is recorded. However, in a special case, the sedimentation is affected by convection, and the time of the sedimentation recorded at this time should be approximately the same as the number of unprecipitated flocs moving downward.
6) after 15min At the time of precipitation, the thickness of the floc at the bottom of the Beaker was recorded. The water sample was drawn at 1/2 of the night in the beaker with a pipette, and the cauterization, color and pH of the water sample were measured.

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