KR100733286B1 - Manufacturing method of high basicity aluminium chloride coagulants - Google Patents

Abstract

A method capable of economically preparing an aluminium chloride-based coagulant that has a basicity of 60 to 70%, and can maintain stability for 6 months or longer is provided. In a method of preparing an aluminum chloride-based coagulant for water treatment, a method of preparing a high basicity aluminium chloride-based coagulant with an Al2O3 concentration of 7 to 15 wt.% and a basicity of 60 to 70% comprises stabilizing the homogenized product at 40 to 100 deg.C for 5 to 15 hours after homogenizing a polyaluminum chloride solution having a basicity of 30 to 55% and an Al2O3 concentration of 8 to 18 wt.% with sodium aluminate containing 5 to 25 wt.% of Al2O3 and 4 to 23 wt.% of Na2O for 3 to 60 minutes in a homogenizing reactor in which an agitation rate is maintained to a range from 5000 to 15000 revolutions per minute.

Description

Manufacturing method of high basicity aluminum chloride coagulant {Manufacturing method of high basicity Aluminum chloride coagulants}

1 is a graph comparing the flocculation performance of the flocculant of the present invention and PAC having a basicity of 45%.

Figure 2 is a graph comparing the flocculation performance of the flocculant of the present invention and PAC.

Figure 3 is a graph comparing the stability of the conventional polybasic silicate aluminum sulfate sulfate coagulant and the coagulant of the present invention.

The present invention relates to a method for producing an aluminum chloride flocculant for water treatment, which is used for water treatment or wastewater treatment. Polyaluminum chloride (Poly Aluminum Chloride: PAC) and Poly Aluminum Chloride Silicate (PACS) are generally used as the flocculant for water treatment, but recently, the basicity is 70% or more. Polyaluminum Hydroxy Chloro-Sulfate Silicate (hereinafter referred to as PAHCSS) has also been developed as a coagulant with a high level of coagulant. In the aluminum chloride-based flocculant, the basicity is calculated as follows by the ratio divided by the number of hydroxide ions that can bind the number of hydroxide ions bound to the aluminum ions.

It is well known in the art that the aluminum chloride-based flocculant is more easily prepared with a higher base, and the higher the ionization of the aluminum ion is, the higher the coagulation effect can be obtained with a small dosage according to Schultz-hardy's law. .

 PAC and PACS form polymers through polymerization of aluminum ions compared to monosulfate aluminum sulfate, but the basicity shows only about 40 ~ 55%, which is more satisfactory than the basicity of 60 ~ 70% coagulant. Insufficient as a flocculant. In addition, PAHCSS and PACC (Poly Aluminum Calcium Chloride) are highly coagulants having a basicity of more than 70%, but the stability is not secured, and less than three months later, precipitation occurs and the cohesiveness is lowered.

The present invention relates to a method for producing a high basic degree of aluminum chloride-based flocculant, which can be produced in an economical manner with an aluminum chloride-based flocculant having a basicity of 60 to 70% and can maintain stability for 6 months or more.

There are many known methods for producing a high base aluminum chloride-based flocculant.

Korean Patent No. 0245194 discloses a mixture of polyaluminum chloride (PAC) and a carbonate slurry such as Na ₂ CO ₃ , followed by reaction in a liquid phase at a temperature of 90 to 150 ° C. and a pressure of 3 to 6 atmospheres, and represented by the following general formula: It describes about the method of manufacturing a water treatment agent.

AlM _a (OH) _b Cl _c

In the above formula, M is any one of Na, Ca, and Mg metals, a is the number of moles of the metal, and a, b, and c each satisfy the following ranges.

3 + a = b + c, 0≤a≤1.5, 0.5≤b≤2.5, 0.5≤c≤2.5

PAC is generally prepared by pressurizing Al (OH) ₃ and HCl with a small amount of a polymerization accelerator such as sulfate.

Republic of Korea Patent Registration No. 0497992 discloses an _{Al (OH) 3 15 ~ 18wt} % the concentration of _{Al 2 O 3 40 ~ 68%} , 25 ~ 35% HCl 50 ~ 75wt%, 50 ~ 80% H 2 SO 4 0.5 ~ 10wt %, 0.6-25 wt% of water was mixed, and then reacted at 90-125 ° C. for 5-20 hours to prepare aluminum sulfate (AlClSO ₄ ) having an Al ₂ O ₃ concentration of 9-14% and a basicity of 10 or less. The mixture obtained by mixing 46-74.99wt% of the aluminum chloride sulfate 9-14%, NaOH 10-15wt%, 15-40% NaOH, 0.01-10wt% sodium silicate and 15-35wt% water was 30-60 ℃. A method of producing polysilicate aluminum sulfate [Al _x (OH) _y Cl ₂ (SO ₄ ) _i (SiO ₂ )] by reacting at a temperature is described.

In Korean Patent No. 0192872, a calcium compound is mixed with a mixed solution of polyaluminum chloride and aluminum hydroxide and reacted at 50 to 190 ° C. and 4 to 10 atm to obtain polyaluminum calcium chloride [AlCa _x (OH) _y Cl _z ] Is described.

Conventionally, the method for preparing the aluminum chloride-based flocculant basically adopts a method of increasing the basicity by reacting aluminum hydroxide with an acid to produce an aluminum flocculant having a low base such as PAC and then reacting it with a weak alkaline substance. The conventional method for preparing a high base water flocculant for water treatment is prepared by increasing the basicity by adding an alkaline agent to the basicity lowered by the addition of acid, and the general reaction is as follows.

Al (OH) ₃ (100% base) + acid → low base flocculant (10-50% base)

Low baseline flocculant + alkali → high baseline flocculant (60 to 70% of base) + salt

This method is relatively easy to make a high base flocculant, but lowers the basicity of the entire aluminum and then increases it, which increases the consumption of alkali and increases the manufacturing process costs. Above all, the lack of stability of the produced product is causing problems such as instability of the cohesive performance during long-term storage.

It is an object of the present invention to provide a method for economically preparing an aluminum chloride-based flocculant, which has a basicity of 60 to 70% and can maintain stability for 6 months or more.

In the above, when the high base also prepared the aluminum chloride-based flocculant, the coagulation performance may be improved by inducing polymerization of the aluminum chloride-based flocculant. However, when the high base is also a coagulant is not prepared in the aluminum salt of the polymer state there is a problem that the destabilization reaction to form a large amount of Al (OH) ₂ ⁺ ions in the product easily occurs Al (OH) ₃ precipitate. This precipitation formation was a fundamental problem with the aluminum chloride-based flocculant having a high base. In the case of the aluminum-based high base so far flocculant did not completely overcome this destabilization reaction, causing problems such as precipitation formation from about 3 to 4 months later has caused difficulties in the storage and use of the drug.

 In addition, the conventional high base also has a problem that is not economical to manufacture the coagulant by converting the basicity of all the aluminum ions.

                       Large amount of acid large amount of alkali

Basicity 100% (Al (OH) ₃ ) -------- → Low base Al ----------- → High base Al

The present inventors reacted the aqueous sodium phosphate solution and PAC in a homogenization reactor while stirring at a temperature of 50 to 60 ° C., and then stabilized the reaction mixture at 40 to 100 ° C. for 5 to 15 hours to reduce the amount of alkali used. The present invention was completed by confirming that an aluminum chloride-based flocculant having high stability and high stability can be produced.

In the present invention, a low base aluminum chloride-based flocculant such as PAC made by reacting aluminum hydroxide with acid is used sodium amine hydrate (NaAl (OH) ₄ , Sodium aluminate: hereinafter SA) made by reacting aluminum hydroxide with caustic soda. By using a homogenization reactor to a high base also relates to a method for producing an aluminum chloride-based flocculant.

When using SA to prepare a high base flocculant, it is very economical because it saves 20% and 50% more acid and alkali than the conventional method based on 13% of Al ₂ O ₃ and 65% of basicity. It's how. Preparation of flocculant using SA has been used in the past to produce polyaluminum silicate sulfate (PAS), PACS, and high base flocculant. However, PASS also has a problem of long-term stability has not been widely used. In addition, even when reacting SA with a low base flocculant, the acidic low base can not be directly reacted with the flocculant and the alkaline SA, but can be used after mixing with a silicate or the like. Therefore, the inventors of the present invention have attempted to easily prepare a high base flocculant using inexpensive SA, and to develop a flocculant having a stability of 6 months or more.

Aluminum ions go through the following steps depending on the degree of bonding to the hydroxyl group.

^{Al 3 +, Al (OH)} 2+, Al (OH) 2 +, Al (OH) 3 ( amorphous), Al (OH) ₃ (crystalline), Al (OH) ₄ ^-

In general, the aluminum ion in the inorganic coagulant has a + charge value, whereas the Al ⁺ ion in the coagulant gradually forms an Al (OH) ₃ precipitate over time. The low basicity and stability of the coagulant produced took longer than 1 year to form the precipitate, so there was no problem due to precipitation in the distribution and use of the product.However, the time required to form the precipitate due to the high degree of hydration of the product. This is so short that stability is a problem.

Therefore, in order to complete the present invention, the present inventors have found a reaction condition capable of improving stability and cohesive performance. A device for uniformly dispersing other liquid particles in a liquid to uniformly disperse the liquid mixture is called a homogenizer. In the present invention, a homogenization reactor having a high speed stirring blade is used. Homogenizer is a device capable of reacting acidic low base with flocculant and alkaline SA without precipitation. The high basic degree of flocculant made of the homogenization reactor is then stabilized in order to maintain stability, the present invention is completed.

In the present invention, there are two major improvements in the manufacturing method of the existing high base salt flocculant. First, various alkalis such as Na ₂ CO ₃ , NaHCO ₃ , Ca (HCO ₃ ) ₂ , [(MgCO ₃ ) ₄ ㆍ Mg (OH) ₂ ㆍ 4H ₂ O], etc. It is a manufacturing method to replace these with SA. The economic improvement obtained by using SA as an alkaline agent is briefly described as follows.

To prepare 1000g of high base salt coagulant with 13 wt% Al ₂ O ₃ and 65% basic acid, 45% basic product was prepared with low base salt coagulant, and then the method of Patent No. 245196, which uses Na ₂ CO ₃ , and the method of SA The amount of raw materials used can be seen that the method of the present invention is very economical.

[Table 1] Raw Material Consumption Comparison

The table above summarizes the reaction process below.

First, in the process of preparing low basicity PAC

Al (OH) ₃ + X HCl → Al (OH) _(3-X) Cl _X

Therefore, aluminum hydroxide with Al ₂ O ₃ 60% is required for 1000 × 0.17 / 0.6 〓 283 g to prepare 1,000g of low basicity with Al ₂ O ₃ and 45% basicity.

Since the Al equivalent number is 285 × 0.6 / 102 (Al ₂ O ₃ equivalent) × 6 (Al 2 × 3) 〓 10, the HCl requirement is (100-45)% of the amount of ions bound to aluminum when the base is 45%.

10 × (100-45) / 100 × 36.45 / 0.35 〓 573 (g) is required

Again, to prepare a product 1000g having a basicity of 65% and Al ₂ O ₃ 13wt%

Low baseline products require Al ₂ O ₃ of 17wt%, so 1000 × 13/17 〓 765 (g) is required, and final alkalinity is 45%, so if you supply the required alkali to Na ₂ CO ₃

765 × 0.17 × (0.65-0.45) / 102 × 106 (Na ₂ CO ₃ chemical formula) × 2 (Na ₂ CO ₃ is 2 base)

〓 81 (g)

The remaining water is 154 g

In the same way, the method of the present invention can be applied.

Aluminum hydroxide (60% Al ₂ O ₃ , 100% basicity) and 50wt% NaOH react to make Al ₂ O ₃ 21wt% and 140% SA 1000g aluminum hydroxide 350g, 50wt% NaOH is 395 g, 255 g of water,

In order to prepare 1,000 g of a product having a basicity of 65% and Al ₂ O ₃ 13wt%, the amount of low base product is A, SA is B and the binary first order system is solved.

  0.17 A + 0.21 B 〓 130 (13% 1000 g)

  0.45 A + 0.140 B 〓 650 (65% 1000 g)

Low baseline PAC products require 604 g, SA 130 g and 266 g water

When the basicity of the low base and flocculant as a raw material is 40%, the reduction rate is even greater.

[Table 2] Raw Material Consumption Comparison

Another advantage of the present invention is that by using a relatively small raw material can also reduce the unnecessary salt concentration in the product also helps to prevent the destabilization of the flocculant due to precipitation or the like.

SA is an alkali that was used to prepare PASS and PACS, which have a basicity of about 50% in the flocculant manufacturing process. However, Al (OH) _x ^{(3-x) +} compounds are very acidic in PACs with low basicity, and Al ions in Al are alkalinized with Al (OH) ₄ ⁻ in SA. There was a problem in that stabilization could not be achieved by forming an Al (OH) ₃ precipitate. Therefore, in the previous high baseline flocculant manufacturing reaction, there was a limit in producing a high baseline flocculant using SA despite the economics of SA. In particular, basicity high salt airway coagulant less than 60% is bound to be unstable is increased close to the most ion Al ion thin Al (OH) ₂ ⁺ when not upset polymer. Therefore, it is necessary to convert the polymer compound Al ₁₃ O ₄ (OH) ₂₄ (H ₂ O) ₁₂ ⁷⁺ and Al ₁₃ O ₄ (OH) ₂₆ (H ₂ O) ₁₀ ⁵⁺ to make the compound stable even at high bases. .

For the sake of the satisfactory reaction between the SA and the low base flocculant, the SA was diluted about 5-10% of Al ₂ O ₃ to react in a homogenization reactor, thereby inhibiting the formation of crystalline Al (OH) ₃ precipitate.

In addition, the stabilization process for polymerization is stirred at a linear speed (stirring blade speed) of 0.5 to 10 m / sec at a temperature in the range of 40 to 100 ° C., and a precipitation is formed even if stored for 6 months or more for 6 months. It has been found to be stable without degrading the cohesive performance.

Detailed embodiments of the present invention will be dealt with in the embodiments. However, the reactions mentioned in the examples may be replaced with flocculants of similar components and performance. For example, in the low base of the examples, PAC, which may be represented as Al (OH) _a Cl _b in the flocculant, is substituted with sulfate ion (SO ₄ ^-2 ) in the amount of about 5 to 20 wt% of the chlorine ion (Cl ⁻ ) equivalent in the PAC. It is also possible to mix the active silica component which can improve the cohesive performance in the final reaction product, such as 10wt% or less of the total Al ions equivalent. In addition, the homogenization reaction time may vary slightly depending on the amount of reactants and the performance of the homogenizer according to general experimental methods.

Example 1 (Preparation of Coagulant)

SA was prepared by mixing 350 g of Al ₂ O _{3 with} 60 wt% aluminum hydroxide, 495 g of caustic soda with 50 wt% NaOH, and 155 g of water. 55 g of SA having a concentration of 21 wt% of aluminum oxide (Al ₂ O ₃ ) and 19 wt% of sodium oxide (Na ₂ O) was slowly poured into 145 g of water which was stirred at 100 to 200 rpm at a temperature of 20 to 40 ° C. Dilute to prevent this from happening. 180 g of polyaluminum chloride having a concentration of 17 wt% of aluminum oxide (Al ₂ O ₃ ) and a basicity of 42% was stirred at a stirring speed of 5,000 rpm while maintaining the temperature at 50 to 60 ° C., and 120 g of SA diluted in the solution was stirred for 3 minutes. React with slow addition. The final mixture is stabilized at a temperature of 80 to 90 ° C., a polymerization time of 15 hours, and a stirring speed of 500 rpm. After the reaction was filtered to obtain 290 g of a coagulant as a colorless transparent solution. It can also be used as a flocculant for water treatment high base.

The flocculant prepared by this method has a chemical formula of AlNa _a (OH) _b Cl _{c. As} a result, the concentration of aluminum oxide (Al ₂ O ₃ ) is 12.5 wt% and the basicity is 62%.

Example 2 (Preparation of Coagulant)

3900 g of the SA dilution solution prepared by the method of Example 1 was added to 5100 g of polyaluminum chloride containing ¹⁷ wt% of aluminum oxide (Al ₂ O ₃ ), 43% basicity, and 5 wt% of sulfate ions (SO ₄ ^-2 ). Input and react. At this time, the reaction temperature is 30 ~ 40 ℃, the reaction time is 20 minutes, the stirring speed is 11,000rpm. The final mixture is stabilized at a temperature of 95 ° C., a reaction time of 10 hours, and a stirring speed of 200 rpm. Immediately after the reaction, the mixture was cooled to 30 ° C. or less and filtered to obtain 8900 g of a very pale, clear solution, which can be used as a coagulant for water treatment.

The flocculant prepared by this method has a chemical formula of AlNa _a (OH) _b Cl _c (SO ₄ ) _{d. As} a result of analysis, the concentration of aluminum oxide (Al ₂ O ₃ ) of the flocculant prepared by this method is 12.1 wt%, Was 65%.

Example 3 (Evaluation of Coagulant)

The coagulation performance between PAC and the present invention was compared between raw water in summer and winter in Korea. Using a flocculation device (Jar Tester of Kemira Flocculator 2000), it was subjected to rapid stirring 400rpm 30 seconds, slow stirring 50rpm 10 minutes, and stationary 20 minutes. After the supernatant was collected and turbidity was measured using a turbidity meter (model name: Hach 2100P Turbidity meter).

Figure 1 shows a comparison of the flocculant prepared by the method of Example 1 of the present invention and the coagulation performance for the PAC having a base weight of 45% Al ₂ O _{3 17} %. Raw water is pH 7.26, alkalinity 33.23mg / ℓ, turbidity 92.3 NTU, water temperature 27 ℃, when agglomerated with the present invention, it is necessary to use a large amount of flocculant due to the flow of high turbidity in summer or algae It can be seen that the cohesive performance is maintained even in the water condition.

Figure 2 shows a comparison of the flocculant prepared by the method of Example 1 of the present invention and the flocculation performance of the PAC of ₁₇ wt% Al ₂ O ₃ , 45% basicity. Using the flocculant, the flocculation performance was compared with respect to raw water having pH 7.52, alkalinity 46.40 mg / L, turbidity 1.95 NTU, and water temperature of 3.3 to 4.0 ° C.

The invention used in this experiment had an aluminum oxide (Al ₂ O ₃ ) concentration of 12.5 wt%, a basicity of 62%, a specific gravity of 1.3, and an PAC of 17 wt% of Al ₂ O ₃ concentration and a specific gravity of 1.37. Therefore, the coagulant input amount is usually a coagulant μl added to 1 L of water, and thus the present invention can be said to exhibit the same cohesive performance even when the concentration of aluminum oxide (Al ₂ O ₃ ) is low at 30 wt% in low turbidity water in winter.

Example 4 (Evaluation of Stability of Coagulant)

In order to examine the progress of precipitation of the flocculant prepared by the method of Example 1 of the present invention was followed for 6 months. As a result, the existing high-based airway products began to precipitate white gel material from 2 months after the start of tracking, while the present invention showed excellent stability without any precipitation for 6 months.

Figure 3 shows the results of aggregation experiments for the high baseline flocculant after 4 months. While the cohesive performance of raw water with pH 7.52, alkalinity 46.40 mg / l, turbidity 1.95 NTU, and water temperature of 3.3-4.0 ° C., polysilicate silicate (coagulant prepared by the method of patent 0497992), which is a conventional high base, was found to be somewhat inferior. It can be seen that the present invention maintains the cohesive performance.

The method of the present invention can improve the economics by using sodium aluminate as the alkaline agent added to increase the basicity in the method of manufacturing the aluminum chloride-based flocculant in the high base, and the stability and flocculation performance of the flocculant through the stabilization reaction There is an advantage to improve.

Claims (2)

A method for producing the aluminum chloride-based flocculant for water treatment, the basicity _{30 ~ 55%, Al 2 O} 3 concentration of Al ₂ from the homogenization reactor is maintained at 8 ~ 18wt% of poly aluminum chloride solution, the stirring speed is 5,000 ~ 15,000 rpm After homogenization reaction with sodium phosphate with 5 ~ 25wt% of O _{3 and} 4 ~ 23wt% of Na ₂ O for 3 ~ 60 minutes, stabilized at 40 ~ 100 ℃ for 5 ~ 15 hours and the concentration of Al ₂ O ₃ is 7 ~ 15wt% And a high basic degree of 60-70% of the high salt also a method for producing an aluminum chloride-based flocculant. The method of claim 1, wherein the chlorine ion of polyaluminum chloride is substituted by 5 to 20 wt% with sulfate ions.

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