KR101297435B1 - The preparing method of aluminium sulfate from waste water - Google Patents

Abstract

The present invention provides a method for producing an inorganic coagulant by recycling wastewater and waste generated in an industrial field. The present invention relates to a method of preparing inorganic coagulants having high quality and low cost compared to existing coagulants by pre-treating and recycling aluminum components in wastewater based on the Alum manufacturing method.

Description

The preparing method of aluminum sulfate from waste water

The present invention relates to a method for producing aluminum sulfate from wastewater and waste, and more particularly, to a method for recovering and recycling aluminum used in inorganic flocculants used for wastewater treatment from wastewater and waste.

The present invention relates to a method for producing aluminum sulfate from wastewater and waste, and more particularly, to a method for recovering and recycling aluminum used in inorganic flocculants used for wastewater treatment from wastewater and waste.

Inorganic coagulant is a drug that coagulates and precipitates colloidal particles by neutralizing the surface charge of organic and inorganic colloid particles contained in wastewater. It is one of the important wastewater treatment chemicals that has been used for a long time in order to improve the quality of treated wastewater.

Representative examples of such inorganic flocculants include Alum (aluminum sulfate), iron sulfate, iron chloride, and PAC, and most commonly Alum or Ferric Salt are used depending on industrial wastewater treatment water quality.

The present invention provides a method for recovering and recycling aluminum sulfate from wastewater and wastes.

In order to prepare aluminum sulfate, aluminum hydroxide and sulfuric acid are reacted, and a reaction formula is as follows.

_{2Al (OH) 3 + 3H 2} SO 4 → Al 2 (SO 4) 3 · 6H 2 O

When the aluminum sulfate thus recovered is mixed with ferric salt, an inorganic flocculant having complementary advantages and disadvantages of aluminum sulfate and ferric salt can be produced.

By recovering and recycling aluminum from waste and wastewater by the manufacturing method of the present invention, it is possible to exhibit environmental pollution prevention and resource recycling effects.

In addition, the inorganic flocculant mixed with aluminum sulfate and ferric salt prepared according to the present invention is excellent in the adsorption power of the colloid, sludge settling properties, and excellent performance compared to the conventional inorganic coagulant in COD and heavy metal treatment efficiency.

In order to prepare aluminum sulfate, it is prepared by reacting aluminum hydroxide with sulfuric acid.

_{2Al (OH) 3 + 3H 2} SO 4 → Al 2 (SO 4) 3 · 6H 2 O

In the manufacturing method of the present invention, aluminum components in the wastewater and the waste are recycled as raw materials, and acids contained in the wastewater and the waste are also recycled.

The production method of the present invention consists of adding sulfuric acid to sufficiently react at 110 ~ 115 ℃ using the heat of dissolution and neutralization reaction heat of sulfuric acid, and then cooled to 50 ℃ or less.

The details are as follows.

Recycled aluminum hydroxide, wastewater containing pretreated aluminum, recycled aluminum hydroxide cake, etc. (recycled aluminum hydroxide-Al (OH) ₃ 97.5%, recycled aluminum hydroxide cake-Al (OH) ₃ 25.0%, recycled aluminum wastewater Add Al ₂ O ₃ 17%) and stir to achieve a sufficient slurry.

When mixed with the concentrated sulfuric acid introduced in the next step, the primary water is supplied so that the concentration of sulfuric acid formed is 60-70%.

In order to smoothly add the concentrated sulfuric acid calculated according to the reaction scheme, a dipping pipe is installed near the bottom of the reactor, and the metering pump is operated to be added for about 30 minutes.

The liquid inside the reactor starts to rise in temperature due to the heat of dissolution generated when sulfuric acid is dissolved in water. At this point, sulfuric acid injection is stopped.

Thereafter, the temperature rises to about 115 ° C by synergy of the heat of neutralization reaction. When the temperature starts to fall again, the remaining sulfuric acid is added by adjusting the flow rate of the metering pump so that the reactor internal temperature is maintained at 110 ~ 115 ℃.

The completion of the aluminum sulfate production reaction is based on a 120-minute reaction at 112 ° C based on the reaction solution temperature.

Hereinafter, the present invention will be described in more detail with reference to Examples.

≪ Example 1 >

Examples of recycled aluminum hydroxide and recycled aluminum wastewater

200 g of recycled aluminum hydroxide and 100 g of wastewater containing recycled aluminum were added to a 4L four-necked round flask, and 325 g of primary water was added thereto, followed by stirring to fully slurry. When 452 g of 98% sulfuric acid was slowly added, the heat of dissolution of sulfuric acid and the heat of neutralization reaction were generated and the temperature started to rise. When boiling was started at around 100 ℃, sulfuric acid was stopped and waited until it reached 110 ~ 115 ℃. When the temperature began to drop, the remaining sulfuric acid was slowly added to maintain the temperature of 110-115 ° C. Termination of the reaction was based on the reaction 120 minutes at 112 ℃ based on the reaction solution temperature.

≪ Preparation Example 1 &

Ferric sulfate was added to the reaction product prepared in Example 1 and water was added to adjust the concentration of aluminum sulfate to 5% and the concentration of ferric sulfate to 2%. The final product weighed 2865 g. After aging for 24 hours, the product was filtered.

≪ Preparation Example 2 &

It was prepared in the same manner as in Preparation Example 1 except that ferric hydrochloride was used instead of ferric sulfate.

<Test Example>

Preparation Example 1, 2, 3 Three kinds of 7% aluminum sulfate and 10% ferric salt, which are generally used in industry, were tested to evaluate the present invention.

- Standard wastewater characteristics

Items unit Results pH - 10.5 COD mg / l 1,025 T-N mg / l 22 T-P mg / l 13 SS mg / l 862 T-Cr mg / l 2.5 As mg / l 2.0 Pb mg / l 1.5 Cu mg / l 2.4

- Exam conditions

1) Inorganic coagulant: the same amount for each product

2) pH neutralizer: 25% lime water (pH Target 7.0)

3) Polymer: A-230E (Anionic)

- Test result

7% Alum    10%
   Ferric salt The present invention ( Al2O3  5.0% + Fe3 + 2.0%) Manufacturing example  One Manufacturing example  2
Coagulant input (ppm) 500 500 500 500
Neutralizing agent input (ppm) 1,200 1,350 1,150 1,150
Polymer input (ppm) 4 4 4 4
Floc Size (mm) 1.5 to 2.25 1.0 to 1.5 2.25 to 3.0 2.25 to 3.0
SV30 (%) 22 14 16 16
Treated water  Water quality COD (ppm) 565 600 520 515
COD Removal Rate (%) 44.9 41.5 49.3 49.8
T-N (ppm) 16 17 14 14
T-P (ppm) 1.5 1.7 1.3 1.3
SS (ppm) 12 10 8 7
T-Cr (ppm) 1.0 1.0 0.4 0.4
As (ppm) 0.6 0.5 0.3 0.3
Pb (ppm) 0.6 0.5 0.2 0.2
Cu (ppm) 0.7 0.6 0.2 0.2
Sludge  Generation O.D (gr / l) 2.024 2.520 1.954 2.000

The products of Preparation Examples 1 and 2 of the present invention have excellent CDD removal rate, good heavy metal removal rate, good floc sedimentation, and SS content in treated water, compared to the existing commercially available coagulant, 7% aluminum sulfate and 10% ferric salt. It is low and the sludge dewatering speed is excellent.

Claims (3)

The sulfuric acid is added to the wastewater and wastes containing aluminum and reacted at 110 to 115 ℃ for 2 hours using the heat of dissolution and neutralization reaction of sulfuric acid, and then cooled to a temperature of 10 to 50 ℃.
delete An inorganic flocculant for wastewater treatment, comprising ferric salt of aluminum sulfate and sulfuric acid or hydrochloric acid obtained according to claim 1.