CN103663765A - Treatment method of recycling fur chromium retanning liquid for plurality of times - Google Patents

Abstract

The invention discloses a treatment method for multiple recycling of fur chrome retanning liquor, which is carried out by using plate and frame filter press microfiltration and flocculation-microfiltration combined treatment in stages, and the specific process flow is as follows: microfiltration-recycling 5-10 times → flocculation - microfiltration - recycling 1 time → microfiltration - recycling 5-10 times → flocculation - microfiltration - recycling 1 time → microfiltration - recycling 5-10 times → flocculation - microfiltration - Recycle 1 time→Microfiltration-recycle 5-10 times→...Repeat the recycling of chrome retanning waste liquid. Adopting the method of the present invention can make the fur chrome retanning liquid be recycled for at least 60 times, the retanning liquid maintains good tanning properties, the leather board is not sticky, the hair quilt is not green, sticky, loose, flexible, bright and natural, The shrinkage temperature of the skin board can reach the initial retanning effect of the new solution. It has the characteristics of low processing cost, less sludge generated and less loss of chrome tanning agent.

Description

A kind of treatment method for repeated use of fur chrome retanning liquor

technical field

The application relates to a treatment method for repeated use of fur chrome retanning liquor.

Background technique

In order to improve the quality of fur and its products, one of the following conditions should be met: (1) to make the fur skin board full, soft, extensible and have good physical and mechanical properties; Ironing and other requirements, (3) the effect of making fur and its products heat-resistant, storage-resistant, and washing-resistant, and (4) making fur and its products resistant to chemical reagents, microorganisms, and enzymes. . In the fur processing process, the fur, skin blank or fur clothing sheet must be tanned or retanned with chrome tanning agent.

The main components of the chrome tanning agent are basic sulfate and sodium sulfate of trivalent chromium, among which the basic sulfate of trivalent chromium is mainly used for tanning and retanning. In fur chrome tanning and chrome retanning, in order to prevent hair loss and acid swelling, a large amount of industrial salt or table salt (the main component is sodium chloride, about 40g/L) needs to be added. After a lot of experimental research, tests show that according to different chrome tanning and chrome retanning processes and equipment used, the basic sulfate absorption rate of fur to trivalent chromium is only 25% in the process of chrome tanning and chrome retanning Between -50%, the lowest absorption rate is even only about 20%, and the absorption rate of fur to sodium sulfate and industrial salt is even lower. Therefore, in the process of chrome tanning and chrome retanning, a large amount of chrome tanning agent, sodium sulfate, and industrial salt remain in the waste liquid of chrome tanning and chrome retanning. On the other hand, in the process of chrome tanning and chrome retanning, a large amount of organic matter on the fur enters the wastewater, such as wool fiber, protein, oil and its degradation products.

Because the fur has a rich coat, in order to prevent the wool fibers from tangling during processing, the water consumption in the chrome tanning and chrome retanning process is extremely large, generally 20 times the quality of the fur.

In summary, if the fur chrome tanning and chrome retanning solutions are used once and then discharged, it will not only waste chemical materials such as chrome tanning agent and industrial salt, but also waste water resources, and will cause greater pollution to the environment. Therefore, recycling chrome tanning and chrome retanning liquor is of great significance for saving water and reducing consumption, and reducing environmental pollution caused by chromium and neutral salts. Many fur factories are researching and testing the recycling of fur chrome tanning and chrome retanning solutions, that is, after using them once, add chrome tanning agents and industrial salts before using them. This method is customarily called the direct circulation method. . However, in the process of recycling chrome tanning and chrome retanning liquor, it is found that the direct circulation method, after recycling several times, even if the concentration of chrome tanning agent is kept higher in the tanning liquor, the tanning effect cannot be guaranteed, that is to say, After several cycles, a considerable part of the chrome tanning agent in the tanning solution will not have the tanning effect. On the other hand, after the chrome tanning solution and the retanning solution have been circulated repeatedly, the tanned and retanned fur is green, sticky, and not loose enough, which affects the quality of the final product. After experimental research, it is found that the main reasons for the above phenomenon are: (1) With the increase in the number of cycles, organic substances in the waste liquid accumulate, such as degraded hide protein, hydrolyzed oil, etc. consume chromium salts and adhere to the wool quilt; (2) With the continuous addition of chrome tanning agent and industrial salt, the content of neutral salt in the tanning solution (including sodium sulfate brought in by chrome tanning agent and added industrial salt) accumulates, which changes the composition of chromium complexes and reduces the tanning performance. There are also studies using flocculation sedimentation method, but due to improper selection of flocculants or improper control of flocculation conditions, it will lead to stickiness of fur panels and wool quilts during recycling due to improper flocculant type, usage amount, and use conditions, which will affect the quality of fur , or due to the type of flocculant, the amount of use, and the improper use conditions, the loss rate of chrome tanning agent during the flocculation process is extremely high, and the amount of sludge generated is extremely large.

Contents of the invention

The technical problem to be solved by the present invention is to provide a treatment method for repeated use of fur chrome retanning liquor, which uses microfiltration and flocculation-microfiltration system for joint treatment in stages to remove organic impurities in the chrome retanning liquor, so that The chrome retanning solution can be used repeatedly (at least 60 times), and the loss of chrome tanning agent and the amount of sludge generated by treatment can be minimized; especially cationic and/or non-ionic polypropylene The combination of amide organic flocculant PAM flocculation and plate and frame filter press microfiltration combined with staged treatment makes the chrome retanning liquor achieve the purpose of repeated use (at least 60 times).

The fur chrome retanning liquid is treated by the method of the present invention, so that the fur chrome retanning liquid can be used repeatedly more than 60 times, the retanning liquid can maintain good tanning performance, the leather board is not sticky, and the wool quilt does not turn green or sticky , Loose, flexible, bright and natural, the shrinkage temperature of the skin board can reach the effect of the initial retanning of the new liquid. It has the characteristics of low processing cost, less sludge generated and less loss of chrome tanning agent.

The treatment method for multiple recycling of fur chrome retanning liquor according to the present invention is carried out by plate and frame filter press microfiltration and flocculation-microfiltration joint treatment in stages, and the specific process flow is as follows: microfiltration-recycling 5 -10 times → flocculation-microfiltration-recycle 1 time→microfiltration-recycle 5-10 times→flocculation-microfiltration-recycle 1 time→microfiltration-recycle 5-10 times→flocculation-microfiltration-cycle Use 1 time→microfiltration-recycle 5-10 times→...repeat and recycle the chrome retanning waste liquid for at least 60 times.

Described microfiltration-recycling comprises the following steps:

⑴Chrome retanning

⑵Collection of chrome retanning waste liquid

(3) Microfiltration (plate and frame filter press): Use a non-clogging sewage pipeline pump to pump the chrome retanning waste liquid into the plate and frame filter press for microfiltration, control the pressure of the plate and frame filter press to 18-25kg, and the filter cloth density to 15-25 microns , separate the filtered sludge and collect the supernatant (ie filtrate).

⑷Analysis of the content of active ingredients in the supernatant: use the sodium chromate colorimetric method to measure the concentration of chrome tanning agent in the supernatant (i.e. filtrate), use the argentometric method to measure the concentration of industrial salt (the main component sodium chloride), and use a pH meter to measure pH.

⑸ Recycling of supernatant (chrome retanning): Put the supernatant into the chrome retanning equipment, replenish water as appropriate, and add chrome tanning agent (Chromitan B from BASF, or Chromosal B from Lanxess, or Brother Technology Co., Ltd.'s HLS-C, or other commercially available chrome tanning agent) and industrial salt, adjust the concentration of chrome tanning agent and industrial salt to the initial concentration of the new liquid chrome retanning, and use formic acid to adjust the pH to the new liquid primary chrome Requirements for retanning. Put the hide to be chrome retanned into, and carry out retanning according to the process of new liquid chrome retanning.

According to the above-mentioned ⑴-⑸ sequence, carry out microfiltration-recycle 5-10 times in this way, and then carry out flocculation-microfiltration-recycle 1 time.

Described flocculation-microfiltration-recycling comprises the following steps:

⑴Chrome retanning

⑵Collection of chrome retanning waste liquid

(3) Flocculation: configure the flocculant into a flocculant solution with a concentration of 0.1wt%, and add a flocculant solution with an amount of 0.8%-1.5% (v/v) of the chrome retanning waste liquid to the collected chrome retanning waste liquid, Stir slowly and evenly, let stand for 1-2h.

Selection of flocculants: After screening dozens of flocculants, the flocculants selected in the present invention are cationic and/or nonionic polyacrylamide organic flocculants PAM (produced by Liaocheng Huafeng Chemical Technology Co., Ltd., Shandong Province) Huafeng cationic polyacrylamide organic flocculant PAM, and/or non-ionic polyacrylamide organic flocculant PAM produced by Shanghai Woshan Chemical Co., Ltd.). The ionicity of the flocculant is about 30%-40%, and the molecular weight is 9-10 million. The flocculant selected in the present invention has a good flocculation and precipitation effect on impurities such as organic matter in the waste liquid, and has an extremely low loss rate of chromium, which is lower than 5%, does not affect retanning, and the fur is not sticky after retanning.

⑷ Microfiltration (plate and frame filter press): Use a non-clogging sewage pipeline pump to pump the chromium retanning waste liquid into the plate and frame filter press for microfiltration, control the pressure of the plate and frame filter press to 18-25kg, and the filter cloth density to 15-25 microns , separate the filtered sludge and collect the supernatant (ie filtrate).

⑸Analysis of the content of active ingredients in the supernatant: use the sodium chromate colorimetric method to measure the concentration of chrome tanning agent in the supernatant (i.e. filtrate), use the silver method to measure the concentration of industrial salt (the main component sodium chloride), and use a pH meter Measure the pH.

⑹Recycling of supernatant (chrome retanning): Put the supernatant into the chrome retanning equipment, replenish water as appropriate, and add chrome tanning agent (Chromitan B from BASF, or Chromosal B from Lanxess, or Brother Technology Co., Ltd.'s HLS-C, or other commercially available chrome tanning agent) and industrial salt, adjust the concentration of chrome tanning agent and industrial salt to the initial concentration of the new liquid chrome for retanning, and adjust the pH to the new liquid chrome with formic acid Requirements for retanning. Put the hide to be chrome retanned into, and carry out retanning according to the process of new liquid chrome retanning.

According to the above-mentioned sequence of ⑴-⑹, carry out flocculation-microfiltration-recycle once, and then carry out microfiltration-recycle 5-10 times.

That is, the present invention first carries out microfiltration-recycling 5-10 times to the chrome retanning waste liquid as shown in Figure 1, then carries out flocculation-microfiltration-recycling 1 time to the chrome retanning waste liquid as shown in Figure 2; Carry out microfiltration-recycling 5-10 times to chromium retanning waste liquid according to shown in Figure 1, carry out flocculation-microfiltration-recycling 1 time to chrome retanning waste liquid again according to the method shown in Figure 2; The retanning waste liquid is treated in stages by plate and frame filter press microfiltration and flocculation-microfiltration combined, and recycled. For the retanning of cleaner skins with low oil content, the number of flocculation should be less to save treatment costs and reduce the amount of sludge; on the contrary, for skins with high oil content, the number of flocculation should be more to remove organic impurities.

Analysis and detection method:

1) Determination of pH value: Determination by acidity meter

Use potassium hydrogen phthalate buffer solution with pH=4.00 and potassium dihydrogen phosphate-potassium hydrogen phthalate buffer solution with pH=6.86 to correct the pH meter, pour the sample solution into a beaker, and add saturated calomel Immerse the electrode in the solution to be tested, and read when the pH value is stable (the change of pH value within 1min is not more than 0.01).

2) Determination of sodium chloride content in industrial salt

Determination principle: Determination by silver method. Add potassium chromate as indicator in neutral Cl ^- solution (that is, neutral solution containing sodium chloride), and titrate with silver nitrate standard solution. During the titration process, silver chloride precipitates first, and when the titration reaches near the end point, due to the rapid increase of the concentration of Ag ⁺ ions, the solubility product of silver chromate is reached, and a brick-red Ag ₂ CrO ₄ precipitate is formed immediately, indicating that end point of the titration to calculate the sodium chloride content. The reaction equation is as follows:

AgNO ₃ +NaCl→AgCl↓+NaNO ₃

Potassium chromate is added as an indicator to interact with excess silver nitrate:

2AgNO ₃ +K ₂ CrO ₄ →Ag ₂ CrO ₄ ↓+2KNO ₃

Reagents and materials: 0.1mol/L silver nitrate standard solution, 1% phenolphthalein indicator, 5% potassium chromate indicator, 0.1mol/L sodium hydroxide solution, 0.05mol/L sulfuric acid solution.

Determination steps: draw 10mL of the filtered test solution, pour it into a 100mL volumetric flask, dilute to the mark with distilled water, draw 10mL from it into a 250mL Erlenmeyer flask, add distilled water to 100mL, and add 3 drops of 1% phenolphthalein indicator, use 0.1 mol/L sodium hydroxide solution to neutralize to red, and then back-drip with 0.05mol/L sulfuric acid solution until colorless. Add 1mL of 5% potassium chromate indicator, and then titrate with 0.1mol/L silver nitrate standard solution, the end point should be orange-red.

The industrial salt content (g/L) in the water sample is calculated according to the following formula:

In the formula: c is the concentration of silver nitrate standard solution, mol/L; V is the consumed volume of silver nitrate standard solution, mL.

3) Determination of concentration of chrome tanning agent

Determined by sodium chromate colorimetric method. Cr ³⁺ in waste chromium solution is oxidized to Cr ⁶⁺ with sodium peroxide under alkaline conditions, and turns into pure yellow Na ₂ CrO ₄ under alkaline conditions. As the amount increases, the yellow color deepens, and it is determined by direct colorimetry (wavelength 390nm).

Reagents and materials: Model 721 spectrophotometer, solid sodium peroxide (chemically pure), 0.1mol/L sodium oxide solution.

Chromium standard solution: Weigh and dissolve 0.2827g of K ₂ Cr ₂ O ₇ standard reagent that has been baked in an oven at 130°C for 2 hours, transfer it into a 100mL volumetric flask, and dilute to the marked line. The Cr ⁶⁺ content in this solution is 1 mg/mL, and the solution is diluted 10 times, then the Cr ⁶⁺ content in the solution is 0.1 mg/mL.

Determination steps:

a. To make a standard curve: Add 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0mL standard solutions containing 0.1mgCr/mL to seven 50mL volumetric flasks, and then add 1mL of sodium hydroxide solution (make pH≈9), dilute to the marked line, shake well, and perform colorimetry at 390nm on a spectrophotometer. Use the blank solution without chromium solution as zero point adjustment, take the measured absorbance as the ordinate and the corresponding chromium amount as the abscissa to draw a standard curve.

b. Determination of samples: draw 1mL of waste chromium solution into a 100mL Erlenmeyer flask, add about 0.8g of sodium peroxide, add 20mL of distilled water, and then heat and boil slowly on an electric stove to completely oxidize Cr ³⁺ into Cr ⁶⁺ ( Pure yellow), cool, transfer the solution into a 100mL volumetric flask, dilute to the mark, shake well, and filter. Draw 10mL of the filtrate and dilute to 50mL (the pH of the solution at this time ≈ 9), and measure the absorbance at 390nm on the spectrophotometer with the blank test solution without waste liquid as zero point adjustment. Find the amount of chromium from the standard curve according to the measured absorbance, so as to calculate the amount of Cr ₂ O ₃ in the waste chromium solution.

Chromium content in tanning liquor (equivalent to Cr ₂ O ₃ measurement) (g/L) is calculated by the following formula:

In the formula: m is the amount of Cr found from the standard curve, mg; 1 is the volume of the waste liquid absorbed, mL; 100 is the volume of the diluent, mL; 10 is the volume of the analytical solution absorbed, mL; 152 is Cr ₂ O ₃ molar mass, g; 104 is the amount of chromium in 1 mol Cr ₂ O ₃ , g.

Powdered chrome tanning agent concentration (g/l) = chromium trioxide content (g/L) x 4

Adopt the processing method of the fur chrome retanning liquor of the present invention to be recycled multiple times, and the recycling can be up to at least 60 times. After calculation, the chrome tanning agent added each time is 20%-30% of the newly prepared liquid chrome tanning agent, The amount of added industrial salt is 15%-25% of the new solution, and the added water should not exceed 10%. That is to say, the method of the present invention can save 70%-75% of chrome tanning agent, about 80% of industrial salt, and about 80% of water during recycling; and the shrinkage temperature of the leather board is above 95°C, and the fur is not sticky, which meets the product requirements . Therefore, the processing method of the fur chrome retanning liquor of the present invention is repeatedly used, which greatly increases the number of times of recycling, reduces the cost of waste liquid treatment, produces less sludge, and has a low loss rate of chromium, which can ensure fur tanning and Retanning quality, water saving, chemical material saving and pollution reduction effect are remarkable.

Description of drawings

Fig. 1 is microfiltration of the present invention-circulation process route.

Fig. 2 is the flocculation-microfiltration-recycling process route of the present invention.

Detailed ways

The technical solutions of the present invention are further described in detail below in conjunction with specific examples, but the examples do not limit the protection scope of the present invention.

Example 1 Retanning solution retanning of rex rabbit blanket chrome

1) Chrome retanning (the first retanning with new solution)

Equipment: 1000L slotting

Feeding amount: 40-50kg per groove

Ratio of water to fur liquid: 20 (mass ratio)

Temperature: 32-35°C

Industrial salt (main component sodium chloride): 40g/L

Industrial formic acid: 0.4-0.5g/L

Powdered chrome tanning agent (HLS-C of Brother Technology Co., Ltd.): 15g/L

Operation: After adjusting the water temperature and water volume, add industrial salt and formic acid, paddle evenly, remove the skin, paddle for 30 minutes, pH=3.3-3.5, add powdered chrome tanning agent, paddle for 60 minutes. After 5 minutes every hour, after 4 hours, add soda ash 3g/L (dissolve soda ash with water 10 times the amount of soda ash, add it in three times, add once every 30 minutes), after 30 minutes, measure pH=3.8-4.2, pH After meeting the requirement, paddle for 30 minutes, let it stand for more than 3 hours, raise the temperature to 38°C, paddle for 30 minutes, and let it stand overnight. In the next morning, paddle for 10 minutes, scoop out the skin, and control the fluid on the skin into the scratching groove. Determining the shrinkage temperature of the skin board after retanning requires reaching above 95°C.

2) Microfiltration - recycling

①Collect chrome retanning waste liquid

②Microfiltration (plate and frame filter press)

Use a non-clogging sewage pipeline pump to pump the chrome retanning waste liquid into the plate and frame filter press, use a filter cloth with a density of 15 microns for microfiltration, control the pressure of the plate and frame filter press to 20kg, and separate the filtered sludge after pressing. The supernatant was collected.

③Analyze the content of active ingredients in the supernatant: measure the concentration of chrome tanning agent in the filtrate with sodium chromate colorimetry, and measure the pH value with a pH meter.

④ Recycling of supernatant (retanning): Put the supernatant into a 1000-liter trough, replenish water as appropriate, adjust the pH of the filtrate to 3.3-3.5 with formic acid, and add powdered chrome tanning agent to make the concentration reach the initial Configure the concentration required by the new solution, that is, about 15g/L of powdered chrome tanning agent, and about 5-10g/L of additional industrial salt (sodium chloride). Put the leather base to be retanned into the groove for retanning, and the retanning operation method is the same as that of the first new liquid retanning.

According to the order of chrome retanning→collecting chrome retanning waste liquid→microfiltration (plate and frame filter)→analyzing the content of active ingredients in the supernatant→recycling the supernatant (retanning) for a total of 10 times.

3) The first flocculation - microfiltration - recycling

①Collect chrome retanning waste liquid

② Flocculation: The cationic PAM flocculant (Shandong Liaocheng Huafeng Chemical Technology Co., Ltd.) was configured into a flocculant solution with a concentration of 0.1wt%. Add flocculant solution with 1.0% (v/v) retanning waste liquid to the collected chrome retanning waste liquid, stir slowly and evenly, and let stand for 1h.

③Microfiltration (plate and frame filter press)

Use a non-clogging sewage pipeline pump to pump the flocculated chromium retanning waste liquid into the plate and frame filter press for microfiltration, use a filter cloth with a density of 15 microns for microfiltration, control the pressure of the plate and frame filter press to 20kg, and filter out The sludge was separated and the supernatant was collected.

④ Analyzing the content of active ingredients in the supernatant: use sodium chromate colorimetry to measure the concentration of chrome tanning agent in the filtrate, and use a pH meter to measure the pH value.

⑤ Recycling of supernatant (retanning): put the supernatant into a 1000-liter trough, replenish water as appropriate, adjust the pH of the filtrate to 3.3-3.5 with formic acid, and add powdered chrome tanning agent to make the concentration reach the initial configuration The required concentration of the new solution is about 15g/L of powdered chrome tanning agent, and 10g/L of industrial salt is added. Put the leather base to be retanned into the groove for retanning, and the retanning operation method is the same as that of the first new liquid retanning.

4) Microfiltration - recycling

①Collect chrome retanning waste liquid

②Microfiltration (plate and frame filter press)

Use a non-clogging sewage pipeline pump to pump the chrome retanning waste liquid into the plate and frame filter press, use a filter cloth with a density of 15 microns for microfiltration, control the pressure of the plate and frame filter press to 20kg, and separate the filtered sludge after pressing , the supernatant was collected.

③Analyze the content of active ingredients in the supernatant: measure the concentration of chrome tanning agent in the filtrate with sodium chromate colorimetry, and measure the pH value with a pH meter.

④ Recycling of supernatant (retanning): put the supernatant into a 1000-liter trough, replenish water as appropriate, adjust the pH of the filtrate to 3.3-3.5 with formic acid, and add powdered chrome tanning agent to make the concentration reach the initial configuration The required concentration of the new solution is about 15g/L of powdered chrome tanning agent, and about 5g/L of additional industrial salt (sodium chloride). Put the leather base to be retanned into the slot for retanning, the operation method is the same as the first new liquid retanning.

According to the order of chrome retanning→collecting chrome retanning waste liquid→microfiltration (plate and frame filter)→analyzing the content of active ingredients in the supernatant→recycling the supernatant (retanning) for a total of 10 times.

5) The second flocculation - microfiltration - recycling

The method is the same as the first flocculation-microfiltration and recycling.

6) Microfiltration - recycling

Then follow the sequence of chrome retanning→collecting chrome retanning waste liquid→microfiltration (plate and frame filter)→analyzing the concentration of chrome tanning agent in the supernatant→recycling the supernatant (retanning). A total of 10 cycles are used.

7) The third flocculation - microfiltration - recycling

The method is the same as the first flocculation-microfiltration-cycle.

8) Microfiltration - recycling

Then follow the sequence of chrome retanning→collect chrome retanning waste liquid→microfiltration (plate and frame filter)→analyze the concentration of chrome tanning agent in the supernatant→recycle the supernatant (retanning) for a total of 10 times.

A total of 60 cycles are used.

Table 1 Analysis and detection data of new liquid and partial recycling and the amount of additional chemical materials

It can be seen from Table 1 that the absorption rate of the chrome tanning agent in the retanning process is extremely low, with an average absorption rate of 21.5%, not exceeding 25%. 25%-30% of the added amount of the liquid, each time it can be supplemented according to 25%-30% of the newly prepared liquid; industrial salt can be added according to 15%-25% of the newly prepared liquid; and it is being recycled The amount of water that needs to be added is very small.

Example 2 Recycling of raccoon skin chrome retanning solution

1) Chrome retanning (the first retanning with new solution)

Equipment: 1000L slotting

Feeding amount: 40kg per groove

Liquid ratio: 25 (water to fur mass ratio)

Temperature: 32-35°C

Industrial salt: 40g/L

Formic acid: 0.4-0.5g/L

Powdered chrome tanning agent (HLS-C from Brother Technology Co., Ltd., 33% basicity, 25% chromium trioxide content): 15g/L

Operation: After adjusting the water temperature and water volume, add industrial salt and formic acid, paddle evenly, remove the skin, paddle for 30 minutes, pH=3-3.5, add powdered chrome tanning agent, paddle for 60 minutes. After 5 minutes every hour, after 4 hours, add soda ash 3g/L (dissolve soda ash with water 10 times the amount of soda ash, add it in three times, add once every 30 minutes), after 30 minutes, use a pH meter to measure pH=3.8- 4.0, when the pH reaches the requirement, paddle for 30 minutes, let it stand for more than 3 hours, raise the temperature to 38°C, paddle for 30 minutes, and let it stand overnight. In the next morning, paddle for 10 minutes, scoop out the skin, and control the supernatant to the groove Inside. Determining the shrinkage temperature of the skin board after retanning requires reaching above 95°C.

2) Microfiltration - recycling

①Collect chrome retanning waste liquid

②Microfiltration (plate and frame filter press)

Use a non-clogging sewage pipeline pump to pump the chrome retanning waste liquid into the plate and frame filter press, use a filter cloth with a density of 15 microns for microfiltration, control the pressure of the plate and frame filter press to 20kg, and separate the filtered sludge after pressing , the supernatant was collected.

③Analysis of the content of active ingredients in the supernatant: measure the concentration of chrome tanning agent in the filtrate with sodium chromate colorimetry, and measure the pH value with a pH meter (results are shown in Table 2).

④Supernatant recycling (retanning): Put the supernatant into a 1000-liter trough, replenish water as appropriate, adjust the pH of the filtrate to 3.3-3.5 with formic acid, and add chrome tanning agent to make the concentration reach the initial configuration of the new solution The required concentration is 15g/L of powdered chrome tanning agent and 10g/L of industrial salt. Put the leather base to be retanned into the slot for retanning, the operation method is the same as the first new liquid retanning.

According to the order of chrome retanning→collecting chrome retanning waste liquid→microfiltration (plate and frame filter)→analyzing the content of active ingredients in the supernatant liquid→recycling the supernatant liquid (retanning) to recycle the retanning liquid 9 times .

3) The first flocculation - microfiltration - recycling

①Collect chrome retanning waste liquid

② Flocculation: The non-ionic PAM flocculant (Shanghai Woshan Chemical Co., Ltd.) is configured into a flocculant solution with a concentration of about 0.1%. Add 1.5% flocculant solution to the collected chrome retanning waste liquid, stir slowly and evenly; let stand for 1.5h.

③Microfiltration (plate and frame filter press)

Use a non-clogging sewage pipeline pump to pump the chrome retanning waste liquid into the plate and frame filter press, use a filter cloth with a density of 15 microns for microfiltration, control the pressure of the plate and frame filter press to 20kg, and separate the filtered sludge after pressing , the supernatant was collected.

④ Analyzing the content of active ingredients in the supernatant: measure the concentration of chrome tanning agent in the filtrate with sodium chromate colorimetry, and measure the pH value with a pH meter (results are shown in Table 2).

⑤ Recycling of the supernatant (retanning): Put the supernatant into a 1000-liter trough, replenish water as appropriate, adjust the pH of the filtrate to 3.3-3.5 with formic acid, and add chrome tanning agent to make the concentration reach the initial configuration of the new solution The required concentration is 15g/L of powdered chrome tanning agent and 5g/L of industrial salt. Put the leather base to be retanned into the slot for retanning, the operation method is the same as the first new liquid retanning.

4) Microfiltration - recycling

①Collect chrome retanning waste liquid

②Microfiltration (plate and frame filter press)

Use a non-clogging sewage pipeline pump to pump the chrome retanning waste liquid into the plate and frame filter press, use a filter cloth with a density of 15 microns for microfiltration, control the pressure of the plate and frame filter press to 20kg, and separate the filtered sludge after pressing , the supernatant was collected.

③Analyze the content of active ingredients in the supernatant: measure the concentration of chrome tanning agent in the filtrate with sodium chromate colorimetry, and measure the pH value with a pH meter.

④Supernatant recycling (retanning): Put the supernatant into a 1000-liter trough, replenish water as appropriate, adjust the pH of the filtrate to 3.3-3.5 with formic acid, and add chrome tanning agent to make the concentration reach the initial configuration of the new solution The required concentration is 15g/L of powdered chrome tanning agent and 5g/L of industrial salt. Put the leather base to be retanned into the slot for retanning, the operation method is the same as the first new liquid retanning.

According to the order of chrome retanning→collecting chrome retanning waste liquid→microfiltration (plate and frame filter)→analyzing the content of active ingredients in the supernatant liquid→recycling the supernatant liquid (retanning) to recycle the retanning liquid 9 times .

5) The second flocculation - microfiltration - recycling

The method is the same as the first flocculation-microfiltration-cycle.

6) Microfiltration - recycling

The retanning solution is then recycled in the order of chrome retanning→collecting chrome retanning waste liquid→microfiltration (plate and frame filter)→analyzing the content of active ingredients in the supernatant liquid→recycling the supernatant liquid (retanning).

A total of 60 cycles are used.

Table 2 Analysis and test results of the first 20 cycles of use and the amount of added chemical materials and water

As can be seen from Table 2: the absorption rate of chrome tanning agent is extremely low in the retanning process, and the average absorption rate is 20.56%, no more than 25%. Add 25%-30% of the newly prepared solution; industrial salt can be added according to 15%-25% of the newly prepared solution, and the amount of water that needs to be added during recycling is very small.

Example 3 Recycling of small lake sheepskin chrome retanning solution

1) Chrome retanning (the first retanning with new solution)

Equipment: 1000L slotting

Feeding amount: 40-50kg per groove

Ratio of water to fur liquid: 20 (mass ratio)

Temperature: 32-35°C

Industrial salt: (main component sodium chloride) 40g/L

Formic acid: 0.4-0.5g/L

Powdered chrome tanning agent (HLS-C from Brother Technology Co., Ltd., 33% basicity, 25% chromium trioxide content): 15g/L

Operation: After adjusting the water temperature and water volume, add industrial salt and formic acid, paddle evenly, remove the skin, paddle for 30 minutes, add chrome tanning agent, paddle for 60 minutes. After 5 minutes every hour, after 4 hours, add soda ash: 3g/L (dissolve soda ash with water 10 times the amount of soda ash, add it in three times, add once every 30 minutes), after 30 minutes, use a pH meter to measure pH = 3.8 -4.0, when the pH reaches the requirement, paddle for 30 minutes, let it stand for more than 3 hours, raise the temperature to 38°C, paddle for 30 minutes, and let it stand overnight. Next morning, paddle for 10 minutes, remove the skin, and control the supernatant of the skin to the groove Inside. Determining the shrinkage temperature of the skin board after retanning requires reaching above 95°C.

2) Microfiltration - recycling

① Collect retanning waste liquid

②Microfiltration (plate and frame filter press)

Use a non-clogging sewage pipeline pump to pump the chrome retanning waste liquid into the plate and frame filter press, use a filter cloth with a density of 15 microns for microfiltration, control the pressure of the plate and frame filter press to 20kg, and separate the filtered sludge after pressing , the supernatant was collected.

③ Analyze the concentration and pH of the chrome tanning agent in the supernatant (results are shown in Table 3).

④ Recycling of the supernatant (retanning): Put the supernatant into the trough, replenish water as appropriate, adjust the pH of the filtrate to 3.3-3.5 with formic acid, and add chrome tanning agent to make the concentration reach the requirement for the initial configuration of the new solution Concentration, that is, powdered chrome tanning agent 15g/L, supplementary industrial salt 5-8g/L. Put the leather base to be retanned into the slot for retanning, the operation method is the same as the first new liquid retanning.

According to the order of chrome retanning→collecting chrome retanning waste liquid→microfiltration (plate and frame filter)→analyzing the concentration of chrome tanning agent in the supernatant→recycling the supernatant (retanning), the retanning liquid is recycled and used together. 20 times.

3) The first flocculation - microfiltration - recycling

① Collect retanning waste liquid

② Flocculation: The cationic PAM flocculant (Shandong Liaocheng Huafeng Chemical Technology Co., Ltd.) is configured into a flocculant solution with a concentration of about 0.1%. Add cationic PAM flocculant solution with 1.0% waste liquid amount to the collected chrome retanning waste liquid, stir slowly and evenly, let stand for 1.5h,

③Microfiltration (plate and frame filter press)

Use a non-clogging sewage pipeline pump to pump the chrome retanning waste liquid into the plate and frame filter press, use a filter cloth with a density of 15 microns for microfiltration, control the pressure of the plate and frame filter press to 20kg, and separate the filtered sludge after pressing , the supernatant was collected.

④ Analyze the concentration and pH of the chrome tanning agent in the supernatant.

⑤ Recycling of the supernatant (retanning): Put the supernatant into the trough, replenish water as appropriate, adjust the pH of the filtrate to 3.3-3.5 with formic acid, and add chrome tanning agent to make the concentration reach the requirement for the initial configuration of the new solution Concentration, that is, powdered chrome tanning agent 15g/L, supplementary industrial salt 5-8g/L. Put the leather base to be retanned into the slot for retanning, the operation method is the same as the first new liquid retanning.

4) Microfiltration - recycling

① Collect retanning waste liquid

②Microfiltration (plate and frame filter press)

Use a non-clogging sewage pipeline pump to pump the chrome retanning waste liquid into the plate and frame filter press, use a filter cloth with a density of 15 microns for microfiltration, control the pressure of the plate and frame filter press to 20kg, and separate the filtered sludge after pressing , the supernatant was collected.

③ Analyze the concentration and pH of the chrome tanning agent in the supernatant.

④ Recycling of the supernatant (retanning): Put the supernatant into the trough, replenish water as appropriate, adjust the pH of the filtrate to 3.3-3.5 with formic acid, and add chrome tanning agent to make the concentration reach the requirement for the initial configuration of the new solution Concentration, that is, powdered chrome tanning agent 15g/L, supplementary industrial salt 5-8g/L. Put the leather base to be retanned into the slot for retanning, the operation method is the same as the first new liquid retanning.

According to the order of chrome retanning→collecting chrome retanning waste liquid→microfiltration (plate and frame filter)→analyzing the concentration of chrome tanning agent in the supernatant→recycling the supernatant (retanning), the retanning liquid is recycled and used together. 15 times.

5) The second flocculation-microfiltration

The method is the same as the first flocculation-microfiltration-cycle.

6) Microfiltration - recycling

Then follow the sequence of chrome retanning→collect chrome retanning waste liquid→microfiltration (plate and frame filter)→analyze the concentration of chrome tanning agent in the supernatant→recycle the supernatant (retanning) to recycle the retanning liquid , the method of operation is the same as the first new solution retanning.

A total of 60 cycles are used.

Table 3 Analysis and test results of the first 20 cycles of use and the amount of added chemical materials and water

As can be seen from Table 3: the absorption rate of the chrome tanning agent in retanning is extremely low, and the average absorption rate is lower than 25%. 30%, it can be supplemented according to 25%-30% of the newly prepared solution each time; industrial salt can be supplemented according to 10%-25% of the newly prepared solution, and the amount of water that needs to be added during the entire cycle is very large few.

Table 4 The relationship between the amount of supplementary industrial salt and the concentration of sodium chloride in the retanning waste liquor

As can be seen from Table 4: in the first 5 times of circulation, 20g/L industrial salt was added each time, and the concentration of sodium chloride in the waste liquid increased continuously with the increase of the number of cycles, and the maximum value reached 115g/L. Adding 10g/L salt, the salt content in the waste liquid tends to be stable at about 90g/L, which can meet the process requirements, and the skin does not swell and does not shed hair. Even if the additional amount of 10g/L is added each time, the concentration of sodium chloride can still reach 1.5-2 times of the initial retanning concentration, which is too high. In the above three embodiments, the new liquid requires 40g/L of industrial salt, so when recycling, the amount of added industrial salt is controlled between 5-10g/L each time, and the retanning effect is good.

Comparing the data in Table 1, Table 2, and Table 3, it can be seen that the concentration of chrome tanning agent in the waste liquid does not change much compared with that of flocculation-microfiltration-recycling and only microfiltration-recycling. But flocculation-microfiltration-recycling helps to further remove organic impurities in waste liquid. This shows that the loss rate of the chrome tanning agent is extremely low with the flocculant flocculation selected by the present invention, no more than 5% on average. The cationic flocculant used in this application has a removal rate of 21.7% for NPOC of organic carbon, and the removal rate of nonionic flocculant for NPOC of organic carbon is 20.7%.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the invention can be Modifications or equivalent replacements without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the claims of the present invention.

Claims (7)

1. a treatment method for fur chrome retanning liquor repeatedly recycled, is characterized in that, adopts plate-and-frame filter press microfiltration and flocculation-microfiltration joint staged joint treatment mode to carry out, and concrete technological process is as follows: microfiltration- Recycle 5-10 times → flocculation-microfiltration-recycle 1 time→microfiltration-recycle 5-10 times→flocculation-microfiltration-recycle 1 time→microfiltration-recycle 5-10 times→flocculation-micro Filtration-recycling 1 time→microfiltration-recycling 5-10 times→...and so on to recycle the chrome retanning waste liquid. 2. processing method according to claim 1 is characterized in that, described microfiltration-recycling comprises the following steps: ⑴Chrome retanning ⑵Collection of chrome retanning waste liquid ⑶ microfiltration, plate and frame filter press ⑷Analysis of the content of active ingredients in the supernatant ⑸Recycling of supernatant According to the above ⑴-⑸ sequence, carry out microfiltration-cycle 5-10 times in this way, and then carry out flocculation-microfiltration-cycle 1 time. 3. The processing method according to claim 1, wherein said flocculation-microfiltration-recycling comprises the following steps: ⑴Chrome retanning ⑵Collection of chrome retanning waste liquid (3) Flocculation ⑷Microfiltration, plate and frame filter press ⑸Analysis of the content of active ingredients in the supernatant ⑹The supernatant is recycled According to the above-mentioned sequence of ⑴-⑹, carry out flocculation-microfiltration-recycle once, and then carry out microfiltration-recycle 5-10 times. 4. The treatment method according to claim 2 or 3, characterized in that, the microfiltration and plate and frame filter press steps are: pump the chromium retanning waste liquid into the plate and frame filter press with a non-clogging sewage pipeline pump For microfiltration, control the plate and frame filter press with a pressure of 18-25kg and a filter cloth density of 15-25 microns to separate the filtered sludge and collect the supernatant, namely the filtrate. 5. The treatment method according to claim 2 or 3, characterized in that, said flocculation comprises: configuring the flocculant into a flocculant solution with a concentration of 0.1wt%, and adding A flocculant solution with 0.8%-1.5% (v/v) of chrome retanning waste liquid, stir slowly and evenly, and let it stand for 1-2h. 6. The treatment method according to claim 2 or 3, characterized in that, the step of recycling the supernatant is: putting the supernatant into the chrome retanning equipment, replenishing water, adding chrome tanning agent and industrial Salt, adjust the concentration of chrome tanning agent and industrial salt to meet the initial concentration requirements of new liquid chrome retanning, use formic acid to adjust the pH to the initial pH requirements of new liquid chrome retanning, put the hide to be chrome retanned, according to The new liquid chrome retanning process is used for retanning. 7. The treatment method according to claim 5, characterized in that, the flocculant is cationic and/or nonionic polyacrylamide organic flocculant PAM, the ionicity is 30%-40%, and the molecular weight is 900 -10 million.

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