A treatment method for direct recycling of chrome tanning waste liquid

Abstract

The application discloses a kind of processing methods of direct recycling of chrome tanning waste liquid, and the application relates to the technical field of clean production of tanning, which comprises the following steps: after the chrome tanning waste liquid is filtered by slagging and micropore, the pH value is adjusted to be acidic, and ultrasonic treatment is carried out under heating condition; starch modified water treatment agent and microbial composite flocculant are added, stirred uniformly, and then placed for reaction for 10-15h, then aerated, and the dross is scraped off to prepare a chrome tanning waste liquid direct recycling treatment liquid.The application carries out ultrasonic treatment under heating condition, so that the organic matter combined with chromium ions is decomposed, thereby becoming free-state molecules, and then starch modified water treatment agent and microbial composite flocculant are used to treat organic matter and other impurities in the waste liquid, solving the problem of low removal efficiency of animal fat, keratin, cellulose and tannin and other organic matter in the chrome tanning waste liquid in the prior art.

Description

Technical Field

[0001] This invention relates to the field of clean production technology in leather tanning, specifically to a method for the direct recycling of chromium tanning wastewater. Background Technology

[0002] While the leather industry brings economic benefits and satisfies people's material needs, it also places a significant burden on the environment, especially on wastewater. Chrome tanning wastewater is a major component of this wastewater, and chrome tanning is widely used in leather production due to its irreplaceable superior leather-making effect. However, traditional chrome tanning processes do not achieve a high binding rate of trivalent chromium, typically only 60-70%, leaving 30-40% residual chromium in the wastewater. This results in chromium concentrations as high as 2000-5000 mg / L (calculated as Cr2O3). The discharge of such high-chromium wastewater not only causes serious environmental pollution but also represents a significant waste of resources. Therefore, the recovery and utilization of chromium from chrome tanning wastewater, turning waste into treasure, has become the best way to reduce chromium pollution in leather enterprises. Currently, the main methods for treating chrome tanning wastewater both domestically and internationally include alkaline precipitation recovery and direct recycling. Direct recycling reduces raw material consumption, lowers leather production costs, and reduces environmental pollution from tanneries, making it an economical and practical production technology. However, the direct recycling method still has the following problems to be solved: the chrome tanning waste liquid contains organic matter such as animal fats, keratin, cellulose and tannins. As the number of recycling times increases, impurities accumulate, which in turn affects the quality of the finished leather. Therefore, the problem of impurity removal must be solved in the recycling of chrome tanning waste liquid. Summary of the Invention

[0003] In order to solve the above-mentioned technical problems, the purpose of this invention is to provide a treatment method for the direct recycling of chrome tanning waste liquid, so as to solve the problem of low removal efficiency of organic matter such as animal fats, keratin, cellulose and tannins in chrome tanning waste liquid in the prior art.

[0004] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for directly recycling chromium tanning waste liquor is provided, comprising the following steps:

[0005] (1) After removing slag and filtering through micropores, the pH of the chromium tanning waste liquid is adjusted to acidity and then subjected to ultrasonic treatment under heating conditions to obtain reaction solution one;

[0006] (2) In the reaction solution obtained in step (1), add starch-modified water treatment agent and microbial composite flocculant, stir evenly, let stand for 10-15 hours, then purge and scrape off the scum to obtain chromium tanning waste liquid for direct recycling treatment.

[0007] The beneficial effects of this invention are as follows: The main reason why the tanning performance of the recovered chromium tanning agent is relatively poor is that the chromium tanning waste liquid contains a large number of small organic carboxylic acid molecules and small polypeptide molecules degraded from the leather. The carboxyl groups in these small molecules will form a strong coordination bond with chromium ions, so that the chromium salts in the waste liquid can no longer bind with the carboxyl groups on the leather fibers, thus losing their tanning properties. At the same time, the waste liquid also contains organic matter such as animal fats, keratin, cellulose and tannins. The chromium salts bound with organic small molecules are relatively dark in color, making the tanned wet blue leather darker in color. Therefore, most leather tanning companies are unwilling to use the recovered chromium tanning agent.

[0008] This invention employs slag removal and microporous filtration to remove large molecular impurities, followed by ultrasonic treatment under heating conditions to decompose organic matter bound to chromium ions, thus transforming it into free molecules. Then, a starch-modified water treatment agent and a microbial composite flocculant are used for synergistic treatment. On one hand, the starch-modified water treatment agent can effectively remove soluble oils, proteins, and other impurities from wastewater; on the other hand, the starch residue can be adsorbed by the microbial composite flocculant, thereby effectively removing organic matter and other impurities from the waste liquid.

[0009] Based on the above technical solution, the present invention can be further improved as follows:

[0010] Furthermore, in step (1), the pH value is 2.6-3.

[0011] Furthermore, in step (1), the pore size of the microporous filter is 10-15 μm.

[0012] Furthermore, in step (1), the temperature is increased to 80-100°C.

[0013] Furthermore, in step (1), apply 0.1-0.2 W / cm for 3-5 minutes. 3 Ultrasound.

[0014] Further, in step (2), the starch-modified water treatment agent is prepared by the following method: starch and sodium hydroxide are mixed evenly, ball milled for 10-20 minutes under heating conditions, then etherifying agent is added, stirred and heated for 15-20 minutes to obtain the starch-modified water treatment agent.

[0015] Furthermore, the mass ratio of starch to sodium hydroxide is 70-80:5-6.

[0016] Furthermore, the etherifying agent is 2,3-epoxypropyltrimethylammonium chloride or 3-chloro-2-hydroxypropyltrimethylammonium chloride.

[0017] Furthermore, the molar ratio of starch to etherifying agent is 1:3-5.

[0018] Furthermore, the starch is amylose.

[0019] Furthermore, in step (2), the amount of starch-modified water treatment agent used in reaction solution one is 15-25 mg / L.

[0020] Furthermore, in step (2), the mass ratio of starch-modified water treatment agent to microbial composite flocculant is 20:10-20.

[0021] Further, in step (2), the microbial composite flocculant includes the following raw materials in parts by weight: 10-20 parts of Streptomyces rubrum ferment, 10-20 parts of Nocardia rubrum ferment and 15-18 parts of chitosan.

[0022] Furthermore, the Streptomyces rubrum ferment is prepared by the following method: Streptomyces rubrum is inoculated into MRS liquid medium and cultured aerobically at 28-35℃ for 50-60h. Then, growth factors are added and cultured aerobically at 28-35℃ for another 40-50h. Finally, the mixture is filtered, centrifuged, and concentrated to obtain the Streptomyces rubrum ferment.

[0023] Furthermore, the volume ratio of Streptomyces rubrum to MRS liquid medium was 1:50-70.

[0024] Furthermore, the MRS liquid culture medium includes: peptone, beef extract, yeast extract, glucose, citrate, sodium acetate, Tween 80, and agar; the concentration of peptone in the MRS liquid culture medium is 8-12 g / L, the concentration of beef extract is 8-12 g / L, the concentration of yeast extract is 10-15 g / L, the concentration of glucose is 18-22 g / L, the concentration of citrate is 1-2 g / L, the concentration of sodium acetate is 3-5 g / L, the concentration of Tween 80 is 1-2 g / L, and the concentration of agar is 10-12 g / L.

[0025] Furthermore, the Nocardia rubra ferment is prepared by the following method: Nocardia rubra is cultured using the same method as Streptomyces rubrum to obtain the Nocardia rubra ferment.

[0026] Furthermore, the growth factor is kelp extract.

[0027] Furthermore, the kelp extract was prepared by the following method:

[0028] (2.1) Wash and crush the kelp, then add water and hydrolyze for 1-3 hours to obtain kelp hydrolysate;

[0029] (2.2) Add a compound enzyme to the kelp hydrolysate obtained in step (2.1), and enzymatically hydrolyze it at 55-60℃ for 3-4 hours. Then, inactivate the enzyme at 100-110℃ for 2-3 minutes. After filtration and concentration, kelp extract is obtained.

[0030] Furthermore, in step (2.1), the mass ratio of kelp to water is 1:20-30.

[0031] Furthermore, in step (2.2), the mass ratio of kelp hydrolysate to complex enzyme is 100:3-5.

[0032] Furthermore, the complex enzymes include lipase, protease, cellulase, and pectinase.

[0033] Furthermore, the volume ratio of growth factors to MRS liquid culture medium is 4-8:50-70.

[0034] Furthermore, in step (2), the diameter of the air bubble is 100-500 μm.

[0035] The present invention also provides a chromium tanning waste liquor directly recycled by the above-mentioned method for recycling chromium tanning waste liquor.

[0036] The present invention has the following beneficial effects:

[0037] 1. The microbial composite flocculant prepared in this invention utilizes a complex of *Streptomyces rubrum* fermentation product and *Nocardia rubrum* fermentation product. The two fermentation products work synergistically with chitosan, which contains amino groups that can react with H+ in water. + Combine to form -NH3 + Positively charged, it adsorbs negatively charged colloidal impurities and organic matter in flocculated water through charge neutralization and bridging, causing them to destabilize, coagulate, and precipitate. It has advantages such as being non-toxic and environmentally friendly that cannot be matched by other synthetic flocculants. The microbial composite flocculant of this invention can work synergistically with starch-modified water treatment agents to effectively remove impurities from wastewater.

[0038] 2. In preparing *Streptomyces rubrum* and *Nocardia rubrum* ferments, this invention adds kelp extract, which is rich in various mineral elements and bioactive components. Among them, one bioactive substance is kelp polysaccharide, which, as an inherent intercellular polysaccharide of brown algae such as kelp, is an important component of all living organisms and plays an important role in controlling cell division, regulating cell growth, and maintaining the normal metabolism of living organisms. By adding kelp extract during the fermentation process, the generation of ferments can be effectively promoted, thereby obtaining a microbial composite flocculant with high bioactivity and large yield, which can better remove organic matter.

[0039] 3. The treatment method of the present invention is simple, the raw materials are readily available, and it is easy to promote. At the same time, the treatment agents used are all environmentally friendly products and will not cause secondary pollution to the waste liquid, thus having broad application prospects. Detailed Implementation

[0040] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0041] Example 1:

[0042] A method for directly recycling chromium tanning waste liquor includes the following steps:

[0043] (1) After removing slag with a slag remover and filtering with a 12μm micropore, the pH of the chromium tanning waste liquor was adjusted to 2.8. Then, under heating to 90℃, a solution of 0.15W / cm² was applied for 4 minutes. 3 The ultrasonic waves are used to treat the reaction solution; a reaction solution is then prepared.

[0044] (2) Preparation of starch-modified water treatment agent:

[0045] Corn amyl starch and sodium hydroxide were mixed evenly at a mass ratio of 75:5.5, ball milled at 45°C for 15 min, and then etherifying agent 2,3-epoxypropyltrimethylammonium chloride 5 was added and stirred at 45°C for 18 min to obtain starch-modified water treatment agent; wherein the molar ratio of starch to etherifying agent was 1:4.

[0046] (3) Preparation of microbial composite flocculant:

[0047] (3.1) Wash and crush the kelp, then add water at a kelp-to-water mass ratio of 1:25 and hydrolyze for 2 hours to obtain kelp hydrolysate; add compound enzyme at a kelp hydrolysate-to-compound enzyme mass ratio of 100:4, and enzymatically hydrolyze at 58℃ for 3.5 hours, then inactivate the enzyme at 105℃ for 2.5 minutes, filter through a 200-mesh plate and frame filter, and concentrate to 1 / 4 volume using a double-effect concentrator at 45℃ to obtain kelp extract; wherein, the compound enzyme includes lipase, protease, cellulase and pectinase;

[0048] (3.2) *Streptomyces rubrum* and *Nocardia rubrum* were inoculated into MRS liquid medium (the volume ratio of *Streptomyces rubrum* or *Nocardia rubrum* to MRS liquid medium was 1:60). The mixture was incubated aerobically at 30°C for 55 h. Then, kelp extract was added as a growth factor at a volume ratio of 1:10 to MRS liquid medium, and the mixture was incubated aerobically at 30°C for another 45 h. The bacterial cells were removed by filtration through gauze. The resulting fermentation broth was centrifuged at 2500 rpm for 15 min, and the supernatant was collected. The supernatant was then concentrated using a rotary evaporator at 45°C. The volume was reduced to half to obtain Streptomyces rubrum ferment and Nocardia rubrum ferment, respectively. The MRS liquid medium included peptone, beef extract, yeast extract, glucose, citrate, sodium acetate, Tween 80, and agar. The concentrations of peptone, beef extract, yeast extract, glucose, citrate, sodium acetate, Tween 80, and agar in the MRS liquid medium were 10 g / L, 10 g / L, 12 g / L, 20 g / L, 1.2 g / L, 4 g / L, 1.2 g / L, and 10 g / L, respectively.

[0049] (3.3) By weight, 15 parts of Streptomyces rubrum ferment, 15 parts of Nocardia rubrum ferment and 16 parts of chitosan were mixed to prepare a microbial composite flocculant.

[0050] (4) In the reaction solution one obtained in step (1), add starch-modified water treatment agent and microbial composite flocculant, stir evenly, let stand for 13 hours, and then use an air flotation machine to blow air, control the diameter of the air bubbles to 200 μm, so that the bubbles adhere to the flocs in the waste liquid and float to the water surface with the bubbles to form foam scum. Scrape off the scum to obtain the chrome tanning waste liquid for direct recycling treatment; wherein, the amount of starch-modified water treatment agent in reaction solution one is 20 mg / L, and the mass ratio of microbial composite flocculant to starch-modified water treatment agent is 5:4.

[0051] Example 2:

[0052] A method for directly recycling chromium tanning waste liquor includes the following steps:

[0053] (1) After removing slag with a slag remover and filtering with a 10μm micropore, the pH of the chromium tanning waste liquid was adjusted to 2.6. Then, under heating conditions of 80℃, a solution of 0.15W / cm² was applied for 5 minutes. 3 The ultrasonic waves are used to treat the reaction solution; a reaction solution is then prepared.

[0054] (2) Preparation of starch-modified water treatment agent:

[0055] Corn amylose and sodium hydroxide were mixed evenly at a mass ratio of 70:6, ball-milled at 45°C for 20 min, and then etherified agent 3-chloro-2-hydroxypropyltrimethylammonium chloride was added. The mixture was stirred at 40°C for 20 min to obtain a starch-modified water treatment agent; wherein the molar ratio of starch to etherified agent was 1:3.

[0056] (3) Preparation of microbial composite flocculant:

[0057] (3.1) Wash and crush the kelp, then add water at a kelp to water mass ratio of 1:20 and hydrolyze for 1 hour to obtain kelp hydrolysate; add compound enzyme at a kelp hydrolysate to compound enzyme at a mass ratio of 100:3 and hydrolyze at 55℃ for 4 hours, then inactivate the enzyme at 100℃ for 3 minutes, filter through a 200-mesh plate and frame filter, and concentrate to 1 / 4 volume using a double-effect concentrator at 40℃ to obtain kelp extract; wherein, the compound enzyme includes lipase, protease, cellulase and pectinase;

[0058] (3.2) *Streptomyces rubrum* and *Nocardia rubrum* were inoculated into MRS liquid medium (the volume ratio of *Streptomyces rubrum* or *Nocardia rubrum* to MRS liquid medium was 1:50). The mixture was incubated aerobically at 28°C for 60 h. Then, kelp extract was added as a growth factor at a volume ratio of 4:50 to MRS liquid medium, and the mixture was incubated aerobically at 28°C for another 50 h. The bacterial cells were removed by filtration through gauze. The resulting fermentation broth was centrifuged at 2500 rpm for 15 min, and the supernatant was collected. The supernatant was then evaporated using a rotary evaporator at 40°C. The mixture was concentrated to half its original volume to prepare *Streptomyces rubrum* ferment and *Nocardia rubrum* ferment, respectively. The MRS liquid culture medium included: peptone, beef extract, yeast extract, glucose, citrate, sodium acetate, Tween 80, and agar. The concentrations of peptone, beef extract, yeast extract, glucose, citrate, sodium acetate, Tween 80, and agar in the MRS liquid culture medium were 8 g / L, 8 g / L, 10 g / L, 18 g / L, 1 g / L, 3 g / L, 1 g / L, and 10 g / L, respectively.

[0059] (3.3) By weight, 10 parts of Streptomyces rubrum ferment, 10 parts of Nocardia rubrum ferment and 15 parts of chitosan are mixed to prepare a microbial composite flocculant.

[0060] (4) In the reaction solution one obtained in step (1), add starch-modified water treatment agent and microbial composite flocculant, stir evenly, let stand for 10 hours, and then use an air flotation machine to blow air, control the diameter of the air bubbles to 100 μm, so that the bubbles adhere to the flocs in the waste liquid and float to the water surface with the bubbles to form foam scum. Scrape off the scum to obtain the chrome tanning waste liquid for direct recycling treatment; wherein, the amount of starch-modified water treatment agent in reaction solution one is 15 mg / L, and the mass ratio of microbial composite flocculant to starch-modified water treatment agent is 1:2.

[0061] Example 3:

[0062] A method for directly recycling chromium tanning waste liquor includes the following steps:

[0063] (1) After removing slag with a slag remover and filtering with a 15μm micropore, the pH of the chromium tanning waste liquid was adjusted to 3. Then, under heating to 100℃, a solution of 0.2W / cm² was applied for 5 minutes. 3 The ultrasonic waves are used to treat the reaction solution; a reaction solution is then prepared.

[0064] (2) Preparation of starch-modified water treatment agent:

[0065] Corn amyl starch and sodium hydroxide were mixed evenly at a mass ratio of 80:6, ball milled at 50°C for 10 min, and then etherifying agent 2,3-epoxypropyltrimethylammonium chloride was added. The mixture was stirred at 50°C for 15 min to obtain a starch-modified water treatment agent; wherein the molar ratio of starch to etherifying agent was 1:5.

[0066] (3) Preparation of microbial composite flocculant:

[0067] (3.1) Wash and crush the kelp, then add water at a kelp to water mass ratio of 1:30 and hydrolyze for 3 hours to obtain kelp hydrolysate; add compound enzyme at a kelp hydrolysate to compound enzyme at a mass ratio of 100:5, and hydrolyze at 60℃ for 3 hours, then inactivate the enzyme at 110℃ for 2 minutes, filter through a 200-mesh plate and frame filter, and concentrate to 1 / 4 volume using a double-effect concentrator at 50℃ to obtain kelp extract; wherein, the compound enzyme includes lipase, protease, cellulase and pectinase;

[0068] (3.2) *Streptomyces rubrum* and *Nocardia rubrum* were inoculated into MRS liquid medium (the volume ratio of *Streptomyces rubrum* or *Nocardia rubrum* to MRS liquid medium was 1:70) and cultured aerobically at 35°C for 50 h. Then, kelp extract was added to the growth factor at a volume ratio of 8:70 to MRS liquid medium, and the culture was continued aerobically at 35°C for 40 h. The bacterial cells were then removed by filtration through gauze. The resulting fermentation broth was centrifuged at 2500 rpm for 15 min, and the supernatant was collected. The supernatant was then evaporated using a rotary evaporator at 50°C. The mixture was concentrated to half its original volume to prepare *Streptomyces rubrum* ferment and *Nocardia rubrum* ferment, respectively. The MRS liquid culture medium included: peptone, beef extract, yeast extract, glucose, citrate, sodium acetate, Tween 80, and agar. The concentrations of peptone, beef extract, yeast extract, glucose, citrate, sodium acetate, Tween 80, and agar in the MRS liquid culture medium were 12 g / L, 12 g / L, 15 g / L, 22 g / L, 2 g / L, 5 g / L, 2 g / L, and 12 g / L, respectively.

[0069] (3.3) By weight, 10-20 parts of Streptomyces rubrum ferment, 20 parts of Nocardia rubrum ferment and 18 parts of chitosan are mixed to prepare a microbial composite flocculant;

[0070] (4) In the reaction solution one obtained in step (1), add starch-modified water treatment agent and microbial composite flocculant, stir evenly, let stand for 15 hours, and then use an air flotation machine to blow air, control the diameter of the air bubbles to 500 μm, so that the bubbles adhere to the flocs in the waste liquid and float to the water surface with the bubbles to form foam scum. Scrape off the scum to obtain the chrome tanning waste liquid for direct recycling treatment; wherein, the amount of starch-modified water treatment agent in reaction solution one is 25 mg / L, and the mass ratio of microbial composite flocculant to starch-modified water treatment agent is 1:1.

[0071] Comparative Example 1:

[0072] A method for the direct recycling of chromium tanning wastewater includes the following steps: without microbial composite flocculant, the rest are the same as in Example 1.

[0073] Comparative Example 2:

[0074] A method for the direct recycling of chromium tanning waste liquid includes the following steps: the microbial composite flocculant is prepared without containing Nocardia rubra, and the rest is the same as in Example 1.

[0075] Comparative Example 3:

[0076] A method for the direct recycling of chromium tanning waste liquid includes the following steps: the microbial composite flocculant is prepared without Streptomyces rubrum, and the rest is the same as in Example 1.

[0077] Comparative Example 4:

[0078] A method for the direct recycling of chromium tanning waste liquid includes the following steps: the microbial composite flocculant does not contain the growth factor kelp extract during preparation, and the rest is the same as in Example 1.

[0079] Test case

[0080] I. The chromium tanning waste liquid was treated using the methods of Examples 1-3 and Comparative Examples 1-4 respectively. The turbidity, color and chemical oxygen demand of the treated waste liquid were tested. The specific methods were as follows: turbidity was measured by spectrophotometer, color was measured by platinum-cobalt standard colorimetric method, and chemical oxygen demand (COD) was measured by potassium dichromate method. The results are shown in Table 1.

[0081] As shown in Table 1, the method of the present invention, which combines starch-modified water treatment agent and microbial composite flocculant, can work synergistically to effectively remove organic matter from chromium tanning waste liquid. However, Comparative Example 1 only uses starch-modified water treatment agent, and the effect is obviously not good enough. Comparative Examples 2-3 only use one type of microbial flocculant, and the effect is not as good as that of the present application. Comparative Document 4 does not add growth factors, so the treatment effect is also poor.

[0082] Table 1 COD Removal Rate Detection

[0083] project Turbidity removal rate % Color removal rate % COD removal rate % Example 1 98.7 98.9 94.5 Example 2 97.9 97.6 95.3 Example 3 98.6 97.9 94.8 Comparative Example 1 50.9 50.8 40.6 Comparative Example 2 60.7 61.2 50.7 Comparative Example 3 58.9 55.4 55.6 Comparative Example 4 65.3 67.2 70.8

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for directly recycling chromium tanning waste liquor, characterized in that, Includes the following steps: (1) After removing slag and filtering through micropores, the pH of the chromium tanning waste liquid is adjusted to acidity and then subjected to ultrasonic treatment under heating conditions to obtain reaction solution one; (2) Add starch-modified water treatment agent and microbial composite flocculant to the reaction liquid obtained in step (1), stir evenly, let stand for 10-15 hours, then purge and scrape off the scum to obtain chromium tanning waste liquid for direct recycling treatment. In step (2), the starch-modified water treatment agent is prepared by the following method: starch and sodium hydroxide are mixed evenly, ball milled for 10-20 min under heating conditions, then etherifying agent is added, stirred and heated for 15-20 min to obtain the starch-modified water treatment agent; In step (2), the mass ratio of starch-modified water treatment agent to microbial composite flocculant is 20:10-20; In step (2), the microbial composite flocculant includes the following raw materials in parts by weight: 10-20 parts of Streptomyces rubrum ferment, 10-20 parts of Nocardia rubrum ferment and 15-18 parts of chitosan.

2. The treatment method for direct recycling of chromium tanning waste liquor according to claim 1, characterized in that, In step (1), the pH value is 2.6-3.

3. The treatment method for direct recycling of chromium tanning waste liquor according to claim 1, characterized in that, In step (2), the amount of starch-modified water treatment agent used in reaction solution one is 15-25 mg / L.

4. The treatment method for direct recycling of chromium tanning waste liquor according to claim 1, characterized in that, The Streptomyces rubrum ferment was prepared by the following method: Streptomyces rubrum was inoculated into MRS liquid medium and cultured aerobically at 28-35℃ for 50-60 h. Then, growth factors were added and cultured aerobically at 28-35℃ for another 40-50 h. The mixture was then filtered, centrifuged and concentrated to obtain the Streptomyces rubrum ferment.

5. The treatment method for direct recycling of chromium tanning waste liquor according to claim 1, characterized in that, The Nocardia rubra ferment is prepared by the following method: Nocardia rubra is cultured using the same method as Streptomyces rubrum to obtain Nocardia rubra ferment.

6. The treatment method for direct recycling of chromium tanning waste liquor according to claim 5, characterized in that, The growth factor is kelp extract.