Process for recovering chromium from leather leftovers

Abstract

The invention relates to the technical field of leather chromium removal and reutilization, and provides a process for recovering chromium from leather leftovers, which comprises the following steps: S1, pretreating the leather leftovers, adding the pretreated leather leftovers into alkali liquor, mixing, filtering to obtain filter residues A and filtrate A, and drying the filtrate A to obtain collagen powder; s2, mixing the filter residue A with an acid solution to obtain a mixed solution; s3, the mixed solution and the organic acid salt solution are mixed, and chromium powder is obtained after reduction and drying treatment; the raw material of the acid liquor comprises organic acid, and the organic acid comprises phytic acid and tartaric acid in a mass ratio of 1: 8-9: 1. According to the technical scheme, the problem that the chromium recovery effect is poor when the chromium is recovered from the leather leftovers in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the technical field of leather dechroming and recycling, and in particular to a process for recovering chromium from leather scraps. Background Art

[0002] The leather industry is an important part of the traditional manufacturing industry. With the development of the industry, a large amount of leather scraps are generated. If the chromium contained in the leather scraps is not recycled, it will not only cause serious pollution to the environment, but also lead to waste of resources.

[0003] Since the composition of leather scraps is complex and diverse, in addition to chromium compounds, it also contains a variety of other organic and inorganic components. These impurities may physically or chemically combine with chromium, interfering with the separation and extraction of chromium during the recycling process, resulting in a low chromium removal rate. At the same time, the chromium inside the larger leather particles may not be able to fully contact with the external dechroming agent, so that part of the chromium cannot be effectively dissolved. And in terms of recycling technology, unreasonable process parameters also have an important impact on the recovery of chromium. Therefore, it is necessary to obtain a process for recovering chromium from leather scraps. Improving the recovery of chromium will have important practical significance for reducing environmental pollution. Summary of the invention

[0004] The invention provides a process for recovering chromium from leather scraps, which solves the problem of poor chromium recovery effect when recovering chromium from leather scraps in the related art.

[0005] The technical solution of the present invention is as follows: The present invention provides a process for recovering chromium from leather scraps, comprising the following steps: S1. After pretreatment, leather scraps are added into alkaline solution for mixing, filtered to obtain filter residue A and filtrate A, and the filtrate A is dried to obtain collagen powder; S2, mixing the filter residue A and acid solution to obtain a mixed solution; S3, mixing the mixed solution and the organic acid salt solution, and obtaining chromium powder after oxidation, reduction and drying; The raw materials of the acid solution include organic acid, and the organic acid includes phytic acid and tartaric acid in a mass ratio of 1:8 to 9:1.

[0006] As a further technical solution, the pretreatment is crushing to 500-800 mesh.

[0007] As a further technical solution, the raw materials of the acid solution also include water and a surfactant; the mass ratio of the organic acid, the surfactant and the water is 4:0.1:100-150; The surfactant is a sulfonate anionic surfactant.

[0008] As a further technical solution, the raw materials of the acid solution also include water, a surfactant, and monoethanolamine thioglycolate; the mass ratio of the organic acid, the surfactant, water and monoethanolamine thioglycolate is 4:0.1:100:1-3.

[0009] In the present invention, monoethanolamine thioglycolate is also added to the acid solution, thereby further improving the recovery effect of chromium from leather scraps.

[0010] As a further technical solution, in step S2, the mixing temperature is 40-50°C and the mixing time is 18-24h; In step S1, the mixing temperature is 85-95°C and the mixing time is 4-6 hours; In step S3, the mixing temperature is 40-45° C. and the mixing time is 10-15 hours.

[0011] As a further technical solution, an oxidant is added during the oxidation, and the oxidant is a dichromate, including one of potassium dichromate and sodium dichromate; A reducing agent is added during the reduction, and the reducing agent is sodium sulfite.

[0012] As a further technical solution, the raw materials of the alkali solution include alkali and water in a mass ratio of 1:20-25; the alkali includes at least two of potassium hydroxide, sodium hydroxide, sodium bicarbonate, and sodium carbonate.

[0013] As a further technical solution, the raw materials of the organic acid salt solution include an organic acid salt and water in a mass ratio of 1:10-14.

[0014] As a further technical solution, the organic acid salt includes at least one of tartrate, oxalate and citrate; Preferably, the organic acid salt includes tartrate and citrate.

[0015] In the present invention, when an organic acid salt solution is mixed with the mixed solution and the organic acid salt is tartrate or citrate, the recovery effect of chromium from leather scraps is further improved.

[0016] As a further technical solution, the mass ratio of the tartrate to the citrate is 3:2~4:1.

[0017] In the present invention, when the mass ratio of tartrate to citrate is 3:2-4:1, the recovery effect of chromium from leather scraps is further improved.

[0018] As a further technical solution, the tartrate includes sodium tartrate and / or potassium tartrate; the citrate includes sodium citrate and / or potassium citrate.

[0019] As a further technical solution, the organic acid comprises phytic acid and tartaric acid in a mass ratio of 2:1 to 4:1.

[0020] In the present invention, when the organic acid is phytic acid and tartaric acid in a mass ratio of 2:1 to 4:1, the recovery effect of chromium from leather waste is further improved.

[0021] As a further technical solution, the sulfonate anionic surfactant includes at least one of sodium dodecylbenzenesulfonate and sodium dioctyl sulfosuccinate; Preferably, the anionic surfactant is dioctyl sodium sulfosuccinate.

[0022] In the present invention, when the anionic surfactant is sodium dioctyl sulfosuccinate, after being combined with other components of the acid solution, the recovery effect of chromium from leather scraps is further improved.

[0023] The working principle and beneficial effects of the present invention are: In the present invention, when recovering chromium from leather scraps, the leather scraps are treated with alkali solution, acid solution and organic acid salt solution, and the organic acid in the acid solution treatment is compounded with phytic acid and tartaric acid to complex chromium ions, thereby significantly improving the recovery effect of chromium from leather scraps. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In the following examples, monoethanolamine thioglycolate was purchased from Nanjing Bermuda Biotechnology Co., Ltd.

[0026] Example 1 The process of recovering chromium from leather scraps includes the following steps: S1. Grind 100 g of leather scraps to 500 mesh, mix with 200 g of alkali solution at 85° C. for 6 h, filter to obtain filter residue A and filtrate A, and dry the filtrate A to obtain collagen powder; wherein the raw materials of the alkali solution are potassium hydroxide, sodium hydroxide and water in a mass ratio of 0.5:0.5:20; S2, mixing the filter residue A and 200g of acid solution at 40°C for 24h to obtain a mixed solution; wherein the raw materials of the acid solution are organic acid, sodium dodecylbenzene sulfonate and water in a mass ratio of 4:0.1:120; the organic acid is phytic acid and tartaric acid in a mass ratio of 9:1; S3. Mix the mixed solution and 200 g of organic acid salt solution at 40° C. for 15 h, add 4 g of potassium dichromate and mix at 90° C. for 5 h, add 0.2 g of sodium sulfite and mix for 2 h, and obtain chromium powder after drying; wherein the raw materials of the organic acid salt solution include organic acid salt and water in a mass ratio of 1:12; and the organic acid salt is sodium tartrate.

[0027] Example 2 The process of recovering chromium from leather scraps includes the following steps: S1. Grind 100 g of leather scraps to 600 mesh, mix with 200 g of alkali solution at 90° C. for 5 h, filter to obtain filter residue A and filtrate A, and dry the filtrate A to obtain collagen powder; wherein the raw materials of the alkali solution are potassium hydroxide, sodium bicarbonate and water in a mass ratio of 0.5:0.5:25; S2, mixing the filter residue A and 200g of acid solution at 45°C for 20h to obtain a mixed solution; wherein the raw materials of the acid solution are organic acid, sodium dodecylbenzene sulfonate and water in a mass ratio of 4:0.1:150; the organic acid is phytic acid and tartaric acid in a mass ratio of 1:8; S3. Mix the mixed solution and 200 g of organic acid salt solution at 45° C. for 10 h, add 4 g of sodium dichromate and mix at 90° C. for 5 h, add 0.2 g of sodium sulfite and mix for 2 h, and obtain chromium powder after drying; wherein the raw materials of the organic acid salt solution include organic acid salt and water in a mass ratio of 1:14; and the organic acid salt is sodium tartrate.

[0028] Example 3 The process of recovering chromium from leather scraps includes the following steps: S1. Grind 100 g of leather scraps to 800 mesh, mix with 200 g of alkali solution at 95° C. for 4 h, filter to obtain filter residue A and filtrate A, and dry the filtrate A to obtain collagen powder; wherein the raw materials of the alkali solution are potassium hydroxide, sodium hydroxide and water in a mass ratio of 0.5:0.5:20; S2, mixing the filter residue A and 200g of acid solution at 50°C for 18h to obtain a mixed solution; wherein the raw materials of the acid solution are organic acid, sodium dodecylbenzene sulfonate and water in a mass ratio of 4:0.1:100; the organic acid is phytic acid and tartaric acid in a mass ratio of 1:1; S3. Mix the mixed solution and 200 g of organic acid salt solution at 45° C. for 10 h, add 4 g of potassium dichromate and mix at 90° C. for 5 h, add 0.2 g of sodium sulfite and mix for 2 h, and obtain chromium powder after drying; wherein the raw materials of the organic acid salt solution include organic acid salt and water in a mass ratio of 1:10; and the organic acid salt is sodium tartrate.

[0029] Example 4 The only difference between this embodiment and embodiment 3 is that the organic acid salt is sodium citrate.

[0030] Example 5 The only difference between this embodiment and embodiment 3 is that the organic acid salt is sodium tartrate and sodium citrate in a mass ratio of 5:1.

[0031] Example 6 The only difference between this embodiment and embodiment 3 is that the organic acid salt is sodium tartrate and sodium citrate in a mass ratio of 1:1.

[0032] Example 7 The only difference between this embodiment and embodiment 3 is that the organic acid salt is sodium tartrate and sodium citrate in a mass ratio of 3:2.

[0033] Example 8 The only difference between this embodiment and embodiment 3 is that the organic acid salt is sodium tartrate and sodium citrate in a mass ratio of 4:1.

[0034] Example 9 The only difference between this embodiment and embodiment 7 is that the organic acids are phytic acid and tartaric acid in a mass ratio of 5:1.

[0035] Example 10 The only difference between this embodiment and embodiment 7 is that the organic acids are phytic acid and tartaric acid in a mass ratio of 2:1.

[0036] Embodiment 11 The only difference between this embodiment and embodiment 7 is that the organic acids are phytic acid and tartaric acid in a mass ratio of 4:1.

[0037] Example 12 The difference between this embodiment and embodiment 11 is that sodium dodecylbenzene sulfonate is replaced by sodium dioctyl sulfosuccinate.

[0038] Embodiment 13 The only difference between this embodiment and embodiment 12 is that the raw materials of the acid solution are organic acid, sodium dodecylbenzenesulfonate, water and monoethanolamine thioglycolate in a mass ratio of 4:0.1:100:1; and the organic acid is phytic acid and tartaric acid in a mass ratio of 1:1.

[0039] Embodiment 14 The only difference between this embodiment and embodiment 12 is that the raw materials of the acid solution are organic acid, sodium dodecylbenzenesulfonate, water and monoethanolamine thioglycolate in a mass ratio of 4:0.1:100:3; and the organic acid is phytic acid and tartaric acid in a mass ratio of 1:1.

[0040] Comparative Example 1 The only difference between this comparative example and Example 3 is that the organic acid is phytic acid.

[0041] Comparative Example 2 The only difference between this comparative example and Example 3 is that the organic acid is tartaric acid.

[0042] According to GB / T 24331-2009 "Powdered chrome tanning agent for leather making", the chromium content in the chromium powders prepared in Examples 1 to 14 and Comparative Examples 1 to 2 was analyzed and tested respectively, and the chromium content in the collagen powder was analyzed and tested by ICP-AES. The results are shown in Table 1 below. The above chromium contents are all calculated as Cr2O3.

[0043] Table 1 Chromium content test results

[0044] Compared with Comparative Examples 1-2, the chromium content of the chromium powder recovered from leather scraps in Examples 1-14 is higher, indicating that when recovering chromium from leather scraps, the leather scraps are treated with alkali solution, acid solution and organic acid salt solution, and the organic acid during the acid treatment is compounded with phytic acid and tartaric acid, which significantly improves the recovery effect of chromium from leather scraps.

[0045] Compared with Examples 3 to 4, the chromium content of the chromium powder recovered from leather scraps in Examples 5 to 8 is higher, indicating that the leather scraps are treated with an organic acid salt solution, and when the organic acid salt is tartrate or citrate, the recovery effect of chromium from leather scraps can be further improved.

[0046] Compared with Examples 5-6, the chromium content of the chromium powder recovered from leather scraps in Examples 7-8 is higher, indicating that when the mass ratio of tartrate to citrate is 3:2-4:1, the recovery effect of chromium from leather scraps can be further improved.

[0047] Compared with Example 7 and Example 9, the chromium content of the chromium powder recovered from leather scraps in Examples 10 to 11 is higher, indicating that when the organic acid is phytic acid and tartaric acid in a mass ratio of 2:1 to 4:1, the recovery effect of chromium from leather scraps is further improved; compared with Example 11, the chromium content of the chromium powder recovered in Example 12 is higher, indicating that when the anionic surfactant is sodium dioctyl sulfosuccinate, the recovery effect of chromium from leather scraps is further improved.

[0048] Compared with Example 12, the chromium content of the chromium powder recovered from leather scraps in Examples 13-14 is higher, indicating that monoethanolamine thioglycolate is also added to the acid solution, which further improves the recovery effect of chromium from leather scraps.

[0049] The above are only preferred embodiments of the present invention and are 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 in the protection scope of the present invention.

Claims

1. A process for recovering chromium from leather scraps, characterized in that: The following steps are involved: S1. After pretreatment, leather scraps are added into alkaline solution for mixing, filtered to obtain filter residue A and filtrate A, and the filtrate A is dried to obtain collagen powder; S2, mixing the filter residue A and acid solution to obtain a mixed solution; S3, mixing the mixed solution and the organic acid salt solution, and obtaining chromium powder after oxidation, reduction and drying; The raw materials of the acid solution include organic acid, and the organic acid includes phytic acid and tartaric acid in a mass ratio of 1:8 to 9:

1.

2. A process for recovering chromium from leather scraps according to claim 1, characterized in that: The raw materials of the acid solution also include water and a surfactant; the mass ratio of the organic acid, the surfactant and the water is 4:0.1:100-150; The surfactant is a sulfonate anionic surfactant.

3. A process for recovering chromium from leather scraps according to claim 2, characterized in that: The raw materials of the acid solution also include water, a surfactant, and monoethanolamine thioglycolate; the mass ratio of the organic acid, the surfactant, water and monoethanolamine thioglycolate is 4:0.1:100:1-3.

4. A process for recovering chromium from leather scraps according to claim 1, characterized in that: In step S2, the mixing temperature is 40-50°C and the mixing time is 18-24h; In step S1, the mixing temperature is 85-95°C and the mixing time is 4-6 hours; In step S3, the mixing temperature is 40-45° C. and the mixing time is 10-15 hours.

5. A process for recovering chromium from leather scraps according to claim 1, characterized in that: The raw materials of the alkali solution include alkali and water in a mass ratio of 1:20-25; the alkali includes at least two of potassium hydroxide, sodium hydroxide, sodium bicarbonate, and sodium carbonate.

6. A process for recovering chromium from leather scraps according to claim 1, characterized in that: The raw materials of the organic acid salt solution include organic acid salt and water in a mass ratio of 1:10-14.

7. A process for recovering chromium from leather scraps according to claim 6, characterized in that: The organic acid salt includes at least one of tartrate, oxalate and citrate; Preferably, the organic acid salt includes tartrate and citrate.

8. A process for recovering chromium from leather scraps according to claim 7, characterized in that: The mass ratio of the tartrate to the citrate is 3:2-4:

1.

9. A process for recovering chromium from leather scraps according to claim 1, characterized in that: The organic acid comprises phytic acid and tartaric acid in a mass ratio of 2:1 to 4:

1.

10. A process for recovering chromium from leather scraps according to claim 2, characterized in that: The sulfonate anionic surfactant includes at least one of sodium dodecylbenzenesulfonate and sodium dioctyl sulfosuccinate; Preferably, the anionic surfactant is dioctyl sodium sulfosuccinate.

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