A method for recovering tin from MOCA wastewater waste

Abstract

The application discloses a method for recovering tin from MOCA wastewater and waste materials, which comprises the following steps: pretreating tin-containing MOCA wastewater, pretreating tin-containing MOCA waste materials, preparing a tin-containing hydrochloric acid solution and preparing crude tin oxide, etc., wherein the MOCA wastewater and waste materials are pretreated, then hydrochloric acid is used to separate tin elements in the MOCA production wastewater and the MOCA production waste materials to obtain a tin-containing hydrochloric acid solution, and then the tin-containing hydrochloric acid solution is neutralized by an alkaline substance to form a tin oxide precipitate; the crude tin oxide prepared by the method has a high tin content and less impurities, and can be directly applied to tin smelting raw materials or tin chemical production raw materials; sodium chloride solution is directly recovered through evaporation crystallization; and the MOCA waste materials after tin separation can also return to the MOCA production line, so that the utilization rate of the metal tin and the MOCA raw materials is effectively improved, the generation of hazardous waste is reduced, and good economic and environmental benefits are achieved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of metal recovery, in particular to a method for recovering tin from MOCA wastewater and waste materials. BACKGROUND

[0002] The product name of MOCA is 3,3'-dichloro-4,4'-diaminodiphenyl methane, commonly known as MOCA, which belongs to a diamine chain extender. When MOCA is used as a vulcanizing agent for cast polyurethane wear-resistant rubber, it can be widely applied to the mechanical industry, automobile and aircraft manufacturing industry, mining industry, sports facilities (such as plastic running tracks and plastic floors) and light manufacturing industry, and can also be used as a crosslinking agent for polyurethane coatings and adhesives, a curing agent for epoxy resins, and used for preparing products with high electrical resistance.

[0003] The preparation method of commercial MOCA products is usually as follows: first, o-chloroaniline is used as a raw material to react with hydrochloric acid to generate o-chloroaniline hydrochloride, then the o-chloroaniline hydrochloride is condensed with formaldehyde in the presence of stannous chloride as a catalyst to generate 4,4'-methylenebis(2-chloroaniline) hydrochloride, then the 4,4'-methylenebis(2-chloroaniline) hydrochloride is neutralized with sodium hydroxide to generate MOCA, and then multi-stage washing, oil-water separation, stripping, dehydration and granulation are performed. The synthetic catalyst stannous chloride is not only retained in the synthetic mother liquor but also retained in the wastewater and MOCA waste materials in the washing process. The wastewater is concentrated by evaporation, the recovered distilled water is discharged after reaching the standard, and the catalyst stannous chloride is mixed in the distillation residue and MOCA waste materials in the form of hazardous waste and is safely landfilled.

[0004] This treatment method is a great waste of valuable tin resources, and how to separate and recover the metal tin in the MOCA waste materials is a bottleneck problem to be solved in the industry. SUMMARY

[0005] In order to solve the above-mentioned problems, the application provides a method for recovering tin from MOCA wastewater and waste materials, which comprises the following steps:

[0006] Pretreatment of MOCA wastewater containing tin: 40-60 wt% hydrogen peroxide is added to the MOCA production process wastewater, and stirring is performed until all the stannous ions in the MOCA production process wastewater are converted into stannic ions, then sodium hydroxide is added to adjust the pH to 6-7, and tin mud is recovered by filtration;

[0007] Pre-treatment of tin-containing MOCA waste: the waste (e.g. MOCA, stannous chloride, stannic oxychloride, and dichlorobenzene ammonium, etc.) produced in the MOCA production process is mixed with tin sludge, 25-35 wt% hydrochloric acid solution is added to adjust the pH to 3-5 to obtain a mixture a, 3-5 L of deionized water is added to each 1 kg of the mixture a, and mixed and stirred into a slurry, solid-liquid separation is performed, and such repeated washing is performed 2-5 times to remove the soluble salt (e.g. sodium chloride, etc.) in the tin-containing waste to obtain the pre-treated tin-containing MOCA waste;

[0008] Preparation of tin-containing hydrochloric acid solution: the tin content in the pre-treated tin-containing MOCA waste is detected, 25-35 wt% hydrochloric acid solution is added to the pre-treated tin-containing MOCA waste according to the stoichiometric ratio (1:4-8) mol of tin to hydrogen chloride, and heated for 4-6 h, cooled, and solid-liquid separation is performed to obtain the tin-containing hydrochloric acid solution, and the MOCA waste after tin recovery is returned to the MOCA production line for use;

[0009] Preparation of crude tin oxide: sodium hydroxide or sodium carbonate is added to the tin-containing hydrochloric acid solution to adjust the pH value to 6-7, stirring is then performed, and solid-liquid separation and washing are performed to obtain the crude tin hydroxide and sodium chloride solution.

[0010] Preferably, the mass concentration of hydrogen peroxide is 50 wt% in the process of pre-treating the tin-containing MOCA waste.

[0011] Preferably, the ratio of the MOCA production process wastewater to 40-60 wt% hydrogen peroxide is 1000 L:(1-5) L in the process of pre-treating the tin-containing MOCA waste. Excessive hydrogen peroxide will not only cause the cost of treating the wastewater to be too high, but also cause secondary environmental pollution.

[0012] Preferably, the ratio of the MOCA production process wastewater to 40-60 wt% hydrogen peroxide is 1000 L:(2-3) L in the process of pre-treating the tin-containing MOCA waste.

[0013] Preferably, the stirring time is 2-4 h and the stirring speed is 500-1500 r / min in the process of pre-treating the tin-containing MOCA waste.

[0014] Preferably, the heating temperature is 90-120 °C in the process of preparing the tin-containing hydrochloric acid solution. A reasonable heating temperature can ensure that the hydrochloric acid and the tin compounds in the waste are fully reacted, while avoiding unnecessary side reactions or volatilization loss caused by excessively high temperature.

[0015] Preferably, the heating temperature is 95-110 °C in the process of preparing the tin-containing hydrochloric acid solution.

[0016] Preferably, the mass concentration of the hydrochloric acid solution used in the process of preparing the tin-containing hydrochloric acid solution is 31 wt%

[0017] Preferably, in the preparation of crude tin oxide, the stirring time is 2-4h, and the stirring speed is 500-700r / min. Here, the stirring speed should not be too fast, because too fast stirring speed can easily produce bubbles, leading to inaccurate pH value test. Also, the stirring speed should not be too slow, because too slow stirring speed can lead to uneven stirring and inaccurate pH value test. Moreover, the stirring time should not be too short, because too short stirring time can lead to insufficient reaction.

[0018] Beneficial effects are that: the application first pretreats MOCA wastewater and waste materials, then separates tin elements in MOCA production wastewater and MOCA production waste materials by hydrochloric acid to obtain a tin-containing hydrochloric acid solution, and then neutralizes the tin-containing hydrochloric acid solution by an alkaline substance to form a tin oxide precipitate. The crude tin oxide prepared by this method has a high tin content and less impurities, and can be directly applied to tin smelting raw materials or tin chemical production raw materials. The sodium chloride solution is directly recycled by evaporation crystallization, and the MOCA waste materials after tin separation can also return to the MOCA production line, so as to effectively improve the utilization rate of metal tin and MOCA raw materials, reduce the generation of hazardous waste, and has good economic and environmental benefits. DETAILED DESCRIPTION

[0019] The application will be further described in detail below with reference to specific examples, so that those skilled in the art can more clearly understand the application.

[0020] The following examples are used to illustrate the application, but are not used to limit the scope of the application. Based on the specific examples in the application, all other examples obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0021] In the embodiments of the application, all raw material components are commercially available products well known to those skilled in the art, unless otherwise specified. In the embodiments of the application, the technical means used are conventional means well known to those skilled in the art, unless otherwise specified.

[0022] Raw material sources:

[0023] MOCA wastewater and waste materials were purchased from Huaihe City Starlight New Material Technology Co., Ltd.

[0024] The remaining reagents are all conventional commercially available products.

[0025] Example 1

[0026] A method for recovering tin from MOCA wastewater and waste materials, comprising:

[0027] Pre-treatment of MOCA wastewater containing tin: 40wt% hydrogen peroxide is added to MOCA production process wastewater according to the volume ratio of 1000L: 1L, and stirring is performed until the residual stannous tin in the MOCA production process wastewater is completely converted into tetravalent tin, the stirring time is 2h, the stirring speed is 500r / min, then sodium hydroxide is added to adjust the pH to 6-7, and tin mud is recovered by filtration;

[0028] Pre-treatment of MOCA wastewater containing tin: 40wt% hydrogen peroxide is added to MOCA production process wastewater according to the volume ratio of 1000L: 1L, and stirring is performed until the residual stannous tin in the MOCA production process wastewater is completely converted into tetravalent tin, the stirring time is 2h, the stirring speed is 500r / min, then sodium hydroxide is added to adjust the pH to 6-7, and tin mud is recovered by filtration;

[0029] Pre-treatment of MOCA wastewater containing tin: 40wt% hydrogen peroxide is added to MOCA production process wastewater according to the volume ratio of 1000L: 1L, and stirring is performed until the residual stannous tin in the MOCA production process wastewater is completely converted into tetravalent tin, the stirring time is 2h, the stirring speed is 500r / min, then sodium hydroxide is added to adjust the pH to 6-7, and tin mud is recovered by filtration;

[0030] Pre-treatment of MOCA wastewater containing tin: 40wt% hydrogen peroxide is added to MOCA production process wastewater according to the volume ratio of 1000L: 1L, and stirring is performed until the residual stannous tin in the MOCA production process wastewater is completely converted into tetravalent tin, the stirring time is 2h, the stirring speed is 500r / min, then sodium hydroxide is added to adjust the pH to 6-7, and tin mud is recovered by filtration.

[0031] Example 2

[0032] A method for recovering tin from MOCA wastewater and waste material, comprising:

[0033] Pre-treatment of MOCA wastewater containing tin: 40wt% hydrogen peroxide is added to MOCA production process wastewater according to the volume ratio of 1000L: 1L, and stirring is performed until the residual stannous tin in the MOCA production process wastewater is completely converted into tetravalent tin, the stirring time is 2h, the stirring speed is 500r / min, then sodium hydroxide is added to adjust the pH to 6-7, and tin mud is recovered by filtration;

[0034] Pre-treatment of MOCA wastewater containing tin: 40wt% hydrogen peroxide is added to MOCA production process wastewater according to the volume ratio of 1000L: 1L, and stirring is performed until the residual stannous tin in the MOCA production process wastewater is completely converted into tetravalent tin, the stirring time is 2h, the stirring speed is 500r / min, then sodium hydroxide is added to adjust the pH to 6-7, and tin mud is recovered by filtration;

[0035] Preparation of tin-containing hydrochloric acid solution: detect the tin content in the pretreated tin-containing MOCA waste, according to the stoichiometric ratio of tin to hydrogen chloride 1 mol: 6 mol, add 31 wt% hydrochloric acid solution to the pretreated tin-containing MOCA waste, heat at 95°C for 5h, cool, and solid-liquid separation to obtain a tin-containing hydrochloric acid solution, and the MOCA waste after tin recovery returns to the MOCA production line for use;

[0036] Preparation of crude tin oxide: add sodium hydroxide or sodium carbonate to the tin-containing hydrochloric acid solution, adjust the pH value to 6-7, stir, then solid-liquid separation and washing, the stirring time is 3h, and the stirring speed is 600r / min, to obtain a crude tin hydroxide and sodium chloride solution.

[0037] Example 3

[0038] A method for recovering tin from MOCA wastewater waste, comprising:

[0039] Pretreatment of tin-containing MOCA wastewater: add 55wt% hydrogen peroxide to the MOCA production process wastewater according to a volume ratio of 1000L:3L, stir until all the stannous tin remaining in the MOCA production process wastewater is converted into tetravalent tin, the stirring time is 3.5h, and the stirring speed is 1000r / min, then add sodium hydroxide to adjust the pH to 6-7, filter and recover to obtain tin sludge;

[0040] Pretreatment of tin-containing MOCA waste: mix the waste generated in the MOCA production process with the tin sludge, add 32wt% hydrochloric acid solution to adjust the pH to 4 to obtain a mixture a, add 5L of deionized water to each 1kg of the mixture a, mix and stir into a slurry, solid-liquid separation, and repeat the washing for 4 times to obtain the pretreated tin-containing MOCA waste;

[0041] Preparation of tin-containing hydrochloric acid solution: detect the tin content in the pretreated tin-containing MOCA waste, according to the stoichiometric ratio of tin to hydrogen chloride 1 mol: 7 mol, add 33 wt% hydrochloric acid solution to the pretreated tin-containing MOCA waste, heat at 110°C for 5h, cool, and solid-liquid separation to obtain a tin-containing hydrochloric acid solution, and the MOCA waste after tin recovery returns to the MOCA production line for use;

[0042] Preparation of crude tin oxide: add sodium hydroxide or sodium carbonate to the tin-containing hydrochloric acid solution, adjust the pH value to 6-7, stir, then solid-liquid separation and washing, the stirring time is 3h, and the stirring speed is 600r / min, to obtain a crude tin hydroxide and sodium chloride solution.

[0043] Example 4

[0044] A method for recovering tin from MOCA wastewater waste, comprising:

[0045] Pretreatment of tin-containing MOCA wastewater: Add 60wt% hydrogen peroxide to the MOCA production process wastewater at a volume ratio of 1000L:5L, stir until all residual tin in the MOCA production process wastewater is converted into tetravalent tin, stir for 4 hours, stir at a stirring speed of 1500r / min, then add sodium hydroxide to adjust the pH to 6-7, and filter to recover tin sludge.

[0046] Pre-treatment of tin-containing MOCA waste: Mix the waste generated during the MOCA production process with tin sludge, add 35wt% hydrochloric acid solution to adjust the pH to 3 to obtain mixture a, add 5L of deionized water to each 1kg of mixture a, mix and stir into a slurry, separate the solid and liquid, and repeat the washing process 5 times to obtain pre-treated tin-containing MOCA waste.

[0047] Preparation of tin-containing hydrochloric acid solution: The tin content in the pretreated tin-containing MOCA waste was detected. According to the stoichiometric ratio of tin to hydrogen chloride 1mol: 8mol, 35wt% hydrochloric acid solution was added to the pretreated tin-containing MOCA waste. The mixture was heated to 120℃ and reacted for 6h. After cooling, the solid and liquid were separated to obtain the tin-containing hydrochloric acid solution. The tin-recovered MOCA waste was returned to the MOCA production line for use.

[0048] Preparation of crude tin oxide: Add sodium hydroxide or sodium carbonate to a tin-containing hydrochloric acid solution, adjust the pH to 6-7, stir, then separate the solid and liquid, wash, stir for 4 hours, and stir at a speed of 700 r / min to obtain crude tin hydroxide and sodium chloride solution.

[0049] Test method:

[0050] Crude tin hydroxide was tested according to the Chinese national standard GB / T 24268-2009.

[0051] The test results are shown in Table 1, which shows the tin content in the crude tin hydroxide.

[0052] Table 1. Results of Tin Content Detection in Crude Tin Hydroxide

[0053]

[0054]

[0055] The data in the table above shows that the tin content in the final product, crude tin hydroxide, reaches more than 30%, and the tin conversion rate is high. This indicates that the technical solution can effectively remove impurities, and the crude tin hydroxide produced has a high tin content and few impurities. The final product, crude tin hydroxide, can be directly used as a raw material for tin smelting or tin chemical production.

[0056] The above merely illustrates the embodiments of the present application, but should not be taken as limitations. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be included in the scope of claims of the present application.

Claims

1. A method of recovering tin from MOCA wastewater waste material, characterized by, The application relates to a method for preparing tin-containing tin hydroxide and tin chloride from MOCA (methylol urea formaldehyde) wastewater and MOCA waste. The method comprises the following steps: pretreating tin-containing MOCA wastewater, adding 40-60 wt% hydrogen peroxide into MOCA production process wastewater, stirring until all stannous tin in the MOCA production process wastewater is converted into tetravalent tin, then adding sodium hydroxide to adjust the pH value to 6-7, and filtering to recover tin mud; Pretreating tin-containing MOCA waste: mixing waste generated in a MOCA production process with the tin mud, adding 25-35 wt% hydrochloric acid solution to adjust the pH value to 3-5 to obtain a mixture a, adding 3-5 L of deionized water to 1 kg of the mixture a, mixing and stirring into a slurry, and performing solid-liquid separation, and repeating the washing for 2-5 times to obtain pretreated tin-containing MOCA waste; Preparing tin-containing hydrochloric acid solution: detecting the tin content in the pretreated tin-containing MOCA waste, adding 25-35 wt% hydrochloric acid solution into the pretreated tin-containing MOCA waste according to the stoichiometric ratio (1:4-8) mol of tin and hydrogen chloride, heating and reacting for 4-6 h, cooling, and performing solid-liquid separation to obtain the tin-containing hydrochloric acid solution, and returning the MOCA waste after tin recovery to a MOCA production line for use; Preparing crude tin oxide: adding sodium hydroxide or sodium carbonate into the tin-containing hydrochloric acid solution, adjusting the pH value to 6-7, stirring, and then performing solid-liquid separation and washing to obtain crude tin hydroxide and sodium chloride solution; In the pretreatment process of the tin-containing MOCA wastewater, the ratio of the MOCA production process wastewater to the 40-60 wt% hydrogen peroxide is 1000 L:(2-3) L; In the pretreatment process of the tin-containing MOCA wastewater, the stirring time is 2-4 h, and the stirring speed is 500-1500 r / min; In the preparation process of the tin-containing hydrochloric acid solution, the heating temperature is 95-110 DEG C; In the preparation process of the crude tin oxide, the stirring time is 2-4 h, and the stirring speed is 500-700 r / min.

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