Method for preparing methyltin mercaptide by recovering methyltin compound in wastewater

Abstract

The invention discloses a method for preparing methyltin mercaptide by recovering a methyltin compound in wastewater, and relates to the technical field of wastewater treatment.The method specifically comprises the following steps that 1, hydrogen peroxide is added into the wastewater for an oxidation reaction, then perchloric acid is added for a chlorination reaction, and a methyltin chloride solution is obtained; and (2) adding isooctyl thioglycolate into the methyltin chloride solution, and carrying out esterification reaction to obtain the organic matter methyltin mercaptide. The method comprises the following steps: carrying out oxidation treatment on wastewater rich in methyltin compounds in an acidic medium by using hydrogen peroxide, then adding perchloric acid for further oxidation and chlorination treatment to obtain a methyltin chloride water-phase medium, and then carrying out esterification reaction on the methyltin chloride water-phase medium and isooctyl thioglycolate to obtain a methyltin mercaptide product; the method disclosed by the invention well fills the technical blank of recycling and treating the wastewater rich in the methyltin mercaptide compound in the methyltin mercaptide industry, and greatly improves the comprehensive recycling rate of tin resources.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly relates to a method for recovering methyltin compounds in wastewater to prepare methyltin mercaptide. Background Art

[0002] Methyltin mercaptide is mainly used as a heat stabilizer for PVC products and is obtained by the reaction of methyltin chloride and isooctyl mercaptoacetate. The crude product washing water, floor and equipment flushing water, and leaking materials generated during its production process are uniformly collected by a collection tank. Due to containing a large amount of methyltin mercaptide, monomethyltin trichloride, dimethyltin dichloride, and isooctyl mercaptoacetate, the wastewater collected and settled is an organic oily liquid. Because it is rich in methyltin compounds and organic matter, if directly sent to the sewage treatment system for treatment, on the one hand, it increases the sewage treatment volume and treatment difficulty, increasing the enterprise cost, and on the other hand, it causes waste of tin resources.

[0003] In the current related technologies for recycling wastewater, domestic and foreign literature reports only involve the treatment of wastewater to meet the discharge standards, including physical treatment methods such as adsorption method and membrane separation method, chemical treatment methods such as chemical precipitation method and advanced oxidation method, and biological treatment methods such as biodegradation and biosorption. The above methods are all aimed at treating the organic phase in the wastewater into an inorganic phase, reducing indicators such as heavy metals and chemical oxygen demand, so that the production wastewater meets the discharge standards, which belongs to the category of environmental protection, and there are few reports on the technology of recycling wastewater to prepare methyltin mercaptide.

[0004] Due to the yellow and turbid appearance of the wastewater, high chlorine element and other impurity components, after removing water, it cannot be directly compounded into methyltin mercaptide products. Also, because it is difficult to separate and extract methyltin mercaptide from the wastewater, and the organic phase medium of methyltin chloride does not react with isooctyl mercaptoacetate either. Therefore, to recycle and treat the methyltin compounds in the wastewater, it is necessary to convert the methyltin mercaptide and methyltin chloride in the wastewater into a tin-containing medium that can undergo an esterification reaction with isooctyl mercaptoacetate.

[0005] Therefore, providing a method for recovering methyltin compounds in wastewater to prepare methyltin mercaptide is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To solve the above problems, the present invention provides a method for recovering methyltin compounds in wastewater to prepare methyltin mercaptide. The method uses hydrogen peroxide to oxidize the wastewater rich in methyltin compounds in an acidic medium, then adds perchloric acid for further oxidation and chlorination treatment to obtain a methyltin chloride aqueous medium, and then undergoes an esterification reaction with isooctyl mercaptoacetate to obtain a methyltin mercaptide product. The present invention well fills the technical blank of the recycling treatment of wastewater rich in methyltin compounds in the methyltin mercaptide industry and greatly improves the comprehensive recovery rate of tin resources.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing methyltin mercaptide by recovering methyltin compounds from wastewater, specifically comprising the following steps:

[0009] (1) After adding hydrogen peroxide to the wastewater for an oxidation reaction, perchloric acid is added for a chlorination reaction to obtain a methyltin chloride solution;

[0010] (2) Isooctyl mercaptoacetate is added to the methyltin chloride solution for an esterification reaction to obtain an organic substance, which is methyltin mercaptide.

[0011] Preferably, the chemical reaction equation of the oxidation reaction is:

[0012] 2CH3Sn(SCH2COOC8H 17 )3 + 3H2O2 + 6H + →(CH3Sn)2O3 + 6HSCH2COOC8H 17 + 3H2O,

[0013] 4(CH3)2Sn(SCH2COOC8H 17 )2 + 3H2O2 + 6H + →4(CH3)2SnO + 8HSCH2COOC8H 17 + 2H2O,

[0014] 2CH3SnCl3 + 3H2O2 + 6H + →(CH3Sn)2O3 + 3H2O + 6HCl,

[0015] 4(CH3)2SnCl2 + 3H2O2 + 6H + →4(CH3)2SnO + 2H2O + 8HCl.

[0016] Most of the methyltin compounds in the wastewater are oxidized to methyltin oxide.

[0017] Preferably, the chemical reaction equation of the chlorination reaction is:

[0018] HClO4 + 2H2O2 → HCl + 2H2O + 3O2↑,

[0019] (CH3Sn)2O3 + 6HCl → 2CH3SnCI3 + 3H2O,

[0020] (CH3)2SnO + 2HCl → (CH3)2SnCI2 + H2O.

[0021] Perchloric acid further oxidizes all methyltin compounds to methyltin oxide. The reaction principle is the same as above, and it undergoes a redox reaction with excessive hydrogen peroxide to generate hydrogen chloride, which then reacts with methyltin oxide through chlorination to obtain methyltin chloride.

[0022] Preferably, the chemical reaction equation for the esterification reaction is as follows:

[0023] CH3SnCl3 + 3HSCH2COOC8H 17 →CH3Sn(SCH2COOC8H 17 )3 + 3HCl,

[0024] (CH3)2SnCl2 + 2HSCH2COOC8H 17 →(CH3)2Sn(SCH2COOC8H 17 )2 + 2HCl,

[0025] HCl + NH3·H2O → NH4Cl + H2O.

[0026] Preferably, in step (1), the mass ratio of the hydrogen peroxide to the wastewater is 1 - 1.5:1.

[0027] In the present invention, compared with oxidants such as potassium permanganate and potassium dichromate, hydrogen peroxide reacts gently without fierceness, the process is easy to control, and it is colorless and transparent itself. After the reaction ends, the color of the system will not change.

[0028] Preferably, in step (1), the mass concentration of the hydrogen peroxide is 27.5 - 32%.

[0029] Preferably, in step (1), the conditions for the oxidation reaction are: reacting at normal temperature for 30 - 60 minutes.

[0030] Preferably, in step (1), the oxidation reaction is carried out under acidic conditions;

[0031] The acidic conditions are adjusted by adding concentrated sulfuric acid accounting for 0.2 - 0.5% of the mass of the wastewater.

[0032] The sulfuric acid used in the present invention has certain oxidizing properties and can be used as an oxidant while ensuring an acidic medium.

[0033] In the present invention, compared with nitric acid, sulfuric acid does not produce thick yellow smoke during the reaction and is environmentally friendly.

[0034] Preferably, in step (1), the addition amount of perchloric acid is 0.4 - 1.0 times the mass of the wastewater.

[0035] Preferably, the mass concentration of the perchloric acid is 70 - 72%.

[0036] Preferably, the conditions for the chlorination reaction in step (1) are: reacting at room temperature for 1 - 3 h.

[0037] Preferably, the addition amount of isooctyl thioglycolate in step (2) is 5.1 - 5.5 times the mass of tin in the wastewater.

[0038] Preferably, the specific conditions for the esterification reaction in step (2) are: reacting at 10 - 45 °C until the pH is 7.5 - 10, and then continuing to react for 30 - 50 min.

[0039] Preferably, the esterification reaction further includes adding ammonia water as a pH regulator, and the mass concentration of the ammonia water is 22 - 25%.

[0040] The purpose of adding ammonia water dropwise is to neutralize the hydrogen chloride generated during the esterification reaction to ensure that the acid value of the product meets the product standard of mercapto methyltin, that is, the acid value < 4 mg KOH / g; at the same time, the adjustment of pH by ammonia water and the esterification reaction are carried out simultaneously. When the pH is 7.5 - 10, the esterification reaction has basically ended, so continue to react for 30 - 50 min to ensure complete reaction.

[0041] In addition, there are two advantages in using ammonia water. One is that compared with other alkaline substances such as sodium hydroxide and potassium hydroxide, mercapto methyltin does not stick to the wall and has good fluidity after the esterification reaction; the other is that it is the same as the process of producing mercapto methyltin, and the waste salt generated is ammonium chloride, which is convenient for unified treatment.

[0042] Preferably, the rotation speeds of the oxidation reaction, chlorination reaction, and esterification reaction are all 180 - 200 rpm.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The present invention oxidizes and chlorinates the methyltin compounds in the wastewater, converts the mercapto methyltin and methyltin chloride in the organic phase into methyltin chloride in the aqueous medium, and then esterifies with isooctyl thioglycolate to prepare a qualified mercapto methyltin product. Moreover, the thermal stability performance test of the product is normal, the operation is simple, and the tin recovery rate is above 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. The drawings in this description are only the embodiments of the present invention.

[0046] Figure 1 It is the gas chromatogram of mercapto methyltin prepared in Example 1 of the present invention;

[0047] Figure 2It is a comparison chart of the test results of the dynamic thermal stability performance of the mercapto methyltin products prepared in Examples 1-4 of the present invention. Detailed implementation mode

[0048] The following describes the embodiments of the present invention. The examples are shown in the accompanying drawings. The embodiments described with reference to the accompanying drawings are exemplary and are intended to explain the present invention rather than to be construed as a limitation of the present invention.

[0049] Example 1

[0050] The present invention provides a method for preparing mercapto methyltin by recovering methyltin compounds from wastewater, which specifically includes the following steps:

[0051] Pump 1250 kg of wastewater (containing 13.45% tin) into a 5 m 3 enamel reactor, add 1250 kg of hydrogen peroxide with a concentration of 29% and 25 kg of sulfuric acid with a concentration of 97%, stir at room temperature (185 revolutions / min) for 45 minutes for oxidation reaction; then add 500 kg of perchloric acid with a concentration of 70%, continue to stir at room temperature (185 revolutions / min) for 1.5 hours, after the reaction is completed, add 857.43 kg of isooctyl mercaptoacetate with a concentration of 99.3%, and dropwise add ammonia water with a concentration of 23%, control the reaction temperature at 10-45 °C, stir (185 revolutions / min) for esterification reaction until the pH is 7.5, continue the reaction for 30 minutes, stop, and let it stand for phase separation; separate the lower layer phase, wash, distill, and filter to obtain 852.48 kg of mercapto methyltin product (density is about 1.17 g / cm 3 );

[0052] Sample and analyze each index as follows: Mercapto methyltin (monomethyl): 21.35%, Sn: 19.05%, S: 11.85%, density (20 °C): 1.1762 g / cm 3 , Pt-Co: 5, refractive index: 1.5104, viscosity (20 °C): 73.51 mPa·S, acid value: 1.53 mgKOH / g, light transmittance: 99.8%, tin recovery rate: 96.58%.

[0053] Example 2

[0054] The present invention provides a method for preparing mercapto methyltin by recovering methyltin compounds from wastewater, which specifically includes the following steps:

[0055] Pump 1152 kg of wastewater (containing 12.78% tin) into a 5 m 3In an enamel reactor, 1728 kg of hydrogen peroxide with a concentration of 27.5% and 46.1 kg of sulfuric acid with a concentration of 96.5% were added. Stirring was carried out at room temperature (200 revolutions / min) for an oxidation reaction for 30 min. Then, 691.2 kg of perchloric acid with a concentration of 72% was added, and stirring was continued at room temperature (200 revolutions / min) for 2 h. After the reaction ended, 780.30 kg of isooctyl mercaptoacetate with a concentration of 99.5% was added, and 25% ammonia water was added dropwise while controlling the reaction temperature at 10 - 45°C. Stirring (200 revolutions / min) was carried out for an esterification reaction until the pH reached 8.5, and the reaction was continued for 40 min. Then, the reaction was stopped and allowed to stand for phase separation; the lower layer was separated, washed, distilled, and filtered to obtain 746.13 kg of methyltin mercaptide product (with a density of 1.17 g / cm 3 or so);

[0056] The samples were tested for each index as follows: methyltin mercaptide (monomethyl): 21.74%, Sn: 19.11%, S: 11.80%, density (20°C): 1.1765 g / cm 3 , Pt-Co: 5, refractive index: 1.5098, viscosity (20°C): 75.3 mPa·S, acid value: 1.71 mgKOH / g, light transmittance: 99.8%, tin recovery rate: 96.84%.

[0057] Example 3

[0058] The present invention provides a method for recovering methyltin compounds in wastewater to prepare methyltin mercaptide, which specifically includes the following steps:

[0059] 1361 kg of wastewater (containing 13.14% tin) was pumped into a 5 m 3 enamel reactor. 1633.2 kg of hydrogen peroxide with a concentration of 32% and 68.05 kg of sulfuric acid with a concentration of 98% were added. Stirring was carried out at room temperature (190 revolutions / min) for an oxidation reaction for 50 min. Then, 1361 kg of perchloric acid with a concentration of 70.5% was added, and stirring was continued at room temperature (190 revolutions / min) for 2 h. After the reaction ended, 983.59 kg of isooctyl mercaptide with a concentration of 99.1% was added, and 24% ammonia water was added dropwise while controlling the reaction temperature at 10 - 45°C. Stirring (190 revolutions / min) was carried out for an esterification reaction until the pH reached 8, and the reaction was continued for 50 min. Then, the reaction was stopped and allowed to stand for phase separation; the lower layer was separated, washed, distilled, and filtered to obtain 908.33 kg of methyltin mercaptide product (with a density of 1.17 g / cm 3 or so);

[0060] The samples were tested for each index as follows: methyltin mercaptide (monomethyl): 21.66%, Sn: 19.02%, S: 11.88%, density (20°C): 1.1746 g / cm 3, Pt-Co: 5, refractive index: 1.5102, viscosity (20°C): 79.24 mPa·S, acid value: 2.13 mgKOH / g, light transmittance: 99.8%, tin recovery rate: 96.60%.

[0061] Example 4

[0062] The present invention provides a method for preparing mercapto methyltin by recovering methyltin compounds from wastewater, which specifically includes the following steps:

[0063] Pump 1268 kg of wastewater (containing 13.55% tin) into a 5 m 3 enamel reaction kettle, add 1648.4 kg of hydrogen peroxide with a concentration of 30%, 38.04 kg of sulfuric acid with a concentration of 97.5%, stir at room temperature (188 revolutions / min) for 1 h for oxidation reaction, then add 887.6 kg of perchloric acid with a concentration of 70.8%, continue to stir at room temperature (188 revolutions / min) for 1 h for reaction. After the reaction is completed, add 893.4 kg of isooctyl mercaptoacetate with a concentration of 99.4%, and dropwise add ammonia water with a concentration of 22%. Control the reaction temperature at 10 - 45°C, stir (188 revolutions / min) for esterification reaction until the pH is 10, continue to react for 35 min, stop, and let it stand for phase separation; separate the lower layer, wash, distill, and filter to obtain 858.3 kg of mercapto methyltin product (with a density of about 1.17 g / cm 3 ).

[0064] Sampling and testing each index are as follows: Mercapto methyltin (monomethyl): 21.46%, Sn: 19.09%, S: 11.81%, density (20°C): 1.1788 g / cm 3 , Pt-Co: 5, refractive index: 1.5092, viscosity (20°C): 74.33 mPa·S, acid value: 1.79 mgKOH / g, light transmittance: 99.8%, tin recovery rate: 95.37%.

[0065] Perform gas chromatography analysis on the product of Example 1, and the analysis situation is shown in Figure 1 , perform thermal stability tests on the products prepared in Examples 1 - 4, and the relevant results are shown in Figure 2 , it can be seen from the figure that the product is mercapto methyltin, and each index and the thermal stability test are normal.

[0066] Example 5

[0067] The present invention provides a method for preparing mercapto methyltin by recovering methyltin compounds from wastewater, which specifically includes the following steps:

[0068] Pump 1324 kg of wastewater (containing 13.02% tin) into a 5 m 3In an enamel reactor, 1853.6 kg of hydrogen peroxide with a concentration of 31% and 33.1 kg of sulfuric acid with a concentration of 96% are added. The oxidation reaction is carried out under stirring (180 revolutions per minute) at room temperature for 50 minutes. Then, 1059.2 kg of perchloric acid with a concentration of 71% is added, and the reaction continues under stirring (180 revolutions per minute) at room temperature for 2.5 hours. After the reaction is completed, 896.4 kg of isooctyl mercaptoacetate with a concentration of 99.0% is added, and ammonia water with a concentration of 23.5% is added dropwise while controlling the reaction temperature at 10 - 45°C. The esterification reaction is carried out under stirring (180 revolutions per minute) until the pH reaches 9, and the reaction continues for 45 minutes. Then, the reaction is stopped, and the phases are allowed to separate. The lower phase is separated, washed, distilled, and filtered to obtain 862.6 kg of methyltin mercaptide product (with a density of 1.17 g / cm 3 or so);

[0069] The sampled and tested indicators are as follows: methyltin mercaptide (monomethyl): 22.32%, Sn: 19.14%, S: 11.89%, density (20°C): 1.1765 g / cm 3 , Pt-Co: 5, refractive index: 1.5107, viscosity (20°C): 75.19 mPa·S, acid value: 1.72 mg KOH / g, light transmittance: 99.8%, tin recovery rate: 95.78%.

[0070] Comparative Example 1

[0071] A method for recovering methyltin compounds from wastewater to prepare methyltin mercaptide is provided, which specifically includes the following steps:

[0072] 1250 kg of wastewater (containing 13.45% tin) is pumped into a 5 m 3 enamel reactor. 375.4 kg of potassium dichromate with a purity of 98% and 25 kg of sulfuric acid with a concentration of 97% are added. The oxidation reaction is carried out under stirring (185 revolutions per minute) at room temperature for 45 minutes. Then, 500 kg of perchloric acid with a concentration of 70% is added, and the reaction continues under stirring (185 revolutions per minute) at room temperature for 1.5 hours. After the reaction is completed, 857.43 kg of isooctyl mercaptoacetate with a concentration of 99.3% is added, and ammonia water with a concentration of 23% is added dropwise while controlling the reaction temperature at 10 - 45°C. The esterification reaction is carried out under stirring (185 revolutions per minute) until the pH reaches 7.5, and the reaction continues for 30 minutes. A large amount of heat is released during the esterification reaction, and the reaction system becomes viscous and does not separate into phases, so the methyltin mercaptide product cannot be obtained.

[0073] Comparative Example 2

[0074] A method for recovering methyltin compounds from wastewater to prepare methyltin mercaptide is provided, which specifically includes the following steps:

[0075] 1250 kg of wastewater (containing 13.45% tin) is pumped into a 5 m 3In an enamel reactor, 625 kg of nitric acid with a concentration of 68% is added, and oxidation reaction is carried out with stirring at room temperature (185 revolutions / min) for 45 min. Then, 500 kg of perchloric acid with a concentration of 70% is added, and the reaction continues with stirring at room temperature (185 revolutions / min) for 1.5 h. After the reaction ends, 857.43 kg of isooctyl thioglycolate with a concentration of 99.3% is added, and ammonia water with a concentration of 23% is added dropwise. The reaction temperature is controlled at 10 - 45 °C, and esterification reaction is carried out with stirring (185 revolutions / min) until the pH is 7.5. The reaction continues for 30 min, then stops, and phase separation is carried out by standing; the lower layer is separated, washed, distilled, and filtered to obtain 754.3 kg of methyltin mercaptide product;

[0076] Sampling and testing show the following indicators: methyltin mercaptide (monomethyl): 19.3%, Sn: 17.25%, S: 10.96%, density (20 °C): 1.1628 g / cm3, Pt-Co: 5, refractive index: 1.5106, viscosity (20 °C): 68.3 mPa·S, acid value: 2.44 mgKOH / g, light transmittance: 99.8%, tin recovery rate: 77.39%.

[0077] Comparative Example 3

[0078] A method for recovering methyltin compounds from wastewater to prepare methyltin mercaptide is provided, which specifically includes the following steps:

[0079] Pump 1250 kg of wastewater (containing 13.45% tin) into a 5 m 3 enamel reactor, add 366.2 kg of potassium permanganate with a purity of 99% and 25 kg of sulfuric acid with a concentration of 97%, and carry out oxidation reaction with stirring at room temperature (185 revolutions / min) for 45 min. Then, add 500 kg of perchloric acid with a concentration of 70%, and continue the reaction with stirring at room temperature (185 revolutions / min) for 1.5 h. After the reaction ends, add 857.43 kg of isooctyl thioglycolate with a concentration of 99.3%, and add ammonia water with a concentration of 23% dropwise. The reaction temperature is controlled at 10 - 45 °C, and esterification reaction is carried out with stirring (185 revolutions / min) until the pH is 7.5. The reaction continues for 30 min, then stops, and phase separation is carried out by standing; the lower layer is separated, washed, distilled, and filtered to obtain 828.14 kg of methyltin mercaptide product (yellow);

[0080] Sampling and testing show the following indicators: methyltin mercaptide (monomethyl): 20.28%, Sn: 18.83%, S: 11.74%, density (20 °C): 1.1733 g / cm3, Pt-Co: 63, refractive index: 1.5085, viscosity (20 °C): 78.24 mPa·S, acid value: 2.15 mgKOH / g, light transmittance: 90.5%, tin recovery rate: 92.75%.

[0081] Comparative Example 4

[0082] A method for preparing mercapto methyltin by recycling methyltin compounds in wastewater is provided, which specifically includes the following steps:

[0083] Pump 1250 kg of wastewater (containing 13.45% tin) into a 5 m 3 enamel reactor, add 1250 kg of hydrogen peroxide with a concentration of 29% and 25 kg of sulfuric acid with a concentration of 97%, stir at room temperature (185 revolutions / min) for 45 min for oxidation reaction, then add 500 kg of hydrochloric acid with a concentration of 36.5%, continue to stir at room temperature (185 revolutions / min) for 1.5 h. After the reaction ends, add 857.43 kg of isooctyl mercaptoacetate with a concentration of 99.3%, and dropwise add ammonia water with a concentration of 23%. Control the reaction temperature at 10 - 45 °C, stir (185 revolutions / min) for esterification reaction until the pH is 7.5, continue the reaction for 30 min, then stop and let it stand for phase separation; separate the lower layer, wash, distill, and filter to obtain 585.22 kg of mercapto methyltin product;

[0084] Sampling and testing shows the following indicators: Mercapto methyltin (monomethyl): 17.41%, Sn: 16.69%, S: 9.31%, density (20 °C): 1.1356 g / cm3, Pt-Co: 5, refractive index: 1.5066, viscosity (20 °C): 65.38 mPa·S, acid value: 1.88 mgKOH / g, light transmittance: 99.8%, tin recovery rate: 58.09%.

[0085] It can be seen from the examples and comparative examples that when recycling methyltin compounds in wastewater to prepare mercapto methyltin, in terms of the selection of oxidants, potassium dichromate will release a large amount of heat, and the system will not phase-separate after the esterification reaction, so mercapto methyltin product cannot be obtained; potassium permanganate has a relatively dark color and a violent reaction. After esterification, the product appearance is slightly yellow, the Pt-Co and light transmittance indicators are abnormal, and the tin yield is low; nitric acid will produce yellow smoke during the oxidation reaction, which is not conducive to environmental protection control, and most of the product indicators and tin recovery rate are low after esterification; compared with other oxidants, hydrogen peroxide is both environmentally friendly and can ensure that the recycled wastewater can produce mercapto methyltin products with qualified indicators.

[0086] If hydrochloric acid is directly added in the chlorination reaction, the tin recovery rate is low and the product indicators are abnormal, and the effect is not as good as perchloric acid. On the one hand, hydrochloric acid has no oxidizing property and cannot further oxidize methyltin compounds to completely convert them into methyltin oxide. On the other hand, there is still excessive hydrogen peroxide in the system, which affects the synthesis of mercapto methyltin during the esterification process.

[0087] The production equipment of mercapto methyltin in the present invention can meet the operation requirements. The process is simple, the parameters are easy to control, the tin recovery rate is high, the indicators of the product are normal in various aspects and the thermal stability test is normal, and it can efficiently recycle and treat methyltin compounds in mercapto methyltin wastewater.

[0088] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recovering methyltin compounds in wastewater to prepare methyltin mercaptide, characterized in that: The specific steps include: (1) adding hydrogen peroxide to wastewater for oxidation reaction, and then adding perchloric acid for chlorination reaction to obtain a methyltin chloride solution; (2) adding isooctyl thioglycolate to the methyltin chloride solution to carry out an esterification reaction to obtain an organic substance, namely methyltin mercaptan.

2. A method for recovering methyltin compounds from wastewater to prepare methyltin mercaptide according to claim 1, characterized in that: The mass ratio of the hydrogen peroxide solution to the wastewater in step (1) is 1-1.5:

1.

3. A method for recovering methyltin compounds from wastewater to prepare methyltin mercaptide according to claim 1, characterized in that: The mass concentration of the hydrogen peroxide in step (1) is 27.5-32%.

4. The method for recovering methyltin compounds from wastewater to prepare methyltin mercaptide according to claim 1, characterized in that: The conditions of the oxidation reaction in step (1) are: reaction at room temperature for 30-60 minutes.

5. The method for recovering methyltin compounds from wastewater to prepare methyltin mercaptide according to claim 1, characterized in that: The oxidation reaction in step (1) is carried out under acidic conditions; The acidic condition is adjusted by adding concentrated sulfuric acid at 0.2-0.5% of the mass of the wastewater.

6. The method for recovering methyltin compounds from wastewater to prepare methyltin mercaptide according to claim 1, characterized in that: The amount of perchloric acid added in step (1) is 0.4-1.0 times the mass of the wastewater.

7. The method for recovering methyltin compounds from wastewater to prepare methyltin mercaptide according to claim 1, characterized in that: The conditions of the chlorination reaction in step (1) are: reaction at room temperature for 1-3 hours.

8. The method for recovering methyltin compounds from wastewater to prepare methyltin mercaptide according to claim 1, characterized in that: The amount of isooctyl thioglycolate added in step (2) is 5.1-5.5 times the mass of tin in the wastewater.

9. The method for recovering methyltin compounds from wastewater to prepare methyltin mercaptide according to claim 1, characterized in that: The specific conditions of the esterification reaction in step (2) are: react at 10-45° C. until the pH reaches 7.5-10, and then continue the reaction for 30-50 minutes.

10. A method for recovering methyltin compounds from wastewater to prepare methyltin mercaptide according to claim 9, characterized in that: The esterification reaction further comprises adding ammonia water as a pH adjuster, wherein the mass concentration of the ammonia water is 22-25%.

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