A method for deep detoxification of organic tin waste and simultaneous preparation of sodium stannate

Abstract

The present invention discloses a method for the simultaneous detoxification of organotin waste and the preparation of sodium stannate. The method comprises mixing the organotin waste with a composite additive comprising sodium oxalate and hydrogen peroxide as active ingredients, followed by spray combustion. The combustion exhaust is subjected to dust removal to recover a tin-rich material, which is then water-leached to obtain a sodium stannate solution. By adding sodium oxalate and hydrogen peroxide during the combustion and decomposition of the organotin waste, the method not only enhances the thermal conversion process of the organotin compound, converting its toxic organic functional groups into harmless CO2 and H2O emissions, but also promotes dioxin decomposition, sulfur fixation, and suppresses NOx generation. Furthermore, the method efficiently converts tin into sodium stannate, which is easily recovered by water leaching. The method is simple to operate, highly efficient, and environmentally friendly.

Description

Technical Field

[0001] The invention relates to a method for treating organic tin waste, in particular to a method for deep detoxification of organic tin waste and simultaneous preparation of sodium stannate, belonging to the field of comprehensive utilization of secondary resources. Background Art

[0002] Organotins are primarily used as catalysts, stabilizers (such as dimethyltin, dioctyltin, and tetraphenyltin), agricultural pesticides, fungicides (such as dibutyltin, tributyltin, and triphenyltin), and coatings and mildew inhibitors for everyday products. Currently, domestic consumption of organotins exceeds 50,000 tons, of which over 80% is used to produce catalysts for organic synthesis reactions. Over extended use, organotins come into contact with strong acids, bases, and alloy reactors, constantly dissolving and contaminating various impurities, causing the organotins to deteriorate and transform into waste. Organotins waste contains a variety of active organic functional groups, as well as nitrogen, chlorine, and sulfur-containing groups. Contact with the human respiratory tract, skin, and digestive tract can cause uncontrolled neurological damage, seriously endangering human health. Organotins are non-degradable under natural conditions and accumulate in plants and animals. Therefore, organotins waste is classified as hazardous waste and is listed in the National List of Hazardous Wastes (2021 Edition) under the Law of the People's Republic of China on the Prevention and Control of Environmental Pollution by Solid Wastes (classified as HW06 Waste Organic Solvents and Wastes Containing Organic Solvents). Existing disposal methods primarily rely on biodegradation and acid-base neutralization. The biological method has a long reaction cycle, low conversion rates, and is prone to generating secondary organic pollutants. The acid-base neutralization method merely converts and separates the tin in organotin waste by adding strong acids and alkaline substances, without considering the disposal of the resulting wastewater. Consequently, there are currently no technical methods specifically designed for the harmless disposal and processing of tin-containing organic waste. Therefore, developing simple and efficient methods for the harmless disposal and comprehensive utilization of organotin waste, and achieving centralized disposal of hazardous waste, is of great significance. Summary of the Invention

[0003] In response to the defects of the methods for disposing of organotin waste in the prior art, the first object of the present invention is to provide a method for deep detoxification of organotin waste and simultaneous preparation of sodium stannate. The method adds a composite additive having active ingredients of sodium oxalate and hydrogen peroxide during the combustion and decomposition process of the organotin waste. The composite additive can not only enhance the thermal conversion process of the organotin compound and convert toxic organic functional groups into harmless CO2 and H2O emissions, but also promote dioxin decomposition, sulfur fixation, and inhibition of NOx generation. Tin can also be efficiently converted into sodium stannate, which is easy to recover by water leaching. The method is simple to operate, efficient, environmentally friendly, and conducive to industrial production.

[0004] In order to achieve the above technical objectives, the present invention provides a method for deep detoxification of organic tin waste and simultaneous preparation of sodium stannate. The method comprises the following steps: mixing the organic tin waste with a composite additive whose active ingredients are sodium oxalate and hydrogen peroxide, spraying and burning the mixture, removing dust from the combustion exhaust, and recovering tin-rich material. The tin-rich material is then soaked in water to obtain a sodium stannate solution.

[0005] The key to the technical solution of the present invention is the addition of a composite additive containing sodium oxalate and hydrogen peroxide as active ingredients during the combustion process of organotin waste. The two ingredients have a significant synergistic effect, which can efficiently promote the high-temperature pyrolysis process of organotin compounds and reduce the emission of harmful components, while converting tin into sodium stannate that is easy to recover by water leaching. The sodium oxalate in the composite additive neutralizes some of the acidic substances in the organotin waste and provides oxalate radicals. Oxalate radicals promote the dissociation of organotin compounds by complexing tin ions, and the active sodium ions catalyze and promote reactions such as the condensation and decomposition of organic groups. Oxalate radicals release reducing substances through thermal decomposition at high temperatures, which can suppress the production of NOx during combustion. The active sodium ions promote the decomposition of dioxins and bind to and solidify the organic sulfur in the organotin compounds at high temperatures. The active sodium ions also convert tin into water-soluble sodium stannate. Hydrogen peroxide generates active oxygen at high temperatures, promoting the complete oxidation and dissociation of organic functional groups in the organotin waste. These organic functional groups are completely converted into harmless CO2 and H2O emissions, avoiding the formation of incomplete oxides (such as phenols and aldehydes). In summary, the interaction between the two active ingredients, sodium oxalate and hydrogen peroxide, completely decomposes the organic functional groups in the tin waste, achieving detoxification, while suppressing the release of harmful components and converting the tin into sodium stannate.

[0006] During the high-temperature combustion process of the organic tin waste material of the present invention, the organic tin components are oxidatively decomposed, and the tin is simultaneously converted into sodium stannate, which is rapidly condensed and precipitated from the flue gas to form smoke dust. Finally, the tin-rich material can be recovered through a dust removal system, and finally the sodium stannate in the sample is recovered through water immersion and separation to directly prepare a high-value product.

[0007] As a preferred scheme, the composite additive is composed of the following mass percentage components: sodium oxalate 60-70%, hydrogen peroxide 30-40%. Oxalate and sodium ion will play the role of suppressing NOx generation and fixing SO2 generation in the combustion process, and in situ react with tin oxide to generate sodium stannate under high temperature conditions. An appropriate amount of hydrogen peroxide is introduced, and hydrogen peroxide can be utilized to decompose and produce oxygen to promote the combustion and decomposition of organic functional groups. If the ratio of hydrogen peroxide is too low, it will affect the combustion and decomposition effect of organic functional groups. However, the solubility of hydrogen peroxide in organic systems is lower. If its proportion is too high, it will cause organic slurry stratification etc. to be unfavorable for mixing combustion. Therefore, the ratio of sodium oxalate and hydrogen peroxide needs to be controlled within the appropriate range, which is conducive to the combustion and decomposition process of organotin waste.

[0008] As a preferred solution, the composite additive and the organic tin waste are mixed at a Na / Sn molar ratio of 2.1 to 2.5:1. Sodium oxalate provides an appropriate sodium source for binding to the tin in the organic system. The theoretical sodium-tin ratio for generating sodium stannate is 2:1. The present invention selects an appropriate excess of sodium oxalate to ensure that the tin is fully converted into sodium stannate. Furthermore, the excess active sodium ions can also bind to sulfur compounds to inhibit SO2 gas generation.

[0009] As a preferred solution, the main component of the organic tin waste is liquid organic tin, such as dimethyltin, dioctyltin, tetraphenyltin, dibutyltin, tributyltin, triphenyltin, etc., which are all common organic tin compounds in the prior art.

[0010] As a preferred embodiment, the spray combustion conditions are: an air-fuel ratio of 15-25 and a combustion temperature of 1150-1250°C. The organic groups in the organotin compounds in the organotin waste contain high carbon and hydrogen contents and have a certain calorific value. High-temperature oxygen-enriched combustion significantly promotes the oxidative decomposition of the organic components, resulting in CO2 and H2O as the final products. Simultaneously, by regulating the air-fuel ratio and temperature, the conversion of nitrogen, chlorine, and sulfur components is promoted, effectively reducing the generation of combustion-related harmful gases such as NOx, dioxins, and SO2.

[0011] As a preferred solution, the hydrogen peroxide can be industrial hydrogen peroxide, and its conventional concentration is 30%.

[0012] As a preferred embodiment, the water leaching conditions are: a temperature of 50-75°C and a liquid-to-solid ratio of 3-5 mL:1 g. During the high-temperature combustion process, the tin is completely converted into sodium stannate. A small amount of free sodium salt increases the pH of the aqueous solution during the water leaching process, effectively inhibiting the hydrolysis of the sodium stannate and increasing the tin leaching rate.

[0013] Compared with the existing technology, the technical solution of the present invention brings the following beneficial technical effects:

[0014] The invention discloses a method for deep detoxification of organic tin waste and simultaneous preparation of sodium stannate. In the high-temperature combustion process of the organic tin waste, a composite additive having active ingredients of sodium oxalate and hydrogen peroxide is used. The method can promote the complete combustion and decomposition of organic functional groups in the organic tin waste, with a conversion rate of 99.9%. All carbon and hydrogen are converted into CO2 and H2O, while the conversion of nitrogen, chlorine and sulfur therein into new harmful gas substances is suppressed. The concentrations of NOx and SO2 in the flue gas are respectively lower than 50 ppm and 20 ppm, and no dioxins are generated. At the same time, all tin is converted into a sodium stannate product that is easily leached out of water, with a tin conversion rate of greater than 98%. The method is simple to operate, highly efficient, and does not generate secondary organic pollutants, thus being conducive to industrial production. DETAILED DESCRIPTION

[0015] The following examples are intended to further illustrate the present invention, but are not intended to limit the scope of protection of the claims of the present invention.

[0016] In the following examples, hydrogen peroxide is 30% industrial hydrogen peroxide, and sodium oxalate is an analytical grade reagent.

[0017] Comparative Example 1

[0018] A waste dibutyltin oxide (Sn, C, S, and N contents of 5.5%, 52.1%, 0.51%, and 6.3%, respectively) was treated. The mixed material was then spray-combusted with an air-fuel ratio of 15:1 and a combustion temperature of 1250°C. The tin-rich material was recovered through a dust removal system. The water leaching temperature was 50°C, the liquid-to-solid ratio was 5mL:1g, and the leaching time was 60 minutes. Under these conditions, the tin leaching yield was 0.8%, and the NOx and SO2 concentrations in the flue gas were 482ppm and 120ppm, respectively. The flue gas composition did not meet emission standards, and the tin-containing dust contained a high content of organic components, preventing efficient tin recovery.

[0019] Comparative Example 2

[0020] A waste dibutyltin oxide (DBTO) was treated (Sn, C, S, and N contents of 5.5%, 52.1%, 0.51%, and 6.3%, respectively). The organic tin waste was first mixed with an additive (sodium oxalate: hydrogen peroxide ratio = 60:40, by mass) at a Na / Sn molar ratio of 2.1:1. The mixed material was then spray-combusted at a controlled air-fuel ratio of 10:1 and a combustion temperature of 1400°C. The tin-rich material was recovered via a dust removal system. The leaching temperature was 50°C, the liquid-to-solid ratio was 5 mL:1 g, and the leaching time was 60 min. Under these conditions, the tin leaching yield was 21.6%, the sodium stannate conversion rate was 21.2%, and the NOx and SO2 concentrations in the flue gas were 131 ppm and 102 ppm, respectively. The flue gas composition did not meet emission standards, and the high content of organic components in the tin-containing dust prevented efficient tin recovery.

[0021] Comparative Example 3

[0022] Using dibutyltin oxide waste as the treatment target (Sn, C, S, and N contents of 5.5%, 52.1%, 0.51%, and 6.3%, respectively), the organic tin waste was first mixed with an additive (sodium oxalate) at a Na / Sn molar ratio of 2.1:1. The mixed material was then spray-combusted at a controlled air-fuel ratio of 15:1 and a combustion temperature of 1250°C. The tin-rich material was recovered via a dust removal system. The leaching temperature was 50°C, the liquid-to-solid ratio was 5 mL:1 g, and the leaching time was 60 minutes. Under these conditions, the tin leaching yield was 32.6%, the sodium stannate conversion rate was 30.2%, and the NOx and SO2 concentrations in the flue gas were 320 ppm and 77 ppm, respectively, which did not meet emission standards. The high content of organic components in the tin-containing dust prevented efficient tin recovery.

[0023] Comparative Example 4

[0024] Using a waste dibutyltin oxide (Sn, C, S, and N contents of 5.5%, 52.1%, 0.51%, and 6.3%, respectively) as the treatment target, the organic tin waste was first mixed thoroughly with a 5% by weight additive (hydrogen peroxide). The mixed material was then spray-combusted at a controlled air-fuel ratio of 15:1 and a combustion temperature of 1250°C. The tin-rich material was recovered via a dust removal system. The leaching temperature was 50°C, the liquid-to-solid ratio was 5mL:1g, and the leaching time was 60 minutes. Under these conditions, the tin leaching yield was 0.6%, and the NOx and SO2 concentrations in the flue gas were 120ppm and 320ppm, respectively, which did not meet emission standards. The high content of organic components in the tin-containing dust prevented efficient tin recovery.

[0025] Example 1

[0026] Using dibutyltin oxide waste as the treatment target (Sn, C, S, and N contents of 5.5%, 52.1%, 0.51%, and 6.3%, respectively), the organic tin waste was first mixed with an additive (sodium oxalate:hydrogen peroxide ratio = 60:40, by mass) at a Na / Sn molar ratio of 2.1:1. The mixed material was then spray-combusted at a controlled air-fuel ratio of 15:1 and a combustion temperature of 1250°C. Tin-rich material was recovered via a dust removal system. Leaching was performed at a temperature of 50°C, a liquid-to-solid ratio of 5 mL:1 g, and a leaching time of 60 minutes. Under these conditions, the tin leaching rate was 98.6%, the sodium stannate conversion rate was 98.2%, the organic matter content was less than 0.1%, and the NOx and SO2 concentrations in the flue gas were 31 ppm and 12 ppm, respectively, meeting emission standards. This demonstrates the deep detoxification of the organic tin waste and the resource utilization of the tin.

[0027] Example 2

[0028] Using dibutyltin oxide waste as the treatment target (Sn, C, S, and N contents of 5.5%, 52.1%, 0.51%, and 6.3%, respectively), the organic tin waste was first mixed with an additive (sodium oxalate:hydrogen peroxide ratio = 60:40, by mass) at a Na / Sn molar ratio of 2.5:1. The mixed material was then spray-combusted at a controlled air-fuel ratio of 25:1 and a combustion temperature of 1150°C. Tin-rich material was recovered via a dust removal system. Leaching was performed at a temperature of 75°C, a liquid-to-solid ratio of 3 mL:1 g, and a leaching time of 60 minutes. Under these conditions, the tin leaching rate was 99.0%, the sodium stannate conversion rate was 98.9%, the organic matter content was less than 0.1%, and the NOx and SO2 concentrations in the flue gas were 33 ppm and 10 ppm, respectively, meeting emission standards. This demonstrates the deep detoxification of the organic tin waste and the resource utilization of the tin.

[0029] Example 3

[0030] Using tributyltin chloride waste as the treatment target (Sn, C, S, and N contents of 4.2%, 58.1%, 0.30%, and 4.9%, respectively), the organic tin waste was first mixed with an additive (sodium oxalate:hydrogen peroxide ratio = 65:35, by mass) at a Na / Sn molar ratio of 2.3:1. The mixed material was then spray-combusted at a controlled air-fuel ratio of 20:1 and a combustion temperature of 1200°C. The tin-rich material was recovered via a dust removal system. The leaching temperature was 70°C, the liquid-to-solid ratio was 4 mL:1 g, and the leaching time was 60 minutes. Under these conditions, the tin leaching rate was 99.6%, the sodium stannate conversion rate was 99.2%, the organic matter content was less than 0.1%, and the NOx and SO2 concentrations in the flue gas were 39 ppm and 13 ppm, respectively, meeting emission standards. This demonstrates the deep detoxification of the organic tin waste and the resource utilization of the tin.

[0031] Example 4

[0032] Using tributyltin chloride waste as the treatment target (Sn, C, S, and N contents of 4.2%, 58.1%, 0.30%, and 4.9%, respectively), the organic tin waste was first mixed with an additive (sodium oxalate:hydrogen peroxide ratio = 60:40, by mass) at a Na / Sn molar ratio of 2.1:1. The mixed material was then spray-combusted at a controlled air-fuel ratio of 15:1 and a combustion temperature of 1250°C. Tin-rich material was recovered via a dust removal system. The leaching temperature was 70°C, the liquid-to-solid ratio was 5 mL:1 g, and the leaching time was 60 minutes. Under these conditions, the tin leaching rate was 99.5%, the sodium stannate conversion rate was 99.2%, the organic matter content was less than 0.1%, and the NOx and SO2 concentrations in the flue gas were 45 ppm and 16 ppm, respectively, meeting emission standards. This demonstrates the deep detoxification of the organic tin waste and the resource utilization of the tin.

Claims

1. A method for deep detoxification of organotin waste and simultaneous preparation of sodium stannate, characterized in that: Organotin waste is mixed with a composite additive comprising sodium oxalate and hydrogen peroxide as active ingredients, and then spray-combusted. Tin-rich material is recovered from the combustion exhaust through dust removal, and the tin-rich material is soaked in water to obtain a sodium stannate solution. The spray-combustion conditions are: an air-fuel ratio of 15-25 and a combustion temperature of 1150-1250°C. The composite additive comprises the following components in percentage by weight: 60-70% sodium oxalate and 30-40% hydrogen peroxide.

2. The method for preparing sodium stannate by deep detoxification of an organotin waste according to claim 1, wherein: The ratio of the composite additive to the organic tin waste is measured according to a Na / Sn molar ratio of (2.1-2.5):

1.

3. The method for preparing sodium stannate by deep detoxification of an organotin waste according to claim 2, wherein: The main component of the organic tin waste is liquid organic tin.

4. The method for preparing sodium stannate by deep detoxification of an organotin waste according to claim 1, wherein: The conditions for the water immersion are: a temperature of 50-75° C. and a liquid-to-solid ratio of 3-5 mL:1 g.