CN116065036A - A method for recovering tin from tin slag and a process method for coupling tin recovery and Fenton reaction - Google Patents

Abstract

The invention provides a method for recovering tin in tin slag and a process method of coupling tin recovery and Fenton reaction. The tin slag is soaked in acid to dissolve tin and filter to obtain a mixed solution containing tin salt and stannous salt , adding a solution containing Fe ³⁺ therein to adjust the pH to 0.5-3. After the reaction, the solid and liquid are separated, and the obtained solid is roasted to obtain SnO ₂ . Using the above method, the effluent of the Fenton reaction can be used as a solution containing Fe ³⁺ to be introduced into the above-mentioned tin recovery process, and after the reaction, Fe ³⁺ is reduced to Fe ²⁺ , while the pH of the reaction solution is low, and the filtrate can be directly Back to the Fenton reaction, the two reaction processes form a coupling. The tin recovery method of the present invention can control most of the Sn ⁴⁺ or even complete precipitation by controlling the reaction pH condition, has extremely high recovery rate and purity, not only saves the cost of solid waste treatment, but also achieves the recovery and reuse of tin slag The purpose of this method can also realize the coupling with the Fenton reaction process.

Description

A method for recovering tin from tin slag and a process method for coupling tin recovery and Fenton reaction

technical field

The invention belongs to the technical field of solid waste recycling, and in particular relates to a method for recovering tin in tin slag and a process method for coupling tin recovery and Fenton reaction.

Background technique

In recent years, with the continuous development of the electronics and electrical industries, the gradual introduction of lead-free soldering technology will further lead to a sharp increase in tin consumption, and tin slag is a solid waste, and its treatment cost has also increased significantly. In this case, the recycling of tin slag is undoubtedly a good choice for saving resources and costs.

Solder slag is a source of tin slag. It is the substance that remains on the surface of the tin liquid after the tin in the welding machine furnace is oxidized after being oxidized by high temperature with lead-free tin wire in the electronics factory. The common treatment process of solder slag is mainly fire method or melting treatment. Most of them are heated to melt the solder into liquid. Tin slag recycling uses gravity to separate the liquid solder from the oxide, and the oxide will not be melted. However, the temperature rise of solder slag is slow, and heating to 240°C will cause energy waste, and the efficiency is low. Therefore, effective recovery of solder slag is an important means to reduce the reaction cost.

Patent CN110872649A discloses a method for recovering tin from tin-containing lead slag. Sodium stannate product is prepared by chlorination-water immersion-alkali fusion-water immersion-concentration and crystallization process. This invention effectively reuses tin slag, but introduces chlorination reagents into the reaction, volatilizes and condenses tin-lead slag for many times, and the chlorinated residue and filtrate produced will cause certain secondary pollution, and post-processing increases response cost.

Patent CN111573715A discloses a method for preparing tin dioxide by using tin oxide slag. In the reaction, sulfuric acid and tin oxide slag are put into a closed container at a ratio of 4 to 8:1, and oxygen is introduced into the closed container. The reaction pressure is ≥0.5 MPa, the reaction temperature is 130-200°C, and the reaction time is 4-8 hours. The reaction uses sulfuric acid as a carrier to react the tin in the tin oxide slag with oxygen to synthesize tin dioxide until the reaction is completed. In this invention, tin slag and oxygen are not easy to react completely, and the products tend to contain heteroatoms and produce harmful gases.

Contents of the invention

In order to solve the deficiencies in the prior art, the invention provides a method for recovering tin in tin slag and a method for coupling tin recovery and Fenton reaction, by acidifying the solder slag, adjusting conditions, reacting with Fe ³⁺ and roasting , and finally get SnO ₂ solid, realizing a higher tin recovery rate; this method is coupled with the Fenton reaction, not only can use the Fenton reaction to produce Fe ³⁺ in water, but also can reduce it to the Fe required by the Fenton reaction ²⁺ , and based on the control of the reaction conditions, it has the pH required by the Fenton reaction, and can be directly returned to the Fenton reaction unit for use, realizing the ingenious coupling of the two units.

The present invention realizes above-mentioned technical purpose through following technical scheme:

The first aspect of the present invention provides a method for recovering tin in tin slag, comprising the following steps: immersing tin slag in acid, dissolving tin, filtering to obtain a mixed solution of tin-containing salt and stannous salt, adding The pH of the solution containing Fe ³⁺ is adjusted to 0.5-3. After the reaction, the solid and liquid are separated, and the obtained solid is roasted to obtain SnO ₂ .

Further, the acid is sulfuric acid or hydrochloric acid, in terms of mass fraction, the concentration of the hydrochloric acid is 20%-38%, and the concentration of the sulfuric acid is 40%-60%, preferably 40%-50%. Among them, sulfuric acid is preferred.

Further, after the tin slag is soaked in acid, adjust the temperature to 40-80°C, preferably 50-60°C, to fully dissolve the tin. The processing time is 1-2h. During this process, the tin in the dross is transformed into Sn ²⁺ and Sn ⁴⁺ . In order to improve efficiency, the mixing ratio of tin slag and acid solution is controlled so that the mass concentration of tin salt and stannous salt is 80%-98%, preferably 90%-95%.

Further, the concentration of Fe ³⁺ in the solution containing Fe ³⁺ is 5 mg/L-100 mg/L, and the amount added is based on the molar ratio of Fe and Sn being 3:1-2:1.

Further, after adding the solution containing Fe ³⁺ , it is preferable to adjust the pH to 1-2, more preferably to adjust the pH to 1.1-1.3. At least 90% of Sn can be precipitated in the form of Sn(OH) _4. In the preferred technical solution, more than 98% of Sn can be precipitated in the form of Sn(OH) ₄ , and then SnO can be obtained through subsequent separation and roasting processes. ₂ , the purity of SnO ₂ is above 95%.

Further, after adding the solution containing Fe ³⁺ , at least one of sulfuric acid, NaOH solution or ammonia water is used to adjust the pH.

Further, the calcination temperature is 400°C-700°C, preferably 600-650°C; the calcination time is 2-5h, preferably 2.5-3.5h.

Further, the tin slag generally refers to solid wastes containing tin in industrial production, and may also contain other metal impurities including copper and the like. The technical solution of the present invention preferably deals with solder slag, which is the substance that remains on the surface of the tin liquid after the tin in the welding machine furnace is oxidized after being oxidized with lead-free tin wire used in electronics factories. Usually tin slag contains 90%-98% tin, and also contains copper, antimony, silver and other miscellaneous metals. Due to the limited recovery rate of tin in pyro-refining, the tin slag is directly acidified and alkali-precipitated to remove impurities in the tin slag under the premise of ensuring its recovery rate.

In the above-mentioned technical scheme of the present invention, through acidification treatment, the solid tin solvent is first _made into an ionic state, and then through the adjustment of Fe ³⁺ and pH, more than 90% of Sn is roasted in the form of Sn(OH) to obtain SnO ₂ , to achieve tin recovery.

The technical purpose of the second aspect of the present invention is to provide a process for coupling tin recovery and Fenton reaction, comprising: immersing tin slag in sulfuric acid, dissolving tin, and filtering to obtain a mixed solution of tin-containing salt and stannous salt , adding effluent from the Fenton reaction to adjust the pH to 0.5-3. After the reaction, the solid and liquid are separated, the obtained solid is roasted to obtain SnO ₂ , and the obtained liquid is passed into the Fenton reaction.

Further, the mass concentration of the sulfuric acid is 40%-60%, preferably 40%-50%. The mass concentration in the mixed solution of the tin-containing salt and the stannous salt is 80%-98%, preferably 90%-95%.

Further, after the solder slag is soaked in sulfuric acid, the temperature is adjusted to 40-80° C., preferably 50-60° C., to fully dissolve the tin. The processing time is 1-2h.

Further, the effluent of the Fenton reaction is organic wastewater treated by Fenton oxidation, COD is lower than 150mg/L, preferably lower than 50mg/L; iron ion concentration is 10mg/L-30mg/L, preferably 15-20mg/L, the amount added is based on the molar ratio of Fe to Sn is 3:1-2:1.

Further, the mixing ratio of tin slag and sulfuric acid solution is controlled so that the mass concentration of tin salt and stannous salt is 80%-98%, preferably 90%-95%; The mixed solution of salt is mixed according to the volume ratio of 3:1-6:1.

Further, after adding the effluent from the Fenton reaction, the pH is preferably adjusted to 1-2, more preferably adjusted to 1.1-1.3. The reaction time is 0.5-1h.

Further, at least one of sulfuric acid, NaOH solution or ammonia water is used to adjust the pH.

Further, the calcination temperature is 400°C-700°C, preferably 600-650°C; the calcination time is 2-5h, preferably 2.5-3.5h.

Further, the solder slag is the substance that remains on the surface of the tin liquid after the tin in the welding machine furnace is oxidized after being oxidized by the lead-free tin wire used in the electronics factory to weld the electronic components. Usually tin slag contains 90%-98% tin, and also contains copper, antimony, silver and other miscellaneous metals.

Compared with the prior art, the present invention has the following advantages:

(1) The present invention uses the tin slag produced in welding as raw material to directly treat the solid waste, acidify first, and then use Fe ³⁺ as the oxidant to oxidize Sn ²⁺ to Sn ⁴⁺ , and control the pH condition of the reaction that is Most of Sn ⁴⁺ can even be completely precipitated, with extremely high recovery rate and purity, the recovery rate can reach more than 80%, and the purity can reach more than 95% based on SnO ₂ ; it not only saves the cost of solid waste treatment, but also reaches the level of tin The purpose of slag recovery and reuse.

(2) In particular, the recovery of solder slag in the present invention is coupled with the Fenton reaction, and the Sn ²⁺ in the mixed liquid is oxidized by using Fe ³⁺ in the Fenton reaction water, and it is successfully oxidized to Sn ⁴⁺ , realizing Reuse of Fenton effluent. At this time, Fe ³⁺ in the Fenton effluent is reduced to Fe ²⁺ , and the pH of the reaction solution is low. The liquid after solid-liquid separation is directly used for the Fenton reaction, providing a source of ferrous iron for the Fenton reaction. With good acidic conditions, the cost of Fenton reaction is effectively reduced.

Other features and advantages of the present invention will be described in detail in the detailed description that follows.

Detailed ways

The following non-limiting examples can enable those skilled in the art to understand the present invention more fully, but do not limit the present invention in any way.

The experimental methods in the following examples are conventional methods in the art unless otherwise specified. The experimental materials used in the following examples were purchased from conventional biochemical reagent stores unless otherwise specified.

The pH value in the present invention is determined by the method "Glass Electrode Method for Determination of pH Value in Water Quality" (GB/T6920), COD is determined by the method "Potassium Dichromate Method for Determination of Water Quality COD" (GB/T 11914), and metal ions are determined by "Microwave digestion/inductively coupled plasma mass spectrometry" (ICP-MS) method determination.

Example 1

When an electronics factory uses lead-free tin wire for soldering, it produces solder slag with a tin content of 90%-95%. The organic wastewater produced by a coal chemical enterprise was oxidized by Fenton, the pH was 4.2, the COD was 80mg/L, and the iron content was 17mg/L.

Soak the solder slag in 50% sulfuric acid, heat and stir at 60°C and 100r/min for 2 hours, wait until the slag is fully dissolved, separate the solid and liquid, filter out the insoluble matter at the bottom, the mass concentration of tin salt and stannous salt in the filtrate 90%. Mix the Fenton oxidation effluent with the filtrate at a volume ratio of 4:1, the molar ratio of Fe to Sn is 2:1, react for 0.5h, adjust the pH to 2.0 with sodium hydroxide, separate the solid and liquid, dry the filter residue for later use, and The filtrate was used back in the Fenton reaction system. The dried filter residue was calcined at 600°C for 3 hours to obtain SnO ₂ solids with a mass percentage of more than 98%, and the calculated Sn recovery rate was 86%.

Example 2

When an electronics factory uses lead-free tin wire for soldering, it produces solder slag with a tin content of 90%. The organic wastewater produced by a coal chemical enterprise was oxidized by Fenton, the pH was 3.9, the COD was 50mg/L, and the iron content was 16mg/L.

Soak the solder slag in 50% sulfuric acid, heat and stir at 60°C and 100r/min for 2 hours, wait until the slag is fully dissolved, separate the solid and liquid, filter out the insoluble matter at the bottom, the mass concentration of tin salt and stannous salt in the filtrate 88%. Mix the Fenton oxidation effluent and the filtrate at a volume ratio of 6:1, the molar ratio of Fe to Sn is 3:1, react for 1 h, adjust the pH to 2.0 with sodium hydroxide, separate the solid and liquid, dry the filter residue for later use, and dry the filtrate Back to the Fenton reaction system. The dried filter residue was roasted at 600°C for 3 hours to obtain SnO ₂ solids with a mass percentage of more than 99%, and the calculated Sn recovery rate was 85%.

Example 3

When an electronics factory uses lead-free tin wire for soldering, it produces solder slag with a tin content of 90%-95%. The organic wastewater produced by a coal chemical enterprise was oxidized by Fenton, the pH was 4.0, the COD was 65mg/L, and the iron content was 20mg/L.

Soak the solder slag in 50% sulfuric acid, heat and stir at 60°C and 100r/min for 2 hours, wait until the slag is fully dissolved, separate the solid from the liquid, and filter out the incompatible substances at the bottom. The mass concentration of tin salt and stannous salt in the filtrate 89%. Mix the Fenton oxidation effluent and the filtrate at a volume ratio of 5:1, the molar ratio of Fe to Sn is 2.5:1, react for 0.5h, adjust the pH to 3.0 with sodium hydroxide, separate the solid and liquid, and dry the filter residue for later use. The filtrate was used back in the Fenton reaction system. The dried filter residue was calcined at 600°C for 3 hours to obtain a mixed solid of 92% SnO ₂ and 6% Fe ₂ O ₃ by mass, and the recovery rate of Sn was calculated to be 78%.

It can be found from the above examples that the tin dioxide produced by the present invention has higher purity and can be used in subsequent industrial applications.

Example 4

The solder slag used and the process are the same as those in Example 1, except that the pH is adjusted to 2.7 with sodium hydroxide after adding Fenton oxidation effluent. Finally, the mass percentage of SnO ₂ solid obtained is more than 95%, and the recovery rate of Sn is calculated to be 80%.

Example 5

The solder slag and the process used are the same as those in Example 1, except that the pH is adjusted to 1.5 with sodium hydroxide after adding Fenton oxidation effluent. Finally, the mass percentage of SnO ₂ solids obtained was more than 99%, and the recovery rate of Sn was calculated to be 88%.

Example 6

The solder slag used and the process are the same as those in Example 1, except that the pH is adjusted to 1.3 with sodium hydroxide after adding Fenton oxidation effluent. Finally, the mass percentage of SnO _solid above 99% was obtained, and the recovery rate of Sn was calculated to be 89%.

Comparative example 1

Adjust the mixing ratio of solder slag and sulfuric acid so that the mass concentration of tin salt and stannous salt in the obtained filtrate is 60%, and the rest of the operating conditions are the same as in Example 1. Finally, the mass percentage of SnO _solid above 97% was obtained, and the recovery rate of Sn was calculated to be 55%.

Comparative example 2

The solder slag used and the process are the same as those in Example 1, except that the pH is adjusted to 3.1 with sodium hydroxide after adding Fenton oxidation effluent. Finally, the mass percentage of SnO _solid above 90% was obtained, and the recovery rate of Sn was calculated to be 75%.

Claims (15)

1. the recovery method of tin in a kind of tin slag, comprises the following steps: tin slag is soaked in the acid, tin is dissolved, filters, obtains the mixed solution that contains tin salt and stannous salt, adds wherein containing Fe ³⁺ solution, the pH of which is adjusted to 0.5-3, and after the reaction, the solid and liquid are separated, and the obtained solid is roasted to obtain SnO ₂ . 2. recovery method according to claim 1, is characterized in that, described acid is sulfuric acid or hydrochloric acid, and in mass fraction, the concentration of described hydrochloric acid is 20%-38%, and the concentration of described sulfuric acid is 40%- 60%, preferably 40%-50%. 3. The recovery method according to claim 1, characterized in that, after the tin slag is soaked in acid, the temperature is adjusted to 40-80°C, preferably 50-60°C, and the treatment time is 1-2h. 4. recovery method according to claim 1, is characterized in that, described Fe is contained in the solution The ^{concentration} of Fe in the solution is 5mg/L ^～ 100mg/L, and add-on is 3 by the mol ratio of Fe and Sn :1-2:1 join. 5. The recovery method according to claim 1, characterized in that, after adding the solution containing Fe ³⁺ , adjust the pH to be 1-2, more preferably adjust the pH to be 1.1-1.3. 6. The recovery method according to claim 1, characterized in that, after adding the solution containing Fe ³⁺ , adjusting the pH uses at least one of sulfuric acid, NaOH solution or ammonia. 7. The recovery method according to claim 1, characterized in that further, the calcination temperature is 400°C-700°C, preferably 600-650°C; the calcination time is 2-5h, preferably 2.5-3.5h. 8. A process for tin recovery coupled with Fenton's reaction, comprising: immersing tin slag in sulfuric acid, dissolving tin, filtering to obtain a mixed solution of tin-containing salt and stannous salt, adding Fenton's reaction thereto Water is discharged, and the pH is adjusted to 0.5-3. After the reaction, the solid and liquid are separated, and the obtained solid is roasted to obtain SnO ₂ , and the obtained liquid is passed into the Fenton reaction. 9. process according to claim 8, is characterized in that, the concentration of described sulfuric acid is 40%-50%. 10. The process according to claim 8, characterized in that, after the tin slag is soaked in sulfuric acid, the temperature is adjusted to 40-80°C, and the treatment time is 1-2h. 11. process method according to claim 8, is characterized in that, the effluent of described Fenton reaction is organic waste water after Fenton oxidation treatment, COD is lower than 150mg/L, and iron ion concentration is 10mg/L- 30mg/L. 12. The process according to claim 8, characterized in that the mixing ratio of tin slag and sulfuric acid solution is controlled so that the mass concentration of tin salt and stannous salt is 80%-98%. 13. The process according to claim 12, characterized in that the effluent of the Fenton reaction is mixed with the mixed solution of the tin-containing salt and the stannous salt at a volume ratio of 3:1-6:1. 14. The process according to claim 8, characterized in that, after adding the effluent of the Fenton reaction, the pH is preferably adjusted to be 1-2, more preferably adjusted to be 1.1-1.3. 15. The process according to claim 8, characterized in that the pH adjustment uses at least one of sulfuric acid, NaOH solution or ammonia.