A method for resourceful treatment of waste sulfuric acid production wastewater

Abstract

A kind of waste sulfuric acid production wastewater resource treatment method, the method is specifically the following steps: step one, dilute sulfuric acid wastewater is filtered through zeolite filter and then put into electrochemical reaction chamber, hydrogen peroxide is added, and the clear solution is obtained after 60-120min reaction under the condition of PH<1;The clear solution in step one is evaporated by rotary evaporation reactor, the water vapor evaporated is condensed by condenser, then enters heat exchanger, the cooling water used by condenser comes from cooling tower, and is recycled by heat exchange effect;After the moisture content of liquid in rotary evaporator is reduced, high-concentration sulfuric acid solution is obtained for resource utilization, and condensed water is recycled.The present application realizes the comprehensive recovery and utilization of dilute sulfuric acid and water resources in wastewater, and the recycled resources have the characteristics of low COD and shallow color, which significantly improves the reuse potential of waste sulfuric acid, realizes the dual unity of economic benefit and environmental benefit.

Description

Technical Field

[0001] This invention belongs to the field of treatment and resource utilization of strongly acidic industrial wastewater, and specifically relates to a method for resource utilization treatment of waste sulfuric acid production wastewater. Background Technology

[0002] With the advancement of science and technology and the rapid development of the social economy, sulfuric acid, as a basic hazardous chemical, is widely used in various fields such as steel, petrochemicals, chlor-alkali, pharmaceuticals, new energy, dyes, papermaking, and military engineering. However, in these fields, due to incomplete material conversion, a large amount of sulfuric acid solution is inevitably generated as a byproduct. Direct discharge of this untreated sulfuric acid wastewater not only leads to resource waste but also poses a significant potential threat to environmental and ecological security. Therefore, promoting and improving the comprehensive utilization of sulfuric acid wastewater is of great importance.

[0003] Currently, various methods for treating sulfuric acid wastewater have been proposed in engineering, including neutralization, high-temperature pyrolysis, extraction, and oxidative decomposition. Neutralization of sulfuric acid wastewater consumes a large amount of alkali, and the high salt content limits the resource recovery and utilization of by-products. Existing technologies disclose organic extraction processes for sulfuric acid recovery, where the organic extractant is a mixture of triisooctylamine and trioctylamine, which improves extraction efficiency. Phase modifiers include 2-octanol and tributyl phosphate (TBP). Although this process is closed-loop, the minimum 2-octanol mass fraction is over 20%, resulting in a large consumption of the organic extract phase and making subsequent purification relatively difficult. Existing technologies disclose membrane-based methods for recovering sulfuric acid from titanium dioxide wastewater. The membrane material is a homogeneous dialysis anion exchange membrane, which shows good separation effects for H₂SO₄, FeSO₄, and Ti(SO₄)₂. However, the sulfuric acid concentration change is small, indicating that the sulfuric acid cannot be enriched for recycling. Existing technologies also disclose pretreatment methods for organic matter in waste acid, involving adsorption by an adsorbent followed by photoelectrocatalytic degradation, achieving efficient removal of organic matter. However, the modified activated carbon used in these methods is classified as hazardous waste after adsorption, resulting in high disposal costs and limited adsorption capacity, thus restricting the economic viability of recycling industrial waste sulfuric acid. In summary, the application of the above methods is limited by many problems, including low separation efficiency, high energy consumption, poor operational stability, severe secondary pollution, and complex structure.

[0004] Recently, single-effect evaporation and multi-stage flash evaporation have effectively improved the thermal efficiency of thermal separation, enabling the recovery of concentrated sulfuric acid and water, thus leading to the widespread application of thermal treatment and resource utilization technologies for dilute sulfuric acid wastewater. Among these, membrane distillation (MD) possesses excellent separation performance and the advantages of low operating temperature and pressure, and has been applied in seawater desalination, wastewater treatment, food processing, and the pharmaceutical industry. An experimental study was conducted on sulfuric acid solution treatment using an air-gap membrane distillation (AGMD) system, achieving a higher discharge concentration of 40% at a feed concentration of 2%. Mechanical vapor recompression (MVR) has attracted widespread attention in recent decades. It can effectively utilize internal sensible and latent heat through compressor compression, thus effectively improving the energy conversion efficiency of evaporation systems. Existing patents combine vacuum membrane distillation (VMD), solar energy, and MVR technologies to achieve high-purity separation of sulfuric acid wastewater while maintaining high efficiency and energy saving. However, the low solar energy intensity and utilization rate per unit area restricts the large-scale treatment and utilization of sulfuric acid wastewater; for example, this technology is significantly limited for sulfuric acid wastewater treatment plants with a daily processing capacity of 1000-3000 cubic meters. Based on the inspiration from the above technologies, existing patents disclose an internal rotating disc heating film evaporation dryer with a hollow central shaft inside the cylinder and several hollow rotating discs coaxially arranged on it. This increases the contact area between the material and the heat medium inside the cylinder and improves the thermal efficiency. In addition, improvements have been made to the above by adding a jacket and a stirring scraper. Although the thermal efficiency has been improved, the problems of acid recovery and comprehensive utilization of water resources have not been solved.

[0005] In addition to the large volume of sulfuric acid industrial wastewater, actual industrial wastewater often contains impurities such as organic matter. For example, the dye industry discharges huge amounts of dilute sulfuric acid wastewater, which often contains dye intermediates, dyes, and small amounts of raw materials. These organic substances generate significant color, negatively impacting sulfuric acid recycling. When treating sulfuric acid wastewater using the ammonia method, the high levels of impurities and color result in extremely low ammonium sulfate prices, leading to poor economic returns and limited willingness to recycle. Therefore, it is necessary to develop a systematic treatment technology for dilute sulfuric acid wastewater, incorporating pretreatment, efficient thermal separation, and auxiliary heat exchange devices. This technology can not only efficiently recover sulfuric acid, creating economic benefits for enterprises, but also degrade and remove residual pollutants in the wastewater, ensuring that the treated wastewater meets discharge standards. Furthermore, it can recover some water resources for multiple recycling cycles, improving energy conservation and emission reduction levels while simultaneously addressing environmental issues for enterprises. Summary of the Invention

[0006] To overcome the above shortcomings, this invention provides a method for the resource-based treatment of waste sulfuric acid production wastewater. Based on the characteristics of sulfuric acid wastewater and combined with the compositional properties of pollutants, sulfuric acid, and water, this method enables efficient removal of organic matter, recovery of sulfuric acid, and reuse of water resources, achieving a balance between environmental and economic benefits.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for resource-based treatment of waste sulfuric acid production wastewater, characterized in that the method specifically comprises:

[0009] Step 1: After filtering the dilute sulfuric acid wastewater through a zeolite filter, it is placed into an electrochemical reaction chamber, hydrogen peroxide is added, and the reaction is carried out for 60-120 minutes under the condition of pH < 1. After removing impurities, a clear solution is obtained.

[0010] Step 2: The clear solution from Step 1 is evaporated through a rotary evaporator. The evaporated water vapor is condensed in a condenser and then enters a heat exchanger. The cooling water used in the condenser comes from a cooling tower and is recycled through heat exchange. After the water content of the liquid in the rotary evaporator is reduced, a high-concentration sulfuric acid solution is obtained, and the condensate is recycled.

[0011] Further optimization involves using 1-5 mol of the transition metal catalyst, which is composed of thiol compound and disulfide compound.

[0012] In a further optimization, the dilute sulfuric acid water in step one is adjusted in a regulating tank before entering the zeolite filter to regulate the water quality and quantity.

[0013] Further optimization is achieved by setting the current density in the electrochemical reaction chamber of step one to 10~35 mA / cm². 2 The dosage of hydrogen peroxide is 12-20‰.

[0014] In a further optimization, the anode in the electrochemical reaction cell is a Ti-MnO2 composite electrode, the cathode plate is an iridium-ruthenium electrode with an Ir-RuO2 surface active layer, and an activated carbon layer with functional groups is attached to the electrode surface.

[0015] Further optimization involves setting the vacuum level during rotary evaporation in step two to -110 to -96 KPar and the evaporation temperature to 47°C to 64°C.

[0016] The beneficial effects of this invention are as follows:

[0017] (1) This sulfuric acid wastewater and resource utilization process can not only concentrate and recover sulfuric acid for secondary use, but also recover some water resources, saving treatment costs;

[0018] (2) The sulfuric acid wastewater and resource utilization process has the combined advantages of electrochemistry + hydrogen peroxide advanced oxidation and rotary evaporation. It not only efficiently oxidizes organic matter in water and purifies sulfuric acid, but also effectively solves the problems of high treatment cost and inability to utilize sulfuric acid wastewater. Attached Figure Description

[0019] Appendix Figure 1 This is a flowchart of the process flow of the present invention.

[0020] Figure descriptions: 1. Equalization tank, 2. Zeolite filter, 3. Electrochemical reaction chamber, 4. Heat exchanger, 5. Rotary evaporator reactor, 6. Boiler, 7. Vacuum pump, 8. Condenser, 9. Cooling tower. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings.

[0022] A method for resource recovery treatment of waste sulfuric acid production wastewater, the method specifically comprising the following steps:

[0023] Step 1: Dilute sulfuric acid wastewater with a mass fraction of 8-12% is introduced into equalization tank 1 and left for 8-12 hours. Then it is pumped into zeolite filter 2 for filtration. Suspended solids are removed by filtration. The wastewater then enters electrochemical reaction chamber 3 for electrolysis. The current density is 10-35 mA / cm2. In order to improve the electrolysis rate and save energy, hydrogen peroxide with a mass fraction of 8% is added to electrochemical reaction chamber 3 during the electrolysis process. The dosage is 12-20‰. The reaction is carried out for 60-120 minutes under the condition of pH < 1. Defoamer is added to prevent a large amount of foam generated on the surface of the water during the electrolysis process from overflowing the electrochemical reaction chamber. After the electrolysis is completed, a clear solution is obtained.

[0024] Step 2: The clear solution from Step 1 is evaporated in rotary evaporator 5. The evaporation vacuum is -110~-96KPar, and the evaporation temperature is 47~64℃. During the evaporation process, vacuum pump 7 evacuates rotary evaporator 5 to increase the vacuum level, which can effectively reduce the boiling point of the processed material, improve evaporation efficiency, and recover the concentration of sulfuric acid. Water vapor is drawn into condenser 8 by vacuum pump 7. The cooling water in condenser 8 enters cooling tower 9 for cooling and is then recycled to achieve better cooling. The cooling water in condenser 8 is pumped into heat exchanger 4 for heat exchange, heating the cooling water to improve thermal efficiency. Heat exchanger 4 receives the heat from the condensate to preheat the sulfuric acid wastewater, realizing the recycling of condensate. After evaporation, sulfuric acid is recovered.

[0025] In this invention, heat exchanger 4 receives heat from condensate to preheat sulfuric acid wastewater, thereby achieving the recycling of condensate. Steam generated by boiler 6 heats the sulfuric acid wastewater and then supplements it with a small amount of pure water for recirculation heating. The energy utilization rate is improved through a multi-stage heat exchange system.

[0026] Under negative pressure, the boiling temperature of sulfuric acid wastewater drops sharply, and the volatility of residual organic matter is greatly reduced, thus decreasing the concentration and color of organic matter in the evaporator and laying the foundation for the reuse of condensate in the condenser. Secondly, the improvement in thermal efficiency is mainly influenced by the heat exchange area. For example, plate heat exchangers with a large surface area are more efficient than tube heat exchangers with a small surface area. In this evaporation process, the steam consumption per ton of water is 0.14-0.2t, and the power consumption per ton of water is 12-18kWh. Compared with the 0.25t steam consumption and 15.5kWh power consumption of the traditional process, this represents a saving of 20% and 9.8%, respectively.

[0027] The anode in the electrochemical reaction cell is a Ti-MnO2 composite electrode, and the cathode is an iridium-ruthenium electrode with an Ir-RuO2 surface active layer. An activated carbon layer with functional groups is attached to the electrode surface. When voltage is applied to the activated carbon, it achieves excellent decolorization and improves COD removal rate. Iron salts, copper salts, and other metal salts are commonly used to catalyze the mineralization of organic pollutants; however, they introduce metal ions and cause secondary pollution. The activated carbon material on the surface of the electrochemical electrode contains sufficient oxygen functional groups. These oxygen functional groups act as electron transfer media to activate H2O2, generating reactive free radicals, which facilitates the oxidative degradation of organic pollutants.

[0028] The water quality of the sulfuric acid concentrate effluent and the quality of the reused condensate after treatment according to this invention are compared with the water quality of the untreated sulfuric acid wastewater, as shown in Tables 1, 2, and 3, respectively:

[0029] Table 1. Water quality of the sulfuric acid wastewater to be treated

[0030]

[0031] Table 2. Water quality of the effluent from the treated concentrated sulfuric acid solution

[0032]

[0033] Table 3. Water quality of treated and reused condensate

[0034]

[0035] Table 1 shows that the original sulfuric acid wastewater has high color, low pH, and high COD. The high color and high COD originate from dye intermediates and unreacted raw materials in the wastewater, while the low pH facilitates the resource recovery of acidic substances. After treatment with resource recovery technology, zeolite blocks suspended solids and adsorbs a small amount of organic matter, providing a low-turbidity environment for the electrochemical device. After the electrochemical device efficiently removes the color-producing organic matter, the wastewater enters a rotary evaporator to remove water, yielding high-concentration, resource-recovered sulfuric acid. The compositional characteristics of this resource-recovered sulfuric acid are shown in Table 2. Table 2 shows that the pH of the treated effluent is still less than 1, indicating that acidic substances are retained; the COD decreases to between 800-1200 mg / L, indicating an organic matter removal rate of approximately 90%; and the color removal rate is approximately 78%. These water quality characteristics demonstrate the feasibility of large-scale resource recovery and utilization of sulfuric acid. The water quality data in Table 3 are the characteristics of the recovered condensate, with a near-neutral pH and extremely low concentrations of suspended solids (SS), color, and organic matter, making it suitable for production reuse.

[0036] Sulfuric acid wastewater treatment and resource recovery processes can recover high-concentration sulfuric acid, saving treatment costs. Sulfuric acid wastewater treatment and resource utilization technologies efficiently address the problem of high-concentration organic matter in sulfuric acid wastewater and condensate, significantly reducing the operating costs of treating and reusing sulfuric acid wastewater.

[0037] The foregoing has shown and described the main features, usage methods, basic principles, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention based on actual circumstances without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for the resource-based treatment of waste sulfuric acid production wastewater, characterized in that, The method specifically comprises the following steps: Step 1: Dilute sulfuric acid wastewater is filtered through a zeolite filter and then placed into an electrochemical reaction chamber. Hydrogen peroxide is added, and the reaction is carried out for 60-120 minutes under pH < 1 conditions. After impurity removal, a clear solution is obtained. The anode in the electrochemical reaction chamber is a Ti-MnO2 composite electrode, and the cathode plate is an iridium-ruthenium electrode with an Ir-RuO2 surface active layer. An activated carbon layer with oxygen-containing functional groups is attached to the electrode surface. Step 2: The clear solution from Step 1 is evaporated through a rotary evaporator. The evaporated water vapor is condensed in a condenser and then enters a heat exchanger. The cooling water used in the condenser comes from a cooling tower and is recycled through heat exchange. After the water content of the liquid in the rotary evaporator is reduced, a high-concentration sulfuric acid solution is obtained, and the condensate is recycled.

2. The method for resource-based treatment of waste sulfuric acid production wastewater as described in claim 1, characterized in that, In step one, the dilute sulfuric acid water passes through an equalization tank to adjust the water quality and quantity before entering the zeolite filter.

3. The method for resource-based treatment of waste sulfuric acid production wastewater as described in claim 1, characterized in that, In step one, the current density in the electrochemical reaction chamber is 10–35 mA / cm². 2 The dosage of hydrogen peroxide is 12-20‰.

4. The method for resource-based treatment of waste sulfuric acid production wastewater as described in claim 1, characterized in that, In step two, the vacuum degree during rotary evaporation is -110 to -96 KPar, and the evaporation temperature is 47°C to 64°C.

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