Method for treating detergent wastewater by using foundry waste sand regeneration waste

Abstract

The invention relates to the technical field of detergent wastewater treatment, in particular to a method for treating detergent wastewater by utilizing foundry waste sand regeneration waste. According to the method, waste generated after foundry waste sand regeneration is taken as a basis, and the detergent wastewater is pretreated by establishing a'Fenton oxidation + flocculation precipitation 'dual system, so that the problem of waste discharge of a novel regeneration process is solved, efficient degradation of COD (Chemical Oxygen Demand) content in the detergent wastewater is also realized, and the purposes of'waste recycling' and'treating waste with waste 'are achieved.

Description

A method for treating detergent wastewater using foundry waste sand recycling waste. Technical Field

[0001] This invention relates to the field of detergent wastewater treatment technology, and more particularly to a method for treating detergent wastewater using recycled foundry waste sand. Background Technology

[0002] my country is a major foundry country, with an estimated 50 million tons of waste foundry sand generated annually. Behind this massive production scale lies the problem of large-scale accumulation of waste foundry sand. In recent years, to implement the concept of sustainable development in the foundry industry, how to carry out green recycling and reuse of waste foundry sand has become a new research direction. Currently, waste sand recycling methods mainly include mechanical dry recycling, thermal recycling, wet recycling, and combined methods. While these methods can effectively treat waste silica sand, they also present the challenge of how to dispose of the waste generated during recycling. Therefore, constructing an efficient and green treatment system for waste foundry sand is key to achieving the resource-based recycling and reuse of waste foundry sand.

[0003] Detergents are everyday chemical products specifically formulated for cleaning processes. In recent years, with scientific advancements and improved hygiene, the demand for detergents has increased dramatically, making them an essential part of daily life. As the detergent industry has rapidly developed globally, detergent consumption has also grown significantly, leading to a greater environmental impact.

[0004] Detergent wastewater mainly consists of soluble substances such as surfactants, polyphosphates, bleach, and animal and vegetable oils, as well as non-soluble impurities such as soil, short fibers, and others. For this type of wastewater, which is complex in composition and difficult to treat, existing treatment methods generally suffer from problems such as complex operation, high costs, or high risks of secondary pollution.

[0005] Therefore, how to effectively transform foundry waste sand recycling waste into resources for treating detergent wastewater, and build an efficient, green, and low-cost collaborative treatment system to achieve "waste treatment with waste" is a resource utilization and environmental governance direction worthy of in-depth research. Summary of the Invention

[0006] The purpose of this invention is to provide a method for efficiently treating detergent wastewater based on foundry waste sand recycling. Using the waste generated after foundry waste sand recycling as a basis, a dual system of "Fenton oxidation + flocculation sedimentation" is established to pretreat detergent wastewater. This not only solves the waste discharge problem of the new recycling process, but also achieves efficient degradation of COD content in detergent wastewater, thus achieving the goals of "waste reuse" and "waste treatment".

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

[0008] A method for treating detergent wastewater using foundry waste sand recycling waste, the method comprising the following steps: (1) crushing foundry waste sand, then performing magnetic separation to remove magnetic substances from the waste sand, and sieving through a graded vibrating screen to obtain fine sand; (2) mixing H2O2 and H2SO4 to obtain solution A; (3) adding solution A obtained in step (2) to the fine sand obtained in step (1) for oxidation and acidolysis, magnetic stirring for one step, settling for one step, separating the recycled sand to obtain solution B; (4) adding solution B to detergent wastewater, magnetic stirring for two steps to obtain solution C; (5) adding 0.01 mol / L H2SO4 to solution C obtained in step (4) to adjust the pH to 4, stirring at room temperature, settling for two steps to obtain solution D; (6) adding FeSO4 to solution D obtained in step (5), filtering after no bubbles are generated to obtain solution E; (7) adding 0.1 mol / L NaOH to solution E obtained in step (6) to neutralize the solution to pH=7, and filtering.

[0009] In the above technical solution, further, in step (1), the foundry waste sand is crushed to a particle size of less than 2 mm by a jaw crusher; the particle size of the fine sand is 30~200 mesh, preferably 80~120 mesh.

[0010] In the above technical solution, further, in step (2), the mass concentration of H2O2 is 3%~10%; the molar concentration of H2SO4 is 0.01 mol / L; the volume ratio of H2O2 to H2SO4 is 3:1~6:1, preferably 3:1~4:1.

[0011] In the above technical solution, further, in step (3), the liquid-solid ratio of solution B to fine sand is 1:0.5; the magnetic stirring time is 5~30 min, preferably 10~15 min; and the standing time is 5 h.

[0012] In the above technical solution, further, in step (4), the volume ratio of solution B to detergent wastewater is 1:1 to 5:1, preferably 1:1 to 3:1; the magnetic stirring time is 5 to 20 min, preferably 10 to 15 min.

[0013] In the above technical solution, further, in step (5), the stirring time is 1~5 h, preferably 2~3 h; the standing time is 30 min.

[0014] In the above technical solution, further, in step (6), the solid-liquid ratio of solution D to FeSO4 is 80:1 to 120:1, preferably 90:1 to 110:1.

[0015] The beneficial effects of this invention are as follows: This invention provides a process for recycling and regenerating foundry waste sand. It regenerates foundry waste sand through hydrogen peroxide oxidation, utilizing the resulting waste (hydrogen peroxide, small molecule organic matter, and ferrous ion compounds) to construct a two-system approach of "Fenton oxidation + flocculation precipitation" for pretreatment of detergent wastewater, thus achieving comprehensive utilization of the waste liquid. Simultaneously, this regeneration process avoids the energy consumption and exhaust gas treatment required during the processing.

[0016] This invention employs a dual-system coupling of "Fenton oxidation + flocculation sedimentation" to treat detergent wastewater. On one hand, the strong oxidizing hydroxyl radicals generated by Fenton's reagent (ferrous sulfate + hydrogen peroxide) under acidic conditions efficiently degrade difficult-to-treat surfactants and organic pollutants in the wastewater, significantly reducing COD load. On the other hand, under normal temperature and pressure conditions, hydrogen peroxide and Fenton's reagent work synergistically in an acidic environment to degrade Fe in the system. 2+ Oxidized to Fe 3+ It also forms polyferric sulfate flocs in situ. Utilizing the excellent adsorption bridging and trapping effects of the flocs, it rapidly flocculates, settles, and separates the large molecular organic matter, colloids, and suspended particulate matter generated and remaining during the oxidation process, further enhancing the pollutant removal effect and making the overall COD removal more thorough and the effluent water quality more stable.

[0017] The method of this invention not only solves the problems of large chemical reagent consumption and difficult treatment of waste generated after waste sand regeneration in conventional advanced oxidation processes, but more importantly, it enhances the subsequent flocculation effect through chemical processes, achieving efficient degradation of COD content in detergent wastewater and achieving the goals of "waste reuse" and "waste treatment". Attached Figure Description

[0018] Figure 1 is a process flow diagram of the present invention. Detailed Implementation

[0019] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0020] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.

[0021] Example 1 (1) The foundry waste sand was crushed by a jaw crusher to obtain crushed sand with a particle size of less than 2 mm. The sand was then magnetically separated by a magnetic separator to remove magnetic materials. After passing through a grading vibrating screen, 50 g of fine sand with a mesh size of 70-100 mesh was obtained. (2) 80 mL of 3% H2O2 and 20 mL of 0.01 mol / L H2SO4 were mixed to obtain solution A. (3) 100 mL of solution A obtained in step (2) was added to the fine sand obtained in step (1) for oxidation and acid hydrolysis. The mixture was magnetically stirred for 20 min, allowed to stand for 5 h, and the regenerated sand was separated to obtain solution B. (4) 20 mL of solution B was measured into a 200 mL beaker, and 20 mL of detergent wastewater was added. The mixture was magnetically stirred for 10 min to obtain solution C. (5) 0.01 mol / L H2SO4 was added to solution C obtained in step (4) to adjust the pH to 4. The mixture was stirred at room temperature for 2 h and allowed to stand for 30 min. min, to obtain solution D; (6) add 0.4 g FeSO4 to solution D obtained in step (5), and after no more bubbles are generated, filter to obtain solution E; (7) add 0.1 mol / L NaOH to solution E obtained in step (6) to neutralize the solution to pH=7, filter to obtain solution F.

[0022] Example 2 (1) The foundry waste sand was crushed by a jaw crusher to obtain crushed sand with a particle size of less than 2 mm. The sand was then magnetically separated by a magnetic separator to remove magnetic materials. After passing through a grading vibrating screen, 50 g of fine sand with a mesh size of 70-100 mesh was obtained. (2) 80 mL of 3% H2O2 and 20 mL of 0.01 mol / L H2SO4 were mixed to obtain solution A. (3) 100 mL of solution A obtained in step (2) was added to the fine sand obtained in step (1) for oxidation and acid hydrolysis. The mixture was magnetically stirred for 20 min, allowed to stand for 5 h, and the regenerated sand was separated to obtain solution B. (4) 20 mL of solution B was measured into a 200 mL beaker, 40 mL of detergent wastewater was added, and the mixture was magnetically stirred for 10 min to obtain solution C. (5) 0.01 mol / L H2SO4 was added to solution C obtained in step (4) to adjust the pH to 4. The mixture was stirred at room temperature for 2 h and allowed to stand for 30 min. min, to obtain solution D; (6) add 0.6 g FeSO4 to solution D obtained in step (5), and after no more bubbles are generated, filter to obtain solution E; (7) add 0.1 mol / L NaOH to solution E obtained in step (6) to neutralize the solution to pH=7, filter to obtain solution F.

[0023] Example 3 (1) The foundry waste sand was crushed by a jaw crusher to obtain crushed sand with a particle size of less than 2 mm. The sand was then magnetically separated to remove magnetic materials. After passing through a grading vibrating screen, 50 g of fine sand with a mesh size of 70-100 mesh was obtained. (2) 80 mL of 3% H2O2 and 20 mL of 0.01 mol / L H2SO4 were mixed to obtain solution A. (3) 100 mL of solution A obtained in step (2) was added to the fine sand obtained in step (1) for oxidation and acid hydrolysis. The mixture was magnetically stirred for 20 min, allowed to stand for 5 h, and the regenerated sand was separated to obtain solution B. (4) 20 mL of solution B was measured into a 200 mL beaker, 10 mL of detergent wastewater was added, and the mixture was magnetically stirred for 10 min to obtain solution C. (5) 0.01 mol / L H2SO4 was added to solution C obtained in step (4) to adjust the pH to 4. The mixture was stirred at room temperature for 2 h and allowed to stand for 30 min. min, to obtain solution D; (6) add 0.3 g FeSO4 to solution D obtained in step (5), and after no more bubbles are generated, filter to obtain solution E; (7) add 0.1 mol / L NaOH to solution E obtained in step (6) to neutralize the solution to pH=7, filter to obtain solution F.

[0024] For Example 1 The chemical oxygen demand (COD) of the solution F obtained in step (7) of step 3 was analyzed. The test reagent was Huajianlianke rapid water quality test kit (COD: 0~10000 mg / L). The same amount of water sample was tested three times, and the average value of the results was taken. The test results are shown in Table 1.

[0025] Table 1

[0026] As shown in Table 1, the method of the present invention significantly reduces the chemical oxygen demand (COD) of wastewater to less than 50 mg / L, while the national first-level standard for COD in integrated wastewater discharge is 60 mg / L. The results show that the COD content of the treated wastewater meets the national discharge standard.

[0027] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for treating detergent wastewater using recycled foundry waste sand, characterized in that: The method includes the following steps: (1) crushing the foundry waste sand, then performing magnetic separation to remove magnetic materials from the waste sand, and sieving through a graded vibrating screen to obtain fine sand; (2) mixing H2O2 and H2SO4 to obtain solution A; (3) adding solution A obtained in step (2) to the fine sand obtained in step (1) for oxidation and acid hydrolysis, magnetic stirring once, standing for one time, separating the regenerated sand to obtain solution B; (4) adding detergent wastewater to solution B, magnetic stirring twice to obtain solution C; (5) adding 0.01 mol / L H2SO4 to solution C obtained in step (4) to adjust the pH to 4, stirring at room temperature, standing for two times to obtain solution D; (6) adding FeSO4 to solution D obtained in step (5), and filtering after no bubbles are generated to obtain solution E; (7) adding 0.1 mol / L NaOH to solution E obtained in step (6) to neutralize the solution to pH=7, and filtering.

2. The method for treating detergent wastewater using foundry waste sand recycled waste as described in claim 1, characterized in that: In step (1), the foundry waste sand is crushed to a particle size of less than 2 mm using a jaw crusher; the fine sand has a particle size of 30~200 mesh.

3. The method for treating detergent wastewater using recycled foundry waste sand according to claim 1, characterized in that: In step (2), the mass concentration of H2O2 is 3%~10%; the molar concentration of H2SO4 is 0.01 mol / L; and the volume ratio of H2O2 to H2SO4 is 3:1~6:

1.

4. The method for treating detergent wastewater using recycled foundry waste sand according to claim 3, characterized in that: In step (2), the volume ratio of H2O2 to H2SO4 is 3:1 to 4:

1.

5. The method for treating detergent wastewater using foundry waste sand recycled waste as described in claim 1, characterized in that: In step (3), the liquid-solid ratio of solution B to fine sand is 1:0.5; the magnetic stirring time is 5~30 min; and the settling time is 5 h.

6. The method for treating detergent wastewater using recycled foundry waste sand according to claim 1, characterized in that: In step (4), the volume ratio of solution B to detergent wastewater is 1:1 to 5:1; the magnetic stirring time is 5 to 20 min.

7. The method for treating detergent wastewater using recycled foundry waste sand according to claim 1, characterized in that: In step (4), the volume ratio of solution B to detergent wastewater is 1:1 to 3:

1.

8. The method for treating detergent wastewater using recycled foundry waste sand according to claim 1, characterized in that: In step (5), the stirring time is 1~5 h; the settling time is 30 min.

9. The method for treating detergent wastewater using foundry waste sand recycled waste as described in claim 1, characterized in that: In step (6), the solid-liquid ratio of solution D to FeSO4 is 80:1 to 120:

1.

10. The method for treating detergent wastewater using foundry waste sand recycled waste as described in claim 1, characterized in that: In step (6), the solid-liquid ratio of solution D to FeSO4 is 90:1 to 110:1.

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