Wastewater treatment adsorbent as well as preparation method and application thereof

Abstract

The invention discloses a wastewater treatment adsorbent as well as a preparation method and application thereof. The wastewater treatment adsorbent is prepared from copper smelting slag, red mud and lime as main raw materials. The wastewater treatment adsorbent disclosed by the invention is simple in preparation process and low in cost, and has excellent adsorption performance and stability; the method not only can realize resource utilization of solid waste, but also can ensure up-to-standard discharge of thallium and COD in the wastewater after adsorption, can also reduce the treatment cost of the wastewater and the solid waste, and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste recycling, and particularly relates to a wastewater treatment adsorbent, a preparation method thereof, and an application thereof. Background Art

[0002] At present, copper smelting slag and red mud can be used as high-value-added products, such as cement additives, filling materials, glass-based composite materials, etc., but the usage amount is relatively low, and efficient resource utilization cannot be achieved. Therefore, to avoid environmental risks, there is an urgent need for an environmentally friendly method to solve the disposal problem through the resource utilization of industrial solid wastes.

[0003] A large amount of smelting wastewater is generated during the smelting of copper, lead, zinc, etc. It has the characteristics of high acidity, heavy metals, fluorine and chlorine, high dissolved solid concentration, and contains organic substances, with complex composition, large fluctuations, and high toxicity. The "Discharge Standard of Pollutants for Lead and Zinc Industries GB25466-2010" and its amendment stipulate that the total thallium discharge concentration limit for wastewater in lead-zinc smelting workshops or production facilities is 0.017 mg / L, and the direct discharge concentration limit for COD (chemical oxygen demand) is 60 mg / L; the "Discharge Standard of Pollutants for Copper, Nickel, and Cobalt Industries GB 25467-2010" stipulates that the direct discharge concentration limit for COD in pyrometallurgical copper smelting is 60 mg / L; according to the requirements of the "Yunnan Thallium Pollution Prevention and Control Plan (Trial)" (Yunhuan Tong

[2023] No. 126), the total thallium discharge limit for wastewater from copper, indium, germanium, and arsenic smelting enterprises shall be implemented with reference to the amendment of GB25467-2010, and follow the regulations after the relevant standards are issued. At present, the conventional methods for treating smelting wastewater mainly include lime neutralization method, high-concentration slurry method, sulfidation method, lime + ferric salt method, electrochemical method, biological agent method, membrane method, and the combination of several of these methods. Except for the reverse osmosis membrane method, other methods usually have difficulty in treating total thallium and COD to meet the discharge standards. In view of this situation, currently, advanced oxidation methods (such as ozone catalytic oxidation method, Fenton oxidation method, persulfate catalytic oxidation method, etc.), adsorption methods (such as activated carbon adsorption method, etc.), and electrochemical methods (such as electro-Fenton method, electrocatalytic oxidation method, etc.) are usually used to remove COD in wastewater; adding thallium removal reagents is used to remove total thallium in wastewater, but these methods usually have disadvantages such as high treatment cost and large amount of slag production. Therefore, there is an urgent need for an economical and efficient treatment method.

[0004] At present, many scholars are studying the use of industrial solid waste to prepare flocculants and adsorbents to remove heavy metals in wastewater, but there are few reports on the use of copper smelting slag and red mud as the main raw materials to prepare composite adsorbents to remove total thallium and organic matter (i.e., COD) in smelting wastewater. In response to the above problems, the present invention has developed a simple, low-cost method for preparing wastewater treatment adsorbents using copper smelting slag and red mud as the main raw materials, which can alleviate the serious pollution problem caused by the accumulation of industrial solid wastes and provide a solution for the sustainable development of the non-ferrous smelting industry. At the same time, the prepared adsorbent can be used to treat smelting wastewater to ensure that the total thallium and COD of the treated wastewater meet the discharge requirements. Summary of the invention

[0005] The first purpose of the present invention is to provide a wastewater treatment adsorbent; the second purpose is to provide a method for preparing the wastewater treatment adsorbent; and the third purpose is to provide an application of the wastewater treatment adsorbent.

[0006] The first object of the present invention is achieved in that the wastewater treatment adsorbent is prepared from copper smelting slag, red mud and lime as main raw materials.

[0007] The second object of the present invention is achieved by comprising pre-treatment, preparation and post-treatment steps, specifically comprising: A. Pre-treatment: 1) drying and grinding the copper smelting slag, red mud and lime in a given proportion respectively, and passing through a 100-mesh sieve to obtain pretreated copper smelting slag a, pretreated red mud b and pretreated lime c; 2) putting the pretreated copper smelting slag a, the pretreated red mud b and the pretreated lime c into a ball mill for ball milling to obtain a ball milled mixture d; B. Preparation: Add sodium silicate solution and boiling water to the ball-milled mixture d and stir thoroughly to obtain a paste e; C. Post-processing: 1) The paste e is made into spheres with a diameter of 8 to 12 mm and then dried to obtain spherical material f; 2) The spherical material f is crushed and ground through a 100-mesh sieve to obtain the target wastewater treatment adsorbent.

[0008] The specific operations are as follows: A. Dry, grind, and sieve the copper smelting slag, red mud, and lime through a 100-mesh sieve, and place them in a dryer for later use. The copper smelting slag mainly consists of: Fe 2 O 3 38~48%, SiO 2 28~36%, Al 2 O 3 5~8%, CaO 3~5%, ZnO 1~3%, MgO 1~3%, Na 2O is 1-2%. The red mud is Bayer red mud, with a pH of 10-12, and the main minerals are aragonite and calcite, with a content of 60-65%. The main components are: SiO 2 10~20%, CaO 3~9%, Al 2 O 3 22~32%, Fe 2 O 3 is 20~35%, Na 2 O is 3~10%, TiO 2 The main component of lime is CaO; B. The copper smelting slag, red mud and lime prepared in step A are respectively put into a ball mill at a mass ratio of 20:(1-2):(1-2), and ball milled for 1 h at a ball-to-material ratio of 2:1 and 600 r / min to improve the activity of the powder adsorbent and the pore structure; C. Put the ball-milled mixture prepared in step B, sodium silicate solution and boiling water into an electric stirrer at a mass volume ratio of 4 (g): 1 (ml): 1 (ml), and stir and mix them thoroughly at 160 r / min to form a paste to enhance the gelling performance. The effective ingredient of the sodium silicate solution is 50%; D. Make the paste into spheres with a diameter of about 10 mm and put them into a tray. Place the tray in a drying oven and dry at a constant temperature of 80°C for 6 hours. E. The dried spherical material is crushed and ground, and after passing through a 100-mesh sieve, a high-efficiency composite adsorbent for wastewater treatment of red mud-based activated copper smelting slag is obtained.

[0009] The third object of the present invention is achieved by using the wastewater treatment adsorbent in the preparation of a high-efficiency composite adsorbent for wastewater treatment.

[0010] The adsorbent wastewater treatment process comprises the following steps: A. Taking copper smelting wastewater as the object, an appropriate amount of sodium sulfide is first added to the wastewater, and heavy metals react with S2- to form metal sulfide precipitation; the supernatant is adjusted to pH 8.0 with 10% lime milk, and further precipitated to remove fluorine and some residual heavy metals; B. Add the wastewater treated in step A at a volume mass ratio of 100:(1-2) ml / g to the adsorbent, stir at 180r / min for 1-2h at 25°C, let it settle for 30-60min, take the supernatant for testing, and the total thallium and COD meet the discharge requirements;

[0011] C. Adsorbent regeneration: After collecting the failed adsorbent and letting it air dry naturally, put it into 0.5 mol / L sulfuric acid and stir it for 2 hours, then wash it with pure water for 3 times and dry it at 60°C for 3 hours to achieve adsorbent regeneration. The regenerated adsorbent can be reused many times.

[0012] The preparation and adsorption removal mechanism of the wastewater treatment adsorbent described in the present invention are as follows: Adsorbent preparation mechanism: In the system for preparing the powder adsorbent from copper smelting slag - red mud - lime, alumina is effectively activated by lime to form complex hydrated products; copper smelting slag, red mud, and lime are ball-milled according to the mass ratio, which can improve the activity of the adsorbent and improve the pore structure; red mud has potential gelling properties, which mainly originate from alumina. With the addition of an appropriate amount of sodium silicate solution, the gelling performance of the adsorbent can be enhanced.

[0013] Adsorption removal mechanism: (1) Adsorption type: This adsorption is a spontaneous endothermic reaction. The adsorption of thallium and organic matter (i.e., COD) includes monolayer chemical adsorption and multilayer physical adsorption. (2) The adsorption mechanism mainly includes the following three: ① Electrostatic attraction: Under the action of mechanical or hydraulic stirring of the wastewater, thallium and organic matter will diffuse to the surrounding of the adsorbent and undergo electrostatic attraction with the adsorbent. This is mainly due to the presence of chemical groups Si - O - Si and Si - O - Al, which cause the adsorbent to show electronegativity; in addition, the combination of -OH with Tl(I), Tl(III), and organic matter through acidic groups can promote adsorption; ② Ion exchange: The main crystal phase of the adsorbent (Fe 2 SiO 4 dissolves to form new chemical bonds and will undergo ion exchange with Tl(I) and Tl(III); Ca(II) on the adsorbent exchanges ions with Tl(I) and Tl(III) to form new compounds; ③ Surface precipitation: Under alkaline conditions, the adsorbed Tl(III) will react with OH － to generate Tl(OH) 3 precipitate, which adheres to the surface of the adsorbent. Therefore, the adsorption mechanism mainly includes electrostatic attraction, ion exchange, and surface precipitation.

[0014] The advantages of the present invention are as follows: (1) Using copper smelting slag and red mud as the main raw materials to prepare the wastewater treatment adsorbent, the preparation process is simple, the cost is low, and it is easy to industrialize production; combining the advantages of each raw material, the preparation method can optimize the structure and performance of the adsorbent, improve the adsorption efficiency and stability, and has excellent adsorption performance; (2) This adsorbent is not only applicable to treating heavy metal-containing wastewater but also can treat organic matter-containing wastewater, with a wide range of applications and broad application prospects; (3) This adsorbent can deeply remove thallium and organic matter in smelting wastewater, ensuring that thallium and COD in the discharged wastewater meet the discharge standard requirements; (4) Using this adsorbent to treat wastewater can not only reduce the environmental pollution of wastewater but also realize the resource utilization of industrial solid waste, while reducing the treatment costs of wastewater and industrial solid waste, providing an efficient, environmentally friendly, and economical solution for wastewater treatment. Specific embodiments

[0015] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention belong to the protection scope of the present invention.

[0016] The wastewater treatment adsorbent of the present invention is prepared from copper smelting slag, red mud and lime as main raw materials.

[0017] The mass ratio of the copper smelting slag, red mud and lime is 20:(1-2):(1-2).

[0018] The main components of the copper smelting slag are: Fe 2 O 3 38~48%, SiO 2 28~36%, Al 2 O 3 5~8%, CaO 3~5%, ZnO 1~3%, MgO 1~3%, Na 2 O is 1~2%.

[0019] The red mud is Bayer red mud, with a pH of 10-12, and the main minerals are aragonite and calcite, with a content of 60-65%. The main components are SiO 2 10~20%, CaO 3~9%, Al 2 O 3 22~32%, Fe 2 O 3 is 20~35%, Na 2 O is 3~10%, TiO 2 It is a trace amount ~6%.

[0020] The main component of the lime is CaO.

[0021] The method for preparing the wastewater treatment adsorbent of the present invention comprises pre-treatment, preparation and post-treatment steps, specifically comprising: A. Pre-treatment: 1) drying and grinding the copper smelting slag, red mud and lime in a given proportion respectively, and passing through a 100-mesh sieve to obtain pretreated copper smelting slag a, pretreated red mud b and pretreated lime c; 2) putting the pretreated copper smelting slag a, the pretreated red mud b and the pretreated lime c into a ball mill for ball milling to obtain a ball milled mixture d; B. Preparation: Add sodium silicate solution and boiling water to the ball-milled mixture d and stir thoroughly to obtain a paste e; C. Post-processing: 1) The paste e is made into spheres with a diameter of 8 to 12 mm and dried to obtain spherical material f; 2) Crush, grind, and sieve the spherical material f through a 100-mesh sieve to obtain the target wastewater treatment adsorbent.

[0022] The ball milling described in step 2) of A is carried out at a ball-to-material ratio of 2:1 and a speed of 600 r / min for 0.5 - 1.5 h.

[0023] In step B, the mass-to-volume ratio of the ball-milled mixture d, sodium silicate solution, and boiling water is (g, 3 - 5):(ml, 0.5 - 1.5):(ml, 0.5 - 1.5).

[0024] The drying described in step 1) of C is carried out at a constant temperature of 70 - 90 °C for 5 - 7 h.

[0025] The application described in the present invention is the application of the wastewater treatment adsorbent in the preparation of a highly efficient composite adsorbent for wastewater treatment.

[0026] The following is a further description of the present invention with specific examples: In all the following examples, total thallium is determined by inductively coupled plasma atomic emission spectrometry, and COD is determined according to "Water Quality - Determination of Chemical Oxygen Demand - Dichromate Method" (HJ 828 - 2017).

[0027] The emission concentration limits of total thallium and COD in smelting wastewater are shown in Table 1. According to the requirements of "Yunnan Thallium Pollution Prevention and Control Plan (Trial)" (Yun Huan Tong

[2023] No. 126), the total thallium emission limit for copper, indium, germanium, and arsenic smelting enterprises in Yunnan Province shall be implemented with reference to the amendment of the "Pollutant Discharge Standards for Lead and Zinc Industries". After the relevant standards are issued, they shall be followed.

[0028] Table 1 Emission Concentration Limits of Total Thallium and COD in Smelting Wastewater

[0029] Example 1

[0030] Adsorbent preparation: A. After drying, grinding, and sieving through a 100-mesh sieve, the copper smelting slag, red mud, and lime are placed in a desiccator for standby. The main components of the copper smelting slag are: Fe 2 O 3 is 38 - 48%, SiO 2 is 28 - 36%, Al 2 O 3 is 5 - 8%, CaO is 3 - 5%, ZnO is 1 - 3%, MgO is 1 - 3%, Na 2 O is 1 - 2%. The red mud is Bayer red mud with a pH of 10 - 12. The main minerals are aragonite and calcite, with a content of 60 - 65%. The main components are: SiO 2 is 10 - 20%, CaO is 3 - 9%, Al 2 O3 is 22 - 32%, Fe 2 O 3 is 20 - 35%, Na 2 O is 3 - 10%, TiO 2 is trace - 6%. The main component of the lime is CaO. B. Put the copper smelting slag, red mud and lime prepared in step A into a ball mill according to a mass ratio of 20:1:1 respectively, and ball mill for 1 h under the conditions of a ball - to - material ratio of 2:1 and 600 r / min; C. Put the ball - milled mixture prepared in step B, sodium silicate solution and boiling water into an electric stirrer according to a mass - to - volume ratio of 4(g):1(ml):1(ml) respectively, and fully stir and mix to make a paste under the condition of 160 r / min. The effective component of the sodium silicate solution is 50%; D. Make the paste into spheres with a diameter of about 10 mm and put them on a tray, place the tray in a drying oven, and dry at a constant temperature of 80°C for 6 h; E. Crush and grind the dried spherical materials, and pass through a 100 - mesh sieve to obtain a high - efficiency composite adsorbent for wastewater treatment of red - mud - based activated copper smelting slag.

[0031] Adsorbent for treating wastewater: Take 5 L of copper smelting wastewater and place it in a plastic bucket. First, add an appropriate amount of sodium sulfide, and the heavy metals in the wastewater react with S 2- to form metal sulfide precipitates; then adjust the pH of the supernatant to 8.0 with 10% lime milk to further precipitate and remove fluorine and residual heavy metals. Take the supernatant for inspection. The test results are: total thallium is 0.0423 mg / L, COD is 102 mg / L, both of which do not meet the discharge standard requirements. Finally, take two 500 - mL aliquots of the supernatant and place them in two 1 - L beakers respectively. Adjust the pH to 7.0 with dilute sulfuric acid, and add 5.0 g and 10.0 g of the adsorbent respectively. Stir at a speed of 180 r / min at 25°C for 1.0 h, and let it stand for 30 min. After precipitation, the total thallium in the supernatant with 5.0 g of the adsorbent added is 0.009 mg / L, COD is 48 mg / L, while the total thallium in the supernatant with 10.0 g of the adsorbent added is 0.005 mg / L, COD is 36 mg / L, both of which are lower than the discharge concentration limit requirements in Table 1.

[0032] Example 2

[0033] Adsorbent preparation: The copper smelting slag, red mud and lime are ball - milled according to a mass ratio of 20:1:2 respectively, and the ball - milled mixture, sodium silicate solution and boiling water are stirred according to a mass - to - volume ratio of 4(g):1(ml):1(ml) respectively, and the rest is the same as in Example 1.

[0034] Treatment of wastewater with adsorbent: Take 5 L of copper smelting wastewater and place it in a plastic bucket. After sulfide precipitation and lime neutralization precipitation (the steps are the same as in Example 1), take the supernatant for testing. The test results show that the total thallium is 0.0375 mg / L and the COD is 96 mg / L, both of which do not meet the discharge standard requirements. Take two 500 mL portions of the supernatant and place them in two 1 L beakers respectively. Adjust the pH to 7.0 with dilute sulfuric acid, and add 5.0 g and 10.0 g of adsorbent respectively. Stir at a speed of 180 r / min at 25 °C for 2.0 h. After standing and precipitating for 60 min, the total thallium in the supernatant with 5.0 g of adsorbent added is 0.008 mg / L and the COD is 42 mg / L, while the total thallium in the supernatant with 10.0 g of adsorbent added is 0.003 mg / L and the COD is 32 mg / L, both of which are lower than the discharge concentration limit requirements in Table 1.

[0035] Example 3

[0036] Preparation of adsorbent: Copper smelting slag, red mud and lime are ball-milled according to a mass ratio of 20:2:1 respectively. The ball-milled mixture, sodium silicate solution and boiling water are stirred according to a mass-volume ratio of 4(g):1(ml):1(ml), and the rest is the same as in Example 1.

[0037] Treatment of wastewater with adsorbent: Take 5 L of copper smelting wastewater and place it in a plastic bucket. After sulfide precipitation and lime neutralization precipitation (the steps are the same as in Example 1), take the supernatant for testing. The test results show that the total thallium is 0.0512 mg / L and the COD is 89 mg / L, both of which do not meet the discharge standard requirements. Take two 500 mL portions of the supernatant and place them in two 1 L beakers respectively. Adjust the pH to 7.0 with dilute sulfuric acid, and add 5.0 g and 10.0 g of adsorbent respectively. Stir at a speed of 180 r / min at 25 °C for 1.0 h. After standing and precipitating for 30 min, the total thallium in the supernatant with 5.0 g of adsorbent added is 0.010 mg / L and the COD is 43 mg / L, while the total thallium in the supernatant with 10.0 g of adsorbent added is 0.006 mg / L and the COD is 31 mg / L, both of which are lower than the discharge concentration limit requirements in Table 1.

[0038] Example 4

[0039] Preparation of adsorbent: Copper smelting slag, red mud and lime are ball-milled according to a mass ratio of 20:2:2 respectively. The ball-milled mixture, sodium silicate solution and boiling water are stirred according to a mass-volume ratio of 4(g):1(ml):1(ml), and the rest is the same as in Example 1.

[0040] Treatment of wastewater with adsorbent: 5 L of copper smelting wastewater was placed in a plastic bucket. After sulfide precipitation and lime neutralization precipitation (the same steps as in Example 1), the supernatant was taken for testing. The test results showed that the total thallium was 0.0453 mg / L and the COD was 95 mg / L, both of which did not meet the discharge standard requirements. Two 500 mL aliquots of the supernatant were placed in two 1 L beakers respectively. The pH was adjusted to 7.0 with dilute sulfuric acid, and 5.0 g and 10.0 g of adsorbent were added respectively. The mixture was stirred at 180 r / min for 2.0 h at 25 °C. After standing and precipitating for 60 min, the total thallium in the supernatant with 5.0 g of adsorbent added was 0.007 mg / L and the COD was 45 mg / L, while the total thallium in the supernatant with 10.0 g of adsorbent added was 0.005 mg / L and the COD was 30 mg / L, both of which were lower than the discharge concentration limit requirements in Table 1.

[0041] Example 5

[0042] Regeneration of adsorbent: The spent adsorbent was collected and air-dried naturally, then put into 0.5 mol / L sulfuric acid and stirred for 2 h, then washed with pure water three times and dried at 60 °C for 3 h to realize the regeneration of the adsorbent.

[0043] Treatment of wastewater with the regenerated adsorbent: For the copper smelting wastewater after sulfide precipitation and lime neutralization precipitation, the supernatant was taken for testing. The test results showed that the total thallium was 0.0453 mg / L and the COD was 95 mg / L, both of which did not meet the discharge standard requirements. For the first time, 500 mL of the supernatant was placed in a 1 L beaker, the pH was adjusted to 7.0 with dilute sulfuric acid, 10.0 g of adsorbent was added, and the mixture was stirred at 180 r / min for 2.0 h at 25 °C, then allowed to stand and precipitate for 30 min. The supernatant was sent for testing the concentrations of total thallium and COD, and the adsorbent was regenerated according to the above method. The adsorption-regeneration test was repeated 5 times with the same supernatant, indicating that the adsorbent could be regenerated and reused. The test results are shown in Table 2. From Table 2, it can be seen that as the number of times of adsorbent regeneration and reuse increases, the adsorption and removal rates of total thallium and COD in the wastewater show a gradually decreasing trend, but still have a good adsorption and removal effect.

[0044] Table 2 Results of adsorption-regeneration test 。

Claims

1. A wastewater treatment adsorbent, characterized in that: The wastewater treatment adsorbent is prepared from copper smelting slag, red mud and lime as main raw materials.

2. The wastewater treatment adsorbent according to claim 1, characterized in that: The mass ratio of the copper smelting slag, red mud and lime is 20:(1-2):(1-2).

3. The wastewater treatment adsorbent according to claim 1 or 2, characterized in that: The main components of the copper smelting slag are: Fe2O3 is 38-48%, SiO2 is 28-36%, Al2O3 is 5-8%, CaO is 3-5%, ZnO is 1-3%, MgO is 1-3%, and Na2O is 1-2%.

4. The wastewater treatment adsorbent according to claim 1 or 2, characterized in that: The red mud is Bayer process red mud with a pH of 10-12. The main minerals are aragonite and calcite with a content of 60-65%. The main components are: SiO2 of 10-20%, CaO of 3-9%, Al2O3 of 22-32%, Fe2O3 of 20-35%, Na2O of 3-10%, and TiO2 of trace amount to 6%.

5. The wastewater treatment adsorbent according to claim 1 or 2, characterized in that: The main component of the lime is CaO.

6. A method for preparing a wastewater treatment adsorbent according to any one of claims 1 to 5, characterized in that: It includes pre-treatment, preparation and post-treatment steps, specifically including: A. Pre-treatment: 1) drying and grinding copper smelting slag, red mud and lime in a given proportion respectively, and passing through a 100-mesh sieve to obtain pretreated copper smelting slag a, pretreated red mud b and pretreated lime c; 2) putting pretreated copper smelting slag a, pretreated red mud b and pretreated lime c into a ball mill for ball milling to obtain a ball milled mixture d; B. Preparation: Add sodium silicate solution and boiling water to the ball-milled mixture d and stir thoroughly to obtain a paste e; C. Post-processing: 1) The paste e is made into spheres with a diameter of 8 to 12 mm and then dried to obtain spherical material f; 2) The spherical material f is crushed and ground through a 100-mesh sieve to obtain the target wastewater treatment adsorbent.

7. The preparation method according to claim 6, characterized in that: The ball milling described in step A 2) is carried out under the conditions of ball-to-material ratio of 2:1 and 600 r / min for 0.5 to 1.5 h.

8. The preparation method according to claim 6, characterized in that: In step B, the mass volume ratio of the ball-milled mixture d, the sodium silicate solution and the boiling water is (g, 3-5): (ml, 0.5-1.5): (ml, 0.5-1.5).

9. The preparation method according to claim 6, characterized in that: C. The drying described in step 1) is carried out at a constant temperature of 70-90°C for 5-7h.

10. Use of the wastewater treatment adsorbent according to any one of claims 1 to 5, characterized in that: The wastewater treatment adsorbent is used in preparing a high-efficiency composite adsorbent for wastewater treatment.

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