Functional ceramsite for efficiently purifying phosphorus-containing wastewater, preparation method and application thereof

Abstract

This invention relates to a highly efficient functional ceramsite for purifying phosphorus-containing wastewater, its preparation method, and its application. Based on a complementary functional strategy, it uses natural clay rich in Al2O3 and SiO2 as a binder and calcium-rich industrial solid waste as the calcium-rich active component. Functional additives are also added to mitigate pH changes caused by calcium oxide reactions. The above raw materials are calcined at high temperature to obtain inexpensive, calcium-rich functional ceramsite with high mechanical strength, large adsorption capacity, and ecological safety. This effectively solves the common problems of increased water pH and poor phosphate adsorption capacity at neutral pH in calcium-based ceramsite, achieving highly efficient phosphorus purification in water. This invention uses inexpensive and readily available natural clay and calcium-rich industrial solid waste as raw materials, resulting in low cost, good effect, and effective application in the treatment of low-pollution water.

Description

Technical Field

[0001] This invention belongs to the field of water pollution control technology, specifically relating to a functional ceramsite for efficiently purifying phosphorus-containing wastewater, its preparation method, and its application. Background Technology

[0002] In recent decades, excessive anthropogenic phosphorus input leading to eutrophication of rivers, lakes, and reservoirs has been a major global water environment problem. Among these, low-pollution waters such as wastewater treatment plant effluent and agricultural runoff have become significant contributors to eutrophication in my country. Although these water bodies have met discharge standards after pollution control, phosphorus concentrations still exceed the Class III water quality standard limit in the "Surface Water Environmental Quality Standard." The continued accumulation of phosphorus will further deteriorate water quality, causing harmful algal blooms and seriously threatening aquatic ecosystems and human health. With the comprehensive advancement of the Beautiful China initiative and the ongoing campaign to protect clean water, developing low-concentration phosphorus control technologies for low-pollution waters to prevent eutrophication has become a research hotspot in the field of water environment ecological restoration.

[0003] Adsorption methods, with their advantages of low energy consumption, simple operation, and high purification efficiency for low-concentration phosphorus, are considered one of the most promising low-concentration phosphorus treatment technologies for removing large volumes of low-pollution water. The preparation of phosphorus-removing functional ceramsite is crucial for removing phosphorus from surface water using adsorption. In recent years, industrial solid waste (such as fly ash, steel slag, and iron tailings) has been frequently used as a primary raw material to prepare inexpensive ceramsite for removing low-concentration phosphates from large volumes of surface water due to its low cost, wide availability, and large output. Among these, calcium-rich (Ca) industrial solid waste (such as carbide slag, papermaking mud, calcium-rich fly ash, and gypsum tailings) is rich in calcium-rich active components, which can chemically precipitate with phosphates in water to generate perapatite or hydroxyapatite (5Ca). 2+ +3PO4 3- +OH - →Ca5(PO4)3(OH)↓ and Ca 2+ +HPO4 3-The phosphorus removal performance of functional ceramsite is effectively improved by adsorbing the phosphorus (+2H2O→CaHPO4·2H2O) onto the ceramsite. However, ceramsite prepared from calcium-rich solid waste generally suffers from increased water pH and poor phosphate adsorption capacity at neutral pH after use. Patent (CN 102584177B) discloses a method for preparing phosphorus-removing ceramsite using fly ash, bentonite, and slaked lime as raw materials. Patent (CN 109111207A) discloses a method for preparing phosphorus-removing ceramsite using fly ash, pore-forming agent, bentonite powder, crop straw, nitrocellulose, and silica as raw materials. The aforementioned patents all use fly ash, bentonite, and calcium-rich solid waste as the main raw materials to prepare sintered ceramsite, which shows good phosphorus removal effect under alkaline conditions. However, none of them have considered the problem of increased water pH and poor phosphate adsorption capacity under neutral pH after use. Excessively high effluent pH will also cause secondary pollution to the environment and affect the growth and reproduction of aquatic organisms.

[0004] Currently, using natural clays such as bentonite as binders and calcium-rich solid waste carbide slag as the calcium-rich active component, while adding functional additives to alleviate pH changes caused by the hydrolysis of calcium oxides and their compounds, inexpensive calcium-rich functional ceramsite is prepared. This effectively solves the problems of pH increase and limited adsorption capacity after the use of functional ceramsite, and achieves efficient phosphorus removal under neutral conditions. However, no related research has been reported. Summary of the Invention

[0005] This invention aims to provide a functional ceramsite for efficiently purifying phosphorus-containing wastewater, its preparation method, and its application. This functional ceramsite has the advantages of simple preparation process and low cost, and solves the problems of increased water pH and poor phosphate adsorption capacity at neutral pH, as well as limited adsorption capacity, which are common problems with calcium-rich functional ceramsite.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A functional ceramsite for highly efficient purification of phosphorus-containing wastewater uses natural clay minerals rich in Al2O3 and SiO2 as binders, calcium-rich industrial solid waste as calcium-rich active components, and adds functional additives to alleviate pH changes caused by calcium oxide reactions. The functional ceramsite for highly efficient purification of phosphorus-containing wastewater is prepared by pretreatment, mixing, granulation, drying, calcination and cooling of the raw materials.

[0008] The calcium-rich active component is one or two of carbide slag and papermaking sludge; the functional additive is one or two of desulfurized gypsum and salt gypsum.

[0009] The raw material ratio is as follows: binder 20-40%, calcium-rich active component 15-50%, and functional additives 20-40%.

[0010] Furthermore, the binder is one or more of bentonite, attapulgite, and kaolin; the desulfurized gypsum contains 93-95% CaSO4 by mass.

[0011] Preferably, the raw material mass ratio is: 20-40% binder, 20-40% calcium-rich active component, and 20-40% functional additives.

[0012] A method for preparing functional ceramsite for highly efficient purification of phosphorus-containing wastewater, the specific steps of which are as follows:

[0013] 1) Pretreatment: Grind the binder, calcium-rich active components and functional additives through a 100-180 mesh sieve;

[0014] 2) Mixing: Add the pretreated raw materials from step 1) to a mixer in proportion and mix for 5-10 minutes;

[0015] 3) Granulation: The mixed material in 2) is granulated in a granulator. During the granulation process, deionized water is sprayed at a solid-liquid ratio of 1:0.5 to 1:1 to obtain spherical ceramic blanks with a diameter of 5 to 10 mm.

[0016] 4) Drying: The spherical ceramic blanks prepared in step 3) are dried at room temperature for 20-30 hours, and then placed in an oven and dried at 80-120℃ for 2-4 hours.

[0017] 5) Firing: The dried spherical ceramic blanks are pre-fired at 300-500℃ for 5-25 minutes, and then fired at 1150-1200℃ for 5-25 minutes.

[0018] 6) Cooling: Turn off the power to the tubular furnace and cool for 6-12 hours to obtain functional ceramsite for highly efficient purification of phosphorus-containing wastewater, which is a calcium-rich functional ceramsite.

[0019] Further, in step 2), the stirring rate during the mixing process is 60–120 r / min; in step 3), the rotation speed of the granulator disc during the granulation process is 30–80 r / min; in step 4), the pre-calcination heating rate during the calcination process is 2–10 °C / min, and the calcination heating rate is 6–14 °C / min.

[0020] This invention also protects the application of a functional ceramsite for efficiently purifying phosphorus-containing wastewater, using calcium-rich functional ceramsite to treat phosphorus-containing wastewater, such as sewage treatment plant effluent, farmland surface runoff, rivers, lakes, and reservoirs.

[0021] The phosphorus-containing wastewater has a concentration of 0.1–200 mg / L and a pH of 6–9. The amount of functional ceramic particles used is 0.05–10 g / L. The particles are shaken at 25°C for 12–24 h at a shaking rate of 100–400 r / min. The concentration of phosphorus is determined by taking the supernatant before and after adsorption to determine the adsorption capacity of the functional ceramic particles. The compressive strength of the phosphorus adsorbent is tested using a compressive strength tester.

[0022] Furthermore, the phosphorus concentration in the phosphorus-containing wastewater is 80-100 mg / L.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention incorporates functional additives such as desulfurized gypsum and salt gypsum, which not only remove phosphorus but also stabilize pH levels. Working synergistically with calcium-rich active components, it effectively addresses the issue of increased solution pH after the use of calcium-rich solid waste. Simultaneously, it achieves highly efficient phosphorus removal from water by functional ceramsite under neutral pH conditions, even with relatively low concentrations of calcium-rich active components, achieving a removal efficiency of 82–99.5% and an adsorption capacity of 82–99.5 mg / g. The high adsorption capacity of this invention significantly extends its service life during application, saving costs.

[0025] The raw materials required for this invention are inexpensive natural clay and industrial solid waste, which are widely available, low in cost, and have a simple preparation process that is easy to scale up. Detailed Implementation

[0026] To better understand the content of this invention, the following description, in conjunction with embodiments, further illustrates the invention. However, the examples given do not limit the scope of protection of this invention.

[0027] Example 1

[0028] (1) A functional ceramsite for highly efficient purification of phosphorus-containing wastewater. The preparation steps of this ceramsite are as follows:

[0029] 1) Raw material ratio: 30% bentonite, 30% carbide slag, and 40% desulfurized gypsum. The CaO content in the carbide slag is 55-70%; the CaSO4 content in the desulfurized gypsum is 93-95% by mass.

[0030] 2) Mixing: Grind bentonite, carbide slag and desulfurized gypsum through a 120-mesh sieve, add them to a mixer in proportion and mix for 5 minutes;

[0031] 3) Granulation: The mixed materials are granulated in a granulator. During the granulation process, deionized water is sprayed at a solid-liquid ratio of 1:0.8 to obtain 8mm spherical ceramic blanks.

[0032] 4) Drying: Dry the spherical ceramic blank at room temperature for 24 hours, and then dry it in an oven at 105℃ for 2 hours;

[0033] 5) Firing: The dried spherical ceramic blanks are fired in a muffle furnace, pre-fired at 500℃ for 15 minutes, and then fired at 1175℃ for 5 minutes.

[0034] 6) Cooling: Turn off the power to the tubular furnace and cool for 12 hours to obtain functional ceramsite.

[0035] (2) The above-mentioned functional ceramsite was used for the removal of phosphates from wastewater. The specific steps of the adsorption experiment are as follows:

[0036] The prepared functional ceramsite was ground and pulverized, then passed through a 120-mesh sieve. 0.1 g of ceramsite powder was weighed and placed in an Erlenmeyer flask. 100 mL of a potassium dihydrogen phosphate aqueous solution with a phosphorus concentration of 100 mg / L (pH adjusted to 7.0) was added to the Erlenmeyer flask. The Erlenmeyer flask was placed in a constant temperature shaker, with the temperature controlled at 25 °C and the shaking rate controlled at 200 r / min. After shaking for 24 h, a sample was taken. The solution was filtered through a 0.45 μm membrane filter, and the pH value was measured with a pH meter. The concentration of phosphate in the water sample was determined by ammonium molybdate spectrophotometry.

[0037] The results showed that the functional ceramsite had an adsorption capacity of 99.5 mg / g and a phosphate removal efficiency of 99.5% in wastewater. The pH of the solution after adsorption was 8.3. The synergistic effect of specific bentonite components and calcium-rich active components in calcium-rich solid waste resulted in high mechanical strength and adsorption efficiency of the ceramsite. Furthermore, the functional ceramsite adsorption did not significantly alter the pH of the solution, and the water met the requirements of the "Surface Water Environmental Quality Standard" GB3838-2002.

[0038] Example 2

[0039] The specific steps of the raw materials, preparation steps and adsorption experiment of the functional ceramsite for high-efficiency purification of phosphorus-containing wastewater in this embodiment are the same as those in Example 1. The difference is that the proportions of the raw materials in this embodiment are: 50% bentonite, 20% carbide slag and 30% desulfurized gypsum.

[0040] The functional ceramic particles have an adsorption capacity of 82 mg / g and a phosphate removal efficiency of 82% in wastewater. The pH of the solution after adsorption is 7.8.

[0041] Example 3

[0042] The specific steps of the raw materials, preparation steps and adsorption experiment of the functional ceramic particles for high-efficiency purification of phosphorus-containing wastewater in this embodiment are the same as those in Example 1. The difference is that the calcination conditions of the raw materials in this embodiment are: pre-calcination at 300℃ for 15 minutes and calcination at 1200℃ for 5 minutes.

[0043] Its adsorption capacity is 90 mg / g, and its phosphate removal efficiency can still reach 90%. The pH of the solution after adsorption is 7.7.

[0044] Example 4

[0045] The raw materials and preparation steps of the functional ceramic particles for highly efficient purification of phosphorus-containing wastewater in this embodiment are the same as those in Example 1. The difference is that in this embodiment, the phosphate concentration in the solution is measured after shaking for 12 hours during the adsorption experiment.

[0046] The results showed that the ceramsite had an adsorption capacity of 92 mg / g and a phosphate removal efficiency of 92% in wastewater. The pH of the solution after adsorption was 8.1. This indicates that the ceramsite of the present invention can achieve efficient phosphate removal in a short time.

[0047]

[0048] Example 5

[0049] The preparation steps and component contents of the functional ceramsite in this embodiment are the same as those in Example 1. The difference is that papermaking mud is used instead of carbide slag in this embodiment.

[0050] Comparative Example 1

[0051] Only the bentonite described in this application is added, and the mixture is processed according to the mixing, granulation, drying, calcination, and cooling conditions of Example 1.

[0052] Comparative Example 2

[0053] Only the desulfurized gypsum described in this application is added, and the mixture is processed according to the mixing, granulation, drying, calcination, and cooling conditions of Example 1.

[0054] Comparative Example 3

[0055] Only the calcium carbide slag described in this application is added, and the mixture is processed according to the mixing, granulation, drying, calcination, and cooling conditions of Example 1.

[0056] Comparative Example 4

[0057] Only one type of commercial ceramsite is used.

[0058] The adsorbent materials obtained above were subjected to adsorption experiments under the conditions of Example 1, and the results are listed below:

[0059]

[0060] As shown in the table above, bentonite, desulfurized gypsum, or commercial ceramsite have low phosphate removal rates. While direct use of carbide slag can effectively adsorb phosphates in water, it leads to an increase in water pH, causing secondary pollution. The present invention, using a specific formula, produces inexpensive, calcium-rich ceramsite that, after calcination, exhibits the best phosphate removal effect in water, and the pH of the water after adsorption meets the requirements of the "Surface Water Environmental Quality Standard" GB3838-2002.

[0061] Furthermore, compared to the applicant's existing technology, this invention has a higher adsorption capacity, requires less ceramsite at the same wastewater concentration, reducing costs, or, under the same treatment conditions and with the same amount of ceramsite, reduces the frequency of ceramsite replacement and extends its service life during application. The ceramsite of this invention can achieve higher removal efficiency at higher wastewater concentrations, significantly improving its treatment capacity, and its phosphate adsorption capacity is significantly enhanced at neutral pH.

[0062] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A functional ceramsite for highly efficient purification of phosphorus-containing wastewater, characterized in that, Using natural clay minerals rich in Al2O3 and SiO2 as binders, calcium-rich industrial solid waste as calcium-rich active components, and adding functional additives to alleviate pH changes caused by calcium oxide reactions, functional ceramsite for highly efficient purification of phosphorus-containing wastewater is prepared by pretreatment, mixing, granulation, drying, calcination, and cooling of the raw materials. The calcium-rich active component is one or two of carbide slag and papermaking sludge; the functional additive is one or two of desulfurized gypsum and salt gypsum. The raw material mass ratio is as follows: binder 20-40%, calcium-rich active component 15-50%, functional additives 20-40%, and the sum of the raw material mass ratios must meet 100%. The specific steps of the preparation method of the functional ceramsite for highly efficient purification of phosphorus-containing wastewater are as follows: 1) Pretreatment: Grind the binder, calcium-rich active components and functional additives through a 100-180 mesh sieve; 2) Mixing: Add the pretreated raw materials from step 1) to a mixer in proportion and mix for 5-10 minutes; 3) Granulation: The mixed material in 2) is granulated in a granulator. During the granulation process, deionized water is sprayed at a solid-liquid ratio of 1:0.5 to 1:1 to obtain spherical ceramic blanks with a diameter of 5 to 10 mm. 4) Drying: The spherical ceramic blanks prepared in step 3) are dried at room temperature for 20-30 h, and then placed in an oven and dried at 80-120℃ for 2-4 h. 5) Firing: The dried spherical ceramic blanks are pre-fired at 300~500℃ for 5~25 min, and then fired at 1150~1200℃ for 5~25 min; 6) Cooling: Turn off the power to the tubular furnace and cool for 6~12 hours to obtain functional ceramsite for highly efficient purification of phosphorus-containing wastewater; The phosphorus-containing wastewater has a concentration of 0.1–200 mg / L and a pH of 6–9. The amount of functional ceramsite used is 0.05–10 g / L. The mixture is shaken at 25°C for 12–24 h at a shaking rate of 100–400 r / min. The phosphorus concentration is determined by taking the supernatant before and after adsorption to determine the adsorption capacity of the functional ceramsite. The compressive strength of the phosphorus adsorbent is tested using a compressive strength tester. The functional additives not only remove phosphorus but also stabilize pH. Working synergistically with calcium-rich active components, they effectively address the issue of increased solution pH after the use of calcium-rich solid waste. Furthermore, they enable highly efficient phosphorus removal from water by functional ceramsite under neutral pH conditions, even at lower calcium-rich active component concentrations, achieving a removal efficiency of 82-99.5% and an adsorption capacity of 82-99.5 mg / g. The ceramsites also achieve higher removal efficiency at higher wastewater concentrations, significantly improving their treatment capacity, and their phosphate adsorption capacity is significantly enhanced under neutral pH.

2. The functional ceramsite according to claim 1, characterized in that: The binder is one or more of bentonite, attapulgite, and kaolin; the desulfurized gypsum contains 93-95% CaSO4 by mass.

3. The functional ceramsite according to claim 1, characterized in that: The raw material mass ratio is: binder 20-40%, calcium-rich active component 20-40%, functional additives 20-40%.

4. The functional ceramsite according to claim 1, characterized in that, Step 2) The stirring rate during the mixing process is 60~120 r / min; Step 3) The rotation speed of the granulator disc during the granulation process is 30~80 r / min; Step 5) The pre-calcination heating rate during the calcination process is 2~10℃ / min, and the calcination heating rate is 6~14℃ / min.

5. The application of the functional ceramsite for highly efficient purification of phosphorus-containing wastewater as described in any one of claims 1 to 4, characterized in that: The functional ceramsite is used to treat phosphorus-containing wastewater, including wastewater treatment plant effluent, farmland surface runoff, and phosphorus-containing water in rivers, lakes, and reservoirs.

6. The application according to claim 5, characterized in that, The phosphorus concentration in the phosphorus-containing wastewater is 80-100 mg / L.

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