Sludge-based charcoal dechlorination material as well as preparation and application thereof

Abstract

The invention discloses preparation and application of a sludge-based biochar dechlorination material. The method comprises the following steps: adding a sodium hydroxide solution into sludge of a town sewage plant, introducing ozone under an alkaline condition, heating, stirring, centrifuging, taking supernate, drying, and grinding into powder to obtain a sludge organic matrix; the preparation method comprises the following steps: uniformly mixing a sludge organic matrix with slag powder and red mud in proportion, placing the obtained mixture in an inert atmosphere for pyrolysis and carbonization, cooling and grinding after the pyrolysis is finished, and carrying out water washing and acid pickling to obtain the sludge-based biochar dechlorination material. Adding a certain amount of the sludge-based biochar dechlorination material into the chloride ion solution, and introducing ozone while stirring; the invention not only provides a solution for treating solid wastes such as sludge, slag powder and red mud, but also develops a more economical and practical biochar dechlorination material. The dechlorination material can be applied to chloridion environmental pollution treatment and has a wide application prospect.

Description

Technical Field

[0001] The invention relates to a dechlorination material, in particular to a sludge-based biochar dechlorination material and a preparation and application thereof, belonging to the technical field of sludge treatment and water treatment. Background Art

[0002] As a common pollutant in water, chloride ions have brought a series of hazards to human production and life. High concentrations of chloride ions may react with organic matter to form organic chlorides, which have a negative impact on ecosystems and biodiversity. In addition, chloride ions also react with other substances to form ozone-depleting substances, such as chlorinated hydrocarbons and chlorates, which can destroy the ozone layer in the atmosphere and lead to environmental problems such as the greenhouse effect and the formation of ozone holes. At present, new dechlorinators include bismuth-based materials and calcium aluminum stone. However, bismuth-based dechlorinators are expensive and take a long time to remove chlorine; calcium aluminum stone has average efficiency and may produce a large amount of solid waste, increasing treatment costs and environmental pollution risks.

[0003] Municipal sludge is the main solid waste generated in the biochemical treatment process of sewage treatment plants. Traditional sludge treatment and disposal methods, such as sanitary landfill, land use and incineration, are limited by the selection of landfill sites and high environmental risks. Therefore, how to safely and effectively treat and dispose of municipal sludge has become a hot issue in environmental protection and urban sustainable development.

[0004] Patent application CN115970641A discloses a chlorine removal composite material and its preparation method and application. The application mixes Ca-Al-LDO obtained by calcining calcium aluminum hydrotalcite and activated carbon material obtained by calcining municipal sludge to form a composite material, and uses it for dechlorination of wastewater. The chloride ion removal rate is about 70%, which has not yet achieved the purpose of efficient chlorine removal. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for preparing a sludge-based biochar dechlorination material, which has simple steps and low cost.

[0006] The second object of the present invention is to provide a sludge-based biochar dechlorination material prepared by the above preparation method, which has a significant dechlorination effect.

[0007] The third object of the present invention is to provide the application of the above-mentioned sludge-based biochar dechlorination material.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] In a first aspect, a method for preparing a sludge-based biochar dechlorination material is provided, the method comprising the following steps:

[0010] Step 1: adding sodium hydroxide solution to the sludge of a municipal sewage plant, introducing ozone at a pH of 8-12, heating and stirring, centrifuging, drying, and grinding into powder to obtain a sludge organic matrix;

[0011] Step 2: The sludge organic matrix obtained in step 1 is mixed evenly with slag powder and red mud in proportion to obtain a mixture;

[0012] Step 3: placing the mixture obtained in step 2 in an inert atmosphere for pyrolysis and carbonization, taking out the solid product after the pyrolysis is completed, cooling it, grinding it, washing it with water and acid washing it in sequence, and drying it to obtain the sludge-based biochar dechlorination material.

[0013] In one embodiment of the first aspect, the concentration of the introduced ozone is 5-20 mg / L, the gas flow rate is 1 L / min, and the ventilation time is 10 min.

[0014] In one embodiment of the first aspect, the stirring time of step 1 is 6-12 hours; the heating temperature is 45-80°C, preferably 45-75°C.

[0015] In one embodiment of the first aspect, the dry mass of the slag powder and red mud accounts for 0%-45% of the total dry mass of the mixture of sludge organic matrix and slag powder and red mud, preferably 0%-40%, more preferably 1%-40%.

[0016] In one embodiment of the first aspect, the temperature of the pyrolysis carbonization is 300-900°C, preferably 300-800°C.

[0017] In one embodiment of the first aspect, the pyrolysis carbonization time is 180-420 min, preferably 180-360 min.

[0018] In one embodiment of the first aspect, the temperature of the distilled water used in washing the sludge-based biochar dechlorination material is 40-65°C.

[0019] In one embodiment of the first aspect, the acid used in the acid washing of the sludge-based biochar dechlorination material is one or more of nitric acid, hydrofluoric acid, etc.

[0020] In one embodiment of the first aspect, the molar concentration of the acid in the acid washing of the sludge-based biochar dechlorination material is 3 mol / L. Preferably, the temperature of the acid in the acid washing of the sludge-based biochar dechlorination material is 10-60°C.

[0021] In a second aspect, the present application provides a sludge-based biochar dechlorination material prepared by the preparation method of the first aspect.

[0022] In a third aspect, the present application provides a method for dechlorination using the sludge-based biochar dechlorination material of the second aspect, the method comprising:

[0023] Step a: adding sludge-based biochar dechlorination material to the chloride ion solution and stirring;

[0024] Step b: Under stirring, ozone is introduced into the system of step a.

[0025] In one embodiment of the third aspect, the amount of the sludge-based biochar dechlorination agent is 20 mg / g TS based on the total amount of chloride ions in the chloride ion solution.

[0026] In one embodiment of the third aspect, the ozone concentration is 20 mg / L, the gas flow rate is 1 L / min, the ventilation time is 20 min, and the ozone dosage is 10% of the chloride ion content.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention synergistically treats three types of solid waste: urban sewage plant sludge, slag powder and red mud. Slag powder and red mud have a catalytic effect in the carbonization process of sludge, which helps to promote the carbonization process of sludge, form more porous structures, and improve the adsorption performance of sludge-based biochar. Among them, the main components of red mud and slag powder, CaO and Al2O3, show a high removal effect on chloride ions by generating calcium-aluminum-chloride compounds. In addition, part of CaO and Al2O3 will form calcium aluminum oxide (Ca2O3) during the carbonization process. 12 Al 14 O 33 ), the cage-like calcium aluminum oxide will react with water to form layered calcium aluminum oxide, and show obvious OH - Group, through OH - and Cl - Direct anion exchange between - Fixed in the inner layer of Ca2Al(OH)6Cl·2H2O, the reaction equations involved are shown in (1) and (2).

[0029] Ca 14 Al 14 O 33 +33H2O→14Al(OH)4 - +12Ca 2+ +10OH - (1)

[0030] Al(OH)4 - +2Ca 2+ +Cl - +2OH -+2H2O→Ca2Al(OH)6Cl·2H2O (2)

[0031] The Fe2O3 in red mud and the hydroxyl and carbonyl groups on the surface of sludge-based biochar can catalyze ozone to produce hydroxyl radicals, which can not only oxidize and remove chloride ions, but also oxidize organic matter, increase the exposure of pore gaps, and reduce competition with chloride ions for binding sites. Components such as SiO2 in slag powder and red mud can provide skeleton support for the newly generated sludge charcoal, allowing more sludge charcoal to be deposited thereon, thereby improving the adsorption effect of sludge-based biochar. The sludge-based biochar dechlorination material prepared by the present invention has a significant adsorption efficiency for chloride ions under the catalytic oxidation of ozone, and the maximum removal rate can reach 90%.

[0032] (2) The present invention reduces the cost of sludge pyrolysis treatment and provides technical support for the engineering application of sludge pyrolysis technology; reduces the cost of dechlorination. Since the cost of commercial activated carbon is relatively high, sludge is obviously a cheaper material for preparing dechlorination agents; and is beneficial to the development of metallurgical enterprises and can provide a resource technology reference for metallurgical enterprises to make high-value use of metallurgical solid wastes such as slag powder.

[0033] (3) As a strong oxidant, ozone does not produce any harmful residues or secondary pollution during the treatment process. Compared with traditional chemical treatment methods, ozone conditioning of sludge is more environmentally friendly and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of the method of the present application.

[0035] Figure 2 XRD pattern of sludge-based biochar chlorine removal material.

[0036] Figure 3 SEM image of sludge-based biochar dechlorination material.

[0037] Figure 4 Elemental content diagram of sludge-based biochar dechlorination materials. DETAILED DESCRIPTION

[0038] "Scope" disclosed herein is expressed in the form of lower limit and upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundary of a particular range. All ranges that can be defined in this way include end values ​​and can be combined with each other, i.e. any lower limit can be combined with any upper limit to form a range. For example, for a specific parameter, a range of 60-120 and 80-110 is listed, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​listed are 1 and 2, and the maximum range values ​​3, 4 and 5 are listed at the same time, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0039] In this application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations.

[0040] In the present application, "above" or "below" following a number includes the number itself. For example, "below 5" means less than or equal to 5, and "above 7" means greater than or equal to 7.

[0041] In this application, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution.

[0042] In this application, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0043] In the present application, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0044] In this application, if there is no special explanation, the "including" mentioned herein means open or closed. For example, the "including" may mean that other components not listed may also be included, or only the listed components may be included.

[0045] The above expressions are also commonly used in the art. It should be emphasized that what is shown in the drawings and described below are only some specific embodiments of the present invention, and the protection scope of the present invention is not limited to these specific embodiments. The protection scope of the present invention is defined by the claims of the present invention, and may include any technical methods within the scope of the claims, including but not limited to further improvements and substitutions to these specific embodiments.

[0046] In a first aspect, a method for preparing a sludge-based biochar dechlorination material is provided, wherein the route is as follows: Figure 1 As shown, the method may include the following steps 1-3.

[0047] Step 1: adding sodium hydroxide solution to the sludge of a municipal sewage plant, introducing ozone at a pH of 8-12, heating and stirring, centrifuging, drying, and grinding into powder to obtain a sludge organic matrix;

[0048] In a specific embodiment, the concentration of ozone introduced is 5 mg / L, 10 mg / L, 15 mg / L or 20 mg / L.

[0049] In a specific embodiment, the alkaline condition has a pH of 8-12, such as a pH of 8, 9, 10, 11 or 12.

[0050] In a specific embodiment, the stirring time is 6-12 h, for example, the stirring time is 6, 7, 8, 9, 10, 11 or 12 h.

[0051] In a specific embodiment, the heating temperature is 45-80°C, preferably the temperature is 45-75°C, for example, the temperature is 45, 55, 65, 70 or 75°C.

[0052] Step 2: The sludge organic matrix is ​​mixed evenly with the slag powder and the red mud in a certain proportion to obtain a mixture;

[0053] The main components of slag powder and red mud are listed in Table 1 below:

[0054] Table 1 Content of red mud and slag powder

[0055]

[0056] In a specific embodiment, the dry weight of the slag powder and red mud accounts for 0%-45% of the total dry weight of the sludge organic matrix and the mixture of slag powder and red mud, preferably 0%-40%, and more preferably 1%-40%. For example, the dry weight of the slag powder and red mud accounts for 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40% of the total dry weight of the mixture of sludge organic matrix and slag powder and red mud.

[0057] Step 3: placing the mixture in an inert atmosphere for pyrolysis and carbonization, taking out the solid product after a period of constant temperature, cooling it, and crushing the solid product to obtain the sludge-based biochar dechlorination material;

[0058] Preferably, in step 3, in order to improve the adsorption capacity of the sludge-based biochar dechlorination material, the sludge-based biochar dechlorination material is washed with water and acid washed, and the iodine value of the sludge-based biochar dechlorination material is increased after drying.

[0059] In a specific embodiment, the temperature of the pyrolysis carbonization is 300-900° C., preferably 300-800° C. For example, the pyrolysis temperature is 300, 400, 500, 600, 700 or 800° C.

[0060] In a specific embodiment, the constant temperature period is 180-420 min, preferably 180-360 min. For example, the constant temperature period is 180, 240, 300 or 360 min.

[0061] In a specific embodiment, the temperature of the distilled water in the water washing of the sludge-based biochar dechlorination material is 40-65° C. For example, the temperature of the water in the water washing of the sludge-based biochar dechlorination material is 50, 55, 60 or 65° C.

[0062] In a specific embodiment, the acid used in the acid washing of the sludge-based biochar dechlorination material is one or more of nitric acid, hydrofluoric acid, etc. In a specific embodiment, the activator is nitric acid. In another specific embodiment, the activator is hydrofluoric acid.

[0063] In a specific embodiment, the molar concentration of the acid in the acid washing of the sludge-based biochar dechlorination material is 3 mol / L. Preferably, the temperature of the acid in the acid washing of the sludge-based biochar dechlorination material is 10-60°C. For example, the temperature of the acid in the acid washing of the sludge-based biochar dechlorination material is 10, 20, 30, 40, 50 or 60°C.

[0064] In a second aspect, the present application provides a sludge-based biochar dechlorination material prepared by the preparation method of the first aspect.

[0065] In a third aspect, the present application provides a method for dechlorination using the sludge-based biochar dechlorination material of the second aspect, the method comprising the following steps ab.

[0066] Step a: adding a certain amount of sludge-based biochar dechlorination material to the chloride ion solution and stirring;

[0067] In a specific embodiment, the amount of the sludge-based biochar dechlorination material is 20 mg / g TS based on the total amount of chloride ions in the chloride ion solution.

[0068] Step b: Under stirring, ozone is introduced into the product of step a.

[0069] In a specific embodiment, the concentration of ozone introduced is 20 mg / L, the gas flow rate is 1 L / min, the ventilation time is 20 min, and the ozone dosage is 10% of the chloride ion content.

[0070] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0071] In the following examples, sludge was taken from Changzhou Shenshui Chengbei Sewage Treatment Plant; slag powder and red mud were purchased from Yantai Anda Environmental Protection Technology Co., Ltd.

[0072] Example 1-12: Preparation of biochar dechlorination material using organic sludge, slag powder, red mud and KOH solution.

[0073] Weigh the sludge from the urban sewage plant shown in Table 2 below, add ozone with a concentration shown in Table 2 below, add 5 mol / L NaOH solution to adjust the pH to that shown in Table 3 below, stir with a magnetic stirrer for 8 hours, centrifuge, dry at the temperature shown in Table 3 below, and grind into powder to obtain the sludge organic matrix; weigh the slag powder and red mud shown in Table 2 below, mix them evenly with the organic matrix, place them in a pyrolysis device, use N2 as a protective gas, and heat them to the temperature shown in Table 3 below at 10°C / min. The pyrolysis carbonization time is shown in Table 3 below. After the end, cool and grind to the micron level, sieve with a 200-mesh sieve, wash with 3 mol / L dilute nitric acid and clean water in turn, and the acid washing temperature is 25°C. After drying, an organic sludge-based biochar dechlorinator can be obtained, and the iodine value is measured as shown in Table 3 below.

[0074] Table 2 Preparation conditions of some biochar dechlorination materials

[0075]

[0076]

[0077] Table 3 Preparation conditions of some biochar dechlorination materials

[0078] Example pH Drying temperature (℃) Pyrolysis temperature(℃) Pyrolysis carbonization time (h) Iodine value (mg / g) 1 10 60 700 4 1030 2 12 70 650 5 1030 3 11 65 700 5 1060 4 10 50 700 6 1050 5 11 75 750 4 1100 6 12 75 700 5 1070 7 11 70 700 5 960 8 10 80 800 6 980 9 12 70 750 5 980 10 11 75 750 4 930 11 11 75 750 4 1000 12 11 75 750 4 1010

[0079] Depend on Figure 3 It can be seen from the SEM image that the sludge-based biochar dechlorination material prepared by the present invention has a small particle size, most of which are micrometer-sized, and the surface is rough and uneven, indicating that it has produced many pores during the pyrolysis process, the specific surface area is increased, and more sites that can bind to chloride ions are formed. Figure 2 XRD patterns and Figure 4 The element content diagram shows that a large amount of metal oxides, such as Al2O3 and Ca, are distributed in the material. 12 Al 14 O 33 etc., which can effectively catalyze ozone to produce reactive oxygen free radicals; some Ca 2+ Can precipitate CO3 2- , HCO 3- , improve the indirect oxidation effect of ozone; Ca 12 Al 14 O 33 Can be through OH - and Cl - Direct anion exchange between Cl - Fixed in the inner layer of Ca2Al(OH)6Cl·2H2O. In addition, the hydroxyl groups on the metal oxide surface of biochar can effectively catalyze ozone to generate active oxygen free radicals, enhance the indirect oxidation efficiency of ozone, and improve the oxidation removal rate of chloride ions.

[0080] Example 13: Chlorine removal effect

[0081] Weigh 6.585g NaCl and dilute it with deionized water in a 1000mL volumetric flask to prepare a 4000mg / L chloride ion solution. Add 2g of the biochar dechlorination material prepared in Examples 1-12 to 50mL of a chloride ion solution with a concentration of 4000mg / L as a chloride ion adsorbent, stir on a magnetic stirrer, and pass 20mg / L of ozone for catalytic oxidation. The gas flow rate is 1L / min and the ventilation time is 20min. After waiting for the reaction for 60min, centrifuge, draw 2mL of the supernatant and dilute it with deionized water to a 10mL volumetric flask, draw 2-3mL of the solution with a syringe, filter it through the filter head and store it in a 5mL test tube. Weigh 0.38g of sodium carbonate and dilute it with deionized water in a 1000mL volumetric flask. After suction filtration, ultrasonicate for 10min to obtain the eluent. Determination of Cl by ion chromatography -The concentration was calculated to determine the chloride ion removal rate. The results of the chloride ion removal rates of the biochar dechlorination materials prepared in Examples 1-12 are shown in Table 4 below:

[0082] Table 4 Results of removal efficiency of chloride ions by biochar dechlorination materials

[0083]

[0084] It can be seen from the above examples that the sludge-based biochar dechlorination material prepared by the present invention has a significant adsorption efficiency for chloride ions under ozone catalytic oxidation, and the maximum removal rate can reach 90%.

[0085] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a sludge-based biochar dechlorination material, characterized in that: The steps include: Step 1: adding sodium hydroxide solution to the sludge of a municipal sewage plant, introducing ozone at a pH of 8-12, heating and stirring, centrifuging, drying, and grinding into powder to obtain a sludge organic matrix; Step 2: The sludge organic matrix obtained in step 1 is mixed evenly with slag powder and red mud in proportion to obtain a mixture; Step 3: placing the mixture obtained in step 2 in an inert atmosphere for pyrolysis and carbonization, taking out the solid product after the pyrolysis is completed, cooling it, grinding it, washing it with water and acid washing it in sequence, and drying it to obtain the sludge-based biochar dechlorination material.

2. The method for preparing a sludge-based biochar dechlorination material according to claim 1, characterized in that: The ozone concentration introduced was 5-20 mg / L, the gas flow rate was 1 L / min, and the ventilation time was 10 min.

3. The method for preparing a sludge-based biochar dechlorination material according to claim 1, characterized in that: The stirring time of step 1 is 6-12 hours; the heating temperature is 45-75°C.

4. The method for preparing a sludge-based biochar dechlorination material according to claim 1, characterized in that: The dry basis weight of the slag powder and red mud accounts for 1%-40% of the total dry basis weight of the mixture of sludge organic matrix and slag powder and red mud.

5. The method for preparing a sludge-based biochar dechlorination material according to claim 1, characterized in that: The temperature of the pyrolysis carbonization is 300-800° C., and the time of the pyrolysis carbonization is 180 min-360 min.

6. The method for preparing a sludge-based biochar dechlorination material according to claim 1, characterized in that: The water washing temperature is 40-65°C, the acid in the pickling is nitric acid or hydrofluoric acid, and the pickling temperature is 10-60°C.

7. A sludge-based biochar dechlorination material prepared by the preparation method according to any one of claims 1 to 6.

8. A method for dechlorination using the sludge-based activated carbon dechlorination material according to claim 7, characterized in that: The method comprises: Step a: adding sludge-based biochar dechlorination material to the chloride ion solution and stirring; Step b: Under stirring, ozone is introduced into the system of step a.

9. The method according to claim 8, characterized in that Based on the total amount of chloride ions in the chloride ion solution, the amount of the sludge-based biochar dechlorinator is 20 mg / g TS.

10. The method according to claim 9, characterized in that 5-30 mg / L ozone is introduced into the chloride ion solution, the gas flow rate is 1 L / min, the ventilation time is 20 minutes, and the ozone dosage is 2.5%-15% of the chloride ion content.

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