A photocatalyst based on industrial by-product gypsum, its preparation method and application

Abstract

This invention relates to the fields of solid waste resource utilization and wastewater purification technology, specifically to a photocatalyst based on industrial by-product gypsum, its preparation method, and its application. Using industrial gypsum waste residue and organic waste as raw materials, this invention can prepare heavy metal adsorbents and photocatalysts, which can efficiently adsorb and remove heavy metals from wastewater and degrade organic pollutants. Simultaneously, it rationally utilizes industrial gypsum waste residue and organic waste, achieving good economic and environmental benefits and possessing broad industrial application prospects.

Description

Technical Field

[0001] This invention relates to the fields of solid waste resource utilization and wastewater purification technology, specifically to a photocatalyst based on industrial by-product gypsum, its preparation method, and its application. Background Technology

[0002] Industrial by-product gypsum is a solid waste generated during industrial production processes, primarily composed of calcium sulfate dihydrate. It mainly includes flue gas desulfurization gypsum, phosphogypsum, titanium gypsum, fluorogypsum, citric acid gypsum, salt gypsum, and lactic acid gypsum. my country has a large stockpile of industrial by-product gypsum, accumulating over 1.1 billion tons over the years, with an annual discharge of 280 million tons, equivalent to 40% of the country's natural gypsum mining output. It is an important renewable resource to replace natural gypsum. Currently, the resource utilization of industrial by-product gypsum is mainly concentrated in building materials production, underground filling, ecological restoration, and soil remediation. However, the comprehensive utilization rate is far from the target of 73% by 2025 required by the Ministry of Industry and Information Technology (MIIT) Regulation

[2021] No. 178. Therefore, there is an urgent need to seek and establish efficient, environmentally friendly, and high-volume methods for the resource utilization of industrial by-product gypsum.

[0003] Water pollution caused by heavy metal ions is widely recognized as a serious environmental problem worldwide, primarily stemming from frequent mining, smelting, electroplating, battery manufacturing, and other human activities. Adsorption is an effective means of achieving deep purification of heavy metals. Given that most metal ions can form insoluble or sparingly soluble compounds with sulfides, sulfide-containing materials have become potential candidates for removing heavy metals from water. However, the preparation process of sulfide-containing materials is relatively complex and often involves toxic sulfur-containing reagents such as sodium sulfide, carbon disulfide, and thiourea. There is an urgent need to develop methods for preparing adsorbent materials that are simple to prepare, have low raw material costs, produce high-performance products, and are environmentally friendly. Furthermore, heavy metal ions and organic pollutants often coexist in water, making the development of novel materials capable of simultaneously removing heavy metal ions and organic pollutants imperative.

[0004] In recent years, industrial by-product gypsum has gained increasing attention in the adsorption and removal of pollutants (including heavy metals, phosphorus, fluorine, selenium, etc.) due to its rich content of active sites such as calcium, iron, and sulfur (J Environ Manage, 345(2023)18781; Bioresour Technol, 371(2023)128609). However, raw industrial by-product gypsum has shortcomings such as poor adsorption performance and difficulty in meeting national standards for pollutant concentration. Under reducing pyrolysis conditions, industrial by-product gypsum can be reduced to sulfide minerals (Thermochim. Acta 559(2013)23-31), which are expected to exhibit better adsorption performance for heavy metal ions. However, the disposal of adsorbents after adsorption saturation is a major challenge in the environmental field. Given that most metal sulfides have certain photocatalytic activity, upgrading the adsorbent after heavy metal adsorption into a photocatalyst has become a potential pathway for waste resource utilization. For example, Chen et al. (Appl Surf Sci 558(2021)149647) reported a method to upgrade heavy metal adsorbents into photocatalysts. By adding sodium sulfide to hydrated calcium silicate after heavy metal ion adsorption, it can be converted into a photocatalyst for CO2 photocatalytic reduction driven by a 300W Xe lamp. However, this preparation process involves toxic reagents such as sodium sulfide, and additional metal co-catalysts and hole scavengers need to be added to the photocatalytic reduction system. The conversion of industrial by-product gypsum into heavy metal adsorbents, and then further upgrading it into a photocatalyst for the catalytic degradation of organic pollutants, especially the photocatalytic degradation of organic pollutants driven by low-power LEDs, has not yet been reported. Patent ZL201910410735.4 discloses a gypsum fiberboard with adsorption and photocatalytic properties, its preparation method and application. The photocatalytic performance of this material mainly comes from the high TiO2 content in the raw material high-titanium slag, but it requires a 254nm ultraviolet light source and the photocatalytic efficiency is as low as 10%. Tian Yu (Master's thesis, Beijing University of Chemical Technology, 2021) used calcium sulfate whiskers prepared from desulfurized gypsum as a carrier and prepared a zinc-supported photocatalyst by impregnation method. It can degrade 90% of methylene blue within 6 hours of visible light irradiation, but it requires the introduction of additional chemical reagents and the preparation process involves complex processes such as impregnation and calcination.

[0005] Therefore, a solution is needed to address the technical problems existing in the current technology. Summary of the Invention

[0006] This invention provides a photocatalyst based on industrial by-product gypsum, its preparation method, and its application, which can at least solve some of the problems existing in the prior art.

[0007] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0008] A method for preparing a photocatalyst based on industrial by-product gypsum, wherein the preparation method includes the following steps:

[0009] (1) Dry and grind industrial by-product gypsum residue and organic waste separately, and then mix them in a certain proportion to obtain a raw material mixture;

[0010] (2) The raw material mixture is placed in an atmosphere furnace for pyrolysis activation, and the heavy metal adsorbent is obtained after cooling.

[0011] (3) The heavy metal adsorbent is dispersed in heavy metal wastewater, and after adsorption reaction at room temperature, it is transferred to a reaction vessel lined with polytetrafluoroethylene. After hydrothermal reaction for a certain period of time, after cooling, solid-liquid separation, water washing to neutrality, and drying are carried out to finally obtain the photocatalyst.

[0012] As a preferred embodiment of the method for preparing a photocatalyst based on industrial by-product gypsum according to the present invention, wherein: the industrial by-product gypsum waste residue in step (1) is at least one of flue gas desulfurization gypsum, phosphogypsum, fluorogypsum, titanium gypsum, salt gypsum, and citric acid gypsum generated during industrial production, wherein the mass content of calcium sulfate dihydrate is not less than 60%.

[0013] As a preferred embodiment of the method for preparing a photocatalyst based on industrial by-product gypsum according to the present invention, wherein: the organic waste in step (1) is at least one of agricultural waste rich in organic matter, forestry waste, and sewage treatment plant sludge.

[0014] As a preferred embodiment of the preparation method of a photocatalyst based on industrial by-product gypsum according to the present invention, wherein: in step (1), the proportion of industrial by-product gypsum waste residue in the raw material mixture is 80-99 wt%, and the proportion of organic waste is 1-20 wt%.

[0015] As a preferred embodiment of the preparation method of photocatalyst based on industrial by-product gypsum according to the present invention, wherein: the atmosphere in the atmosphere furnace in step (2) is an oxygen-deficient, vacuum or inert atmosphere, the pyrolysis activation temperature is 500-800℃, and the pyrolysis activation time is 1-5 hours.

[0016] As a preferred embodiment of the method for preparing a photocatalyst based on industrial by-product gypsum according to the present invention, wherein: the heavy metal in the heavy metal wastewater in step (3) is at least one of cadmium, zinc, copper, molybdenum, cobalt and lead, and the heavy metal concentration is 10-500 mg / L.

[0017] As a preferred embodiment of the method for preparing a photocatalyst based on industrial by-product gypsum according to the present invention, the hydrothermal reaction temperature is 100-200℃ and the time is 1-8 hours.

[0018] To solve the above-mentioned technical problems, according to another aspect of the present invention, the present invention provides the following technical solution:

[0019] The photocatalyst prepared using the aforementioned method for preparing photocatalysts based on industrial by-product gypsum

[0020] The aforementioned photocatalyst is used to achieve the photocatalytic degradation of organic pollutants under LED driving.

[0021] Compared with the prior art, the present invention has the following technical effects:

[0022] (1) The heavy metal adsorbent and photocatalyst prepared by the present invention use industrial by-product gypsum as the main raw material and organic waste as the activator. Through a one-step pyrolysis activation process, a highly efficient and stable heavy metal adsorbent can be prepared. After the adsorbent adsorbs heavy metals, it is then subjected to hydrothermal treatment to prepare a photocatalyst with excellent photocatalytic activity, thereby effectively solving the problem of resource utilization and disposal of industrial by-product gypsum.

[0023] (2) The heavy metal adsorbent and photocatalyst prepared by the present invention not only have high adsorption capacity and thorough removal of heavy metals, but also have a wide light absorption range (covering ultraviolet light and visible light), and can effectively utilize ultra-low power LED white light to achieve efficient removal of organic pollutants.

[0024] (3) The method for preparing heavy metal adsorbents and photocatalysts based on industrial by-product gypsum disclosed in this invention has the advantages of simple operation, low cost and green environmental protection, and has good industrial application prospects in the field of environmental pollution purification. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the preparation process of the heavy metal adsorbent and photocatalyst of the present invention;

[0027] Figure 2 The photocatalytic degradation effect of the photocatalyst 4-1 prepared in this invention on antibiotic SMT under three LED light irradiation conditions is shown in the figure.

[0028] Figure 3 The photocatalytic degradation effect of the photocatalyst 5-1 prepared in this invention on antibiotic SMT under three LED light conditions is shown in the figure.

[0029] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0030] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0032] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0033] This invention utilizes a one-step pyrolysis activation method to transform industrial by-product gypsum into a heavy metal adsorbent rich in sulfides, enabling efficient purification of various heavy metal ions in complex water bodies at room temperature. After adsorbing heavy metal ions, the adsorbent undergoes a hydrothermal reaction to further transform into a photocatalyst with excellent photocatalytic activity, achieving efficient photocatalytic degradation of various organic pollutants in water bodies under ultra-low power LED driving. The heavy metal adsorbent and photocatalyst prepared by this invention enable the resource utilization of industrial by-product gypsum and effectively purify water bodies polluted by heavy metals and organic matter, showing broad application prospects. Similar methods have not yet been reported domestically or internationally.

[0034] This invention provides a method for preparing a photocatalyst based on industrial by-product gypsum, the method comprising the following steps:

[0035] (1) Dry and grind industrial by-product gypsum residue and organic waste separately, and then mix them in a certain proportion to obtain a raw material mixture;

[0036] (2) The raw material mixture is placed in an atmosphere furnace for pyrolysis activation, and the heavy metal adsorbent is obtained after cooling.

[0037] (3) The heavy metal adsorbent is dispersed in heavy metal wastewater, and after adsorption reaction at room temperature, it is transferred to a reaction vessel lined with polytetrafluoroethylene. After hydrothermal reaction for a certain period of time, after cooling, solid-liquid separation, water washing to neutrality, and drying are carried out to finally obtain the photocatalyst.

[0038] Preferably, the industrial by-product gypsum waste residue in step (1) is at least one of flue gas desulfurization gypsum, phosphogypsum, fluorogypsum, titanium gypsum, salt gypsum, and citric acid gypsum generated during industrial production, wherein the mass content of calcium sulfate dihydrate is not less than 60%.

[0039] Preferably, the organic waste in step (1) is at least one of agricultural waste rich in organic matter, forestry waste, and sewage treatment plant sludge.

[0040] Preferably, in step (1), the proportion of industrial by-product gypsum waste residue in the raw material mixture is 80-99 wt%, and the proportion of organic waste is 1-20 wt%.

[0041] Preferably, the atmosphere in the furnace in step (2) is an oxygen-deficient, vacuum, or inert atmosphere, the pyrolysis activation temperature is 500-800℃, and the pyrolysis activation time is 1-5 hours.

[0042] Preferably, the heavy metal in the heavy metal wastewater in step (3) is at least one of cadmium, zinc, copper, molybdenum, cobalt, and lead, and the heavy metal concentration is 10-500 mg / L.

[0043] Preferably, the hydrothermal reaction temperature is 100-200℃ and the time is 1-8 hours.

[0044] The present invention also provides a method for preparing a photocatalyst based on industrial by-product gypsum.

[0045] This invention also provides an application of the aforementioned photocatalyst for photocatalytic degradation of organic pollutants under LED driving. The method for LED-driven photocatalytic degradation of organic pollutants is as follows: the photocatalyst is directly dispersed in water bodies polluted by organic matter, and the reaction is carried out in a dark environment for 1 hour until adsorption-desorption equilibrium is reached. Then, the LED light source (power 3-5W, wavelength 365-760nm) is turned on to carry out the photocatalytic degradation reaction.

[0046] To better illustrate the present invention in detail, the following embodiments are provided:

[0047] Example 1

[0048] Dryed and ground industrial by-product gypsum and organic waste were mixed in the proportions shown in Table 1. The raw material mixture was then placed in an atmosphere furnace and pyrolyzed and activated for 2 hours under the conditions shown in Table 1, followed by natural cooling to room temperature to prepare a series of heavy metal adsorbents 1-7, of which 1, 2, and 7 were control samples. 50 mg of the above-prepared heavy metal adsorbents 1-7 were added to 50 mL of polluted water containing 10-500 mg / L of heavy metal ions, respectively, for static adsorption experiments.

[0049] Table 1. Preparation conditions and heavy metal removal rates of heavy metal adsorbents based on industrial by-product gypsum.

[0050]

[0051] The results shown in Table 1 indicate that, except for control samples 1, 2, and 7, the adsorption and removal rates of all other heavy metal adsorbents for heavy metal ions are above 95%, demonstrating that the heavy metal adsorbent based on industrial by-product gypsum prepared in this invention can be used efficiently for the adsorption and purification of various heavy metal ions in water.

[0052] Example 2

[0053] The heavy metal adsorbent 4 prepared in Example 1 was transferred to a polytetrafluoroethylene-lined reactor after adsorbing Cd(II). The reactor was subjected to hydrothermal reaction at 100°C for 2 hours. After cooling, the solid and liquid were separated, washed with water until neutral, and dried to obtain photocatalyst 4-1.

[0054] Photocatalyst 4-1 was dispersed in a solution of a sulfonamide antibiotic (sulfadimidine 0.05 mmol / L) at a dosage of 0.2 g / L. The reaction was carried out in darkness for 1 hour to ensure adsorption-desorption equilibrium was reached. Then, an LED light source (365 nm, 420 nm, white light) was turned on, and after a certain reaction time, samples were taken, filtered, and the concentration of pollutants after the reaction was measured using high-performance liquid chromatography (HPLC). The experimental results are shown below. Figure 2 As shown, photocatalyst 4-1 can achieve highly efficient photocatalytic degradation of SMT under LED 365nm driving, with an SMT removal rate of over 80% after 6 hours; while 420nm and white light cannot effectively drive photocatalyst 4-1.

[0055] Example 3

[0056] The heavy metal adsorbent 5 prepared in Example 1 adsorbed Cd(II) and Zn(II) and was transferred to a polytetrafluoroethylene-lined reactor. It was hydrothermally reacted at 200°C for 4 hours. After cooling, solid-liquid separation was performed, and the mixture was washed with water until neutral and dried to obtain photocatalyst 5-1.

[0057] Photocatalyst 5-1 was dispersed in a solution of a sulfonamide antibiotic (sulfadimidine 0.05 mmol / L) at a dosage of 0.2 g / L. The reaction was carried out in darkness for 1 hour to ensure adsorption-desorption equilibrium was reached. Then, an LED light source (365 nm, 420 nm, white light) was turned on, and after a certain reaction time, samples were taken, filtered, and the concentration of pollutants after the reaction was measured using high-performance liquid chromatography (HPLC). The experimental results are shown below. Figure 3 As shown, photocatalyst 4-2 can achieve different photocatalytic degradation effects on SMT under three LED driving conditions, where: 365nm > 420nm > white light, and the SMT removal rates after 6 hours are 97%, 69%, and 34%, respectively.

[0058] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing a photocatalyst based on industrial by-product gypsum, characterized in that, The preparation method includes the following steps: (1) Dry and grind industrial by-product gypsum waste and organic waste separately, and then mix them in a certain proportion to obtain a raw material mixture. In step (1), the proportion of industrial by-product gypsum waste in the raw material mixture is 80-99 wt%, and the proportion of organic waste is 1-20 wt%. (2) The raw material mixture is placed in an atmosphere furnace for pyrolysis activation, and after cooling, a heavy metal adsorbent is obtained. The atmosphere in the atmosphere furnace is an oxygen-deficient, vacuum, or inert atmosphere. The pyrolysis activation temperature is 500-800℃ and the pyrolysis activation time is 1-5 hours. (3) The heavy metal adsorbent is dispersed in the heavy metal wastewater. After the adsorption reaction at room temperature, it is transferred to a reaction vessel lined with polytetrafluoroethylene. The hydrothermal reaction is carried out for a certain period of time. After cooling, the solid-liquid separation, water washing to neutrality, and drying are carried out to finally obtain the photocatalyst. The heavy metal in the heavy metal wastewater is at least one of cadmium, zinc, copper, molybdenum, cobalt, and lead. The heavy metal concentration is 10-500 mg / L, the heavy metal removal rate is above 95%, the hydrothermal reaction temperature is 100-200℃, and the time is 1-8 hours.

2. The method for preparing a photocatalyst based on industrial by-product gypsum according to claim 1, characterized in that, The industrial by-product gypsum waste in step (1) is at least one of the following: flue gas desulfurization gypsum, phosphogypsum, fluorogypsum, titanium gypsum, salt gypsum, and citric acid gypsum generated during industrial production, wherein the mass content of calcium sulfate dihydrate is not less than 60%.

3. The method for preparing a photocatalyst based on industrial by-product gypsum according to claim 1, characterized in that, In step (1), the organic waste is at least one of the following: agricultural waste rich in organic matter, forestry waste, and sewage treatment plant sludge.

4. A photocatalyst prepared by any one of claims 1-3 based on an industrial by-product gypsum.

5. The application of the photocatalyst according to claim 4 in the photocatalytic degradation of organic pollutants under LED driving, wherein the LED light source power is 3-5W and the wavelength is 365-760nm.

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