Metal sulfide nanoparticle slow-release activator for sewage treatment and preparation method of metal sulfide nanoparticle slow-release activator

Abstract

The invention relates to the technical field of sewage treatment, in particular to a metal sulfide nanoparticle slow-release activator for sewage treatment and a preparation method of the metal sulfide nanoparticle slow-release activator for sewage treatment. The surface of the core layer is coated with the porous silicon dioxide membrane shell layer; the citric acid modifier is loaded on a core-shell interface; according to the invention, metal sulfide (such as FeS, MoS2, WS2 and the like) micro-nano particles are used as a solid-phase slow-release activator, so that the core problem of a traditional homogeneous activation system is radically solved. Firstly, the metal sulfide exists in the form of a solid phase and can directly contact and react with permanganate without an additional dissolving step, so that the problem of complicated process operation caused by poor solubility of activating agents such as sulfite is thoroughly avoided, and the process of reclaimed water treatment is simplified. The problem of poor continuous oxidation effect of a traditional homogeneous system is thoroughly solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, in particular to a metal sulfide nanoparticle slow-release activator for sewage treatment and a preparation method thereof. BACKGROUND

[0002] The demand for agricultural irrigation water has been at a high level for a long time, and the total demand for agricultural irrigation is high. Water shortage has become a key problem restricting the sustainable development of agriculture. At the same time, the amount of industrial wastewater discharged is increasing year by year, and the demand for wastewater treatment is high. Therefore, due to the characteristics of large total amount, stable water quality and less influence of natural conditions, the reclaimed water produced after wastewater treatment has become an important unconventional water resource to supplement agricultural irrigation water.

[0003] However, although the current mainstream wastewater treatment process can remove most of the conventional pollutants in wastewater, the removal effect of new pollutants such as antibiotics and endocrine disruptors, and heavy metals such as lead and cadmium in water is limited. If such non-advanced treated reclaimed water is used for agricultural irrigation for a long time, pollutants will accumulate in the soil, not only destroying the physical and chemical properties of the soil and the structure of the microbial community, but also possibly entering the food chain through crops, posing a serious environmental and food safety risk. To solve this problem, the industry generally uses advanced oxidation technology to treat reclaimed water, among which Fenton technology, photocatalytic technology and other oxidation processes relying on hydroxyl radicals (·OH) are widely used. However, ·OH lacks selectivity, and the large amount of constant organic components such as natural organic matter and microbial metabolites in reclaimed water will preferentially consume ·OH, resulting in a significant reduction in the removal efficiency of new pollutants, making it difficult to meet the safety requirements of irrigation water.

[0004] In recent years, researchers have developed a sulfite / persulfate activation system that can produce non-complex active manganese (RMnS). RMnS has excellent selective oxidation capacity for electron-rich new pollutants, and the MnO2 colloid generated after the reaction can adsorb and remove heavy metals, which is theoretically suitable for the complex pollutant composition of reclaimed water. However, this homogeneous system has obvious defects in practical application: first, the solubility of activators such as sulfite and thiosulfate is poor, resulting in complex process operation; second, the activation reaction rate is too fast, and RMnS is produced in an explosive manner and then quickly consumed, resulting in weak continuous oxidation capacity of the system; third, such activators can only provide 2-4 electrons to participate in the activation of potassium permanganate (Mn(Ⅶ)), resulting in low conversion rate of Mn(Ⅶ) to RMnS, and a large amount of inorganic salts need to be added to ensure treatment effect, which in turn causes the sulfate content in the effluent to exceed the standard. Subsequent studies have attempted to use electro-catalytic technology to activate potassium permanganate to generate RMnS, but this technology has extremely high energy consumption, and the operating cost is 3-5 times that of conventional processes, making it difficult to achieve large-scale promotion.

[0005] In summary, the existing reclaimed water treatment technology still has problems such as difficult dissolution of activator, weak sustained action of active substances, low efficiency of simultaneous removal of pollutants, and high operation cost, and the industry needs an efficient, slow-release, and low-cost activation technology to achieve the simultaneous deep removal of new pollutants and heavy metals in reclaimed water, ensure the safety of reclaimed water for agricultural irrigation, and promote the deep combination of wastewater resource utilization and sustainable development of agriculture. SUMMARY

[0006] The purpose of the present application is to provide a metal sulfide nanoparticle slow-release activator for wastewater treatment.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions: A metal sulfide nanoparticle slow-release activator for wastewater treatment comprises: a rare earth-zinc dual-doped metal sulfide nanoparticle core layer; a porous silica membrane shell layer coated on the surface of the core layer; a citric acid modifier loaded on the core-shell interface; wherein the metal sulfide is a compound of iron sulfide and molybdenum sulfide, and the mass ratio is 1:0.5-0.7; the dual-doped agent is composed of lanthanum nitrate and zinc nitrate, and the total doping amount is 0.3-0.6wt% of the total mass of the metal sulfide, and the mass ratio of lanthanum nitrate to zinc nitrate is 2:1; the particle size of the dual-doped metal sulfide nanoparticle is 80-150nm; the loading amount of the citric acid modifier is 1.0-1.2wt%, and the binding rate with the hydroxyl group on the surface of the metal sulfide is ≥85%.

[0008] As a further technical solution, the specific surface area of the activator is 5.0-6.0m 2 / g.

[0009] As a further technical solution, the thickness of the porous silica membrane shell layer is 15-25nm, the pore size is 5-15nm, and the porosity is 35-45%.

[0010] As a further technical solution, under the condition of 25℃ and pH=7, the degradation rate of the activator to bisphenol A is 88-92%, the adsorption rate of lead ions is 90-93%, the slow-release period is 100-120h, and the attenuation of the release rate of potassium permanganate is 5-8% / 24h.

[0011] As a further technical solution, the doping amount of lanthanum nitrate in the dual-doped agent is 0.2-0.4wt% of the total mass of the metal sulfide, and the doping amount of zinc nitrate is 0.1-0.2wt% of the total mass of the metal sulfide.

[0012] The preparation method of the metal sulfide nanoparticle slow-release activator for sewage treatment comprises the following steps: (1) Iron sulfide and molybdenum sulfide powders are weighed in proportion, added into deionized water and ultrasonically dispersed for 30-40 minutes to form a mixed suspension with a concentration of 0.05-0.1 g / mL; a mixed solution of lanthanum nitrate and zinc nitrate is added into the suspension, and after uniform stirring, the suspension is transferred into a hydrothermal reaction kettle, and reacted at 180-200 DEG C and 0.5-0.8 MPa for 12-16 hours; after cooling, centrifugal separation, washing to neutral and vacuum drying, the dual-doped metal sulfide nanoparticles are obtained; (2) The nanoparticles obtained in step (1) are dispersed in an ethanol-water mixed solution, and tetraethyl orthosilicate and ammonia water are added, and stirred and reacted at 60-70 DEG C for 4-6 hours to form a silica coating layer; wherein the mass ratio of the nanoparticles, the tetraethyl orthosilicate, the ammonia water is 1:0.8-1.2:0.3-0.5, and the volume ratio of ethanol to water is 3:1; (3) The core-shell structure particles obtained in step (2) are dispersed in a citric acid solution with a mass concentration of 2-3%, and stirred and reacted at 50-60 DEG C for 2-3 hours to make citric acid molecules loaded on the core-shell interface through hydroxyl bonding; (4) The product obtained in step (3) is centrifugally separated, washed with deionized water for 3-4 times, and vacuum dried at 60-80 DEG C for 8-10 hours to obtain the slow-release activator.

[0013] As a further technical solution, the ultrasonic dispersion power in step (1) is 300-400 W, the ultrasonic frequency is 25-30 kHz, and the concentration of the mixed solution of lanthanum nitrate and zinc nitrate is 0.01-0.02 mol / L.

[0014] As a further technical solution, the concentration of the ammonia water in step (2) is 25-28 wt%, the stirring rate is 300-500 r / min, and the reaction process is carried out by using a stepwise temperature rising mode, with an increase of 5 DEG C per hour.

[0015] As a further technical solution, the liquid-solid ratio of the citric acid solution to the core-shell structure particles in step (3) is 10-15:1 (mL:g), the stirring rate is 200-300 r / min, and the pH of the reaction system is controlled at 4.0-5.0.

[0016] As a further technical solution, the vacuum drying in step (4) is carried out by using a gradient temperature rising mode, starting from 40 DEG C, and increasing by 10 DEG C every 2 hours to 60-80 DEG C.

[0017] Compared with the prior art, the present application has the following beneficial effects: 1. The application adopts metal sulfide (such as FeS, MoS2, WS2, etc.) micro-nanoparticles as solid-phase slow-release activators, which fundamentally solves the core problem of traditional homogeneous activation systems. First, the metal sulfide exists in a solid phase, which can directly contact with permanganate without additional dissolution steps, completely avoiding the problem of complex process operation caused by poor solubility of activators such as sulfite, simplifying the process of reclaimed water treatment. From the perspective of electron transfer mechanism, S(-II) in metal sulfide can provide 8 electrons to participate in the activation of Mn(VII), compared with the characteristics of sulfite which can only provide 2-4 electrons, which theoretically increases the conversion rate of Mn(VII) to RMnS by 1-3 times, not only reducing the dosage of permanganate, but also greatly reducing the consumption of inorganic salts, reducing the sulfate content in the effluent by 50%-75%, avoiding the risk of secondary salt pollution. More importantly, the oxidation reaction of permanganate on the surface of metal sulfide particles is progressive from the surface to the inside, and the solid-phase particles can slowly release active sites, effectively controlling the generation rate of RMnS, avoiding its explosive consumption, and maintaining the stable oxidation capacity of the system within 100-120h, completely solving the problem of poor sustained oxidation effect of traditional homogeneous systems.

[0018] 2. The non-complexed manganese oxidation system of the application establishes a dual removal mechanism for new pollutants and heavy metals. On the one hand, the RMnS produced by the activation of metal sulfide controlled by dual doping (lanthanum-zinc) has a highly adapted electron transfer path with the benzene ring structure of electron-rich new pollutants such as bisphenol A, so even if there are constant organic pollutants with COD≤50mg / L in the water, they will not compete for the oxidation active sites of RMnS, and the bidirectional anchoring function of the citric acid modifier loaded on the core-shell interface: both through the hydroxyl group to connect with the hydroxyl group on the surface of the core layer metal sulfide to limit the excessive aggregation of RMnS on the surface of the core layer, and through the interaction between the carboxyl group and the inner wall of the shell layer porous channel to guide the slow release of RMnS along the channel, avoiding the blockage of the pores inside the shell layer, so that the degradation rate of new pollutants is stable at more than 88%; at the same time, the hydrophilic group of the citric acid modifier can improve the dispersibility of the core-shell structure in water, avoiding the shielding of active sites caused by particle aggregation, so that the RMnS yield of per unit mass of activator is increased. On the other hand, the MnO2 colloid generated after the reaction of RMnS, due to the sensitization of the hydroxyl group of the citric acid modifier on the core-shell interface: the carboxyl group of the citric acid molecule can form a bidentate coordination structure with the hydroxyl group on the surface of the MnO2 colloid, so that the density of the hydroxyl group on the surface of the colloid is increased, which can adsorb Pb 2+ , Cd 2+The complexation constant of the heavy metal ions is improved, the adsorption rate of lead ions is improved, the adsorption rate of cadmium ions is also improved, and the ternary complex (MnO2-citric acid-heavy metal) formed after adsorption has no desorption phenomenon in the pH 3-9 range, thereby realizing effective fixation of the heavy metals. In addition, the citric acid modifier at the core-shell interface also plays a role of active site protection: in the reaction process of permanganate and the core layer, the citric acid molecules can preferentially interact with the excess Mn(VII), thereby avoiding direct attack of Mn(VII) on the core active site of the core layer metal sulfide and reducing irreversible damage to the active site, so that the activator still maintains high oxidation ability at the end of the slow-release period; and the gradient temperature vacuum drying in step (4) can further strengthen the binding strength of the citric acid modifier and the core-shell interface, avoid the falling off of the modifier during the drying process, and ensure that the function of the modifier is stably exerted throughout the process. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0020] The present application provides a metal sulfide nanoparticle slow-release activator for sewage treatment and a preparation method thereof, and aims to solve the technical problems of existing activators for sewage treatment, such as easy agglomeration of nanoparticles, poor slow-release performance, low degradation and adsorption efficiency of pollutants, and insufficient stability. The slow-release activator of the present application adopts a three-layer structure design of core-shell-modifier: the core layer is a rare earth-zinc dual-doped metal sulfide nanoparticle (iron sulfide and molybdenum sulfide are compounded at a mass ratio of 1:0.5-0.7), which provides core catalysis and adsorption activity; the shell layer is a porous silica film (thickness 15-25 nm, pore size 5-15 nm, porosity 35-45%), which realizes long-acting slow release of active ingredients; and the core-shell interface is loaded with a citric acid modifier (loading amount 1.0-1.2 wt%, binding rate ≥85%), which enhances the dispersibility and interface stability of the particles. The preparation process controls dual doping through hydrothermal reaction, coats a silica shell layer through sol-gel method, and performs directional modification of citric acid, so that the final product has the advantages of long slow-release period (100-120 h), high degradation and adsorption rate of pollutants (bisphenol A degradation rate 88-92%, lead ion adsorption rate 90-93%), and good stability, and can be efficiently applied in the field of sewage treatment.

[0021] Raw material description: The raw materials used in the embodiments of the present application are all conventional products on the market, and the specific specifications are as follows: Iron sulfide powder: purity ≥99.0%, particle size 50-100 nm, brand Aladdin on the market; Molybdenum sulfide powder: purity ≥ 99.5%, particle size 50-100 nm, commercially available brand Maclean; Lanthanum nitrate: analytical pure, purity ≥ 99.0%, commercially available brand Sinopharm Group; Zinc nitrate: analytical pure, purity ≥ 99.0%, commercially available brand Sinopharm Group; Tetraethyl orthosilicate: analytical pure, purity ≥ 99.0%, commercially available brand Shanghai Titan; Ammonia water: concentration 25-28 wt%, analytical pure, commercially available brand Sinopharm Group; Citric acid: analytical pure, purity ≥ 99.5%, commercially available brand Shanghai Yuan Ye; Ethanol: analytical pure, purity ≥ 99.7%, commercially available brand Sinopharm Group; Deionized water: resistivity ≥ 18.2 MΩ·cm, self-made.

[0022] The following are specific embodiments of the present application: Example 1: Preparation of metal sulfide nanoparticle slow-release activator for wastewater treatment: Take 10 g of iron sulfide powder and 5 g of molybdenum sulfide powder, with a mass ratio of 1:0.5, add 200 mL of deionized water, and ultrasonically disperse under the conditions of ultrasonic power 350 W and ultrasonic frequency 28 kHz for 35 minutes to form a mixed suspension. Add a mixed solution of lanthanum nitrate and zinc nitrate with a concentration of 0.015 mol / L to the suspension, with a mass ratio of lanthanum nitrate to zinc nitrate of 2:1, and control the total doping amount of the dual-doping agent to be 0.45 wt% of the total mass of the metal sulfide. Stir with a magnetic stirrer for 30 minutes until the mixture is uniform, then transfer the mixture to a hydrothermal reaction kettle. Place the reaction kettle in an oven and react at 190℃ and 0.65 MPa for 14 hours. After the reaction is completed, the reaction kettle is naturally cooled to room temperature, and the product is removed for centrifugal separation at a speed of 8000 r / min for 15 minutes. The centrifuged product is repeatedly washed with deionized water until the pH of the filtrate is 7.0. Finally, the washed product is placed in a vacuum drying oven at 70℃ for 12 hours to obtain dual-doped metal sulfide nanoparticles. The particle size is measured by a particle size tester and is 110 nm.

[0023] Preparation of core-shell structure particles: 10 g of the dual-doped metal sulfide nanoparticles obtained in step 1 were dispersed in 120 mL of an ethanol-water mixed solution with a volume ratio of ethanol to water of 3:1, and ultrasonic dispersion was performed for 10 minutes using an ultrasonic instrument with a power of 300 W and a frequency of 25 kHz until the particles were uniformly dispersed. 10 g of tetraethyl orthosilicate and 4 g of ammonia water with a concentration of 25 wt% were added to the dispersion, and at this time, the mass ratio of the nanoparticles, tetraethyl orthosilicate, and ammonia water was 1:1.0:0.4. The mixed system was placed in a constant-temperature water bath, and the stirring rate was set to 400 r / min. The reaction process was subjected to stepwise temperature increase from room temperature, and the temperature was increased by 5°C every hour until the temperature reached 65°C. The system was continuously stirred at this temperature for 5 hours to allow the tetraethyl orthosilicate to hydrolyze and condense on the surface of the nanoparticles to form a silica coating layer. After the reaction was completed, the system was subjected to centrifugal separation at a speed of 8000 r / min for 15 minutes to obtain the core-shell structure particles. Citric acid modification and loading: 10 g of the core-shell structure particles obtained in step 2 were dispersed in 120 mL of a citric acid solution with a mass concentration of 2.5%, and the liquid-solid ratio was 12 mL:1 g. The pH of the reaction system was adjusted to 4.5 using dilute hydrochloric acid, and the stirring rate was set to 250 r / min. The mixed system was placed in a constant-temperature water bath at 55°C, and stirring was performed for 2.5 hours to allow the citric acid molecules to be loaded on the core-shell interface through hydroxyl bonding. Preparation of slow-release activator: The product obtained in step 3 was subjected to centrifugal separation at a speed of 8000 r / min for 15 minutes, and the centrifuged product was washed 4 times with deionized water to remove free citric acid that was not combined. Subsequently, the washed product was placed in a vacuum drying oven and dried using a gradient temperature increase method: starting from 40°C, increasing the temperature by 10°C every 2 hours until the temperature reached 70°C, and vacuum drying at this temperature for 9 hours. Finally, the metal sulfide nanoparticle slow-release activator for wastewater treatment was obtained.

[0024] Example 2: Preparation of a metal sulfide nanoparticle slow-release activator for wastewater treatment: Preparation of dual-doped metal sulfide nanoparticles Take 10 g of iron sulfide powder and 7 g of molybdenum sulfide powder, with a mass ratio of 1:0.7, add 240 mL of deionized water, and ultrasonically disperse under the conditions of ultrasonic power 400 W and ultrasonic frequency 30 kHz for 40 minutes to form a mixed suspension. Add a mixed solution of lanthanum nitrate and zinc nitrate with a concentration of 0.02 mol / L to the suspension, with a mass ratio of 2:1, and control the total doping amount of the dual dopant to be 0.6 wt% of the total mass of the metal sulfide. After stirring for 30 minutes until uniform, transfer to a hydrothermal reaction kettle, react at 200°C and 0.8 MPa for 16 hours. After cooling to room temperature, centrifugal separation is performed at a speed of 8000 r / min for 15 minutes, washed with deionized water until neutral, and vacuum dried at 80°C for 12 hours to obtain dual-doped metal sulfide nanoparticles with a particle size of 150 nm. Preparation of core-shell structure particles Take 10 g of the nanoparticles obtained in step 1, disperse in 130 mL of an ethanol-water mixed solution with a volume ratio of ethanol to water of 3:1, ultrasonically disperse for 10 minutes, then add 12 g of tetraethyl orthosilicate and 5 g of ammonia water with a concentration of 28 wt%, at this time the mass ratio of the three is 1:1.2:0.5. Set the stirring rate to 500 r / min, and stepwise heat to 70°C (increase by 5°C per hour), stir at this temperature for 6 hours, centrifugal separation at a speed of 8000 r / min for 15 minutes to obtain core-shell structure particles. Citric acid modification and loading Take 10 g of the core-shell structure particles obtained in step 2, disperse in 150 mL of a 3% citric acid solution, liquid-solid ratio 15 mL:1 g, adjust the pH to 5.0 with dilute hydrochloric acid, and stir at a rate of 300 r / min in a constant temperature water bath at 60°C for 3 hours. Preparation of slow-release activator Centrifugal separation at a speed of 8000 r / min for 15 minutes, then washed with deionized water 4 times, and vacuum drying using gradient heating: start from 40°C, increase by 10°C every 2 hours to 80°C, vacuum drying at 80°C for 10 hours to obtain the slow-release activator.

[0025] Example 3: Preparation of metal sulfide nanoparticle slow-release activator for wastewater treatment: Preparation of dual-doped metal sulfide nanoparticles Take 10 g of iron sulfide powder and 6 g of molybdenum sulfide powder, with a mass ratio of 1:0.6, add 320 mL of deionized water, and ultrasonically disperse under the conditions of ultrasonic power 300 W and ultrasonic frequency 25 kHz for 30 minutes to form a mixed suspension. Add a mixed solution of lanthanum nitrate and zinc nitrate with a concentration of 0.01 mol / L to the suspension, with a mass ratio of 2:1, and control the total doping amount of the dual dopant to be 0.3 wt% of the total mass of the metal sulfide. After stirring for 30 minutes until uniform, transfer to a hydrothermal reaction kettle and react at 180°C and 0.5 MPa for 12 hours. After cooling to room temperature, centrifugal separation is performed at a speed of 8000 r / min for 15 minutes, washed with deionized water until neutral, and vacuum dried at 60°C for 12 hours to obtain dual-doped metal sulfide nanoparticles with a particle size of 80 nm. Preparation of core-shell structure particles: take 10 g of nanoparticles obtained in step 1, disperse in 110 mL of an ethanol-water mixed solution with a volume ratio of ethanol to water of 3:1, ultrasonically disperse for 10 minutes, then add 8 g of tetraethyl orthosilicate and 3 g of 25 wt% ammonia water, at this time the mass ratio of the three is 1:0.8:0.3. Set the stirring rate to 300 r / min, and stepwise heat to 60°C (increase by 5°C per hour), stir and react at this temperature for 4 hours, centrifugal separation is performed at a speed of 8000 r / min for 15 minutes, and core-shell structure particles are obtained. Citric acid modification and loading: take 10 g of core-shell structure particles obtained in step 2, disperse in 100 mL of a 2% mass concentration citric acid solution, liquid-solid ratio 10 mL:1 g, adjust the pH to 4.0 with dilute hydrochloric acid, and stir at a rate of 200 r / min in a 50°C constant temperature water bath for 2 hours. Preparation of slow-release activator: centrifugal separation is performed at a speed of 8000 r / min for 15 minutes, then washed with deionized water for 3 times, and vacuum drying is performed by gradient heating: start from 40°C, increase by 10°C every 2 hours to 60°C, vacuum drying at 60°C for 8 hours to obtain the slow-release activator.

[0026] Comparative Example 1: The preparation method of Example 1 is used, the only difference being that no mixed solution of lanthanum nitrate and zinc nitrate is added in step 1, i.e. no rare earth-zinc dual doping is performed, and the mixed suspension of iron sulfide and molybdenum sulfide is directly transferred to the hydrothermal reaction kettle for reaction. The remaining steps are operated and the parameters are the same as in Example 1, and finally metal sulfide nanoparticle slow-release activator without dual doping is obtained.

[0027] Comparative Example 2: The preparation method of Example 1 is used, the difference being that the porous silica film coating process in step 2 is omitted: after obtaining the dual-doped metal sulfide nanoparticles in step 1, directly disperse them in the citric acid solution for modification and loading in step 3, and the subsequent drying operation and parameters in step 4 are the same as in Example 1, and finally the activator without the porous silica film shell is obtained.

[0028] Comparative Example 3: The preparation method of Example 1 was adopted, except that the citric acid modification loading process of step 3 was omitted: after obtaining the core-shell structure particles of step 2, the centrifugal washing and vacuum drying of step 4 were directly performed, and the operation and parameters of the remaining steps were completely the same as those of Example 1. Finally, the activator without citric acid modifier was obtained.

[0029] Test: Test 1: Contaminant degradation and adsorption performance and slow-release performance test; Bisphenol A degradation rate: According to GB / T32992-2016 "Determination of Bisphenol A in Water - Solid Phase Extraction / High Performance Liquid Chromatography", 500 mL of 10 mg / L bisphenol A solution was prepared, 0.1 g of activator was added, and the constant temperature stirring was carried out at 25°C and pH=7 for 24 hours. After filtering with 0.22 μm filter membrane, the remaining concentration was determined by high performance liquid chromatograph (Agilent 1260), and the degradation rate was calculated; Lead ion adsorption rate: According to GB / T39304-2020 "Determination of Lead in Water - Flame Atomic Absorption Spectrophotometry", 500 mL of 50 mg / L lead ion solution was prepared, 0.1 g of activator was added, and the constant temperature stirring was carried out at 25°C and pH=7 for 24 hours. After centrifugal separation (8000 r / min, 15 minutes), the supernatant concentration was determined by flame atomic absorption spectrophotometer (PerkinElmer AA800), and the adsorption rate was calculated; Slow-release period and release rate attenuation: According to HJ591-2010 "Determination of Chlorine Dioxide in Water - Iodometric Method" (indirect representation of active ingredient release), 0.5 g of activator was loaded into a dialysis bag (molecular weight cut-off 10000 Da), immersed in 500 mL of deionized water, and constant temperature oscillation (150 r / min) was carried out at 25°C. Sample was taken regularly and equal amount of water was added. When the release amount of active ingredient decreased to 10% of the initial value, the time was recorded as the slow-release period. The release rate attenuation rate of every 24 hours was calculated ((the rate of the first 24 hours - the rate of the last 24 hours) / the rate of the first 24 hours x 100%), and the average value was taken as the result, as follows: Table 1

[0030] As can be seen from Table 1, the activators of Examples 1-3 can synergistically achieve high-efficiency degradation adsorption and long-acting slow release. Comparative Example 1 has no lanthanum nitrate to provide additional active sites and no zinc nitrate to adjust the electronic structure, and the catalytic adsorption capacity is significantly reduced, and the poor particle dispersibility leads to uneven release, and the slow release period is shortened by 25 h, proving that dual doping is the key to improving activity and slow release stability; Comparative Example 2: the absence of barrier effect leads to rapid release of active ingredients, and the slow release period is only 30 h, and the specific surface area is reduced due to particle agglomeration, verifying the core role of the shell layer in slow release and dispersibility; Comparative Example 3: without the stability of the interface stabilized by the hydroxyl bond, the active ingredients are prone to fall off, the degradation adsorption rate decreases, and the release attenuation increases to 10.0% / 24 h, indicating that the modifier can enhance the stability and activity retention. Test 2: Modification effect of citric acid and specific surface area test Citric acid loading: According to GB / T5009.157-2016 "Determination of organic acids in food", the citric acid concentration after ultrasonic extraction (300W, 10min) of 0.1g activator was determined by high performance liquid chromatograph (Agilent1260), and the loading was calculated (loading=(mass of citric acid / mass of activator) x 100%); Citric acid binding rate: According to GB / T29249-2012 "Determination of formaldehyde and hexamethylenetetramine content in textiles" (indirect representation of hydroxyl bonding efficiency), 0.5g activator was stirred at 80°C for 1 hour, and the citric acid concentration after elution was determined, and the binding rate=(1-elution amount / total loading) x 100%; Test results of Examples 1-3 and Comparative Example 3 are as follows: Table 2

[0031] As can be seen from Table 2, the citric acid modification effect of Examples 1-3 is good, and the directed loading and stable combination of the modifier can be achieved. Comparative Example 3 has no citric acid modification, and the loading is 0, and the spatial steric effect of citric acid is lacking, and particle agglomeration is easily intensified, indicating that the citric acid modifier can enhance the stability of the interface and provide a structural basis for high-efficiency degradation adsorption.

[0032] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details, and the application is not limited to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of the specification. The embodiments are selected and described in detail in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited by the claims and their entire scope and equivalents.

Claims

1. A metal sulfide nanoparticle slow-release activator for sewage treatment, characterized by, The application relates to a slow-release activator for bisphenol A, which comprises the following: a rare earth-zinc dual-doped metal sulfide nanoparticle core layer; a porous silica film shell layer coated on the surface of the core layer; and a citric acid modifier loaded on the core-shell interface; wherein the metal sulfide is a compound of iron sulfide and molybdenum sulfide, the mass ratio of the two being 1:0.5-0.7; the dual dopant is composed of lanthanum nitrate and zinc nitrate, the total doping amount being 0.3-0.6wt% of the total mass of the metal sulfide, and the mass ratio of the lanthanum nitrate to the zinc nitrate being 2:1; the particle size of the dual-doped metal sulfide nanoparticles is 80-150nm; the loading amount of the citric acid modifier is 1.0-1.2wt%, and the bonding rate with the hydroxyl groups on the surface of the metal sulfide is greater than or equal to 85%; the thickness of the porous silica film shell layer is 15-25nm, the pore size is 5-15nm, and the porosity is 35-45%; under the condition of 25 DEG C and pH=7, the degradation rate of the activator to bisphenol A is 88-92%, the adsorption rate to lead ions is 90-93%, the slow-release period is 100-120h, and the attenuation of the release rate of potassium permanganate is 5-8% / 24h; the doping amount of the lanthanum nitrate in the dual dopant is 0.2-0.4wt% of the total mass of the metal sulfide, and the doping amount of the zinc nitrate is 0.1-0.2wt% of the total mass of the metal sulfide. The application further relates to a preparation method of the slow-release activator for bisphenol A, which comprises the following steps: (1) proportionally weighing iron sulfide and molybdenum sulfide powders, adding the powders into deionized water for ultrasonic dispersion for 30-40 minutes to form a mixed suspension with a concentration of 0.05-0.1g / mL; adding a mixed solution of lanthanum nitrate and zinc nitrate into the suspension, stirring uniformly, and then transferring the suspension into a hydrothermal reaction kettle to react under the condition of 180-200 DEG C and 0.5-0.8MPa for 12-16 hours; after cooling, centrifugal separation, washing to neutral and vacuum drying, dual-doped metal sulfide nanoparticles are obtained; (2) dispersing the nanoparticles obtained in step (1) into an ethanol-water mixed solution, adding tetraethyl orthosilicate and ammonia water, and stirring to react at 60-70 DEG C for 4-6 hours to form a silica coating layer; wherein the mass ratio of the nanoparticles, the tetraethyl orthosilicate, the ammonia water and the ethanol to water is 1:0.8-1.2:0.3-0.5:3:1; (3) dispersing the core-shell structure particles obtained in step (2) into a citric acid solution with a mass concentration of 2-3%, and stirring to react at 50-60 DEG C for 2-3 hours, so that citric acid molecules are loaded on the core-shell interface through hydroxyl bonding; (4) centrifugal separation of the product obtained in step (3), washing with deionized water for 3-4 times, and vacuum drying at 60-80 DEG C for 8-10 hours to obtain the slow-release activator. In step (1), the ultrasonic dispersion power is 300-400W, the ultrasonic frequency is 25-30kHz, and the concentration of the mixed solution of the lanthanum nitrate and the zinc nitrate is 0.01-0.02mol / L. In step (2), the concentration of the ammonia water is 25-28wt%, the stirring rate is 300-500r / min, and the temperature is increased by 5 DEG C per hour in the reaction process. ​ ​ ​ 2. The metal sulfide nanoparticle slow-release activator for sewage treatment according to claim 1, characterized in that, The specific surface area of the activator is 5.0-6.0 m 2 / g.

3. The metal sulfide nanoparticle slow-release activator for sewage treatment according to claim 1, characterized in that, ​ 4. The metal sulfide nanoparticle slow-release activator for sewage treatment according to claim 1, characterized in that, ​ 5. The metal sulfide nanoparticle slow-release activator for wastewater treatment according to claim 1, characterized in that, ​ 6. A method for preparing the metal sulfide nanoparticle slow-release activator for sewage treatment according to any one of claims 1 to 5, characterized by, ​ ​ ​ ​ ​ 7. The method for preparing the slow-release activator of metal sulfide nanoparticles for wastewater treatment according to claim 6, characterized in that, ​ 8. The method for preparing the slow-release activator of metal sulfide nanoparticles for wastewater treatment according to claim 6, characterized in that, ​ 9. The method for preparing the slow-release activator of metal sulfide nanoparticles for wastewater treatment according to claim 6, characterized in that, The liquid-solid ratio of the citric acid solution to the core-shell structure particles in step (3) is 10-15:1 (mL:g), the stirring rate is 200-300 r / min, and the pH of the reaction system is controlled at 4.0-5.

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10. The method of claim 6, wherein the metal sulfide nanoparticle slow release activator for wastewater treatment is prepared by the steps of: The vacuum drying in step (4) is performed in a gradient heating mode, starting from 40 ℃, and increasing by 10 ℃ every 2 hours to 60-80 ℃.

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