Preparation of multi-effect water purification material from waste warmers and three-stage series sewage treatment method

Abstract

The present application belongs to the technical field of sewage treatment, and specifically discloses a kind of multi-effect water purification material and three-stage series sewage treatment method for preparing with waste heating pad as raw material, with waste heating pad as the only core preparation raw material, after water washing, salt removal, acid immersion polymerization activation, organic surface modification, low temperature composite calcination, three kinds of function complementary multi-effect water purification materials of flocculation type, catalytic type and adsorption type are synchronously prepared from one material;And supporting construction electroflocculation coagulation pretreatment-heterogeneous fenton catalytic oxidation-residue adsorption biological advanced purification three-stage series water treatment system.The present application realizes closed-loop recycling utilization of waste treatment, on-site recovery, on-site preparation and on-site application, without additional high-priced metal precursors, without professional technical personnel on duty operation and maintenance, and is suitable for rural decentralized domestic sewage, livestock breeding wastewater and other treatment scenarios.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for preparing multi-effect water purification materials and a three-stage series wastewater treatment method using waste hand warmers as raw materials. Background Technology

[0002] Disposable hand warmers are widely used civilian heating products with a huge market, consuming billions of units annually. Discarded hand warmers have become a typical solid waste item, present in large quantities in urban and rural household waste. The internal filling material of discarded hand warmers mainly consists of iron powder (approximately 30%-50%), activated carbon (approximately 10%-20%), vermiculite (approximately 10%-20%), and inorganic salts (mainly sodium chloride, approximately 5%-15%). If carelessly discarded, the soluble salts can seep into the soil and groundwater, causing salinization and increased water mineralization. Iron powder oxidation and corrosion can easily damage soil aggregate structure, and potential trace components (such as iron and manganese) can easily cause cumulative groundwater pollution. Current conventional disposal methods are mostly sanitary landfill and incineration, which not only occupy scarce land resources and waste valuable components but also easily generate secondary pollution such as dust and volatile harmful substances. From the perspective of resource utilization, iron powder, activated carbon, and vermiculite in waste hand warmers are all common water treatment functional materials. However, the current rate of harmless disposal and high-value resource utilization of solid waste is extremely low, and there is a lack of systematic technical solutions.

[0003] In the field of water treatment material preparation, existing commercial water purification materials (flocculators, catalysts, adsorbents) generally rely on chemical synthesis routes, which present the following prominent problems: Commercial polymerized iron salt flocculants are mostly prepared by high-temperature and high-pressure polymerization using chemical products such as ferrous sulfate and ferric chloride as precursors, resulting in high costs and energy consumption in the production process; advanced oxidation catalysts usually use precious metals or synthetic metal oxides as carriers, with complex synthesis processes and high raw material prices; activated carbon and vermiculite-based adsorbents also rely on mineral resource mining and high-temperature activation. The above-mentioned material preparation routes generally suffer from problems such as non-renewable raw materials, high dependence on chemical raw materials, and secondary pollution caused by the synthesis process, which contradicts the concept of green and low-carbon development.

[0004] In the field of decentralized wastewater treatment, rural and township domestic sewage and livestock and poultry breeding wastewater are generally characterized by large fluctuations in water quality and quantity, high suspended solids (SS) and organic pollutant loads, coexistence of heavy metals, and dispersed collection points. According to existing research, livestock and poultry wastewater is known for its "three highs": high organic matter concentration (COD can reach 3000-30000 mg / L), high ammonia nitrogen (100-2000 mg / L), and high suspended solids (SS exceeding the standard by tens of times), and also contains multiple compound pollutants such as heavy metals and antibiotics. Traditional treatment processes use single flocculation sedimentation, single physical adsorption, or conventional biological treatment modes, which generally have the disadvantages of single function, inability to simultaneously and efficiently remove multiple compound pollutants, large fluctuations in effluent quality, and difficulty in achieving long-term stable compliance with standards. In addition, traditional complete sets of wastewater treatment facilities require large infrastructure investment, complex supporting equipment, and rely on professional technicians for daily operation and maintenance, resulting in high operation and maintenance costs. In remote rural areas, these facilities are often idle due to population loss and process incompatibility, making large-scale implementation and promotion difficult.

[0005] While existing publicly available technologies and literature have attempted to prepare single water purification materials using waste heat packs (warm packs), they all have significant limitations. For example, the technology disclosed by Yu Yanzhen et al. for "preparing polymeric inorganic iron-based flocculants using waste heat packs" only produces a single flocculant material and requires the addition of auxiliary materials such as sodium silicate. Other technologies disclose methods for preparing composite vermiculite mineral filter media or composite carbon filter media using waste heat packs, which require the addition of cement or clay as molding auxiliary materials and only produce single-function filter media. CN116078384B discloses an oxygen-enriched vacancy iron-based catalyst derived from waste heat packs, which uses the contents of waste heat packs as raw materials to obtain a single catalyst through anaerobic calcination and potassium borohydride reduction treatment. However, this technology requires chemical reagents such as potassium borohydride for reduction treatment and only produces a single catalytic material. In addition, the Japanese group GoGreenGroup attempted to process waste hand warmers into iron ion releasing ingots for water purification, which is a single-step, single-function utilization of water purification materials and is far from reaching a systematic technological level.

[0006] In summary, the existing technology has not yet formed a complete technical solution that uses waste hand warmers as the only main raw material, does not add high-priced functional additives, and simultaneously produces three types of functionally complementary water purification materials from one raw material, and supports the construction of a three-stage series purification process to simultaneously remove suspended solids, organic matter, and heavy metals. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for preparing multi-effect water purification materials using waste hand warmers as raw materials and a three-stage series wastewater treatment method.

[0008] To achieve the above objectives, the present invention is implemented according to the following technical solution: The first technical solution provided by this invention is a method for preparing multi-effect water purification materials using waste hand warmers as raw materials, comprising the following steps: S1. Pretreatment and gradient water washing desalination: Disassemble the waste heat packs, peel off the outer covering material, collect the internal heating filler, and pre-dry them in a 40-60℃ forced-air drying oven for 2-4 hours; use multi-stage countercurrent stirring washing combined with ultrasonic-assisted process, wash with deionized water at a liquid-to-solid ratio of 3:1-10:1 gradient until the conductivity of the washing liquid is ≤100μS / cm, ensuring that the removal rate of soluble inorganic salts is ≥95%; after solid-liquid separation, dry to constant weight, and pass through an 80-120 mesh sieve to obtain raw material powder with uniform particle size; S2. Directional acid leaching polymerization modification: The raw material powder obtained in step S1 is added to a dilute acid solution system with a concentration of 0.5-3 mol / L at a liquid-to-solid ratio of 5:1-20:1. The reaction is carried out at room temperature and pressure and a stirring rate of 150-300 r / min for 1-4 hours to convert the zero-valent iron and iron oxide in waste hand warmers into polymerized ferric hydroxide active flocculant components. At the same time, the surfaces of vermiculite and activated carbon are etched to form microporous structures. After solid-liquid separation, the filtrate is washed until the pH of the filtrate is neutral and then dried to obtain the acid-leached modified material. S3. Organic coordination modification: The acid-impregnated modified material obtained in step S2 is added to an organic modifier at a liquid-to-solid ratio of 3:1-15:1. The organic modifier is one of citric acid, tartaric acid, EDTA, chitosan, or sodium dodecylbenzenesulfonate. The mixture is stirred and reacted in a water bath at 40-80℃ for 1-3 hours. The organic functional groups coordinate with the iron-based active sites, and functional groups are introduced onto the surface of activated carbon and vermiculite. After the reaction, the solid and liquid are separated, washed, and dried to obtain the composite modified material. S4. Segmented low-temperature closed calcination: The composite modified material obtained in step S3 is placed in a calcination device and calcined using a segmented heating-heat preservation-oxygen control calcination process; after calcination, it is naturally cooled to room temperature, passed through an 80-200 mesh sieve for classification, and then ball-milled to obtain multi-effect water purification material.

[0009] Furthermore, the concentration of the organic modifier in step S3 is 0.1%-5% (w / v).

[0010] Furthermore, the segmented heating-holding-oxygen-controlled calcination process in step S4 is specifically as follows: In the first stage, the temperature is increased to 200-300℃ at a rate of 5-10℃ / min and held for 1-2 hours. In the second stage, the temperature is further increased to 300-500℃ and held for 1-3 hours under inert gas protection or oxygen-limited conditions to promote the synergistic reduction effect of zero-valent iron and activated carbon, forming carbon-coated iron-based catalytic sites.

[0011] Furthermore, in step S4, the particle size is controlled to be 0.5-1 mm during ball milling to obtain a flocculation-type multi-effect water purification material; the particle size is controlled to be 0.1-0.5 mm during ball milling to obtain a catalytic-type multi-effect water purification material; and the particle size is controlled to be 0.2-1 mm during ball milling to obtain an adsorption-type multi-effect water purification material.

[0012] The second technical solution provided by this invention is a three-stage series wastewater treatment method using the multi-effect water purification material prepared by the above method. It constructs a three-stage coupled water treatment process system centered on the resource utilization of all components of waste hand warmers: electrocoagulation pretreatment, heterogeneous Fenton oxidation degradation based on waste hand warmers, and deep biological purification through adsorption of hand warmer residue. No photocatalytic oxidation unit is included. Specifically, it includes: The first stage is electrocoagulation pretreatment: waste heat pump iron powder and iron oxide components are processed into electrodes, and built-in sodium chloride is used as the endogenous electrolyte. Under the action of electric field, iron ions are electrolyzed and dissolved, and hydrolyzed and polymerized to generate polynuclear hydroxy iron flocs. Through the synergistic effect of electrocoagulation oxidation, adsorption bridging, and net capture and sweeping, the initial separation of solid and liquid is completed. The second stage is heterogeneous Fenton oxidation degradation: the multi-effect water purification material prepared by any of the methods described in claims 1-4 is filled into the oxidation reaction tank; after the pH of the pretreated effluent is adjusted, hydrogen peroxide is added, and under the condition of no ultraviolet light excitation, hydroxyl radicals are catalyzed to break the molecular chains of recalcitrant organic matter. The third stage is residual adsorption and biological deep purification: using the remaining activated carbon, vermiculite and harmless residues from the first two stages of reaction obtained by dismantling waste hand warmers, and sieving and classifying them into composite filter media, an adsorption biological filter is constructed. The residual pollutants are deeply removed through physical adsorption, surface functional microbial metabolic degradation and filter layer interception.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. Resource utilization of all raw materials: This invention is the first to use waste hand warmers as the sole core raw material for water purification materials, maximizing the synergistic utilization value of internal iron powder, activated carbon, and vermiculite components. No external functional fillers are required, achieving the unity of solid waste reduction, harmlessness, and high-value utilization, and eradicating the ecological pollution of soil and water caused by the random disposal of waste hand warmers from the source.

[0014] 2. One material yields three products, and the process is green and efficient: This invention produces three types of complementary water purification materials—flocculation type, catalytic type, and adsorption type—through a unified short-process technology, overcoming the limitation of existing technologies that can only prepare single-function materials. The process is highly versatile; it operates under normal temperature and pressure conditions throughout, with low energy consumption and no external discharge of waste, thus meeting the dual needs of industrial-scale production and small-scale preparation at the grassroots level.

[0015] 3. Three-stage series, tiered load reduction, and synergistic purification: This invention pioneers a graded and precise treatment path of flocculation to remove suspended colloids → catalytic oxidation to reduce organic matter → adsorption for deep biological purification. This effectively overcomes the technical shortcomings of traditional single processes that cannot simultaneously and efficiently remove multiple types of complex pollutants, ensuring that the concentration of pollutants in the effluent remains stable and meets standards in the long term.

[0016] 4. No dependence on external energy input: The second-stage heterogeneous Fenton oxidation of this invention can efficiently catalyze the generation of hydroxyl radicals from hydrogen peroxide for the degradation of organic matter under conditions without ultraviolet light excitation and ultrasonic assistance. This eliminates the external energy consumption required by traditional photo-Fenton and ultrasonic-assisted oxidation, reducing system operating energy consumption and equipment complexity.

[0017] 5. Waste-to-waste treatment and closed-loop recycling: The entire system of this invention uses waste hand warmers as the material source and wastewater treatment as the goal, and disposes of solid waste throughout the entire process; the small amount of sludge and expired filter media generated can be recycled back to the resource preparation process for reuse, realizing a closed-loop material recycling, and the entire process has no secondary pollution from the discharge of waste gas, wastewater, or waste residue.

[0018] 6. Low cost, low maintenance, and easy to promote: The system structure of this invention has a high degree of integration and a simple process flow. The electrocoagulation unit does not require the addition of external electrolyte agents, but only requires periodic addition of hydrogen peroxide, catalyst recycling and regeneration, and simple filter media maintenance. It does not require long-term on-site operation and maintenance by professional technicians, has strong resistance to water quality and quantity shock loads, and is suitable for decentralized sewage treatment scenarios with weak professional operation and maintenance capabilities, such as remote villages and towns and livestock and poultry breeding communities.

[0019] 7. On-site recycling-on-site preparation-on-site application model: This invention forms a closed-loop recycling model of on-site collection of waste hand warmers → on-site green preparation of environmentally friendly water purification materials → on-site purification and treatment of local domestic and aquaculture wastewater, realizing the integrated and coordinated development of solid waste treatment, material preparation and wastewater purification, and has significant environmental, economic and social benefits. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process flow of the three-stage series water treatment system of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0022] Example 1: Preparation of Multi-Effect Water Purification Material Based on Waste Hand Warmers This embodiment uses discarded hand warmers as the sole core raw material to prepare three types of water purification materials in one step through the following steps: (1) Pretreatment and gradient water washing for desalination The collected used hand warmers were manually disassembled and sorted, removing the outer non-woven fabric and adhesive layers to collect the internal black functional powder filler (mainly composed of iron powder, activated carbon, vermiculite, and inorganic salts). The collected filler was then placed in a 50℃ forced-air drying oven for 3 hours to remove residual moisture and prevent clumping during subsequent washing.

[0023] A gradient water washing desalination process was adopted using a "multi-stage countercurrent stirring washing + ultrasonic assistance" technique: deionized water was used for gradient washing at a liquid-to-solid ratio of 5:1, with stirring for 20 minutes each time and ultrasonic power of 150W to assist in the dissociation of salts. This washing was repeated 4 times. After each washing, the conductivity of the supernatant was measured. After the 4th washing, the conductivity decreased to 85 μS / cm, reaching the set target of conductivity ≤100 μS / cm, indicating that Cl... - Na + The removal rate of soluble inorganic salts is ≥95%. Solid-liquid separation is performed by vacuum filtration. The desalinated solid material is dried in a drying oven at 70℃ to constant weight and then passed through a 100-mesh sieve to obtain raw material powder with uniform particle size.

[0024] (2) Directional acid leaching polymerization modification The above-mentioned desalination powder was added to a 1.5 mol / L dilute sulfuric acid solution at a liquid-to-solid ratio of 10:1, along with 1.5% hydrogen peroxide as an auxiliary oxidant. The reaction was carried out at room temperature and pressure (reaction temperature 30℃) and a stirring rate of 200 r / min for 2.5 h. During this process, zero-valent iron and iron oxide in the waste hand warmer filler were converted into polymeric ferric hydroxide (including Fe(OH)2) under acidolysis and oxidation. 2+ [Fe2(OH)2] 4+ The active flocculant components are added, and the surfaces of vermiculite and activated carbon are etched by acid to form a rich microporous structure. After the reaction, the mixture is vacuum filtered and repeatedly washed with deionized water until the pH of the filtrate is neutral (pH≈7.0). The filter cake is then dried in a 95℃ drying oven to obtain the acid-modified material. If necessary, it can be calcined at 150℃ for 0.5h to further enhance the iron-based active sites.

[0025] (3) Organic coordination modification The acid-modified material was added to the organic modifier system at a liquid-to-solid ratio of 8:1. In this embodiment, citric acid concentration of 2% (w / v) was used, and the pH of the system was adjusted to 5.5 to optimize the coordination reaction environment. The reaction was carried out under a 60℃ water bath with stirring at a stirring rate of 180 r / min for 2 h. The carboxyl groups (-COOH) in the citric acid molecules coordinate with the iron-based active sites, while hydrophilic carboxyl functional groups are introduced onto the surfaces of activated carbon and vermiculite, thereby regulating the surface charge and pore structure. After the reaction, the mixture was separated by filtration, washed three times with deionized water to remove unbound modifier, and dried in an 80℃ drying oven to constant weight to obtain the composite modified material.

[0026] (4) Segmented low-temperature closed calcination and graded preparation The composite modified material is placed in a tube furnace and subjected to a segmented heating-holding-oxygen-controlled calcination process: First stage: Heat to 250℃ at a rate of 8℃ / min, hold for 1.5h to remove residual moisture and some volatile components in the organic modifier, and simultaneously strengthen the interfacial bonding of iron-carbon-vermiculite. Second stage: Continue heating to 400℃ and maintain this temperature for 2 hours under nitrogen protection (flow rate 50 mL / min). At this temperature, a reduction synergy occurs between zero-valent iron and activated carbon, forming carbon-coated zero-valent iron catalytic sites. At the same time, the vermiculite interlayer structure is further stabilized, and the activated carbon micropores are fully developed.

[0027] After calcination, the material was allowed to cool naturally to room temperature in the furnace before being removed. It was then sieved through 80-mesh and 200-mesh standard sieves, and further processed by ball milling (controlled at 200 rpm for 15 minutes) to prepare three types of multi-effect water purification materials: Flocculation-type multi-effect water purification material: It retains coarse particle fractions with a particle size of 0.5-1mm. This fraction retains highly active polymeric hydroxyl iron components and has excellent charge neutralization and adsorption bridging capabilities, which are used in the flocculation and sedimentation unit in subsequent wastewater treatment.

[0028] Catalytic multi-effect water purification material: It retains medium-sized particle fractions with a particle size of 0.1-0.5mm. These fractions are rich in carbon-coated zero-valent iron catalytic sites, have a high specific surface area and catalytic activity, and are used in advanced oxidation catalytic degradation units in subsequent wastewater treatment.

[0029] Adsorption-type multi-effect water purification material: a fraction with a particle size of 0.2-1mm (which can be flexibly adjusted according to the actual sorting situation). This fraction is rich in modified vermiculite-activated carbon porous structure, with a well-developed microporous and mesoporous system and abundant surface functional groups, and is used as an adsorption unit for heavy metals and organic pollutants in subsequent wastewater treatment.

[0030] The water washing filtrate generated during the actual preparation process can be reused as washing liquid after neutralization treatment; the acid leaching filtrate can be recycled after replenishing with acid; and the roasting tail gas is treated by alkaline absorption. The entire preparation process does not generate any discharged wastewater, waste gas, or waste residue.

[0031] Example 2: Three-stage series wastewater treatment process Please see Figure 1This embodiment uses wastewater from a pig farm as the treatment target, employing three types of waste hand warmer-based water purification materials prepared in Example 1, and treating it using a three-stage series process. The raw water quality characteristics are: COD (Cr) = 3200 mg / L, SS = 1200 mg / L, NH3-N = 350 mg / L, total copper = 3.5 mg / L, total zinc = 8.2 mg / L, pH = 7.2.

[0032] Level 1: Electrocoagulation Coagulation Pretreatment The iron powder and iron oxide components obtained from the dismantling and sorting of waste hand warmers are processed into electrocoagulation reaction electrodes (both the anode and cathode are made of iron-based materials from hand warmers, with an electrode plate spacing of 15mm). The sodium chloride salts inside the waste hand warmers are directly used as natural endogenous electrolytes (the NaCl concentration in the raw water is about 500-800mg / L), without the need to add additional electrolytes and inorganic flocculants.

[0033] Raw water at 0.5m 3 A flow rate of / h is pumped into the first-stage unit, and a DC voltage (current density 10mA / cm²) is applied. 2 Under the influence of an electric field, Fe is dissolved by electrolysis at the iron electrode. 2+ The mixture then hydrolyzes and polymerizes to form polynuclear hydroxyl iron flocs. Through the synergistic effect of electrocoagulation oxidation, floc adsorption bridging, and netting / sweeping, suspended particulate matter, colloidal substances, and some large organic molecules in the water are rapidly captured, flocculated, and aggregated. After a reaction time of 20 minutes, the mixture is allowed to settle for 30 minutes to complete solid-liquid separation.

[0034] Primary treatment results: SS removal rate reached 85%, COD(Cr) removal rate reached 40%, NH3-N removal rate reached 15%, total copper removal rate reached 35%, and total zinc removal rate reached 30%. The primary effluent quality was: COD(Cr) ≈ 1920 mg / L, SS ≈ 180 mg / L, NH3-N ≈ 298 mg / L, total copper ≈ 2.3 mg / L, and total zinc ≈ 5.7 mg / L. The biodegradability of the wastewater after primary treatment (BOD5 / COD(Cr)) increased significantly from 0.25 to 0.38, creating conditions for subsequent synergistic biological treatment.

[0035] Second stage: Heterogeneous Fenton oxidation degradation The second stage uses an iron-based heterogeneous Fenton catalyst (i.e., the catalytic multi-effect water purification material prepared in Example 1) prepared by acid washing, activation, and low-temperature calcination modification. This catalyst is filled into the oxidation reactor at a filling rate of 60% (effective reactor volume 1.0 m³). 3 ).

[0036] The effluent from the primary pretreatment stage flows by gravity into the secondary oxidation reactor. The pH is adjusted to 3.5-4.0 (the optimal pH range for heterogeneous Fenton reactions), and a 30% hydrogen peroxide solution is added quantitatively at a rate 1.2 times the theoretical COD(Cr) value (i.e., the H2O2:COD(Cr) mass ratio is approximately 1.2:1). Under normal temperature and pressure conditions and without ultraviolet light excitation, the wastewater undergoes a reaction in the catalyst bed with a hydraulic retention time of 90 minutes. The carbon-coated zero-valent iron sites on the surface of the modified catalyst from waste heat packs catalyze the decomposition of hydrogen peroxide, generating a large number of hydroxyl radicals (·OH) with an oxidation potential as high as 2.80V, which efficiently break down and oxidize the molecular chains of recalcitrant organic compounds.

[0037] Secondary treatment results: After 7 days of continuous operation, the average COD (Cr) removal rate reached 75%, with an average effluent COD (Cr) of ≈480 mg / L; the color removal rate exceeded 90%. The catalyst activity decreased by only about 8% after 30 days of continuous operation, and its activity could be restored after simple backwashing and surface regeneration. The iron ion leaching was low (total iron concentration in the effluent <0.5 mg / L), and no secondary pollution from iron sludge was generated.

[0038] Third stage: Residue adsorption and biological deep purification The remaining activated carbon and vermiculite components from dismantling used hand warmers are screened and graded with the hand warmer residue (mainly the partially degraded catalyst discharged periodically after the second stage of use and the residue after drying the first stage sediment sludge) after harmless treatment following the first two stages of reaction. The mixture is then mixed at a volume ratio of activated carbon:vermiculite:residue = 3:2:1 and used as composite filter media to construct an adsorption biological filter (effective filter volume 1.5m³, filter media layer height 1.2m, with a water collection area and backwashing device at the bottom).

[0039] The secondary effluent after Fenton oxidation flows by gravity into the adsorption biological filter, with a filtration rate controlled at 0.8 m / h. In the initial operation phase (first 15 days), physical adsorption and complexation adsorption are primarily achieved through the well-developed microporous structure of activated carbon and vermiculite, and the active functional groups introduced by organic coordination modification, retaining trace amounts of residual organic matter, color, and suspended particles. After 15 days of operation, the filter media surface gradually accumulates fouling-resistant microorganisms (mainly Pseudomonas and Bacillus), and the filter enters the adsorption-biological synergistic operation stage, further degrading residual COD (Cr), ammonia nitrogen, and trace organic pollutants through microbial metabolism.

[0040] The tertiary treatment effect: After 30 days of stable operation, the COD (Cr) of the tertiary effluent decreased to 75 mg / L, SS decreased to 15 mg / L, NH3-N decreased to 18 mg / L, total copper decreased to 0.12 mg / L, total zinc decreased to 0.35 mg / L, and pH=7.0. The concentrations of all pollutants met the first-level standard limit requirements of the "Emission Standard of Pollutants for Livestock and Poultry Breeding Industry" (GB 18596-2001) and the "Emission Standard of Water Pollutants for Rural Domestic Sewage Treatment Facilities" (DB 33 / 973-2015), and can be directly discharged in compliance with standards or reused for farmland irrigation.

[0041] Full-process operation and maintenance The entire three-stage series system operates at ambient temperature and pressure throughout, without any high-temperature, high-pressure, or high-energy-consumption processes. The electrocoagulation unit requires no additional external electrolyte reagents; only hydrogen peroxide needs to be added periodically based on actual consumption (per 100m³ of treated water). 3 The wastewater consumes approximately 15L of a 30% hydrogen peroxide solution. The catalyst undergoes online surface regeneration every 30 days (circulating and rinsing with pH 3.0 dilute acid for 2 hours), and the regenerated solution is reused in the acid leaching and polymerization process of the water purification materials. The adsorption biological filter undergoes backwashing every 60 days; the supernatant after sedimentation is returned to the first-stage treatment unit, and the precipitate residue is reused to replenish the third-stage filter media. The system produces no wastewater, exhaust gas, or waste residue. The entire system is simple to operate, requiring only one operator with basic training for daily management and maintenance, without the need for long-term on-site supervision by specialized technicians.

[0042] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing multi-effect water purification materials using waste hand warmers as raw materials, characterized in that, Includes the following steps: S1. Pretreatment and gradient water washing desalination: Disassemble the waste heat packs, peel off the outer covering material, collect the internal heating filler, and pre-dry them in a 40-60℃ forced-air drying oven for 2-4 hours; use multi-stage countercurrent stirring washing combined with ultrasonic-assisted process, wash with deionized water at a liquid-to-solid ratio of 3:1-10:1 gradient until the conductivity of the washing liquid is ≤100μS / cm, ensuring that the removal rate of soluble inorganic salts is ≥95%; after solid-liquid separation, dry to constant weight, and pass through an 80-120 mesh sieve to obtain raw material powder with uniform particle size; S2, Directional acid leaching polymerization modification: The raw material powder obtained in step S1 is added to a dilute acid solution system with a concentration of 0.5-3 mol / L at a liquid-solid ratio of 5:1-20:

1. The reaction is carried out at room temperature and pressure and a stirring rate of 150-300 r / min for 1-4 hours to convert zero-valent iron and iron oxide in waste hand warmers into polymerized hydroxyl iron active flocculant components. At the same time, the surface of vermiculite and activated carbon is etched to form a micro-mesoporous structure. After solid-liquid separation, the filtrate is washed until the pH of the filtrate is neutral, and then dried to obtain the acid-modified material. S3. Organic coordination modification: The acid-treated material obtained in step S2 is added to an organic modifier at a liquid-solid ratio of 3:1-15:

1. The organic modifier is one of citric acid, tartaric acid, EDTA, chitosan, or sodium dodecylbenzenesulfonate. The mixture is stirred and reacted in a water bath at 40-80℃ for 1-3 hours. The organic functional groups coordinate with the iron-based active sites, and functional groups are introduced onto the surface of activated carbon and vermiculite. After the reaction, solid-liquid separation, washing, and drying were performed to obtain the composite modified material; S4. Segmented low-temperature closed roasting: The composite modified material obtained in step S3 is placed in a roasting equipment and roasted using a segmented heating-heating-oxygen-controlled roasting process. After calcination, the material is naturally cooled to room temperature, then passed through an 80-200 mesh sieve for classification, and finally ball-milled to obtain a multi-effect water purification material.

2. The method for preparing multi-effect water purification materials using waste hand warmers as raw materials according to claim 1, characterized in that, The concentration of the organic modifier in step S3 is 0.1%-5% (w / v).

3. The method for preparing multi-effect water purification materials using waste hand warmers as raw materials according to claim 1, characterized in that, The segmented heating-holding-oxygen-controlled calcination process in step S4 is specifically as follows: In the first stage, the temperature is increased to 200-300℃ at a rate of 5-10℃ / min and held for 1-2 hours. In the second stage, the temperature is further increased to 300-500℃ and held for 1-3 hours under inert gas protection or oxygen-limited conditions to promote the synergistic reduction effect of zero-valent iron and activated carbon, forming carbon-coated iron-based catalytic sites.

4. The method for preparing multi-effect water purification materials using waste hand warmers as raw materials according to claim 1, characterized in that, In step S4, the particle size is controlled to be 0.5-1 mm during ball milling to obtain flocculation-type multi-effect water purification material; the particle size is controlled to be 0.1-0.5 mm during ball milling to obtain catalytic-type multi-effect water purification material; and the particle size is controlled to be 0.2-1 mm during ball milling to obtain adsorption-type multi-effect water purification material.

5. A three-stage series wastewater treatment method using a multi-effect water purification material prepared by any one of claims 1-4, characterized in that: A three-stage coupled water treatment process system is constructed, centered on the resource utilization of all components of waste hand warmers: electrocoagulation pretreatment, heterogeneous Fenton oxidation degradation of waste hand warmer-based materials, and deep biological purification through adsorption of hand warmer residue. No photocatalytic oxidation unit is included. Specifically, this includes: The first stage is electrocoagulation pretreatment: waste heat pump iron powder and iron oxide components are processed into electrodes, and built-in sodium chloride is used as the endogenous electrolyte. Under the action of electric field, iron ions are electrolyzed and dissolved, and hydrolyzed and polymerized to generate polynuclear hydroxy iron flocs. Through the synergistic effect of electrocoagulation oxidation, adsorption bridging, and net capture and sweeping, the initial separation of solid and liquid is completed. The second stage is heterogeneous Fenton oxidation degradation: the multi-effect water purification material prepared by any of the methods described in claims 1-4 is filled into the oxidation reaction tank; after the pH of the pretreated effluent is adjusted, hydrogen peroxide is added, and under the condition of no ultraviolet light excitation, hydroxyl radicals are catalyzed to break the molecular chains of recalcitrant organic matter. The third stage is residual adsorption and biological deep purification: using the remaining activated carbon, vermiculite and harmless residues from the first two stages of reaction obtained by dismantling waste hand warmers, and sieving and classifying them into composite filter media, an adsorption biological filter is constructed. The residual pollutants are deeply removed through physical adsorption, surface functional microbial metabolic degradation and filter layer interception.

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