Preparation method and application of one-step aluminum-modified fish-scale calcium defluorination material

Abstract

The present application relates to the technical field of environmental protection water treatment, in particular to a preparation method and application of one-step aluminum modified fish scale calcium defluorination material; the present application successfully prepares the defluorination material with economy and high efficiency by combining hydrochloric acid demineralization pretreatment with sodium metaaluminate one-step modification process; the removal rate of the composite material prepared by the present application to 10mg / L fluoride ion solution can reach 94.76%, the theoretical maximum adsorption capacity reaches 118.53mg / g, the actual test adsorption capacity reaches 9.56mg / g, and the stable and efficient adsorption performance is maintained in the pH 3-6 range; the process of the present method is simple, the reaction conditions are mild, and the material preparation cost is significantly reduced, which provides an innovative solution with practicability and economy for fluorine-containing wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of environmental protection and water treatment technology, specifically to a one-step method for preparing aluminum-modified fish scale calcium defluorination material and its application. Background Technology

[0002] Water is the source of life for humankind. Compared to other water pollutants, fluoride is a persistent and harmful contaminant. At the same time, fluoride is also a micronutrient essential for the health of both humans and animals, primarily ingested through drinking water. Adequate fluoride intake helps maintain healthy bones and teeth. However, due to rapid urbanization and the world's rapid population growth, fluoride pollution in water bodies has increased dramatically. Once fluoride levels in groundwater exceed permissible limits, serious health problems can arise. Excessive intake can lead to diseases such as dental fluorosis or skeletal fluorosis. When the fluoride ion content in groundwater exceeds 10 mg / L, it may also accelerate the development of hypertension, cancer, and neurological disorders.

[0003] Fish scales (FS) – a byproduct of seafood processing – exhibit significant application potential due to their abundant reserves and low cost. In seafood processing processes such as canning, filleting, pickling, and smoking, fish scales are often discarded as waste, with approximately 7.2 million to 12 million tons of fish processing waste being dumped globally each year. Fish scales are also a unique natural biomaterial, containing 40-90% organic protein, including abundant proline, glycine, alanine, hydroxylamine lysine, and type I collagen composed of hydroxyproline, as well as 10-60% inorganic mineral components (mainly sodium, magnesium, and carbonates) ionicly bound to hydroxyapatite phosphate groups. The highly ordered, layered microstructure and composition of fish scales are similar to human hard tissue, giving them good biocompatibility, degradability, and excellent mechanical properties, making them suitable for tissue engineering, biofilling, wastewater treatment, and flexible electronics. However, due to a lack of commercial value, the practical applications of fish scales are relatively limited, leading to material waste and environmental pollution.

[0004] Currently, methods for removing fluoride from water include chemical precipitation, coagulation, reverse osmosis, electrocoagulation, adsorption, nanofiltration, and ion exchange. When fluoride concentrations in water are high, coagulation and precipitation are two commonly used methods, but these methods also generate large amounts of residues while removing fluoride. Electrocoagulation technology can efficiently remove fluoride ions from water without causing secondary pollutants, but it consumes a large amount of electricity, resulting in high operating costs. Various methods based on nanofiltration and reverse osmosis principles can reduce fluoride concentrations below the limits set by the WHO, but their operating costs are very high and their prices are extremely expensive.

[0005] Adsorption is a method of purifying water by using adsorbents to adsorb fluorides. Using adsorbents for fluoride removal offers several advantages, such as low cost, ease of operation, excellent removal efficiency, and recyclability. Commonly used adsorbents for fluoride removal include activated carbon and its modifications, activated red mud, zeolite, steel slag, diatomaceous earth, nanoparticles, activated alumina, metal-organic frameworks, LDH, metals and their oxides, chitosan, and natural biomaterials. However, biochar, for example, typically has a maximum fluoride adsorption capacity of only 50 mg / g, indicating relatively poor adsorption ability.

[0006] Existing methods for preparing defluorination materials typically involve multiple steps, such as acid treatment followed by alkali activation and finally modification. This not only increases the difficulty of operation but also leads to high energy consumption, increased costs, and makes it difficult to achieve large-scale application. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, this invention aims to provide a one-step method for preparing aluminum-modified fish-scale calcium defluorination materials and their application, solving the problems of insufficient performance, complex processes, or high costs associated with traditional materials.

[0008] To solve the above problems, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a one-step method for preparing aluminum-modified fish-scale calcium defluorination material, comprising:

[0010] Fish scales are pretreated with acid to obtain acidified fish scales;

[0011] Acidified fish scales were modified with NaAlO2 to obtain a synchronously activated aluminum-fish scale calcium composite material.

[0012] Furthermore, the step of pretreating fish scales with acid to obtain acidified fish scales includes:

[0013] Fish scales were mixed with 2-5 wt% HCl solution at a solid-liquid ratio of 1 g: 5 mL, shaken, centrifuged, the supernatant was discarded, and the mixture was washed and dried to obtain acidified fish scale material.

[0014] Furthermore, the process of modifying acidified fish scales with NaAlO2 to obtain a synchronously activated aluminum-fish scale calcium composite material includes:

[0015] Acidified fish scale material with a mass ratio of 2-4:13.12-19.67 was mixed with NaAlO2 powder, and deionized water was added before a water bath reaction was carried out. The supernatant was discarded by centrifugation, and the mixture was washed and dried to obtain a synchronously activated aluminum-fish scale-calcium composite material.

[0016] Furthermore, the fish scales are grass carp scales, which are powdered and have a diameter of <0.178 μm.

[0017] Furthermore, the washing process involves circulating deionized water until neutral, followed by centrifugation at 5000 rpm for 3-5 minutes after each wash.

[0018] Furthermore, the drying temperature is 60°C and the drying time is 12 hours.

[0019] Furthermore, the water bath temperature for the water bath reaction is 60-100℃, and the time is 1-3 hours.

[0020] Furthermore, the oscillation treatment is performed at a temperature of 25°C for 24 hours.

[0021] Secondly, the present invention provides a synchronously activated aluminum-fish-scale calcium composite material prepared by the one-step aluminum-modified fish-scale calcium defluorination material preparation method.

[0022] Secondly, the present invention provides applications of the aforementioned synchronously activated aluminum-fish-scale calcium composite material, including:

[0023] Applications in defluoridation in water treatment;

[0024] Application in the preparation of defluoridation products for water treatment.

[0025] The beneficial effects of this invention are as follows: using waste fish scales as raw material, a high-performance defluorination material was successfully prepared through mineral removal with hydrochloric acid and modification with sodium aluminate solution. Specifically, the hydrochloric acid treatment for mineral removal yields acidified fish scales; sodium aluminate not only provides an aluminum source, but its moderately alkaline environment also effectively decomposes the organic matrix of the fish scales and optimizes their structure. Through this treatment, the material surface is simultaneously loaded with active aluminum components while effectively retaining amino groups; the synergistic effect of these two processes significantly improves the material's defluorination efficiency. Attached Figure Description

[0026] Figure 1 The graph shows the effect of synchronously activated composite aluminum-fish scale calcium defluorinating agent on the adsorption of fluorides at different temperatures; where a is the adsorption isotherm, b is the effect of adsorption dosage, c is the effect of pH, and d is the effect of coexisting anions. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments.

[0028] It should be noted that these embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Simple improvements to the method under the premise of the present invention are all within the scope of protection claimed by the present invention.

[0029] Example 1

[0030] A one-step method for preparing aluminum-modified fish-scale calcium defluorination material specifically includes the following steps:

[0031] Step 1: Mix 20g of fish scales with 5wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and treat with constant temperature shaking at 25℃ for 24h;

[0032] Step 2: After centrifugation, the supernatant of the reaction solution is discarded, and the solution is washed with deionized water until neutral. It is then dried at 60°C for 12 hours to obtain acidified fish scale material (AFS).

[0033] Step 3: Take 2g of the sample from step 2 and mix it with 13.12g of NaAlO2 powder in a beaker, and add 20ml of deionized water;

[0034] Step 4: Place the mixture from step 3 in a water bath at 60°C and react for 3 hours;

[0035] Step 5: After centrifuging the reaction solution from step 4, discard the supernatant, wash with deionized water until neutral, and dry at 60℃ for 12 hours;

[0036] Step 6: Grind the sample from step 5 and pass it through an 80-mesh sieve to obtain synchronously activated aluminum fish scale calcium composite material P01.

[0037] The application of a synchronously activated aluminum-fish scale calcium composite material in water treatment defluoridation: When the above-mentioned PO1 sample was placed under adsorption conditions of 10 mg / L initial fluoride ion concentration (theoretical concentration, the same below), 1 g / L adsorbent dosage, and pH 5, the defluoridation rate of the sample reached 91.82%, and the experimental adsorption capacity was 9.14 mg / g.

[0038] Example 2:

[0039] A one-step method for preparing aluminum-modified fish-scale calcium defluorination material specifically includes the following steps:

[0040] Step 1: Mix 20g of fish scales with 2wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and treat with constant temperature shaking at 25℃ for 24h;

[0041] Step 2: After centrifugation, the supernatant of the reaction solution is discarded, and the solution is washed with deionized water until neutral. It is then dried at 60°C for 12 hours to obtain acidified fish scale material (AFS).

[0042] Step 3: Take 2g of the sample from step 2 and mix it with 13.12g of NaAlO2 powder in a beaker, and add 20ml of deionized water;

[0043] Step 4: Place the mixture from step 3 in a water bath at 60°C and react for 2 hours;

[0044] Step 5: After centrifuging the reaction solution from step 4, discard the supernatant, wash with deionized water until neutral, and dry at 60℃ for 12 hours;

[0045] Step 6: Grind the sample from step 5 and pass it through an 80-mesh sieve to obtain synchronously activated aluminum-fish scale calcium composite material PO2.

[0046] The application of a synchronously activated aluminum-fish scale calcium composite material in water treatment defluoridation: When the above-mentioned PO2 sample was placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the defluoridation rate of the sample reached 90.86%, and the experimental adsorption capacity was 9.35 mg / g.

[0047] Example 3:

[0048] A one-step method for preparing aluminum-modified fish-scale calcium defluorination material specifically includes the following steps:

[0049] Step 1: Mix 20g of fish scales with 3wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and treat with constant temperature shaking at 25℃ for 24h;

[0050] Step 2: After centrifugation, the supernatant of the reaction solution is discarded, and the solution is washed with deionized water until neutral. It is then dried at 60°C for 12 hours to obtain acidified fish scale material (AFS).

[0051] Step 3: Take 2g of the sample from step 2 and mix it with 19.67g of NaAlO2 powder in a beaker, and add 20ml of deionized water;

[0052] Step 4: Place the mixture from step 3 in a water bath at 100°C and react for 4 hours;

[0053] Step 5: After centrifuging the reaction solution from step 4, discard the supernatant, wash with deionized water until neutral, and dry at 60℃ for 12 hours;

[0054] Step 6: Grind the sample from step 5 and pass it through an 80-mesh sieve to obtain crude aluminum-modified fish scale-derived biopolymer defluorinating agent PO3.

[0055] The application of a synchronously activated aluminum-fish scale calcium composite material in water treatment defluoridation: When the above-mentioned PO3 sample was placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the defluoridation rate of the sample reached 91.66%, and the experimental adsorption capacity was 9.43 mg / g.

[0056] Example 4:

[0057] A one-step method for preparing aluminum-modified fish-scale calcium defluorination material includes the following steps:

[0058] Step 1: Mix 20g of fish scales with 4wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and treat with constant temperature shaking at 25℃ for 24h;

[0059] Step 2: After centrifugation, the supernatant of the reaction solution is discarded, and the solution is washed with deionized water until neutral. It is then dried at 60°C for 12 hours to obtain acidified fish scale material (AFS).

[0060] Step 3: Take 3g of the sample from step 2 and mix it with 13.12g of NaAlO2 powder in a beaker, and add 20ml of deionized water;

[0061] Step 4: Place the mixture from step 3 in a water bath at 60°C and react for 2 hours;

[0062] Step 5: After centrifuging the reaction solution from step 4, discard the supernatant, wash with deionized water until neutral, and dry at 60℃ for 12 hours;

[0063] Step 6: Grind the sample from step 5 and pass it through an 80-mesh sieve to obtain synchronously activated aluminum-fish scale calcium composite material PO4.

[0064] The application of a synchronously activated aluminum-fish scale calcium composite material in water treatment defluoridation: When the above-mentioned PO4 sample was placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the defluoridation rate of the sample reached 90.41%, and the experimental adsorption capacity was 9.10 mg / g.

[0065] Example 5:

[0066] A one-step method for preparing aluminum-modified fish-scale calcium defluorination material specifically includes the following steps:

[0067] Step 1: Mix 20g of fish scales with 5wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and treat with constant temperature shaking at 25℃ for 24h;

[0068] Step 2: After centrifugation, the supernatant of the reaction solution is discarded, and the solution is washed with deionized water until neutral. It is then dried at 60°C for 12 hours to obtain acidified fish scale material (AFS).

[0069] Step 3: Take 4g of the sample from step 2 and mix it with 13.12g of NaAlO2 powder in a beaker, and add 20ml of deionized water;

[0070] Step 4: Place the mixture from step 3 in a water bath at 80°C and react for 2 hours;

[0071] Step 5: After centrifuging the reaction solution from step 4, discard the supernatant, wash with deionized water until neutral, and dry at 60℃ for 12 hours;

[0072] Step 6: Grind the sample from step 5 and pass it through an 80-mesh sieve to obtain synchronously activated aluminum-fish scale calcium composite material P05.

[0073] The application of a synchronously activated aluminum-fish scale calcium composite material in water treatment defluoridation: When the above-mentioned PO5 sample was placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the defluoridation rate of the sample reached 94.76%, and the experimental adsorption capacity was 9.56 mg / g.

[0074] Example 6:

[0075] A one-step method for preparing aluminum-modified fish-scale calcium defluorination material specifically includes the following steps:

[0076] Step 1: Mix 20g of fish scales with 5wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and treat with constant temperature shaking at 25℃ for 24h;

[0077] Step 2: After centrifugation, the supernatant of the reaction solution is discarded, and the solution is washed with deionized water until neutral. It is then dried at 60°C for 12 hours to obtain acidified fish scale material (AFS).

[0078] Step 3: Take 2g of the sample from step 2 and mix it with 16.39g of NaAlO2 powder in a beaker, and add 20ml of deionized water;

[0079] Step 4: Place the mixture from step 3 in a water bath at 100°C and react for 3 hours;

[0080] Step 5: After centrifuging the reaction solution from step 4, discard the supernatant, wash with deionized water until neutral, and dry at 60℃ for 12 hours;

[0081] Step 6: Grind the sample from step 5 and pass it through an 80-mesh sieve to obtain synchronously activated aluminum-fish scale calcium composite material P06.

[0082] The application of a synchronously activated aluminum-fish scale calcium composite material in water treatment defluoridation: When the above-mentioned PO6 sample was placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the defluoridation rate of the sample reached 91.09%, and the experimental adsorption capacity was 9.17 mg / g.

[0083] Example 7:

[0084] A one-step method for preparing aluminum-modified fish-scale calcium defluorination material specifically includes the following steps:

[0085] Step 1: Mix 20g of fish scales with 2wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and treat with constant temperature shaking at 25℃ for 24h;

[0086] Step 2: After centrifugation, the supernatant of the reaction solution is discarded, and the solution is washed with deionized water until neutral. It is then dried at 60°C for 12 hours to obtain acidified fish scale material (AFS).

[0087] Step 3: Take 3g of the sample from step 2 and mix it with 16.39g of NaAlO2 powder in a beaker, and add 20ml of deionized water;

[0088] Step 4: Place the mixture from step 3 in a water bath at 80°C and react for 3 hours;

[0089] Step 5: After centrifuging the reaction solution from step 4, discard the supernatant, wash with deionized water until neutral, and dry at 60℃ for 12 hours;

[0090] Step 6: Grind the sample from step 5 and pass it through an 80-mesh sieve to obtain synchronously activated aluminum-fish scale calcium composite material P07.

[0091] The application of a synchronously activated aluminum-fish scale calcium composite material in water treatment defluoridation: When the above-mentioned PO7 sample was placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the defluoridation rate of the sample reached 90.62%, and the experimental adsorption capacity was 9.33 mg / g.

[0092] Example 8:

[0093] A one-step method for preparing aluminum-modified fish-scale calcium defluorination material specifically includes the following steps:

[0094] Step 1: Mix 20g of fish scales with 5wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and treat with constant temperature shaking at 25℃ for 24h;

[0095] Step 2: After centrifugation, the supernatant of the reaction solution is discarded, and the solution is washed with deionized water until neutral. It is then dried at 60°C for 12 hours to obtain acidified fish scale material (AFS).

[0096] Step 3: Take 3g of the sample from step 2 and mix it with 19.67g of NaAlO2 powder in a beaker, and add 20ml of deionized water;

[0097] Step 4: Place the mixture from step 3 in a water bath at 80°C and react for 3 hours;

[0098] Step 5: After centrifuging the reaction solution from step 4, discard the supernatant, wash with deionized water until neutral, and dry at 60℃ for 12 hours;

[0099] Step 6: Grind the sample from step 5 and pass it through an 80-mesh sieve to obtain synchronously activated aluminum-fish scale calcium composite material P08.

[0100] The application of a synchronously activated aluminum-fish scale calcium composite material in water treatment defluoridation: When the above-mentioned P08 sample was placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the defluoridation rate of the sample reached 92.96%, and the experimental adsorption capacity was 9.13 mg / g.

[0101] In the above embodiments, the fish scales can be grass carp scales, crucian carp scales, etc.

[0102] Comparative Example 1

[0103] A method for preparing a fish scale-derived fluoride remover (FS) specifically includes the following steps:

[0104] Step 1: Wash the grass carp scales and dry them until they reach a constant weight;

[0105] Step 2: Grind the dried product from Step 1 and pass it through an 80-mesh sieve to obtain fish scale defluorinating agent (FS).

[0106] In water treatment for defluoridation, with an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, and an adsorption condition of pH 5 (optimal pH condition), the defluoridation rate was 75.21%, and the experimental adsorption capacity was 7.72 mg / g.

[0107] Comparative Example 2

[0108] A method for preparing an acidified fish scale defluoridating agent (AFS) specifically includes the following steps:

[0109] Step 1: Mix 20g of grass carp scales with 5wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and treat with constant temperature shaking at 25℃ for 24h;

[0110] Step 2: After centrifugation, the supernatant is discarded, the mixture is washed with deionized water until neutral, and dried at 60°C for 12 hours to obtain acidified fish scales.

[0111] Step 3: Grind the dried product from step 2 and pass it through an 80-mesh sieve to obtain acidified fish scale defluoridating agent (AFS).

[0112] In water treatment for defluoridation, with an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, and an adsorption condition of pH 5, the defluoridation rate was 80.24%, and the experimental adsorption capacity was 8.07 mg / g.

[0113] Comparative Example 3

[0114] A method for preparing an alkali-activated fish scale defluoridating agent (AAFS) specifically includes the following steps:

[0115] Step 1: Mix 20g of grass carp scales with 5wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and treat with constant temperature shaking at 25℃ for 24h;

[0116] Step 2: After centrifugation, the supernatant is discarded, the mixture is washed with deionized water until neutral, and dried at 60°C for 12 hours to obtain acidified fish scales.

[0117] Step 3: Mix the sample from step 2 with 5wt% NaOH solution at a solid-liquid ratio of 1:10 (g / mL) and react in a water bath at 80℃ for 1 hour;

[0118] Step 4: After centrifugation, the supernatant is discarded, the mixture is washed with deionized water until neutral, and dried at 60°C for 12 hours to obtain alkali-activated fish scale material.

[0119] Step 5: Grind the dried product from step 4 and pass it through an 80-mesh sieve to obtain alkali-activated fish scale defluoridating agent (AAFS).

[0120] In water treatment for fluoride removal, with an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, and an adsorption condition of pH 5, the fluoride removal rate was 83.70%. The experimental adsorption capacity was 8.36 mg / g.

[0121] Comparative Example 4

[0122] A method for preparing a sodium aluminate-modified fish scale-derived defluorinating agent specifically includes the following steps:

[0123] Step 1: Take 8g of grass carp scale powder and 13.12g of NaAlO2 powder and mix them in a beaker, then add 20ml of deionized water;

[0124] Step 2: Place the mixture from Step 1 in a water bath at 80°C and react for 2 hours;

[0125] Step 3: After centrifuging the reaction solution from step 2, discard the supernatant, wash with deionized water until neutral, and dry at 60°C for 12 hours.

[0126] Step 4: Grind the dried product from step 3 and pass it through an 80-mesh sieve to obtain sodium aluminate-modified fish scale defluorinating agent.

[0127] In water treatment for fluoride removal, with an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, and an adsorption condition of pH 5, the fluoride removal rate was 83.13%. The experimental adsorption capacity was 8.35 mg / g.

[0128] Comparative Example 5

[0129] A method for preparing an Al(OH)3 modified fish scale-derived fluoride remover specifically includes the following steps:

[0130] Step 1: Place 8g of washed, dried and ground fish scales into 150mL of 0.1M Al(OH)3 solution.

[0131] Step 2: Place the mixture in a shaking chamber at 220 rpm for 1 hour at room temperature.

[0132] Step 3: Filter, recover and dry the sample from step 2 to obtain Al(OH)3 modified fish scale defluorinating agent.

[0133] In water treatment for fluoride removal, with an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, and an adsorption condition of pH 5, the fluoride removal rate was 63.32%. The experimental adsorption capacity was 6.51 mg / g.

[0134] Comparative Example 6

[0135] A method for preparing a defluorinating agent based on heat-treated fish scales specifically includes the following steps:

[0136] Step 1: Place the washed, dried and pulverized tilapia scales into a sealed container and heat the material to 550℃ at a heating rate of 20℃ / min.

[0137] Step 2: Hold at 550℃ for 1 hour (pyrolyze into carbon in muffle furnace), cool the pyrolyzed material to room temperature, and obtain a defluorinating agent based on heat-treated fish scales.

[0138] In water treatment for fluoride removal, with an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, and an adsorption condition of pH 5, the fluoride removal rate was 43.10%. The experimental adsorption capacity was 4.01 mg / g.

[0139] Comparative Example 7

[0140] A method for preparing a sodium hydroxide-modified fish scale-derived fluoride remover specifically includes the following steps:

[0141] Step 1: Take 20g of grass carp scale powder and mix it with 5wt% NaOH solution at a solid-liquid ratio of 1:5 (g / mL);

[0142] Step 2: Place the mixture from Step 1 in a water bath at 80°C and react for 2 hours;

[0143] Step 3: After centrifuging the reaction solution from step 2, discard the supernatant, wash with deionized water until neutral, and dry at 60°C for 12 hours.

[0144] Step 4: Grind the dried product from step 3 and pass it through an 80-mesh sieve to obtain sodium hydroxide-modified fish scale defluorinating agent.

[0145] In water treatment for fluoride removal, with an initial fluoride ion concentration of 10 mg / L, an adsorbent dosage of 1 g / L, and an adsorption condition of pH 5, the fluoride removal rate was 80.34%. The experimental adsorption capacity was 8.07 mg / g.

[0146] This invention embodiment (P05) achieves significant optimization based on existing fish scale-based defluorinating agents (as shown in Comparative Examples 1-7). The core improvement lies in the adoption of a two-stage modification strategy of "acid pretreatment + sodium aluminate (NaAlO2) modification". Specifically: (1) It inherits and optimizes the individual acid treatment step (comparative Example 2) and sodium hydroxide alkaline treatment (comparative Example 7), effectively removing impurities and exposing active sites; (2) It breaks through the traditional aluminum loading method (superior to the Al(OH)3 immersion method of Comparative Example 5), and uses NaAlO2 powder to react in an 80°C water bath, promoting the deep and uniform combination of aluminum species with the fish scale biopolymer network, forming more efficient defluorinating active sites; (3) It avoids the material structure damage caused by high-temperature pyrolysis in Comparative Example 6; (4) It is a more effective aluminum loading method than "acid treatment + sodium hydroxide alkaline activation" (comparative Example 3). (5) Compared to the adsorption capacity of 7.72 mg / g of the original fish scale powder (Comparative Example 1), the increase was 0.27 mg / g for acid pretreatment alone (Comparative Example 2), and 0.63 mg / g for sodium aluminate treatment alone (Comparative Example 4). However, the increase was 1.84 mg / g for the combined process "acid pretreatment + sodium aluminate (NaAlO2) modification", which is much greater than the sum of the two (0.90 mg / g), achieving an unexpected synergistic effect. Finally, under the same test conditions (10 mg / L F-, 1 g / L, pH 5), this process achieved a fluoride removal rate of up to 94.76% and an adsorption capacity of 9.56 mg / g, significantly surpassing other comparative methods. This demonstrates the superiority, practicality, and novelty of this composite modification strategy in improving the fluoride removal efficiency of fish scale-derived biomaterials.

[0147] It exhibits excellent stability in the pH range of 3-5. When the dosage is 1 g / L, the fluoride removal rate is always >90%, and the experimental adsorption capacity is stable at 9.10–9.56 mg / g. Figure 1 Figure a shows the adsorption isotherm diagram of fluoride according to Example 5 of this application. Under the same pH conditions (pH=5), the maximum theoretical adsorption capacities of fish scale powder, acidified fish scale, and synchronously activated composite aluminum-fish scale calcium for fluoride are 58.04, 66.05, and 118.53 mg / g, respectively. It is particularly noteworthy that the adsorption performance of the modified sodium aluminate is 46.4% higher than that of acidified fish scale and a significant 104.2% higher than that of fish scale powder.

[0148] This application investigated the effect of adsorbent dosage (0.01-1.0 g / L) on its defluorination performance (initial fluoride concentration 10 mg / L, pH 5.0, 25℃, shaking time 24 h). Figure 1As shown in Fig. b, the fluoride removal efficiency varies significantly with the increase in dosage: when the dosage increases from 0.01 g / L to 0.04 g / L, the fluoride ion removal rate increases significantly from 62.82% to 95.05%, which is due to the increase in the effective adsorption surface area providing more active sites. After exceeding 0.04 g / L, the growth of the removal efficiency tends to level off; it reaches 98.28% at 1.0 g / L. At this time, the adsorption sites tend to be saturated, and further increasing the adsorption dosage has little effect on improving the removal efficiency.

[0149] The adsorption performance of fluoride ions in 10 mg / L NaF solution is regulated by the initial pH value of the solution. As Figure 1 shown in Fig. c, the Zeta Potential is the Zeta potential. Within the range of pH 2.0 - 5.0, the adsorption efficiency increases with the increase in pH and reaches a peak at pH 5.0 (average adsorption capacity 9.56 mg / g, removal rate 94.76%). After that, it decreases with the further increase in pH. The measured value of pHpzc (4.84) indicates that when pH < pHpzc, the protonated surface is positively charged, and the adsorption of F- is promoted through electrostatic attraction; when pH > 5.0, the increase in the OH- concentration leads to competitive adsorption, and at the same time, the enhanced surface negative charge generates electrostatic repulsion, jointly reducing the F- removal rate. However, a certain adsorption efficiency is still observed under alkaline conditions, confirming that in addition to the electrostatic effect, the ligand exchange (i.e., the exchange of surface hydroxyl groups with F-) mechanism also plays a role.

[0150] Under the fixed conditions of this application (initial F- 10 mg / L, pH 5.0, 0.04 g / L), the influence of common anions (Cl 2- , - , 3- , , - , 2- , NO3 - , HCO3 - , CO3 2- , SO4 2- , PO4 3- ) in complex water bodies on the defluorination performance was further investigated. As Figure 1 shown in Fig. d, competitive adsorption exists for all co-existing anions, resulting in varying degrees of decline in the fluoride ion removal rate. Among them, the influence of Cl - and NO3 - is relatively weak, probably due to their binding mainly through weak outer-sphere complexation as low-affinity ligands; CO3 2- and HCO3 - may reduce the efficiency by changing the pH value of the solution and thus affecting the surface charge characteristics of the adsorbent; SO4 2- interferes because it can form outer or inner-sphere complexes; while PO4 3- exhibits the strongest competitive inhibition effect.

[0151] It is easy to see from the above comparison that the synchronously activated composite aluminum fish scale calcium of the present invention achieves the technical effect of "1+1>>2" by using hydrochloric acid to remove minerals and sodium aluminate for one-step modification. In practical applications, it further saves water treatment costs and has significant social, environmental and economic benefits.

[0152] By utilizing fish scales, a waste product from aquatic product processing, as the core raw material, this technology achieves the environmental goal of "treating waste with waste." Traditional treatment methods easily lead to environmental pollution and resource waste. This method transforms them into a high-value-added adsorbent, significantly reducing raw material costs while reducing environmental problems caused by solid waste accumulation at the source.

[0153] This invention employs a one-step simultaneous modification process, "acidification + one-step modification," innovatively coupling aluminum loading and bio-matrix modification into a single reaction step. This method significantly simplifies the preparation process, shortens the reaction time, and effectively avoids the additional energy and reagent consumption caused by multi-step operations. Compared with traditional multi-step processes, it saves 60% of energy consumption, and the amount of NaAlO2 used is reduced by 30% compared with traditional aluminum modification methods, greatly improving the synthesis efficiency and economy of the adsorbent.

[0154] The prepared adsorbent maintained a stable fluoride removal rate exceeding 90% within the pH range of 3.0-5.0. Based on the Langmuir model, the maximum theoretical adsorption capacity of the synchronously activated composite aluminum-fish scale calcium for fluoride ions was predicted to be 118.528 mg / g, significantly superior to similar bio-based materials (such as fish scale powder, which only adsorbed 2.41 mg / g). This material also exhibited high adsorption capacity for coexisting anions (Cl...). - NO3 - HCO3 - CO3 2- SO4 2- PO4 3- Even under interference, it maintains a removal rate of over 80%, and a relatively high removal rate (decreased by <5%), which is superior to traditional aluminum-modified materials (decreased by 15%). It demonstrates excellent anti-interference ability and environmental adaptability, and can effectively meet the actual treatment needs of complex water bodies.

[0155] The adsorption process conforms to the dominant mechanism of Langmuir monolayer chemisorption (R 2 =0.963) and pseudo-second-order dynamics model (R 2 =0.999), confirming the strong chemical bonding between the uniform active sites on the surface and fluoride ions. Meanwhile, the thermodynamic parameters (ΔG°<0, ΔH°>0) indicate that the adsorption is a spontaneously endothermic process, which is beneficial for maintaining high-efficiency adsorption performance under conditions ranging from room temperature to medium-high temperatures, providing theoretical support for practical engineering applications.

[0156] It combines environmental and economic benefits, providing an efficient and low-cost solution for the treatment of fluoride pollution in water bodies, and opening up new avenues for the resource utilization of waste fish scales, which is of great significance for promoting the development of circular economy and green water treatment technology.

[0157] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described with reference to preferred embodiments, those skilled in the art should understand that various changes in form and detail can be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method for preparing aluminum-modified fish-scale calcium fluoride-removal material in one step, characterized by, include: Fish scales are pretreated with acid to obtain acidified fish scales; Acidified fish scales were modified with NaAlO2 to obtain a synchronously activated aluminum-fish scale calcium composite material. The process of pretreating fish scales with acid to obtain acidified fish scales includes: Fish scales were mixed with 2-5wt% HCl solution at a solid-liquid ratio of 1g:5mL, shaken, centrifuged and the supernatant was discarded. The mixture was then washed and dried to obtain acidified fish scale material. The process of modifying acidified fish scales with NaAlO2 to obtain a synchronously activated aluminum-fish scale calcium composite material includes: Acidified fish scale material with a mass ratio of 2-4:13.12-19.67 was mixed with NaAlO2 powder, and deionized water was added for water bath reaction. After centrifugation and discarding the supernatant, the mixture was washed and dried to obtain synchronously activated aluminum fish scale calcium composite material.

2. The process for the preparation of one step aluminum modified fish scale calcium fluoride removing material as claimed in claim 1, wherein, The washing process involves circulating deionized water until neutral, followed by centrifugation at 5000 r / min for 3-5 min after each wash.

3. The process for the preparation of one step aluminum modified fish scale calcium fluoride removing material as claimed in claim 2, wherein, The drying temperature is 60℃ and the drying time is 12 h.

4. The process for the preparation of one step aluminum modified fish scale calcium fluoride removing material as claimed in claim 3, wherein, The water bath temperature for the water bath reaction is 60-100℃, and the time is 1-3 hours.

5. The process for the preparation of one step aluminum modified fish scale calcium fluoride removing material as claimed in claim 4, wherein, The oscillation treatment was performed at a temperature of 25°C for 24 hours.

6. The synchronously activated aluminum-fish scale calcium composite material prepared by the one-step aluminum-modified fish scale calcium defluorination material preparation method according to any one of claims 1-5.

7. Use of the synchronously activated aluminum fish scale calcium composite material of claim 6, characterized in that, include: Applications in defluoridation in water treatment; Application in the preparation of defluoridation products for water treatment.

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