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

Abstract

The invention relates to the technical field of environmental protection and water treatment, in particular to a preparation method and application of a one-step aluminum modified fish scale calcium defluorination material. The defluorination material with economical efficiency and high efficiency is successfully prepared through combination of hydrochloric acid demineralization pretreatment and a sodium metaaluminate one-step modification process; the removal rate of the prepared composite material to a 10mg / L fluorine ion solution can reach 94.76%, the theoretical maximum adsorption capacity reaches 118.53 mg / g, the actual test adsorption capacity reaches 9.56 mg / g, and stable and efficient adsorption performance is kept within the pH range of 3-6; the method is simple in technological process and mild in reaction condition, the material preparation cost is remarkably reduced, and an innovative solution with practicability and economical efficiency is provided for fluorine-containing wastewater treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection water treatment, and in particular to a one-step preparation method and application of aluminum-modified fish scale calcium defluoridation material. Background Art

[0002] Water is the source of human life. Compared with other water pollutants, fluoride is a persistent and harmful pollutant. At the same time, fluoride is also a trace nutrient that is vital to the health of both humans and animals. Humans mainly consume it in the form of drinking water. Intake of an appropriate amount of fluoride helps maintain the health of bones and teeth. However, due to the accelerated process of urbanization and the rapid growth of the world's population, fluoride pollution in water bodies has increased dramatically. Once the fluoride content in groundwater exceeds the permitted limit, it will cause serious health problems. Excessive intake may 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 occurrence of hypertension, cancer and neurological diseases.

[0003] Fish scales (FS)—a byproduct of aquatic product processing—show great potential for application due to their abundant reserves and low cost. Fish scales are often discarded as waste during aquatic processing processes such as canning, filleting, pickling, and smoking, with approximately 7.2 to 12 million tons of fish processing waste discarded globally each year. Fish scales are also a unique natural biomaterial, containing 40-90% organic protein, including significant amounts of type I collagen composed of proline, glycine, alanine, hydroxylamine lysine, and hydroxyproline, as well as 10-60% inorganic mineral components (primarily sodium, magnesium, and carbonates) ionically bound to phosphate groups in hydroxyapatite. The highly ordered, hierarchical microstructure and composition of fish scales are similar to those of human hard tissue, resulting in excellent biocompatibility, biodegradability, and mechanical properties. These scales have applications in tissue engineering, biofillers, wastewater treatment, and flexible electronics. However, due to their lack of commercial value, their practical applications 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. Coagulation and precipitation are two commonly used methods for high fluoride concentrations in water, but these methods also produce a large amount of residue while removing fluoride from the water. Electrocoagulation technology can effectively remove fluoride ions from water without causing secondary pollutants, but it consumes a large amount of electricity and is very expensive. Various methods based on the principles of nanofiltration and reverse osmosis can reduce fluoride concentrations to below the limits set by the WHO, but their operating costs are very high and they are very expensive.

[0005] Adsorption is the process of purifying water by adsorbing fluoride from it using adsorbents. Using adsorbents for defluoridation offers numerous advantages, including low cost, ease of operation, excellent removal efficiency, and recyclability. Commonly used adsorbents for defluoridation 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, representing poor adsorption capacity.

[0006] Existing methods for preparing fluorine removal materials usually involve multi-step processing, such as acid treatment followed by alkaline activation and final modification. This not only increases the difficulty of operation, but also leads to high energy consumption, increased costs, and difficulty in achieving large-scale application. Summary of the Invention

[0007] In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide a one-step preparation method and application of aluminum-modified fish scale calcium defluoridation material to solve the problems of insufficient performance of traditional materials, complex processes or high costs.

[0008] In order to solve the above problems, the present invention adopts the following technical solutions:

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

[0010] pre-treating the fish scales with acid to obtain acidified fish scales;

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

[0012] Furthermore, the fish scales are subjected to acid pretreatment to obtain acidified fish scales, comprising:

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

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

[0015] The acidified fish scale material and NaAlO2 powder are mixed in a mass ratio of 2-4:13.12-19.67, and deionized water is added to carry out water bath reaction; the supernatant is discarded by centrifugation, and the mixture is 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 powders with a diameter less than 0.178 m.

[0017] Furthermore, the washing is performed by circulating deionized water until the water becomes neutral, and centrifugation is performed at 5000 r / min for 3-5 minutes after each washing.

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

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

[0020] Furthermore, the temperature of the oscillation treatment is 25° C. and the time is 24 h.

[0021] In a second aspect, the present invention provides a synchronously activated aluminum fish scale calcium composite material prepared by the one-step method for preparing aluminum-modified fish scale calcium defluoridation material.

[0022] In a second aspect, the present invention provides an application of the synchronously activated aluminum fish scale calcium composite material, comprising:

[0023] Application in water treatment and fluoride removal;

[0024] Application in the preparation of water treatment and defluorination products.

[0025] The beneficial effect of the present invention lies in the successful preparation of a high-performance fluoride removal material using discarded fish scales as raw material, through hydrochloric acid demineralization and modification with sodium aluminate solution. The hydrochloric acid demineralization treatment produces acidified fish scales, while the sodium aluminate not only provides an aluminum source, but its moderately alkaline environment also effectively decomposes the scales' organic matrix and optimizes its structure. This treatment simultaneously loads the material's surface with active aluminum components and effectively retains amino groups. The synergistic effect of these two significantly enhances the material's fluoride removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The following are the effects of the simultaneous activation of composite aluminum fish scale calcium defluoridant on the adsorption of fluoride at different temperatures; a is the adsorption isotherm, b is the adsorption dose effect experiment, c is the pH effect experiment diagram, and d is the coexistence anion experiment diagram. DETAILED DESCRIPTION

[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, rather than to limit the present invention. Simple improvements to the method based on the concept of the present invention fall 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 defluoridation material specifically comprises the following steps:

[0031] Step 1: Mix 20 g of fish scales with 5 wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and shake at 25°C for 24 h.

[0032] Step 2: The reaction solution was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12 h 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 mixed system in the third step in a water bath at 60°C for 3 hours;

[0035] Step 5: The reaction solution in step 4 was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12h;

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

[0037] A synchronously activated aluminum fish scale calcium composite material is used in water treatment and fluoride removal. When the above-mentioned P01 sample is 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 fluoride removal rate of the sample can reach 91.82%, and the experimental adsorption capacity is 9.14 mg / g.

[0038] Example 2:

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

[0040] Step 1: Mix 20 g of fish scales with 2 wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and shake at 25°C for 24 h.

[0041] Step 2: The reaction solution was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12 h 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 mixed system in step 3 in a water bath at 60°C for 2 hours;

[0044] Step 5: The reaction solution in step 4 was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12h;

[0045] Step 6: Grind the sample from the fifth step and pass it through an 80-mesh sieve to obtain a synchronously activated aluminum fish scale calcium composite material P02.

[0046] A synchronously activated aluminum fish scale calcium composite material is used in water treatment and fluoride removal. When the above-mentioned P02 sample is placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the fluoride removal rate of the sample can reach 90.86%, and the experimental adsorption capacity is 9.35 mg / g.

[0047] Example 3:

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

[0049] Step 1: Mix 20 g of fish scales with 3 wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and shake at 25°C for 24 h.

[0050] Step 2: The reaction solution was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and 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 mixed system in step 3 in a water bath at 100°C for 4 hours;

[0053] Step 5: The reaction solution in step 4 was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12h;

[0054] Step 6: Grind the sample from step 5 and pass it through an 80-mesh sieve to obtain aluminum-substituted alkali crude fish scale-derived biopolymer defluoridant P03.

[0055] A synchronously activated aluminum fish scale calcium composite material is used in water treatment and fluoride removal. When the above-mentioned P03 sample is placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the fluoride removal rate of the sample can reach 91.66%, and the experimental adsorption capacity is 9.43 mg / g.

[0056] Example 4:

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

[0058] Step 1: Mix 20 g of fish scales with 4 wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and shake at 25°C for 24 h.

[0059] Step 2: The reaction solution was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12 h 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 mixed system in step 3 in a water bath at 60°C for 2 hours;

[0062] Step 5: The reaction solution in step 4 was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12h;

[0063] Step 6: Grind the sample from the fifth step and pass it through an 80-mesh sieve to obtain a synchronously activated aluminum fish scale calcium composite material P04.

[0064] A synchronously activated aluminum fish scale calcium composite material is used in water treatment and fluoride removal. When the above-mentioned P04 sample is placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the fluoride removal rate of the sample can reach 90.41%, and the experimental adsorption capacity is 9.10 mg / g.

[0065] Example 5:

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

[0067] Step 1: Mix 20 g of fish scales with 5 wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and shake at 25°C for 24 h.

[0068] Step 2: The reaction solution was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12 h 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 mixed system in the third step in a water bath at 80°C for 2 hours;

[0071] Step 5: The reaction solution in step 4 was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12h;

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

[0073] A synchronously activated aluminum fish scale calcium composite material is used in water treatment and fluoride removal. When the above-mentioned P05 sample is placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the fluoride removal rate of the sample can reach 94.76%, and the experimental adsorption capacity is 9.56 mg / g.

[0074] Example 6:

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

[0076] Step 1: Mix 20 g of fish scales with 5 wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and shake at 25°C for 24 h.

[0077] Step 2: The reaction solution was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and 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 mixed system in step 3 in a water bath at 100°C for 3 hours;

[0080] Step 5: The reaction solution in step 4 was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12h;

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

[0082] A synchronously activated aluminum fish scale calcium composite material is used in water treatment and fluoride removal. When the above-mentioned P06 sample is placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the fluoride removal rate of the sample can reach 91.09%, and the experimental adsorption capacity is 9.17 mg / g.

[0083] Example 7:

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

[0085] Step 1: Mix 20 g of fish scales with 2 wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and shake at 25°C for 24 h.

[0086] Step 2: The reaction solution was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and 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 mixed system in the third step in a water bath at 80°C for 3 hours;

[0089] Step 5: The reaction solution in step 4 was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12h;

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

[0091] A synchronously activated aluminum fish scale calcium composite material is used in water treatment and fluoride removal. When the above-mentioned P07 sample is placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the fluoride removal rate of the sample can reach 90.62%, and the experimental adsorption capacity is 9.33 mg / g.

[0092] Example 8:

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

[0094] Step 1: Mix 20 g of fish scales with 5 wt% HCl solution at a solid-liquid ratio of 1:5 (g / mL) and shake at 25°C for 24 h.

[0095] Step 2: The reaction solution was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12 h 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 mixed system in the third step in a water bath at 80°C for 3 hours;

[0098] Step 5: The reaction solution in step 4 was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12h;

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

[0100] A synchronously activated aluminum fish scale calcium composite material is used in water treatment and fluoride removal. When the above-mentioned P08 sample is placed under adsorption conditions of 10 mg / L initial fluoride ion concentration, 1 g / L adsorbent dosage, and pH 5, the fluoride removal rate of the sample can reach 92.96%, and the experimental adsorption capacity is 9.13 mg / g.

[0101] The fish scales in the above embodiment can be grass carp scales, crucian carp scales, etc.

[0102] Comparative Example 1

[0103] A method for preparing a fish scale-derived defluoridant (FS) comprises the following steps:

[0104] Step 1: Wash the grass carp scales and dry them to constant weight;

[0105] Step 2: Grind the dried product in the first step and pass it through an 80-mesh sieve to obtain a fish scale source defluoridant (FS).

[0106] In the application of fluoride removal in water treatment, the initial fluoride ion concentration is 10 mg / L, the adsorbent dosage is 1 g / L, and under the adsorption conditions of pH 5 (optimal pH conditions), the fluoride removal rate is 75.21% and the experimental adsorption capacity is 7.72 mg / g.

[0107] Comparative Example 2

[0108] A method for preparing an acidified fish scale source defluoridant (AFS) comprises the following steps:

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

[0110] Step 2: After the reaction solution is centrifuged, the supernatant is discarded, the solution 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 in the second step and pass it through an 80-mesh sieve to obtain an acidified fish scale source defluoridant (AFS).

[0112] In the application of fluoride removal in water treatment, the initial fluoride ion concentration is 10 mg / L, the adsorbent dosage is 1 g / L, and the adsorption conditions are pH 5. The fluoride removal rate is 80.24% and the experimental adsorption capacity is 8.07 mg / g.

[0113] Comparative Example 3

[0114] A method for preparing an alkali-activated fish scale defluoridant (AAFS) comprises the following steps:

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

[0116] Step 2: After the reaction solution is centrifuged, the supernatant is discarded, the solution 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 5 wt% NaOH solution at a solid-liquid ratio of 1:10 (g / mL) and react in a water bath at 80°C for 1 h;

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

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

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

[0121] Comparative Example 4

[0122] A method for preparing a sodium metaaluminate-modified fish scale-derived defluoridant comprises 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, and add 20ml of deionized water;

[0124] Step 2: Place the mixed system from the first step in a water bath at 80°C for 2 hours;

[0125] Step 3: The reaction solution from step 2 was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12h;

[0126] Step 4: Grind the dried product in the third step and pass it through an 80-mesh sieve to obtain a sodium aluminate modified fish scale source defluoridant.

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

[0128] Comparative Example 5

[0129] A method for preparing an Al(OH)3-modified fish scale-derived defluoridant comprises the following steps:

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

[0131] Step 2: Place the mixture in a shaker at 220 rpm for 1 h at room temperature.

[0132] Step 3: Filter, recover and dry the sample in the second step to obtain an Al(OH)3-modified fish scale source defluoridant.

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

[0134] Comparative Example 6

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

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

[0137] The second step is to maintain the temperature at 550°C for 1 hour (pyrolysis in a muffle furnace to convert into carbon), and cool the pyrolyzed material to room temperature to obtain a defluorination agent based on heat-treated fish scales.

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

[0139] Comparative Example 7

[0140] A method for preparing a sodium hydroxide-modified fish scale-derived defluoridating agent comprises the following steps:

[0141] Step 1: Take 20g 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 mixed system from the first step in a water bath at 80°C for 2 hours;

[0143] Step 3: The reaction solution from step 2 was centrifuged and the supernatant was discarded, washed with deionized water until neutral, and dried at 60°C for 12h;

[0144] Step 4: Grind the dried product in the third step and pass it through an 80-mesh sieve to obtain a sodium hydroxide-modified fish scale source defluoridant.

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

[0146] The embodiment of the present invention (P05) has achieved significant optimization on the basis of the existing fish scale-based defluoridation agent (as shown in Comparative Examples 1-7). The core improvement lies in the adoption of a secondary modification strategy of "acid pretreatment + sodium aluminate (NaAlO2) modification". Specifically: (1) Inheriting and optimizing the separate acid treatment steps (comparative example 2) and sodium hydroxide alkaline treatment (comparative example 7), effectively removing impurities and exposing active sites; (2) Breaking through the traditional aluminum loading method (better than the Al(OH)3 immersion method of comparative example 5), using NaAlO2 powder to react in an 80°C water bath to promote the deep and uniform combination of aluminum species with the fish scale biopolymer network, forming more efficient defluoridation active sites; (3) Avoiding the material structure damage caused by high temperature pyrolysis of comparative example 6; (4) A more effective aluminum loading method than "acid treatment + sodium hydroxide alkaline activation" (comparative example 3). (5) Compared with the adsorption capacity of 7.72 mg / g of the original fish scale powder (Comparative Example 1), the increment of acid pretreatment alone (Comparative Example 2) was 0.27 mg / g, and the increment of sodium aluminate treatment alone (Comparative Example 4) was 0.63 mg / g. The increment of the combined process "acid pretreatment + sodium aluminate (NaAlO2) modification" was 1.84 mg / g, which was much greater than the sum of the two 0.90 mg / g, achieving an unexpected synergistic effect. Ultimately, the process achieved a fluorine removal rate of up to 94.76% and an adsorption capacity of 9.56 mg / g under the same test conditions (10 mg / L F-, 1 g / L, pH 5), significantly surpassing other comparative methods, demonstrating the superiority, practicality and novelty of the composite modification strategy in improving the fluorine removal efficiency of fish scale-derived biomaterials.

[0147] It exhibits excellent stability in the pH range of 3-5. When the dosage is 1g / L, the fluoride removal rate is always >90%, and the experimental adsorption capacity is stable at 9.10–9.56mg / g. Figure 1 Figure a shows the adsorption isotherm of fluoride in this application (Example 5). 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 after modification with sodium metaaluminate, its adsorption performance is improved by 46.4% compared to acidified fish scale, and a significant improvement of 104.2% compared to fish scale powder.

[0148] This application investigated the effect of adsorbent dosage (0.01-1.0 g / L) on its fluoride removal performance (initial fluoride concentration 10 mg / L, pH 5.0, 25°C, oscillation time 24 h). Figure 1As shown in Figure b, the fluoride removal efficiency changes significantly with the increase of 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 of 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 Figure c, Zeta Potential is the Zeta potential. In the range of pH 2.0 - 5.0, the adsorption efficiency increases with the increase of pH and reaches the peak at pH 5.0 (average adsorption capacity 9.56 mg / g, removal rate 94.76%). After that, it decreases with the further increase of 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 by electrostatic attraction; when pH > 5.0, the increase of OH- concentration leads to competitive adsorption, and at the same time, the enhancement of 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 fixed conditions (initial F- 10 mg / L, pH 5.0, 0.04 g / L) of this application, the effects of common anions (Cl - , NO3 - , HCO3 - , CO3 2- , SO4 2- , PO4 3- ) in complex water bodies on the defluorination performance were further investigated. As Figure 1 shown in Figure d, competitive adsorption exists for all co-existing anions, resulting in varying degrees of decline in the fluoride ion removal rate. Among them, the effects of Cl - and NO3 - are 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 surface charge characteristics of the adsorbent by altering the solution pH value; SO4 2- interferes because it can form outer-sphere or inner-sphere complexes; while PO4 3- shows the strongest competitive inhibition effect.

[0151] Through the above comparison, it is not difficult to find 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, which further saves water treatment costs in practical applications and has significant social, environmental and economic benefits.

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

[0153] This method utilizes a one-step, simultaneous modification process called "acidification + one-step modification," innovatively coupling aluminum loading and biomatrix modification in a single reaction step. This significantly simplifies the preparation process, shortens reaction time, and effectively avoids the additional energy and reagent consumption associated with multiple steps. Compared to traditional multi-step processes, it saves 60% energy and uses 30% less NaAlO₂ than traditional aluminum modification methods, significantly improving the efficiency and cost-effectiveness of the adsorbent synthesis.

[0154] The prepared adsorbent has a stable removal rate of more than 90% for fluoride in the pH range of 3.0-5.0. According to the Langmuir model, it can be predicted that the maximum theoretical adsorption capacity of synchronously activated composite aluminum fish scale calcium for fluoride ions is 118.528 mg / g, which is much better than similar bio-based materials (such as fish scale powder with an adsorption capacity of only 2.41 mg / g). - 、NO3 - 、HCO3 - 、CO3 2- 、SO4 2- PO4 3- ) still maintains a removal rate of over 80% under interference, and maintains a high removal rate under interference (decline <5%), which is better than traditional aluminum-modified materials (decline 15%). It shows 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 Langmuir monolayer chemical adsorption dominant mechanism (R 2 =0.963) and the pseudo-second-order kinetic model (R 2 =0.999), confirming the strong chemical bonding between the uniform surface active sites and the fluoride ions. Furthermore, the thermodynamic parameters (ΔG° < 0, ΔH° > 0) indicate that adsorption is a spontaneous endothermic process, which facilitates high adsorption performance at room to medium-high temperatures, providing theoretical support for practical engineering applications.

[0156] It has both environmental and economic benefits, not only providing an efficient and low-cost solution for the treatment of fluorine pollution in water bodies, but also opening up a new way to utilize waste fish scales as resources, which is of great significance to 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 limiting. Although the present invention has been described with reference to the preferred embodiments of the present invention, it should be understood by those skilled in the art that various changes can be made in form and details without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A one-step method for preparing aluminum-modified fish scale calcium defluoridation material, characterized in that: include: pre-treating the fish scales with acid to obtain acidified fish scales; The acidified fish scales were aluminum-modified using NaAlO2 to obtain a synchronously activated aluminum fish scale calcium composite material.

2. The method for preparing a one-step aluminum-modified fish scale calcium defluoridation material according to claim 1, wherein: The acid pretreatment of the fish scales to obtain acidified fish scales comprises: The fish scales were mixed with 2-5 wt% HCl solution at a solid-liquid ratio of 1 g:5 mL, and then shaken. The mixture was centrifuged and the supernatant was discarded. The mixture was washed and dried to obtain an acidified fish scale material.

3. The method for preparing the one-step aluminum-modified fish scale calcium defluoridation material according to claim 2, wherein: The method of aluminum-modifying the acidified fish scales with NaAlO2 to obtain a synchronously activated aluminum fish scale calcium composite material comprises: The acidified fish scale material and NaAlO2 powder are mixed in a mass ratio of 2-4:13.12-19.67, and deionized water is added to carry out water bath reaction; the supernatant is discarded by centrifugation, and the mixture is washed and dried to obtain a synchronously activated aluminum fish scale calcium composite material.

4. The method for preparing a one-step aluminum-modified fish scale calcium defluoridation material according to claim 3, wherein: The fish scales are grass carp scales, which are powders with a diameter less than 0.178 m.

5. The method for preparing the one-step aluminum-modified fish scale calcium defluoridation material according to claim 4, wherein: The washing is performed by circulating deionized water until the solution becomes neutral, and centrifuging at 5000 r / min for 3-5 minutes after each washing.

6. The method for preparing the one-step aluminum-modified fish scale calcium defluoridation material according to claim 5, characterized in that: The drying temperature is 60° C. and the drying time is 12 h.

7. The method for preparing a one-step aluminum-modified fish scale calcium defluoridation material according to claim 6, wherein: The water bath temperature of the water bath reaction is 60-100° C., and the reaction time is 1-3 hours.

8. The method for preparing a one-step aluminum-modified fish scale calcium defluoridation material according to claim 7, wherein: The shaking treatment was performed at a temperature of 25° C. for 24 h.

9. A synchronously activated aluminum-fish-scale calcium composite material prepared by the one-step aluminum-modified fish-scale calcium defluoridation material preparation method according to any one of claims 1 to 8.

10. The use of the synchronously activated aluminum fish scale calcium composite material according to claim 9, characterized in that: include: Application in water treatment and fluoride removal; Application in the preparation of water treatment and defluorination products.

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