Preparation of rod-like nanometer hydroxyapatite material and application thereof

Abstract

The present application relates to the preparation method of nano-hydroxyapatite and its application in the field of remediation of heavy metal complex pollution in soil, which solves the problems of complex process in preparation of nano-hydroxyapatite from waste and low efficiency in solidification and stabilization of heavy metal complex pollution in soil.The present application provides a preparation method of rod-shaped nano-hydroxyapatite and its application: ultrasonic cleaning and drying of conospiral shell, then high-temperature calcination and grinding to obtain shell powder;water digestion, aging, and dissolution with dilute nitric acid;titration of quantitative diammonium hydrogen phosphate solution according to the calcium-phosphorus molar ratio of 1.67, ultrasonic treatment for 20-30 min;adjusting the pH of the mixed solution to 8-12 with 8%-10% ammonia water, then ultrasonic treatment, and then aging in a water bath at 60-90 DEG C for 8-48 h, cooling, centrifugation, washing, drying, and grinding to obtain rod-shaped nano-hydroxyapatite.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation and remediation of soil with heavy metal complex pollution, specifically to a method for preparing rod-shaped nano-hydroxyapatite material and its application in the remediation of soil with lead, cadmium, and zinc complex pollution. Background Technology

[0002] Cone snails are a common seafood in the Jiangsu, Zhejiang, Fujian, and Guangdong-Guangxi regions. According to the "Illustrated Guide to Extant Intertidal Shellfish in the Beibu Gulf of China," cone snails are found in places such as Beihai Yintan Town, Leizhou in Guangdong, Haikou in Hainan, and Hongtang in Sanya. The average biomass of this species in Hainan is approximately 40.74 individuals / m³. 2 and 472.07 g / m 2 The largest biomass was found in the Hongtang tidal flat area of ​​Sanya City (100 cells / m²). 2 1041 g / m 2 Furthermore, in recent years, with the expansion of sea cucumber aquaculture, the reproduction rate of cone snails, which share similar feeding habits with sea cucumbers, has been increasing dramatically. According to the "China Fisheries Yearbook 2018" published by the Fisheries Bureau of the Ministry of Agriculture and Rural Affairs, my country's total shellfish production exceeded 15 million tons per year in 2017, making it the world's largest shellfish producer. However, this increased production has also brought a serious problem: due to low resource utilization, only a small amount of shellfish is used as soil conditioner or feed additives during the processing and utilization of shellfish resources. The vast majority of snail shells are randomly piled up on mudflats or transported to landfills as ordinary garbage. This indiscriminate dumping of waste exacerbates the environmental burden and resource waste.

[0003] Heavy metal pollution in soil often involves a single metal element as the predominant element, accompanied by other elements, resulting in complex pollution with multiple metals. For example, in waste battery processing and recycling sites, soil lead concentrations can reach as high as 12,000 mg / kg, while copper and zinc levels are also severely exceeded (1,800–2,200 mg / kg). Lead-zinc mine tailings landfills or wastewater irrigation areas also exhibit excessive levels of multiple metals such as lead, cadmium, zinc, and arsenic. Chemical passivation remediation aims to reduce pollution risk by adding stabilizers to the soil to regulate and alter the physicochemical properties of heavy metals. This induces a series of reactions, including adsorption, complexation, precipitation, ion exchange, and redox reactions, reducing their bioavailability and mobility in the soil environment, thereby decreasing their toxicity to plants and animals. This remediation method, due to its low cost, rapid remediation, and simple operation, is highly advantageous for remediating large areas of low- to medium-level soil pollution and better meets the urgent needs of my country in controlling heavy metal pollution in soil and ensuring the safe production of agricultural products.

[0004] Cone snail shells, as a type of molluskaloid resource, are the shells of animals belonging to the family Cone snails. Their operculum can be used to treat conjunctivitis, and the shell powder can be used to treat hemorrhoids. They also have the effects of clearing heat and detoxifying, and improving eyesight. The main component of cone snail shells is aragonite-phase calcium carbonate, with a content of over 95%, and trace elements such as Fe, Mn, Al, and Cu, while the content of harmful elements Pb, Cd, Zn, and As is extremely low. Cheng et al. (2023) reviewed the current development of marine molluskaloid resources in three areas: bone repair, health and medicinal value, and drug carriers, which has greatly promoted the progress of the biomedical field. Furthermore, they summarized the applications of marine molluskaloid resources in the low-cost, high-efficiency adsorption and purification of crude oil, heavy metal ions, dyes, and other impurities.

[0005] Phosphorus-containing materials not only provide the phosphorus nutrients needed for plant growth, but also serve as passivation and remediation materials for heavy metal contaminated soils, making them one of the most popular materials for remediation of heavy metal-contaminated soils. Hydroxyapatite has the chemical formula Ca. 10 (PO4)6(OH)2 is an important inorganic component of biological bones and teeth. It is characterized by its low cost, easy availability, stable properties, and strong ion exchange capacity, making it an ideal new type of environmental functional material. Research has found that PO4 in soil... 3- Pb and Cd can be immobilized through various pathways, especially Pb. The currently accepted main stabilization mechanism includes Pb-PO4. 3- Cd-PO4 3- Precipitation (including direct precipitation and lime effect) and PO4 3- Adsorption of Pb and Ca (surface adsorption, ion exchange adsorption). Currently, research on the removal of heavy metals using nanoscale hydroxyapatite materials mainly focuses on aqueous solutions, while research on the passivation adsorption of heavy metal ions in soil is relatively limited. Soil environments are complex and variable, with numerous factors influencing the bioavailability of heavy metals, and various heavy metal ions exhibit competitive or synergistic adsorption. However, the effectiveness of nanoscale hydroxyapatite materials in passivating various metal ions in soil, and the optimal methods for preparing nanoscale hydroxyapatite materials with superior passivation adsorption properties for specific heavy metal-contaminated soils, require further in-depth research by those skilled in the art.

[0006] Therefore, based on previous technologies, developing a nano-hydroxyapatite material that can effectively remediate Pb-Cd-Zn composite contaminated soil has significant application value. Summary of the Invention

[0007] Based on the above analysis, the embodiments of the present invention aim to provide a method for preparing rod-shaped nano-hydroxyapatite materials and their application in the remediation of lead-cadmium-zinc heavy metal composite contaminated soil, in order to solve the problem of low passivation remediation efficiency of heavy metal composite pollution. Studies have shown that the nano-hydroxyapatite materials prepared by the method described in this invention have excellent remediation effects on Pb-Cd-Zn contaminated soil; moreover, no modifiers are added, resulting in low cost.

[0008] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0009] (1) Soak the collected snail shells in tap water for 2-3 days, then clean them with deionized water using ultrasound, and dry them in an oven at 60℃-80℃ for 10-24 hours.

[0010] (2) Place the snail shell obtained in step (1) into a corundum crucible, place it in a muffle furnace and calcine it at 900 ℃~1000 ℃ for 1 h~3 h. After it cools to room temperature, grind it and pass it through a 100-mesh sieve to obtain calcined snail shell powder.

[0011] (3) Weigh 5 g to 20 g of the snail shell powder obtained in step (2) and place it in a 500 mL Erlenmeyer flask. Add 25 mL to 200 mL of ultrapure water at 50 ℃ to 80 ℃ according to the ratio of m(water):m(snail shell powder) = 5:1 to 10:1. Place the flask in a magnetic stirring water bath and stir at 200 rpm / min to 500 rpm / min for 30 min to 60 min at a temperature of 50 ℃ to 80 ℃. Then, age the flask at 50 ℃ to 80 ℃ for 20 min to 60 min to obtain a crude calcium hydroxide slurry.

[0012] (4) Cool the calcium hydroxide crude slurry obtained in step (3) to room temperature, add 250 mL of nitric acid solution with a concentration of 0.67 mol / L to 2.69 mol / L, and wait until there is no obvious white precipitate, when the reaction is complete. Then centrifuge at 4000 rpm / min for 5 min to 10 min to obtain the supernatant. Adjust the pH of the supernatant to 10 to 11 with 0.1 mol / L hydrochloric acid or 0.1 mol / L sodium hydroxide solution to obtain solution A;

[0013] (5) Under magnetic stirring, add 100 mL of diammonium hydrogen phosphate solution with a concentration of 0.5 mol / L to 2.0 mol / L to the supernatant A obtained in step (4) at a rate of 5 mL / min. After the addition of diammonium hydrogen phosphate solution is completed, sonicate at 10 kHz to 40 kHz for 20 min to 30 min, and adjust the pH to 8 to 12 with 8% to 10% ammonia water.

[0014] (6) The product obtained in step (5) is sonicated at 10 kHz to 40 kHz for 10 min to 20 min, aged at 60 ℃ to 90 ℃ for 8 h to 48 h, and then naturally cooled to room temperature;

[0015] (7) Centrifuge the product obtained in step (6), wash with deionized water until the pH of the washing solution is about 7.0, wash twice with ethanol, dry in an oven at 60 ℃~80 ℃ for 10 h~15 h, grind, and obtain the rod-shaped nano hydroxyapatite.

[0016] The beneficial effects of the above technical solution are as follows: the raw materials are recycled waste resources, sourced locally (snail shells are collected from the Beibu Gulf), which aligns with the concept of "treating waste with waste." Compared to existing synthesis methods, the ultrasonic-assisted chemical co-precipitation method used in this invention has advantages such as simple operation, ease of learning, and easy promotion. Moreover, the synthesized hydroxyapatite is a novel nanomaterial that is low in cost, highly crystalline, and does not easily agglomerate.

[0017] The inventors further discovered in their research that, in the process of preparing rod-shaped nano-hydroxyapatite using the method described in this invention, the reaction temperature, endpoint pH value, and aging time play an important role in whether the prepared nano-hydroxyapatite has excellent passivation ability for Pb-Cd-Zn composite contaminated soil. The remediation effects of reaction temperature, endpoint pH value, and aging time under different conditions on Pb-Cd-Zn composite contaminated soil are significantly different. Attached Figure Description

[0018] Figure 1 The X-ray diffraction pattern of the rod-shaped nano-hydroxyapatite prepared in Example 1;

[0019] Figure 2 The infrared spectrum of the rod-shaped nano-hydroxyapatite prepared in Example 1;

[0020] Figure 3 The image shows the scanning electron microscope and energy dispersive spectroscopy (EDS) images of the rod-shaped nano-hydroxyapatite prepared in Example 1. Detailed Implementation

[0021] Example 1: Preparation of rod-shaped nano-hydroxyapatite materials

[0022] (1) Soak the collected snail shells in tap water for 3 days, then ultrasonically clean them with deionized water, and dry them in an oven at 80 ℃ for 12 h.

[0023] (2) Place the snail shell obtained in step (1) into a corundum crucible, place it in a muffle furnace and calcine it at 1000 °C for 2 h. After cooling to room temperature, grind it and pass it through a 100-mesh sieve to obtain calcined snail shell powder.

[0024] (3) Weigh 10 g of the snail shell powder obtained in step (2) and place it in a 500 mL Erlenmeyer flask. Add 60 mL of 60 °C ultrapure water according to the ratio of m(water):m(snail shell powder) = 6:1. Place the flask in a magnetic stirring water bath and stir at 400 rpm / min for 30 min at 60 °C. Then age the flask at 60 °C for 30 min to obtain calcium hydroxide crude slurry.

[0025] (4) Cool the calcium hydroxide crude slurry obtained in step (3) to room temperature, add 250 mL of nitric acid solution with a concentration of 1.36 mol / L, and wait until there is no obvious white precipitate, then the reaction is complete. Centrifuge at 4000 rpm / min for 5 min to obtain the supernatant. Adjust the pH of the supernatant to 10.5 with 0.1 mol / L hydrochloric acid or 0.1 mol / L sodium hydroxide solution to obtain solution A.

[0026] (5) Add 100 mL of 1.0 mol / L diammonium hydrogen phosphate solution to the supernatant A obtained in step (4) at a rate of 5 mL / min under magnetic stirring. After the addition of diammonium hydrogen phosphate solution is completed, sonicate at 25 kHz for 20 min and adjust the pH to 10 with 10% ammonia.

[0027] (6) The product obtained in step (5) was sonicated at 20 kHz for 20 min, aged at 70 ℃ for 8 h, and then naturally cooled to room temperature;

[0028] (7) Centrifuge the product obtained in step (6), wash with deionized water until the pH of the washing solution is about 7.0, wash twice with ethanol, dry in an oven at 80 ℃ for 12 hours, grind, and obtain the rod-shaped nano hydroxyapatite.

[0029] The rod-shaped nano-hydroxyapatite prepared in this embodiment was applied to the remediation of soil contaminated with heavy metals:

[0030] The test soil was collected from farmland in the mining area surrounding the Dachang Smelter in Nandan County, Hechi City, Guangxi Zhuang Autonomous Region (107°59'96''E, 24°85'61''W). Weeds, branches, stones, etc., were removed, and the soil was air-dried naturally. It was then sieved through a 100-mesh sieve, thoroughly mixed, and sealed for later use. Soil physicochemical properties: pH 6.51, total lead 624.92 mg / kg, total cadmium 14.51 mg / kg, total zinc 1348.90 mg / kg, and extractable concentrations of lead, cadmium, and zinc were 34.42 mg / kg, 3.71 mg / kg, and 79.60 mg / kg, respectively. Experimental soil remediation experiment: The prepared nano-hydroxyapatite material was added at a ratio of 3% to 100 ml of Pb-Cd-Zn composite contaminated soil and mixed thoroughly. The bottle was sealed with a perforated plastic cap and placed in a constant temperature and humidity incubator. Each treatment was replicated in triplicate, and a control group was included. Soil water holding capacity was maintained at approximately 70% of field capacity by weighing, and the temperature was kept at 25±2 ℃. After 10 days of incubation, soil samples were collected, air-dried, quartered, and sealed for preservation. The available lead, cadmium, and zinc in the soil were determined according to the standard "Determination of Eight Available Elements in Soil - Diethylenetriaminepentaacetic Acid Extraction-Inductively Coupled Plasma Atomic Emission Spectrometry" (HJ 804-2016). After remediation, the concentrations of lead, cadmium, and zinc in the soil decreased from 34.42 mg / kg, 3.71 mg / kg, and 79.60 mg / kg to 3.66 mg / kg, 2.42 mg / kg, and 38.46 mg / kg, respectively. The passivation rates for lead, cadmium, and zinc were 89.36%, 34.77%, and 51.68%, respectively.

Claims

1. A method for preparing rod-shaped nano-hydroxyapatite material, characterized in that: Nano-hydroxyapatite was prepared using waste cone snail shells as the main raw material via chemical co-precipitation synthesis. The material has a rod-like structure with an aspect ratio of 3.5~10.5 and a width of 20 nm. The preparation method includes the following steps: (1) Soak the collected snail shells in tap water for 2-3 days, then clean them with deionized water using ultrasound, and dry them in an oven at 60 ℃-80 ℃ for 10 h-24 h. (2) Place the snail shell obtained in step (1) into a corundum crucible, place it in a muffle furnace and calcine it at 900 ℃~1000 ℃ for 1 h~3 h. After it cools to room temperature, grind it and pass it through a 100-mesh sieve to obtain calcined snail shell powder. (3) Weigh 5 g to 20 g of the snail shell powder obtained in step (2) and place it in a 500 mL Erlenmeyer flask. Add 25 mL to 200 mL of ultrapure water at 50 ℃ to 80 ℃ according to the ratio of m(water):m(snail shell powder) = 5:1 to 10:

1. Place the flask in a magnetic stirring water bath and stir at 200 rpm / min to 500 rpm / min for 20 min to 60 min at a temperature of 50 ℃ to 80 ℃. Then, age the flask at 50 ℃ to 80 ℃ for 20 min to 60 min to obtain a crude calcium hydroxide slurry. (4) Cool the calcium hydroxide crude slurry obtained in step (3) to room temperature, add 250 mL of nitric acid solution with a concentration of 0.67 mol / L to 2.69 mol / L, and wait until there is no obvious white precipitate, then the reaction is complete. Centrifuge at 4000 rpm / min for 5 min to 10 min to obtain the supernatant. Adjust the pH of the supernatant to 10 to 11 with 0.1 mol / L hydrochloric acid or 0.1 mol / L sodium hydroxide solution to obtain solution A. (5) Under magnetic stirring, add 100 mL of diammonium hydrogen phosphate solution with a concentration of 0.5 mol / L to 2.0 mol / L to the supernatant A obtained in step (4) at a rate of 5 mL / min. After the addition of diammonium hydrogen phosphate solution is completed, sonicate at 10 kHz to 40 kHz for 20 min to 30 min, and adjust the pH to 8 to 12 with 8% to 10% ammonia water. (6) The product obtained in step (5) is sonicated at 10 kHz to 40 kHz for 10 min to 20 min, aged at 60 ℃ to 90 ℃ for 8 h to 48 h, and then naturally cooled to room temperature; (7) Centrifuge the product obtained in step (6), wash with deionized water until the pH of the washing solution is 7.0, wash twice with ethanol, dry in an oven at 60 ℃~80 ℃ for 10 h~15 h, grind to obtain the rod-shaped nano hydroxyapatite.

2. A rod-shaped nano-hydroxyapatite material prepared using the method of claim 1, characterized in that, It is a white powder and is a mesoporous material.

3. An application of a rod-shaped nano-hydroxyapatite material prepared using the method of claim 1, characterized in that, The prepared and synthesized nano-hydroxyapatite is used to treat soil heavy metal complex pollution.

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