Preparation method and application of active stable phosphating micro-nano zero-valent iron material
By using a co-thermal method to form a dense phosphating layer on the surface of zero-valent iron, active and stable phosphated micro- and nano-zero-valent iron materials were prepared, solving the problem of passivation of micro- and nano-zero-valent iron materials during storage, achieving high catalytic activity and stability, and simplifying the preparation process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NANKAI UNIV
- Filing Date
- 2024-05-15
- Publication Date
- 2026-08-04
AI Technical Summary
Existing micro/nano zero-valent iron materials are prone to forming an iron oxide shell passivation layer during synthesis and storage, which leads to reduced catalytic activity and makes it difficult to achieve stability and high-efficiency catalytic activity.
A dense and uniform phosphating layer was formed on the surface of zero-valent iron using a co-heating method. The phosphine gas generated by the decomposition of NaH2PO2 reacted with the micro- and nano-sized zero-valent iron to prepare an active and stable phosphating micro- and nano-sized zero-valent iron material.
It achieves stable catalytic activity of zero-valent iron, improves the removal efficiency of organic pollutants in water, avoids oxidation and passivation, extends service life, and simplifies the preparation process.
Smart Images
Figure CN118698570B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional composite materials technology, and particularly relates to a method for preparing an active and stable phosphated micro / nano zero-valent iron material and its application. Background Technology
[0002] Micro- and nano-sized zero-valent iron (ZVFe), with a redox potential of -0.44V, is a highly active iron-based catalytic material. Combined with iron's strong reducing power, excellent electrochemical properties, coordination chemistry, and environmental friendliness, it has attracted widespread attention as a typical transition metal catalyst. Although ZVFe can effectively catalyze the degradation of organic pollutants in the environment by oxidants, it still has certain drawbacks. ZVFe, especially micro- and nano-sized ZVFe (<5μm), has strong surface activity and is prone to forming an iron oxide shell passivation layer during synthesis and storage, hindering electron transfer between ZVFe and the oxidant and reducing catalytic activity. Therefore, solving the deactivation problem of micro- and nano-sized ZVFe caused by oxidation passivation, and preparing micro- and nano-sized ZVFe materials with storage stability and high catalytic activity, has increasingly become a focus of attention.
[0003] Surface modification of zero-valent iron (ZVFe) is an effective means to improve its activity, delay passivation, and extend its service life. For example, many ZVFe modification methods have been developed, including carbonaceous material loading, organic component encapsulation, metal oxide doping, and emerging oxalate sulfidation. The main principle of these modification strategies is to construct a novel multifunctional layer to replace the original iron oxide shell. Although these strategies improve the stability and catalytic activity of ZVFe materials to some extent, the resulting shell is not dense enough, and the coating thickness and density are difficult to control precisely. It is difficult to fundamentally solve the material's reactivity with water and oxygen, and passivation and deactivation of ZVFe still occur during preparation and storage.
[0004] How to form a dense, uniform, and complete phosphating layer on the surface of zero-valent iron through a simple process, while protecting the internal zero-valent iron from oxidation during preparation and storage, slowing down the passivation of zero-valent iron, and extending its service life, is an urgent problem to be solved. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing phosphating zero-valent iron materials in one step using a co-heating process. This one-step co-heating process achieves stable catalytic activity of zero-valent iron for oxidants, while simultaneously enabling the efficient removal of organic pollutants from water by the phosphating zero-valent iron / oxidant system.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] A method for preparing active and stable phosphoric micro / nano zero-valent iron includes the following steps:
[0008] A large crucible is prepared by spreading NaH2PO2 powder as a phosphating agent at the bottom. A smaller crucible containing micro / nano zero-valent iron powder is placed inside the larger crucible, and the larger crucible is then sealed with a lid to form a closed container. The crucible containing NaH2PO2 and micro / nano zero-valent iron is placed in a pyrolysis furnace and heated to 300-700℃ at a rate of 1-10℃ / min under nitrogen protection and maintained for 1-3 hours. During this heating process, when the temperature exceeds 300℃, NaH2PO2 decomposes to generate H3P gas, which diffuses in the sealed large crucible and reacts with the micro / nano zero-valent iron material to generate phosphated micro / nano zero-valent iron material. After natural cooling, the phosphated micro / nano zero-valent iron material is collected in a brown glass bottle and stored in a -20℃ refrigerator for later use, which is the active and stable micro / nano zero-valent iron material.
[0009] Preferably, as a preferred embodiment, the phosphating agent can be replaced with aluminum phosphide or hypophosphite.
[0010] Preferably, as a preferred embodiment, the micro / nano zero-valent iron particles have a size range of 50-10000 nm, and the amount of micro / nano zero-valent iron added is 1-20 g; the mass ratio of phosphating agent to zero-valent iron is m. NaH2PO2 / m 微纳米零价铁 It is 0.5-2 / 1.
[0011] Preferably, as a preferred embodiment, the large crucible has a volume of 50-500 mL and the small crucible has a volume of 10-100 mL.
[0012] Preferably, as a preferred embodiment, the pyrolysis furnace includes an atmosphere furnace and a tube furnace, and the pyrolysis process is carried out under a nitrogen atmosphere.
[0013] Preferably, as a preferred embodiment, the heating rate is 1-10℃ / min; the equilibrium temperature is 300-700℃ and maintained for 1-3h. The heating rate, equilibrium temperature and pyrolysis time are appropriately adjusted according to the particle size of the micro-nano zero-valent iron powder to ensure the full phosphating of the micro-nano zero-valent iron powder.
[0014] Another object of the present invention is to provide an application of the aforementioned active and stable phosphoric micro / nano zero-valent iron material.
[0015] Preferably, as a preferred embodiment, the application includes the following steps: 10-50 mg of the active stable phosphoric micro / nano zero-valent iron material of the present invention is placed in a capped glass bottle, phenol solution is added, and then an oxidant is added to initiate the reaction. The total volume of the final reaction solution is controlled to be 15-100 ml, wherein the phenol concentration is 1-3 mmol / L and the PDS concentration is 1-10 mmol / L. The capped glass bottle is placed in a shaker with a rotation speed of 120-180 rpm. At a fixed reaction time point, 0.5 ml of the reaction solution is taken, filtered through a 0.22 μm filter membrane, and mixed with 0.5 ml of methanol solution to terminate the reaction. The mixture is diluted 10 times and then tested on a machine to calculate the phenol removal rate.
[0016] Preferably, as a preferred embodiment, the oxidant is selected from one or more of persulfate, permonsulfate and hydrogen peroxide, and the concentration is 1-10 mM.
[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0018] 1. This invention prepares micro / nano iron phosphide materials by coating the surface of zero-valent iron particles with a uniform and dense iron phosphide layer, replacing the original iron oxide layer. The iron phosphide layer on the material surface avoids the corrosion and passivation effects of oxygen and water on zero-valent iron, resulting in excellent storage stability of the prepared material. At the same time, the selective activation effect of the iron phosphide layer on oxidants promotes stable catalytic activity in the prepared material, thereby exposing more active sites and significantly improving the catalytic degradation efficiency and mineralization degree of target pollutants.
[0019] 2. This invention achieves full phosphating of zero-valent iron through a simple one-step co-heating method, avoiding the complex pretreatment and post-treatment steps in the traditional preparation of phosphated zero-valent iron materials. This process uses phosphine gas generated by heating the phosphating agent to phosphate the surface of the zero-valent iron, eliminating the need for separation and cleaning steps to obtain a dense phosphated iron shell covering the zero-valent iron material. This maintains the original iron powder particle size and morphology while maximizing the preservation of the original Fe content. 0 The content of [unclear] has the advantages of simple preparation process, high raw material conversion rate, and good structural properties of the prepared material.
[0020] 3. This invention can achieve full phosphating of the surface of zero-valent iron materials in various particle size ranges. The preparation process is simple, time-consuming, low-cost, and has a wide range of applications. Zero-valent iron in various particle size ranges can be used as raw materials to prepare high-quality phosphated zero-valent iron materials in production and daily life. Attached Figure Description
[0021] Figure 1 The catalytic degradation effect of active and stable phosphoric micro / nano zero-valent iron materials prepared at different co-heating temperatures on phenol is shown.
[0022] Figure 2 The catalytic degradation effect of active and stable phosphoric micro / nano zero-valent iron materials prepared under different co-heating times on phenol is shown.
[0023] Figure 3 The study compares the catalytic degradation effects of raw micro / nano zero-valent iron and active stable phosphating micro / nano zero-valent iron materials on phenol.
[0024] Figure 4 Transmission electron microscopy (TEM) images of active, stable phosphorylated micro / nano zero-valent iron materials are shown. Detailed Implementation
[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific embodiments described below further illustrate the present invention.
[0026] Unless otherwise specified, all chemical substances of this invention are commercially available.
[0027] I. Preparation Examples
[0028] 1. Example 1
[0029] The steps for preparing active and stable phosphoric micro / nanomaterials at different co-heating temperatures are as follows:
[0030] Phosphating agent NaH2PO2 powder was spread at the bottom of a 100mL crucible. A smaller crucible (20mL) containing 10g of micro / nano zero-valent iron powder was placed inside the larger crucible, resulting in a NaH2PO2 powder to micro / nano zero-valent iron powder mass ratio of (m... NaH2PO2 / m 微纳米零价铁粉 =1 / 1), and then seal the large crucible with a lid to form a sealed container. Place the crucible containing NaH2PO2 and micro / nano zero-valent iron particles in a pyrolysis furnace, and under nitrogen protection, heat to 300-700℃ at a rate of 5℃ / min and maintain for 2 hours. During this heating process, when the temperature exceeds 300℃, NaH2PO2 decomposes to generate H3P gas, which diffuses in the sealed large crucible and reacts with the micro / nano zero-valent iron powder to generate phosphated micro / nano zero-valent iron material. After natural cooling, collect the phosphated micro / nano zero-valent iron material in a brown glass bottle and store it in a -20℃ refrigerator for later use; this is the active and stable phosphated micro / nano zero-valent iron material.
[0031] 2. Example 2
[0032] Phosphating agent NaH2PO2 powder was spread at the bottom of a 100mL crucible. A smaller crucible (20mL) containing 10g of micro / nano zero-valent iron powder was placed inside the larger crucible, resulting in a NaH2PO2 powder to micro / nano zero-valent iron powder mass ratio of (m... NaH2PO2 / m 微纳米零价铁粉 =1 / 1), and then seal the large crucible with a lid to form a sealed container. Place the crucible containing NaH2PO2 and micro / nano zero-valent iron particles in a pyrolysis furnace, and under nitrogen protection, heat to 600℃ at a rate of 5℃ / min and maintain for 1-3 hours. During this heating process, when the temperature exceeds 300℃, NaH2PO2 decomposes to generate H3P gas, which diffuses in the sealed large crucible and reacts with the micro / nano zero-valent iron powder to generate phosphated micro / nano zero-valent iron material. After natural cooling, collect the phosphated micro / nano zero-valent iron material in a brown glass bottle and store it in a -20℃ refrigerator for later use; this is the active and stable phosphated micro / nano zero-valent iron material.
[0033] II. Performance Testing
[0034] 10 mg of the prepared stable phosphorylated micro / nano zero-valent iron materials with different activities were placed in a capped glass bottle, phenol solution was added, and then an oxidant was added to initiate the reaction. The total volume of the final reaction solution was controlled to be 60 ml, with a phenol concentration of 1.5 mmol / L and a PDS concentration of 6 mmol / L. The capped glass bottle was placed in a shaker at 150 rpm. At a fixed reaction time point, 0.5 ml of the reaction solution was taken, filtered through a 0.22 μm filter membrane, and mixed with 0.5 ml of methanol solution to terminate the reaction. The mixture was diluted 10 times and tested on an instrument to calculate the phenol removal rate.
[0035] The effect of the above-mentioned active and stable phosphoric micro-nano zero-valent iron catalyst on the degradation of phenol by persulfate was detected, and the phenol degradation kinetic curve was obtained. The results are as follows: Figure 1 , 2 As shown in Figure 3. During the preparation process, the active and stable phosphoric acid micro / nano zero-valent iron prepared under the conditions of a heating temperature of 600℃ and a heating time of 2 hours was characterized by transmission electron microscopy. The results are as follows: Figure 4 As shown.
[0036] Depend on Figure 1 , 2 It is evident that this invention, by altering the co-heating temperature and time, regulates the catalytic activity and activity stability of stable micro / nano zero-valent iron. Controlling the co-heating temperature and time to a certain range significantly improves the material's performance and activity stability in activating persulfate to degrade phenol. Figure 3 It can be seen that, in the process of phenol degradation by activated persulfate, the stable micro-nano zero-valent iron exhibits superior catalytic effect compared to the original micro-nano zero-valent iron; from Figure 4It can be seen that the active and stable micro / nano zero-valent iron is composed of a core-shell structure, with an outer shell of ~100nm iron phosphide and an inner core of Fe. 0 This structure is more conducive to improving the catalytic activity, stability, reaction pH range, and electron utilization of micro- and nano-sized zero-valent iron.
[0037] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.
Claims
1. A method for preparing active and stable phosphated micro-nano zero-valent iron material, characterized in that, Includes the following steps: The phosphating agent NaH2PO2 powder was spread at the bottom of a large crucible, and a small crucible containing micro-nano zero-valent iron powder was placed in the large crucible. The large crucible was then sealed with a lid to form a sealed container. The crucible containing NaH2PO2 and micro-nano zero-valent iron was placed in a pyrolysis furnace and heated to 600℃ at 5℃ / min under nitrogen protection and maintained for 2h. During the heating process, NaH2PO2 decomposes to generate H3P gas, which diffuses in a sealed crucible and reacts with micro-nano zero-valent iron materials to generate phosphated micro-nano zero-valent iron materials. After natural cooling, the phosphated micro-nano zero-valent iron materials are collected in brown glass bottles and stored in a -20 ℃ refrigerator for later use, which is the active and stable micro-nano zero-valent iron material. The micro-nano zero-valent iron particles have a particle size range of 50-10000 nm, and the amount of micro-nano zero-valent iron added is 1-20g. The mass ratio m of the phosphating agent to the zero-valent iron NaH2PO2 / m 微纳米零价铁 is 0.5-2 / 1.
2. The method for preparing an active and stable phosphoric micro / nano zero-valent iron material according to claim 1, characterized in that, The large crucible has a volume of 50-500 mL, and the small crucible has a volume of 10-100 mL.
3. The method for preparing an active and stable phosphoric micro / nano zero-valent iron material according to claim 1, characterized in that, The pyrolysis furnace includes an atmosphere furnace and a tube furnace, and the pyrolysis process is carried out under a nitrogen atmosphere.
4. Phosphated micro-nano zero-valent iron material prepared by the method for preparing an active and stable phosphated micro-nano zero-valent iron material according to claim 1.
5. The application of the active and stable phosphoric micro / nano zero-valent iron material according to claim 4 for the remediation of organic pollution in soil and groundwater.
6. Use according to claim 5, characterized in that, The organic pollutant is phenol.