A kind of iron oxyhydroxide hydrogel material for reducing phosphorus concentration in water and preparation method thereof

Abstract

The present invention discloses an iron oxyhydroxide hydrogel material and preparation method for reducing phosphorus concentration in water. The method comprises the following steps: S1: adding 1-5 wt% sodium alginate and amorphous iron oxyhydroxide in a mass ratio of 15:1-2:1 to deionized water, stirring and dissolving in a water bath to obtain a mixed solution, wherein the water bath temperature is 25-40°C and the heating time is 0.5-2 hours; S2: pouring the mixed solution into a mold and freezing it at low temperature to form the mold, wherein the mold diameter is 2-20 mm; S3: placing the frozen mixed solution in a CaCl2 crosslinker with a mass fraction of 2-5 wt%, and curing it at room temperature to obtain the hydrogel material, wherein the curing time is 4-48 hours. The sodium alginate hydrogel prepared by the present invention can reduce interparticle aggregation and form a polymer protective film, effectively controlling the dissolution of amorphous iron oxyhydroxide and improving the adsorption of phosphorus in water. In addition, the particle size of the hydrogel material facilitates separation and recovery.

Description

Technical Field

[0001] The present invention relates to the technical field of water body restoration technology and resource recycling, and in particular to an iron oxyhydroxide hydrogel material capable of reducing phosphorus concentration in water and a preparation method thereof. Background Art

[0002] The 2021 China Ecological Environment Bulletin shows that among China's 209 important lakes (reservoirs), 4.3% are in a moderate eutrophic state and 23% are in a mild eutrophic state. The eutrophication situation is still not optimistic. Among the driving mechanisms of water eutrophication, excessive phosphorus entering the surface water system is considered to be one of the main factors. In 2017, the Ministry of Ecology and Environment issued the "Technical Policy for the Prevention and Control of Lake (Reservoir) Eutrophication", pointing out that the total amount and concentration of total phosphorus entering the lake need to be finely managed in accordance with the principle of "one lake, one policy". According to surveys, the common phosphorus concentration in China's eutrophic rivers and lakes is around 0.1 mg / L, which is higher than the water eutrophication threshold of 0.02 mg / L.

[0003] For the removal of low-concentration phosphorus in rivers and lakes, the adsorption method has the advantages of being economical, efficient, and simple to operate. Iron (hydroxide) adsorption materials have a good removal effect on phosphorus in river and lake water bodies. Among them, amorphous hydroxyl iron oxide has an extremely high specific surface area and reactivity, and can strongly adsorb phosphorus in water bodies. However, amorphous hydroxyl iron oxide particles are prone to agglomeration, resulting in a significant reduction in their specific surface area and reactive sites, thereby affecting the removal performance and efficiency of the pollutant phosphorus. After use, the currently available adsorbent powder needs to be properly and effectively handled for the composite substances formed. In addition, the adsorbent powder is difficult to recycle after being applied to the environment, which will inevitably cause secondary environmental problems. Summary of the Invention

[0004] The purpose of this patent is to address the problems existing in the above-mentioned prior art and propose a ferric oxyhydroxide hydrogel material and preparation method for reducing the phosphorus concentration in water. The technical solution of this patent is implemented as follows, including the following steps:

[0005] S1: Sodium alginate and amorphous ferric oxyhydroxide are added to deionized water, and stirred in a water bath to dissolve to obtain a mixed solution;

[0006] S2: pouring the mixed solution into a mold and freezing it at low temperature to form the mold;

[0007] S3: placing the frozen mixed solution in a CaCl2 cross-linking agent and solidifying it at room temperature to obtain the hydrogel material.

[0008] Preferably, the mass fraction of the sodium alginate in S1 is 1 to 5 wt%;

[0009] Preferably, the mass ratio of sodium alginate to amorphous ferric oxyhydroxide in S1 is no more than 15:1 at most and no more than 2:1 at least;

[0010] Preferably, the water bath temperature in S1 is 25-40° C., and the heating time is 0.5-2 h;

[0011] Preferably, the diameter of the mold in S2 is 2 to 20 mm;

[0012] Preferably, the mass fraction of the CaCl2 cross-linking agent in S3 is 2 to 5 wt%, and the curing time is 4 to 48 hours.

[0013] The present invention has the following advantages: 1) the particle size of the hydrogel material can be in the millimeter and centimeter levels, which is conducive to separation and recovery; 2) the sodium alginate hydrogel can reduce the agglomeration between particles and form a polymer protective film, effectively controlling the dissolution of amorphous ferric oxyhydroxide; 3) the amorphous ferric oxyhydroxide has an extremely high specific surface area and reaction activity, can strongly adsorb phosphorus in water, and can also form divalent iron in the bottom mud of rivers and lakes through the action of iron-reducing bacteria and form blue iron with the adsorbed phosphate, thereby achieving phosphorus fixation and recovery, and has good application prospects in the eutrophication control of rivers and lakes and resource recovery; 4) the hydrogel material has good biocompatibility and has no potential impact on human health and ecosystems; 5) the preparation steps are simple, the energy consumption of the preparation process is low, and it is easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Preparation flow chart

[0015] Figure 2 Physical images of the hydrogel materials provided in this application;

[0016] Figure 3 is a scanning electron microscope image of the interior of the hydrogel material provided in this application;

[0017] Figure 4 This is a diagram showing the deep phosphorus removal effect of the hydrogel material provided in this application; DETAILED DESCRIPTION

[0018] The present invention is further described in detail below with reference to examples. However, the examples are merely exemplary and do not constitute any limitation to the scope of the present invention. The details and forms of the technical solutions of the present invention may be modified and replaced without departing from the scope of the present invention, but such modifications and replacements fall within the scope of protection of the present invention. A ferric oxyhydroxide hydrogel material for reducing phosphorus concentration in water and a preparation method thereof:

[0019] S1: adding 1-5 wt% sodium alginate and amorphous ferric oxyhydroxide in a mass ratio of 15:1-2:1 into deionized water, stirring and dissolving in a water bath to obtain a mixed solution, wherein the water bath temperature is 25-40° C. and the heating time is 0.5-2 h;

[0020] S2: pouring the mixed solution into a mold and freezing it at low temperature to form the mold, wherein the diameter of the mold is 2 to 20 mm;

[0021] S3: placing the frozen mixed solution in a CaCl2 cross-linking agent, wherein the mass fraction of the CaCl2 cross-linking agent is 2 to 5 wt%, and curing at room temperature to obtain the hydrogel material, wherein the curing time is 4 to 48 hours. Specific embodiment 1

[0023] 3 wt% sodium alginate and amorphous ferric hydroxide were added to deionized water in a mass ratio of 3:1, the water bath temperature was adjusted to 35°C, heated for 1.5 hours, and dissolved by stirring in a water bath to obtain a mixed solution; the mixed solution was poured into a 6 mm mold and frozen into shape at low temperature; the frozen-formed mixed solution was placed in a 3 wt% CaCl2 cross-linking agent and cured at room temperature for 36 hours to obtain a ferric hydroxide hydrogel material.

[0024] Iron oxyhydroxide hydrogel materials can be applied to river and lake water bodies. The iron oxyhydroxide hydrogel materials are placed in the matrix and hanging fillers of the ecological floating island and placed in areas with strong fluidity of the river and lake water bodies. The ecological floating island floats on the surface of eutrophic water. After the iron oxyhydroxide hydrogel material removes and recovers phosphorus in eutrophic rivers and lakes for a long time, the phosphorus concentration in rivers and lakes is reduced to below 0.02 mg / L. Specific embodiment 2

[0026] 2 wt% sodium alginate and amorphous ferric hydroxide were added to deionized water in a mass ratio of 10:1, the water bath temperature was adjusted to 35°C, heated for 1.5 hours, and dissolved by stirring in a water bath to obtain a mixed solution; the mixed solution was poured into a 6 mm mold and frozen at low temperature to form; the frozen mixed solution was placed in a CaCl2 cross-linker with a mass fraction of 3 wt%, and cured at room temperature for 24 hours to obtain the ferric hydroxide hydrogel material.

[0027] The iron oxyhydroxide hydrogel material can be applied to the sediment of rivers and lakes. The iron oxyhydroxide hydrogel material is placed in a nylon mesh bag and the nylon mesh bag is dropped into the sediment of rivers and lakes. The iron-reducing bacteria in the sediment reduce the iron oxyhydroxide in the iron-hydrogel composite material to Fe II , Fe II It reacts with phosphorus in the sediment to form blue iron stone. The crystallized blue iron stone can be used as a slow-release fertilizer and realize resource utilization in the agricultural field.

Claims

1. A method for preparing an iron oxyhydroxide hydrogel material for reducing phosphorus concentration in water, characterized in that: The steps include: S1: adding sodium alginate and amorphous ferric oxyhydroxide to deionized water, stirring and dissolving in a water bath to obtain a mixed solution; the mass fraction of the sodium alginate is 1 to 5 wt%; the mass ratio of the sodium alginate to the amorphous ferric oxyhydroxide is no more than 15:1 and no less than 2:1; the water bath temperature is 25 to 40° C., and the heating time is 0.5 to 2 h; S2: pouring the mixed solution into a mold and freezing it at low temperature to form the mold; S3: placing the frozen mixed solution in a CaCl2 cross-linking agent and solidifying it at room temperature to obtain the hydrogel material.

2. The method for preparing an iron oxyhydroxide hydrogel material for reducing phosphorus concentration in water according to claim 1, characterized in that: The diameter of the mold in S2 is 2 to 20 mm.

3. The method for preparing an iron oxyhydroxide hydrogel material for reducing phosphorus concentration in water according to claim 1, characterized in that: The mass fraction of the CaCl2 cross-linking agent in S3 is 2 to 5 wt %, and the curing time is 4 to 48 hours.

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