Magnetic core coated inorganic ion adsorbent for removing Cs ions in radioactive wastewater and preparation method thereof

Patent metadata

Field	Value
Publication number	US-9586191-B2
Application number	US-201314428437-A
Country	US
Kind code	B2
Filing date	Sep 18, 2013
Priority date	Sep 19, 2012
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

The invention discloses a micron-grade magnetic core coated ferrocyanide adsorbent for removing Cs ions in radioactive wastewater and a preparation method thereof. The adsorbent takes magnetic Fe 3 O 4 as a core, the surface is coated with a dense SiO 2 single layer serving as a protective layer, and an active component is metal ion stabilized potassium ferrocyanide coated on the outer layer, wherein stabilized metal ions comprise Ti, Zn, Cu, Ni, Co, and Zr. The particle size of the adsorbent is 0.2-5 μm, the adsorbent in the outermost layer is conductive to improving the adsorption efficiency for Cs + ions, and an external magnetic field is adopted for realizing solid-liquid phase separation. The preparation method comprises the following steps: coating a hydrated metal oxide of Ti, Zr or Co, Ni, Cu or Zn on the surface of Fe 3 O 4 SiO 2 to form a composite magnetic material, wherein the hydrated oxide performs hydroxyl polymerization reaction with the surface of SiO 2 to produce M—O—Si bonds to improve the bonding strength between M and the surface of SiO 2 ; and finally reacting the composite magnetic material with a potassium ferrocyanide solution to form the required composite adsorbent, wherein the metal ions M achieve the effects of stabilizing the ferrocyanide and also achieve a bridge effect for bonding the ferrocyanide and the composite magnetic material together.

First claim

The invention claimed is:

1. A magnetic core coated inorganic ion adsorbent for removing Cs ions in radioactive wastewater, characterized in that the adsorbent takes a composite magnetic carrier Fe 3 O 4 /SiO 2 coated with a dense single layer SiO 2 on the surface as a core, a hydrated metal oxide transition layer is coated outside the Fe 3 O 4 /SiO 2 , and a ferrocyanide adsorption material layer is coated outside the transition layer; wherein the hydrated metal oxide is TiO 2 .H 2 O or ZrO 2 .H 2 O or ZnO.H 2 O or CuO.H 2 O or NiO.H 2 O or O CoO.H 2 O wherein the coating amount of TiO 2 .H 2 O is 50-55 wt. %, and the coating amount of each of other hydrated metal oxides is 40-50 wt. %.

2. The adsorbent according to claim 1 , characterized in that the particle size range of the adsorbent is 0.2-5.0 μm, and the specific saturation magnetization is 3-10 emu/g.

3. The adsorbent according to claim 1 , characterized in that the specific saturation magnetization of the composite magnetic carrier Fe 3 O 4 /SiO 2 is more than 70 emu/g.

4. The adsorbent according to claim 1 , characterized in that the particle size range of the Fe 3 O 4 in the composite magnetic carrier is 10-60 nm, the specific saturation magnetization is more than 75 emu/g, and the content of organic matters is lower than 1%; and the coating amount of the SiO 2 is 4-5wt %.

5. The adsorbent according to claim 1 , characterized in that the hydrated metal oxide transition layer is coated outside the single layer SiO 2 , and the specific saturation magnetization of the obtained composite magnetic material is more than 40 emu/g.

6. A method for preparing the adsorbent according to claim 1 , characterized by taking a composite magnetic carrier Fe 3 O 4 /SiO 2 coated with a dense single layer SiO 2 on the surface as a core, firstly coating a hydrated metal oxide transition layer on the surface of the composite magnetic carrier, and then coating a ferrocyanide adsorbent layer outside the transition layer wherein the hydrated metal oxide is TiO 2 .H 2 O or ZrO 2 .H 2 O, and the details of steps of the method are as follows:
1) preparing a hydrated titanium oxide or zirconium oxide transition layer by a sol-gel method;
a) dissolving tetrabutyl titanate in isopropanol, and controlling the volume ratio of the tetrabutyl titanate to the isopropanol at 0.005:1-0.05:1 to form a solution A1 for later use; dissolving zirconium isopropoxide in isopropanol, and controlling the volume ratio of the zirconium isopropoxide to the isopropanol at 0.01:1-0.1:1 to form a solution A2 for later use; and mixing isopropanol with ultra-pure water to form a solution B for later use, wherein the volume ratio of the isopropanol to the water is 5:1-2:1;
b) adding a composite magnetic carrier Fe 3 O 4 /SiO 2 coated with a dense single layer SiO 2 on the surface into the solution B,performing ultrasonic dispersion for 30 min, then adding concentrated ammonia water, and uniformly stirring by using a polytetrafluoroethylene stirrer; and controlling the concentration by mass-to-volume ratio of the Fe 3 O 4 /SiO 2 to the solution B within the range of 0.005-0.02 g/mL and the volume ratio of the concentrated ammonia water to the solution B within the range of 0.02-0.05;
c1) slowly dropping the solution A1 into the reaction system prepared in the step b) at room temperature, and controlling the amount of tetrabutyl titanate added into per gram of Fe 3 O 4 /SiO at 2.0-3.0 mL; performing stirring reaction at room temperature for 4-6 h after dropping, separating an obtained precipitate by using an external magnetic field, washing with anhydrous ethanol, and drying in a vacuum oven at 80° C. to obtain a composite magnetic material Fe 3 O 4 /SiO 2 /TiO 2 .H 2 O with the surface TiO 2 coating amount of 50-55wt % wherein the specific saturation magnetization is more than 40 emu/g;
c2) under the same operation conditions with c1), slowly dropping the solution A2 into the reaction system prepared in the step b), and controlling the amount of zirconium isopropoxide added into per gram of Fe 3 O 4 /SiO 2 at 1.5-2.5 mL; performing stirring reaction at room temperature for 4-6 h after dropping, separating an obtained precipitate by using an external magnetic field, washing with anhydrous ethanol, and drying in a vacuum oven at 80° C. to obtain a composite magnetic material Fe 3 O 4 /SiO 2 /ZrO 2 with the surface ZrO 2 coating amount of 40-50 w %, wherein the specific saturation magnetization is more than 40 emu/g;
2) preparing a ferrocyanide adsorbent layer:
soaking the prepared Fe 3 O 4 /SiO 2 /TiO 2 .H 2 O or Fe 3 O 4 /SiO 2 /ZrO.H 2 O in a hydrochloric acid solution of potassium ferrocyanide, wherein the concentration of the potassium ferrocyanide is 0.5-1.5 mol/L, the concentration of the hydrochloric acid is 1.0-2.0 mol/L, and the concentration by mass-to-volume ratio of the Fe 3 O 4 SiO 2 / TiO 2 H 2 O or Fe 3 O 4 /SiO 2 /ZrO 2 .H 2 O is 0.01-0.03 g/mL; reacting the system at room temperature,
stirring for 30 min every 2-4 h,
separating the precipitate by using the external magnetic field after reacting for 20-24 h,
fully washing the precipitate with ultra-pure water till flushing liquid is colorless,
further washing with anhydrous ethanol,
and drying in the vacuum oven at 80° C. to obtain the required black and blue magnetic core coated composite adsorbent.

7. A method for preparing the adsorbent according to claim 1 , characterized b taking a composite magnetic carrier Fe 3 O 4 /SiO 2 coated with a dense single layer SiO 2 on the core, firstly coating a metal oxide transition layer on the surface of the composite magnetic carrier, and then coating a ferrocyanide adsorbent layer outside the transition layer characterized in that the hydrated metal oxide is MO—H 2 O, wherein M is one of Co, Ni, Cu and Zn, and the details of steps of the method are as follows:
1) Preparing a hydrated copper oxide, zinc oxide, nickel oxide or cobalt oxide transition layer by adopting a surface deposition precipitation method;
a) dissolving a soluble sulfate, acetate, nitrate or chloride of the metal M in 100mL of anhydrous ethanol or isopropanol to form a solution CM, wherein M is one of Co, Ni, Cu and Zn, and the molar concentration of metal M ions is controlled within the range of 0.04-0.06 mol/L;
b) adding the composite magnetic carrier Fe 3 O 4 /SiO 2 coated with the dense single layer SiO 2 on the surface, and performing ultrasonic dispersion for 30 min, wherein the concentration by mass-to-volume ratio of the Fe 3 O 4 /SiO 2 is controlled within the range of 0.005-0.015 g/mL;
c) slowly dropping a 0.02-0.05 mol/L NaOH water solution into the reaction system prepared in the step e) at room temperature, uniformly stirring by using the polytetrafluoroethylene stirrer, controlling endpoint pHs as follows respectively: Zn: 6.5-8; Cu: 7-9 and Ni/Co: 10-12 to realize complete deposition of the ions on the surface of the Fe 3 O 4 /SiO 2 ; and aging the reaction system for 2-4 h at room temperature after titration, then separating the precipitate by using the external magnetic field, firstly washing with ultra-pure water till the pH is neutral, further washing with anhydrous ethanol, and drying the Fe 3 O 4 /SiO 2 in the vacuum oven to obtain a composite magnetic material Fe 3 O 4 /SiO 2 /MO.H 2 O with the surface coating amount of 40-50 wt %, wherein the specific saturation magnetization is more than 40 emu/g;
2) preparing a ferrocyanide adsorbent layer:
soaking the prepared Fe 3 O 4 /SiO 2 /MO.H 2 O in a hydrochloric acid solution of potassium ferrocyanide, wherein the concentration of the potassium ferrocyanide is 0.5-1.5 mol/L, the concentration of the hydrochloric acid is 1.0-2.0 mol/L, and the concentration by mass-to-volume ratio of the Fe 3 O 4 /SiO 2 /MO.H 2

Assignees

• Zhao Xuan
• Wei Jiying
• Li Fuzhi
• Univ Tsinghua

Inventors

• Zhao Xuan
• Wei Jiying
• Li Fuzhi

Classifications

• C02F2101/20

  Heavy metals or heavy metal compounds · CPC title

• B01J20/3204

  Inorganic carriers, supports or substrates · CPC title

• B01J20/103

  comprising silica · CPC title

• B01J20/3293

  Coatings on a core, the core being particle or fiber shaped, e.g. encapsulated particles, coated fibers · CPC title

• B01J20/28009

  Magnetic properties · CPC title