CARBON AND USE THEREOF

Field of the invention

The present invention relates to an activated carbon, in particular to a method for preparing a modified activated carbon and a use thereof.

Background of the invention

At present, industries such as metallurgy, electrolysis, pharmaceuticals, paints, alloys and electroplated manufacturing discharge large amounts of industrial waste water containing chromium and arsenic each year. The chromium, arsenic and compounds thereof in this waste water can become concentrated in fish and other aquatic organisms, and cause serious harm to humans and the surrounding ecosystem through water consumption and the food chain. Thus, the question of how to reduce harmful pollution by chromium and arsenic has become an environmental problem in urgent need of solution.

Activated carbon, as a porous non-polar adsorbent, has a huge specific surface area on account of its special pore structure, as well as being plentiful and inexpensive, so is one of the adsorbents most widely used in water treatment at present. It has good adsorbency and stable chemical properties, can withstand strong acids and strong bases, can withstand the effects of immersion in water, high temperature and high pressure, and may also be regenerated by activation.

Iron-containing adsorbents has good capacity for adsorbing anions and cations. The development, manufacture and application of adsorbents in which the principal adsorbing component is elemental iron has already drawn wide attention in the market. Amongst these, nano-iron (including zero valent iron, iron oxide and magnetite particles etc.) is being given serious attention on a broad scale in the treatment of waste water containing chromium and arsenic due to its advantages such as small size, large surface effect and strong adsorption capacity. However, powdered nano-iron particles are tiny, easily deactivate and aggregate in water, and are difficult to recover and reuse. Summary of the invention

First aspect of the present invention provides a method for preparing a nano oFe2C>3 modified activated carbon, the method comprising steps of: a. treating activated carbon in dilute nitric acid, washing with water and anhydrous solvent, and drying at 60 to 80°C, to obtain treated activated carbon;

b. providing an FeC solution with a solution concentration from 167 to 835 mol/L in an anhydrous solvent, and adding urea in a concentration of 250 to 1250 mol/L, and stirring to mix evenly;

c. transferring the solution obtained from step b into a high-pressurizable vessel, adding the treated activated carbon obtained from step a, and stirring;

d. heating the pressurizable vessel from step c at a temperature in the range of 150 to 180°C to obtain processed activated carbon; and e. washing the processed activated carbon obtained from step d with an anhydrous solvent, and drying at 60 to 80°C to obtain nano a-Fe2C>3 modified activated carbon.

Second aspect of the present invention provides a nano a-Fe203 modified activated carbon (2) obtained by the method of the first aspect.

Third aspect of the present invention provides a filter core, comprising a filter core body, and a nano a-Fe203 modified activated carbon, wherein the nano a-Fe203 modified activated carbon is prepared by the method of the first aspect and is packed in the filter core body.

Fourth aspect of the present invention provides use of nano alpha iron(lll) oxide in an activated carbon-based filter to adsorb heavy metals.

Fifth aspect of the present invention provides use of nano alpha iron(lll) oxide in a method according to the first aspect to prepare activated carbon-based filter for adsorbing heavy metals. Another aspect of the present invention provides use of nano alpha iron(lll) oxide obtained by a method according to first aspect for removal of heavy metals from water.

Brief Description of the accompanying drawings

Fig. 1 is a structural schematic diagram of of the present invention.

Fig. 2 is a curve for the first determination method as provided in the present invention.

Fig. 3 is a curve for the second determination method as provided in the present invention.

Fig. 4 is a curve for the third determination method as provided in the present invention. Fig. 5 is a curve for the fourth determination method in embodiment 4 of the present invention.

Fig. 6 is a curve for the fifth determination method as provided in the present invention.

The names of the parts represented by numerals in the drawings are as follows: 1 - filter core body; 2 - nano a-Fe2C>3 modified activated carbon.

Detailed description of the invention

In response to the problems affecting iron-containing adsorbents in the prior art, namely that they easily deactivate and aggregate in water, and are difficult to recover and reuse, the present invention provides a method for preparing a nano oFe2C>3 modified activated carbon and a use thereof.

The term nano a-Fe2C>3 means nano sized a-Fe2C>3, which is magnesium oxide Nanomaterials with diameters of <100 nm, wherein a-Fe2C>3 is alpha Iron(lll) oxide or Iron(lll) oxide in the alpha phase.

To solve the abovementioned technical problem, the present invention employs the following technical solution:

A method for preparing a nano a-Fe2C>3 modified activated carbon, the method comprising steps of: a. treating activated carbon in dilute nitric acid, washing with water and anhydrous solvent, and drying at 60 to 80°C, to obtain treated activated carbon;

b. providing an FeC solution with a solution concentration from 167 to 835 mol/L in an anhydrous solvent, and adding urea in a concentration of 250 to 1250 mol/L, and stirring to mix evenly;

c. transferring the solution obtained from step b into a high-pressurizable vessel, adding the treated activated carbon obtained from step a, and stirring;

d. heating the pressurizable vessel from step c at a temperature in the range of 150 to 180°C to obtain processed activated carbon; and e. washing the processed activated carbon obtained from step d with an anhydrous solvent, and drying at 60 to 80°C to obtain nano a-Fe2C>3 modified activated carbon.

It is preferred that the anhydrous solvent is anhydrous ethanol.

It is preferred that in step a, the volume ratio of anhydrous solvent to water ranges from 1 :3 to 1 :1 and the washing time in each case is from 0.5 to 2 hours.

It is preferred that particle size of the activated carbon in step a ranges from 10 to 20 mesh (2mm to 0.8mm).

It is preferred that the treatment in step a is immersing the activated carbon in dilute nitric acid for 0.5 to 2 hours.

It is preferred that in step b the high-pressurizable vessel is provided with a polytetrafluoroethylene liner.

It is preferred that the pressurizable vessel has a volume in the range of from 70 to 200 ml_. It is preferred that in step d the heating at temperatures in the range of 150 to 180°C is for 3.5 to 6.5 hours, and the pressure inside the pressurizable vessel ranges from 1.0 to 2.0 MPa .

The present invention provides a nano a-Fe203 modified activated carbon obtained by the method of the present invention.

The present invention provides a filter core, comprising a filter core body, and a nano o Fe203 modified activated carbon, wherein the nano a-Fe203 modified activated carbon is prepared by the method of the present invention and is packed in the filter core body.

It is preferred that the filter core body is made of meltblown polypropylene fiber.

It is preferred that the filter core body is cylindrical with an internal diameter of 25 to 35 mm and an external diameter of 60 to 65 mm.

The present invention provides use of nano alpha iron(lll) oxide in an activated carbon- based filter to adsorb heavy metals.

The present invention also provides use of nano alpha iron(lll) oxide in a method to prepare activated carbon-based filter for adsorbing heavy metals.

The present invention also provides use of nano alpha iron(lll) oxide obtained by a method according to the present invention for removal of heavy metals from water.

Preferably, the present invention provides a method for preparing a nano oFe2C>3 modified activated carbon, comprising the following steps: a. immersing activated carbon in dilute nitric acid, then washing alternately with water and anhydrous ethanol, to remove substances adhering to the surface, and sun-drying, air-drying, or oven-drying at 60 - 80°C, in preparation for use; b. using FeCI3-6H20 as a precursor, making up an FeCI3 solution with a solution concentration of 167 - 835 mol/L with anhydrous ethanol as a solvent, and then adding 250 - 1250 mol/L urea, and stirring to mix evenly; c. transferring the solution processed in step b into a -pressurizable vessel, then adding the activated carbon processed in step a, and stirring thoroughly to remove gas bubbles from the solution;

d. putting the pressurizable vessel from step c into a blast oven and performing hydrothermal treatment;

e. washing the activated carbon processed in step d with anhydrous ethanol, and sun-drying, air-drying, or oven-drying at 60 to 80°C, to obtain nano a-Fe2C>3 modified activated carbon.

The a-Fe2C>3 modified activated carbon obtained by this method can greatly improve the ability of ordinary activated carbon to adsorb heavy metals.

Preferably, the volume ratio of ethanol to water in step a is 1 : 3 to 1 : 1 , and the washing time in each case is 0.5 to 2 h.

Preferably, the particle size of activated carbon in step a is 10 to 20 mesh.

Preferably, the concentration of dilute nitric acid is 0.1 M, the immersion time is 0.5 to 2 h, and every 100 g of activated carbon is washed in 1 L of dilute nitric acid. Impurities on the surface of the activated carbon can be effectively removed through immersion in dilute nitric acid, to prevent non-uniformity when loading nano a-Fe2C>3 modified activated carbon.

Preferably, a polytetrafluoroethylene (PTFE) liner is provided in the pressurizable vessel in step b. PTFE will not react with the solution, so will not introduce impurities. Through the provision of the PTFE liner, the solution can be effectively prevented from not coming into contact with a stainless steel inside wall of the high-pressurizable vessel, thereby enabling the -pressurizable vessel to serve a sealing function, and maintain high temperature and high pressure inside the high-pressurizable vessel.

Preferably, the volume of the high-pressurizable vessel is 70 to 200 ml_.

Preferably, the hydrothermal treatment in step d consists of external heating by means of the blast oven for 3.5 to 6.5 h, such that the temperature is kept at 150 - 180°C and the pressure is kept at 1 .0 to 2.0 MPa inside the high-pressurizable vessel. The internal space of the high-pressurizable vessel is kept in a high-temperature, high-pressure state by such external heating. The nano material can be endowed with different morphologies in such a state; these special morphologies can increase the specific surface area of the material, and thereby increase the adsorption capacity of the material.

A filter core, comprising a filter core body, with nano a-Fe2C>3 modified activated carbon packed in the filter core body.

Preferably, the filter core body is made of meltblown polypropylene fibres.

Preferably, the filter core body is cylindrical, with an internal diameter of 25 to 35 mm and an external diameter of 60 to 65 mm.

Due to the adoption of the technical solution described above, the present invention has marked technical effects:

In the present invention, a-Fe2C>3 is loaded on the surface of, or in the pores of, activated carbon by a hydrothermal synthesis method, to obtain the nano oFe2C>3 modified activated carbon, which can not only retain the intrinsic characteristics of a nano material but also enhance the stability thereof, and can efficiently adsorb the heavy metals chromium and arsenic in drinking water. Ordinary activated carbon has virtually no ability to adsorb the heavy metals chromium and arsenic, whereas 300 g of the nano oFe2C>3 modified activated carbon of the present invention, in water with 10 times the allowed content of Cr or As, can guarantee that the water outputted meets the national safety standard for drinking water for half a month. In addition, the material is suited to reactor operations, and has characteristics such as an easily controlled reaction, easy operations and convenient maintenance, so has very broad prospects for market application and development.

Method

A method for preparing a nano a-Fe2C>3 modified activated carbon, the method preferably comprising the following steps: a. 10 g of activated carbon particles with mesh number 10 are immersed in 100 mL of dilute nitric acid with a concentration of 0.1 M for 2 h, then washed alternately in water and anhydrous ethanol; the volume ratio of ethanol to water is 1 :3 - 1 :1 , and the washing time in each case is 0.5 h. Substances adhering to the surface are removed, and oven-drying at 80°C is performed, in preparation for use;

b. using FeCI3-6H20 as a precursor, making up an FeCI3 solution with a solution concentration of 167 mol/L with anhydrous ethanol as a solvent, and then adding 250 mol/L urea, and stirring to mix evenly;

c. transferring the solution processed in step b into a -pressurizable vessel (in this embodiment, the pressurizable vessel has a volume of 70 ml and a PTFE liner is provided therein), then adding the activated carbon processed in step a, and stirring thoroughly to remove gas bubbles from the solution; d. putting the pressurizable vessel from step c into a blast oven and performing hydrothermal treatment; externally heating by means of the blast oven for 3.5 - 6.5 h, such that the temperature is kept at 150 - 180°C and the pressure is kept at 1 .0 MPa inside the pressurizable vessel. The internal space of the - pressurizable vessel is kept in a high-temperature, high-pressure state by such external heating. The nano material can be endowed with different morphologies in such a state.

e. washing the activated carbon processed in step d with anhydrous ethanol, and oven-drying at 60°C, to obtain nano a-Fe2C>3 modified activated carbon.

The present invention also provides a method for preparing a nano oFe2C>3 modified activated carbon, the method preferably comprising the following steps: a. 10 g of activated carbon particles with mesh number 10 are immersed in 100 mL of dilute nitric acid with a concentration of 0.1 M for 0.5 h, then washed alternately in water and anhydrous ethanol; the volume ratio of ethanol to water is 1 : 3 to 1 : 1 , and the washing time in each case is 2 h. Substances adhering to the surface are then removed, and sun-drying is performed, in preparation for use; b. using FeCI3-6H20 as a precursor, making up an FeCI3 solution with a solution concentration of 500 mol/L with anhydrous ethanol as a solvent, and then adding 800 mol/L urea, and stirring to mix evenly;

c. transferring the solution processed in step b into a pressurizable vessel (in this embodiment, the pressurizable vessel has a volume of 135 mL and a PTFE liner is provided therein), then adding the activated carbon processed in step a, and stirring thoroughly to remove gas bubbles from the solution; d. putting the high-pressurizable vessel from step c into a blast oven and performing hydrothermal treatment; externally heating by means of the blast oven for 3.5 - 6.5 h, such that the temperature is kept at 150 - 180°C and the pressure is kept at 2.0 MPa inside the pressurizable vessel. The internal space of the pressurizable vessel is kept in a high-temperature, high-pressure state by such external heating. The nano material can be endowed with different morphologies in such a state.

e. washing the activated carbon processed in step d with anhydrous ethanol, and oven-drying at 80°C, to obtain nano a-Fe203 modified activated carbon.

The present invention also provides a method wherein, preferably in step b, instead of using FeC^-ei-bO as a precursor, an FeC solution with a solution concentration of 835 mol/L is made up with anhydrous ethanol as a solvent, and then 1250 mol/L urea is added, and the mixture is stirred to mix evenly; and in step c, the high-pressurizable vessel has a volume of 200 mL.

The present invention also provides a method wherein, preferably a filter core, as shown in Fig. 1 , comprises a filter core body 1 , with the nano a-Fe2C>3 modified activated carbon 2 that was made in embodiment 1 or embodiment 2 or embodiment 3 packed in the filter core body 1 ; the filter core body 1 is cylindrical, and is made of meltblown polypropylene fibres.

In this case, nano oFe2C>3 modified activated carbon 2 is used to treat heavy metal in drinking water by adsorption; water containing heavy metal is passed into the filter core packed with nano oFe2C>3 modified activated carbon 2, then the original water and the water coming out are respectively sampled to measure the change in heavy metal concentration, wherein the specific determination methods are divided into the following types:

First type: Original waters containing the heavy metals chromium and arsenic and both having a concentration of 10 mg/L are respectively made up, the initial pH is adjusted to 7, and the flow speed is adjusted by means of an electromagnetic flow meter, such that the incoming water has a flow speed of 100 mL/min, being pressed in from the outside of the filter core body 1 , and after passing through the nano a-Fe203 modified activated carbon, comes out; the original water and the water coming out are respectively sampled to measure the change in heavy metal concentration. See Fig. 2 for the results.

Second type: Original water containing the heavy metal chromium at a concentration of 10 mg/L is made up, the pH is adjusted to 4 and 10 respectively, and the flow speed is adjusted by means of an electromagnetic flow meter, such that the incoming water has a flow speed of 100 mL/min, being pressed in from the outside of the filter core body 1 , and after passing through the nano a-Fe203 modified activated carbon, comes out; the original water and the water coming out are respectively sampled to measure the change in heavy metal concentration. See Fig. 3 for the results.

Third type: Original water containing the heavy metal arsenic at a concentration of 10 mg/L is made up, the pH is adjusted to 4 and 10 respectively, and the flow speed is adjusted by means of an electromagnetic flow meter, such that the incoming water has a flow speed of 100 mL/min, being pressed in from the outside of the filter core body 1 , and after passing through the nano a-Fe203 modified activated carbon, comes out; the original water and the water coming out are respectively sampled to measure the change in heavy metal concentration. See Fig. 4 for the results.

Fourth type: Original water containing the heavy metal chromium at a concentration of 10 mg/L is made up, the initial pH is adjusted to 7, and the flow speed is adjusted by means of an electromagnetic flow meter; the incoming water flow speed is adjusted to 1000 mL/min and 2000 mL/min respectively, pressed in from the outside of the filter core body (1 ), and after passing through the nano a-Fe203 modified activated carbon, water comes out; the original water and the water coming out are respectively sampled to measure the change in heavy metal concentration. See Fig. 5 for the results. Fifth type: Original water containing the heavy metal arsenic at a concentration of 10 mg/L is made up, the initial pH is adjusted to 7, and the flow speed is adjusted by means of an electromagnetic flow meter; the incoming water flow speed is adjusted to 1000 mL/min and 2000 mL/min respectively, pressed in from the outside of the filter core body (1 ), and after passing through the nano a-Fe2C>3 modified activated carbon, water comes out; the original water and the water coming out are respectively sampled to measure the change in heavy metal concentration. See Fig. 6 for the results.

During actual application, the flow speed is often an important factor restricting material application. Summarizing the above, it can be seen that the ability of nano oFe2C>3 modified activated carbon to adsorb the heavy metals chromium and arsenic will not change significantly with a change in flow speed. Thus, when a water purification apparatus is being designed, there is no need to take flow speed into account, so this material has considerable room for actual application. Furthermore, this material has simple preparation and application operations, and is very easy to industrialize, so has broad application prospects in the field of the removal of heavy metals from drinking water.

In summary, the embodiments above are merely preferred embodiments of the present invention. All equivalent changes and modifications made within the patent application scope of the present invention shall be included in the scope of the present invention patent.