KR20180005358A - Method for selectively adsorbing hazardous pollutants using mesoporous silica coated with thermo-responsive polymer - Google Patents

Abstract

Mesoporous silica surface-treated with poly(N-isopropyl acrylamide) according to the present invention is coated with a thermosensitive polymer so as to selectively adsorb and remove anionic metal according to temperature control. The ionic metal contained in an aqueous solution can be effectively adsorbed and removed with high efficiency while maintaining the high safety of an adsorbent at a relatively low pH range, because no secondary treatment is required during the metal adsorption.

Description

[0001] METHOD FOR SELECTIVELY ADSORBING HAZARDOUS POLLUTANTS USING MESOPOROUS SILICA COATED WITH THERMO-RESPONSIVE POLYMER [0002]

The present invention relates to a selective adsorption method of a contamination source using mesoporous silica coated with a thermosensitive polymer. More particularly, the present invention relates to a selective adsorption method of anionic metal contaminants using mesoporous silica surface-treated with poly (N-isopropylacrylamide) and aminopropyltriethoxysilane.

The importance of developing an adsorbent for the effective control of anionic metallic contaminants in aquatic environments, which are naturally occurring or artificially discharged at various industrial sites, is becoming increasingly important. In the environment, anionic metallic pollutants are found in groundwater, surface waters and soils, and accumulate in various organic or inorganic forms of plants and animals, which ultimately have detrimental effects on humans.

As the awareness of the risks associated with ingestion of food containing anionic metal contaminants and drinking water has increased, reverse osmosis, ion exchange, flocculation, adsorption or landfill methods have been applied to remove contaminated water containing anionic metals (Poonkuzhali et al., 2014). However, in order to operate these processes, selective removal of pollutants is not possible or high cost is required for treatment.

On the other hand, as a method for selectively adsorbing contaminants in a water system, there is a method of introducing a thermosensitive polymer such as N-isopropylacrylamide into an existing adsorbent. The temperature-sensitive polymer is phase-transformed in the form of a sol or gel depending on the temperature, and the temperature at this time is referred to as a lower critical solution temperature (LCST). The thermosensitive polymer is sensitive to temperature changes and has the advantage of easily controlling the temperature of the low-critical solution by preparing various compounds and copolymers.

Recently, various researches have been conducted on the selective carrying, adsorption and drug delivery system (DDS) of a specific substance using a thermosensitive polymer, N-isopropylacrylamide. N-isopropylacrylamide has long been studied for phase transitions due to temperature changes and has been applied in various fields such as drug delivery and material separation (Tokuyama and Iwama, 2007). N-isopropylacrylamide exhibits phase transition at a temperature of 32 ° C or higher, and the use of mesoporous silica as a carrier of thermosensitive N-isopropylacrylamide has a wide surface area, a wide pore volume, and relatively regular pores (Blin et al., 2013; Yang et al., 2013).

Previously reported studies on the introduction of various chelating agents into mesoporous silica for adsorption of selective heavy metal contaminants from aqueous solutions have been reported (Bibby and Mercier, 2002; Araghi et al., 2015). In particular, among the chelating agents used, compounds containing amine (-NH ₂ ) functional groups can exhibit excellent adsorption performance on oxoanions or cationic metals selectively depending on the pH (Mureseanu et al. 2008).

As a specific example, Korean Patent Registration No. 0347254 relates to a method for producing a mesoporous silica to which a chelating ligand is bonded, wherein a reactor such as aminopropyltriethoxysilane and mercaptopropyltrimethoxysilane is bonded to the surface of silica, - adsorbents of heavy metal contaminants in which ligand compositions are synthesized. In this study, the synthesis of mesoporous silica and the introduction of thermosensitive polymer on the surface of mesoporous silica were carried out by using the adsorbent based on the preparation method of SBA-15 and Chang et al. (2004) .

In order to increase the efficiency of selective adsorption and recovery of anionic specific contaminants and rare metals from wastewater solutions, it is necessary to provide a temperature sensitive adsorbent having superior performance. Accordingly, the present inventors have found that selective adsorption of anionic metal contaminants The functional groups for adsorption on thermosensitive polymer and anionic metal contaminants were introduced into mesoporous silica with relatively uniform pore and surface area.

The present invention provides a mesoporous silica coated with a thermosensitive polymer for selective adsorption of contaminants. More specifically, the present invention relates to a process for the preparation of mesoporous silica which is surface-treated with aminopropyltriethoxysilane and poly (N-isopropylacrylamide), optionally with adsorptivity to anionic metal contaminants, And a method for producing the same.

The present invention has been made to solve the above problems

(A) synthesizing a mesoporous silica-contaminant sorbent-thermosensitive polymer complex by adding a pollutant sorbent and a thermosensitive polymer to the mesoporous silica; And

(B) N-isopropylacrylamide is added to the mesoporous silica-contaminant adsorbent-thermosensitive polymer complex and the polymerization reaction is induced in a nitrogen atmosphere to obtain a mesoporous silica-contaminant adsorbent-N-isopropylacrylamide polymer And synthesizing the complex,

Wherein the contaminant sorbent is aminopropyltriethoxysilane,

Wherein the thermosensitive polymer is (trimethoxysilyl) propyl methacrylic acid. The present invention also provides a method for producing mesoporous silica coated with thermosensitive polymer for selective adsorption of contaminants. FIG. 1 shows a schematic diagram of a process for producing a thermosensitive polymer-coated mesoporous silica according to the present invention.

For example, mesoporous silica (MS) is synthesized, aminopropyltriethoxysilane and (trimethoxysilyl) propylmethacrylic acid are mixed with the mesoporous silica, and mesoporous silica-contaminant adsorbent-temperature sensitive polymer (MS @ APTES @ MOP), followed by the addition of N-isopropylacrylamide to MS @ APTES @ MOP to induce polymerization to form a mesoporous silica-contaminant sorbent-poly (N-isopropylacrylamide) The polymer complex MS @ APTES @ PNIPAm can be prepared.

The method for preparing a thermosensitive polymer-coated mesoporous silica for selectively adsorbing contaminants according to the present invention is characterized in that the step (A) comprises adding 1 to 2 parts by weight of a contaminant adsorbent to 1 part by weight of mesoporous silica, And 1 to 2 parts by weight of a hygroscopic polymer are added.

In the process for preparing a thermosensitive polymer-coated mesoporous silica for selective adsorption of a contaminant according to the present invention, the step (B) is a step of dissolving 1 part by weight of the mesoporous silica-contaminant adsorbent-temperature responsive polymer composite 1 part by weight of azobisisobutynitrile is added to induce the polymerization reaction of N-isopropylacrylamide.

In accordance with the present invention, there is provided a method for preparing a thermosensitive polymer-coated mesoporous silica for selective adsorption of a contaminant, wherein the contaminant is an anionic metal. The anionic metal may include an anionic heavy metal, an anionic valent metal or an anionic rare metal. For example, the anionic metal may be hexavalent chrome or arsenic.

In the method for preparing mesoporous silica coated with thermosensitive polymer for selective adsorption of contaminants according to the present invention, the contaminants may exhibit high adsorption performance in the range of pH 2.5 to pH 4.0.

The mesoporous silica coated with thermosensitive polymer may be subjected to a thermal treatment at 25 ° C. for 5 to 10 minutes, at a temperature of 40 ° C. to 200 ° C., Contaminants can be adsorbed within 300 minutes.

1 is a schematic diagram for the synthesis of mesoporous silica surface-treated with poly (N-isopropylacrylamide) and aminopropyltriethoxysilane.
2 is a thermogravimetric analysis graph of mesoporous silica surface-treated with aminopropyltriethoxysilane and (trimethoxysilyl) propylmethacrylic acid and mesoporous silica surface-treated with poly (N-isopropylacrylamide) .
FIG. 3 is a graph showing the results of measurement of mesoporous silica surface treated with mesoporous silica, aminopropyltriethoxysilane and (trimethoxytrimethoxysilyl) propylmethacrylic acid, and mesoporous silica surface treated with poly (N-isopropylacrylamide) BET analysis graph of silica.
4 is a graph showing the degree of removal of selective contaminants depending on the temperature of mesoporous silica surface-treated with poly (N-isopropylacrylamide) and aminopropyltriethoxysilane.
FIG. 5 is a graph showing the reaction rate when adsorbing metal contaminants on mesoporous silica surface-treated with poly (N-isopropylacrylamide) and aminopropyltriethoxysilane.
FIG. 6 is a graph showing the results of isothermal adsorption experiments confirming the adsorption performance of pollutants in the synthesized thermosensitive medium of poly (N-isopropylacrylamide) and mesoporous silica surface-treated with aminopropyltriethoxysilane.
7 is a graph showing adsorption of anionic metal contaminants depending on pH of mesoporous silica surface-treated with poly (N-isopropylacrylamide) and aminopropyltriethoxysilane.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for further illustrating the present invention, and the scope of the present invention is not limited by these examples.

<Examples>

Example  One: Mesoporous  Synthesis of silica (MS)

Polyethylene oxide-polypropylene oxide-polyethylene oxide and tetraethyl orthosilicate as a silica precursor are slowly added to a 0.2 M hydrochloric acid solution having a pH ranging from 1 to 2. When the prepared solution was stirred in a 40 ° C reactor for 12 hours, the mixed solution became opaque during the reaction. After 12 hours, the reaction solution was placed in a steel pressor and aged in an oven at 120 ° C for 8 hours. The aged solution was cooled at room temperature, filtered and washed with a vacuum filter, and dried at room temperature. After drying, calcination was carried out at 550 ° C. for 6 hours using an electric furnace to finally synthesize mesoporous silica having fine mesopores.

Example  2: Mesoporous  To silica Aminopropyltriethoxysilane  And ( Trimethoxysilyl ) &Lt; / RTI &gt; propyl methacrylate mixed MS @ APTES @ MOP

1.0 g of the mesoporous silica prepared in Example 1 was dispersed in 100 mL of toluene, and 1.17 mL of organic silane compounds having organic functional groups, 1.17 mL of trimethylsilylacetoxypropylmethacrylate and 1.82 mL of (trimethoxysilyl) propylmethacrylic acid Was slowly added dropwise. The prepared mixed solution was refluxed at 100 占 폚 for 12 hours in an oil bath and then cooled at room temperature. The particles were separated by centrifugation, washed three times with methanol, and then dried under vacuum at room temperature for 12 hours.

The particles prepared above were named MS @ APTES @ MOP and used as a precursor material for synthesizing mesoporous surface-treated with poly (N-isopropylacrylamide).

Example  3: MS @ APTES @ MOP with N-isopropyl Acrylamide  Preparation of the MS @ APTES @ PNIPAm added

500 mg of MS @ APTES @ MOP prepared in Example 2 was uniformly dispersed in 100 mL of acetonitrile solution using an ultrasonic washing machine, and then recrystallized N-isopropylacrylamide was adjusted to 300 mM. To induce polymerization of N-isopropylacrylamide in the mixed solution, 0.05 g of recrystallized azobisisobutyronitrile (2,2'-azobisisobutyronitrile) was added. The polymerization was carried out in a reactor adjusted to a nitrogen atmosphere Followed by refluxing at 90 DEG C for 16 hours. The particles were separated by centrifugation, washed with ethanol three times, and dried under vacuum at room temperature for 12 hours.

The particles prepared above were designated as MS @ APTES @ PNIPAm, and their characterization and removal experiments on anionic metal contaminants were performed.

Example  4: Thermogravimetric analysis of MS @ APTES @ MOP and MS @ APTES @ PNIPAm

FIG. 2 shows a thermogravimetric analysis (SDT Q900 TA instrument) graph of MS @ APTES @ MOP and MS @ APTES @ PNIPAm prepared in Example 2 and Example 3, respectively.

Referring to the graph of the thermogravimetric analysis of the synthesized mediums of FIG. 2, the ratio of aminopropyltriethoxysilane and (trimethoxysilyl) propylmethacrylate surface-treated to mesoporous silica in MS @ APTES @ (About 24%), and the poly (N-isopropylacrylamide) surface-treated on finally synthesized MS @ APTES @ PNIPAm is about 19.6% by weight.

Example  5: MS, MS @ APTES @ MOP, MS @ APTES @ PNIPAm BET analysis

A graph of the BET analysis results of MS, MS @ APTES @ MOP, and MS @ APTES @ PNIPAm prepared in Examples 1 to 3 is shown in FIG.

Referring to the graph of the BET analysis results of the synthesized media of FIG. 3, the media synthesized from the above examples exhibit the H1 type hysteresis pore shape, and the result is that the pores of the synthesized medium are cylindrical in shape, Slit shape. It also shows that the amount of gas adsorbed to the mesoporous silica by the surface treatment is greatly reduced. This result shows that the polymer material has been successfully treated on the surface and pores of the mesoporous silica.

< Experimental Example >

Cr (VI) was used as an anionic contaminant and general characteristics of Cr (VI) are shown in Table 1 below.

Name Hexavalent chromium Molecular formula K ₂ Cr ₂ O ₇ Formula weight (g / mol) 294.185 Density (g / cm ³ ) 2.676 Odor odorless

Experimental Example  One. Anionic  Influence of Initial Temperature on Adsorption of Metal Contaminants and Kinetics Analysis

The effect of temperature and reaction time were analyzed in the removal of anionic metal contaminants using the synthesized thermosensitive media. For this experiment, 50 mL of aqueous solution was added to a 250 mL Erlenmeyer flask, and the pH was adjusted to 2.5, the temperature was adjusted to 25 ° C. and 40 ° C., and the mixture was stirred with 0.01 g of MS @ APTES @ PNIPAm for 1 hour Poly (N-isopropylacrylamide) present on the mesoporous silica surface was induced to swell and condense sufficiently. The concentration of the anionic metal contaminant was adjusted to 31 mg / L in the 50 mL reaction solution, and sampling was performed at regular intervals to confirm the adsorption of contaminants and the influence of temperature on the contact time. The sampled samples were centrifuged to remove the medium remaining in the solution, and the anionic metal contaminants remaining in the solution were separated by the diphenylcarbazide method to form complexes. The absorbance was analyzed by a spectrophotometer and the adsorption capacity was calculated 4. The concentration of anionic metal contaminants was determined and the reaction rate was calculated using a pseudo-first order, pseudo-second order model. The results are modeled and shown in FIG.

The results of FIG. 4 show the influence of the initial temperature on the adsorption of anionic contaminants and the reaction time analysis results. In the case of removing the anionic metallic contaminants using the temperature sensitive medium, the initial temperatures of 25 ° C. and 40 ° C. 38.6% and 79.7%, respectively.

5, the adsorption capacities of the anionic metal contaminants of mesoporous silica surface treated with poly (N-isopropylacrylamide) were 56.4 mg at initial temperatures of 25 ° C and 40 ° C, respectively / g and 121.4 mg / g, respectively. The time for reaching the adsorption equilibrium was confirmed within 5 to 10 minutes at 25 ° C and 200 to 300 minutes at 40 ° C.

Experimental Example  2. With poly (N-isopropylacrylamide)  Surface-treated Mesoporous  Using silica Anionic  Isotherm analysis of metals

Isothermal adsorption analysis experiment was conducted to confirm the adsorption performance of contaminants in synthesized thermosensitive media. In the experiment, 50 mL of an aqueous solution having a pH of 2.5 and a constant temperature of 25 ° C. and 40 ° C. was added to a 250 mL Erlenmeyer flask, and 0.01 g of MS @ APTES @ PNIPAm was added thereto. After stirring for 1 hour in the reaction solution, Poly (N-isopropylacrylamide) present on the surface of the porous silica was sufficiently swollen and condensed. The concentration of anionic metal contaminants in the 50 mL reaction solution was varied from 19.1 to 124.6 mg / L, and the flask was agitated at 160 rpm for 24 hours. After the adsorption equilibrium is reached, the concentration of the contaminants remaining in the solution is checked, and the adsorption performance, binding affinity and adsorption curve of the maximum anionic group contaminants are modeled using the Langmuir model and shown in FIG. 6 and Table 2.

Referring to the isothermal adsorption graph of FIG. 6, the maximum adsorption amount of the anionic metal contaminants of the mesoporous silica surface-treated with poly (N-isopropylacrylamide) was 414.9 mg / g and the affinity was 0.015 L / g Showing excellent anionic metal adsorption performance.

Langmuir coefficients q _max (mg / g) b (L / mg) R ² 414.9 0.015 0.982

Experimental Example  3. Anionic  Effect of pH on Adsorption of Metal Contaminants

Experiments were conducted to confirm the effect of pH on the removal of anionic metal contaminants using mesoporous silica surface treated with thermosensitive polymer. 50 mL of anionic metal contaminants at 30.9 to 31.7 mg / L and 0.01 g of MS @ APTES @ PNIPAm, which were adjusted to pH 2.5 to 10 using 0.1 M HCl or 0.1 M NaOH, were added to a 250 mL Erlenmeyer flask And stirred at 160 rpm for 24 hours in a 40 DEG C stirrer. After the adsorption equilibrium was reached, the complexes were formed using the diphenylcarbazide method to confirm the concentration of the contaminants remaining in the solution. The complexes were then formed using a spectrophotometer (UV-Vis spectrophotometer, JASCO, V-550) , And the results are shown in Fig.

7, the adsorption results of anionic metal contaminants on mesoporous silica surface treated with poly (N-isopropylacrylamide) are shown in the range of pH 2.5 and pH 4.0 Indicating a high adsorption capacity at a relatively low pH range.

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (7)

(A) synthesizing a mesoporous silica-contaminant sorbent-thermosensitive polymer complex by adding a pollutant sorbent and a thermosensitive polymer to the mesoporous silica; And
(B) N-isopropylacrylamide is added to the mesoporous silica-contaminant adsorbent-thermosensitive polymer complex and the polymerization reaction is induced in a nitrogen atmosphere to obtain a mesoporous silica-contaminant adsorbent-N-isopropylacrylamide polymer And synthesizing the complex,
Wherein the contaminant sorbent is aminopropyltriethoxysilane,
Wherein the thermosensitive polymer is (trimethoxysilyl) propyl methacrylic acid. 2. The method of claim 1, wherein the thermosensitive polymer is (trimethoxysilyl) propyl methacrylate.
The method according to claim 1,
Wherein step (A) comprises adding 1-2 parts by weight of a pollutant adsorbent to 1 part by weight of mesoporous silica and 1-2 parts by weight of a temperature responsive polymer. Lt; RTI ID = 0.0 &gt; mesoporous &lt; / RTI &gt;
The method according to claim 1,
Step (B) is characterized in that 1 part by weight of azobisisobutynitrile is added to 1 part by weight of the mesoporous silica-contaminant adsorbent-temperature responsive polymer composite to induce polymerization reaction of N-isopropylacrylamide A process for the preparation of thermosensitive polymer coated mesoporous silica for the selective adsorption of contaminants.
The method according to claim 1,
Wherein the contaminant is an anionic metal. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
. 5. The method of claim 4,
Wherein the anionic metal comprises an anionic heavy metal, an anionic valent metal or an anionic rare metal. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
The method according to claim 1,
Wherein the contaminant exhibits a high adsorption performance in the pH range of 2.5 to pH 4.0. 2. The method of claim 1, wherein the contaminant exhibits a high adsorption performance in the range of pH 2.5 to pH 4.0.
The method according to claim 1,
Wherein the thermosensitive polymer-coated mesoporous silica adsorbs contaminants within 5 minutes to 10 minutes at &lt; RTI ID = 0.0 &gt; 25 C &lt; / RTI &&Lt; / RTI &gt;

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