KR20170117742A - Adsorbents for selective removal of arsenic and adsorbent manufacturing method - Google Patents

Abstract

A method of making an adsorbent for selective arsenic removal is disclosed. A method for preparing an adsorbent for selective arsenic removal comprising the steps of: a) dissolving 24.9 g of ferrous sulfate in 1 L of a 0.1 M hydrochloric acid aqueous solution to prepare an iron aqueous solution; b) adjusting the pH of the aqueous solution of iron to be 4 - 14 using sodium hydroxide; And c) reacting the iron aqueous solution having a pH adjusted to 4 - 14 for 30 minutes to 24 hours, and recovering the precipitated iron oxide as an adsorbent. According to the method for preparing an adsorbent for selective arsenic removal according to the present invention, an adsorbent composed of iron oxides having a low specific gravity and a low specific gravity, synthesized by reacting iron oxide with pH 6.0 for 1 hour, It is possible to provide an effect that the arsenic can be selectively removed by adsorption.

Description

Technical Field [0001] The present invention relates to an adsorbent for selective arsenic removal and a method for producing the adsorbent,

The present invention relates to an adsorbent for selective arsenic removal and a method for preparing the same, and more particularly, to a method for selectively removing arsenic from an aqueous solution contaminated with various kinds of heavy metals by selectively adsorbing it with an adsorbent composed of iron oxide And to a method for producing the adsorbent.

Arsenic (As) causes serious environmental problems for humans and animals. In most studies the problem with arsenic is related to groundwater and is caused by dissolution by weathering and geochemical changes in rocks. Arsenic contamination is caused by human activities such as mine waste, petroleum refining, sludge, pesticides, and coal fly ash.

Arsenic is associated with water treatment related to human health. Inorganic arsenic compounds are more toxic than organic arsenic compounds and As (III) -arsenite is more toxic than As (V) -arsenate. The chemical species of arsenic are different depending on the hydrogen ion concentration of the solution (hereinafter referred to as 'pH' below pH), and 3 and 5 are the microorganisms, oxidation-reduction potential, pH, iron sulfide, iron / manganese / aluminum oxidation / And the presence of the. Toxicity is arsenite> arsenate> monomethylarsonate> dimethylarsenate 3 is more than 60 times more toxic than 5, inorganic arsenic is 100 times more toxic than organic arsenic Lt; / RTI >

Metal deposits, including gold ore deposits developed in Korea in the past, are contained in mine tailings containing large amounts of arsenic-bearing iron-bearing minerals (mine tailings) Arsenic contamination of the surrounding environment has been reported to be serious due to arsenate and arsenate type arsenic.

The co-precipitation and adsorption techniques using the chemical properties of arsenic are the most technological and most economical technologies for removing arsenic. Recently, the removal of arsenic from iron (oxide) has been widely used. Recently, the adsorption of arsenic using oxides such as manganese, zinc, cobalt and zero valence iron has been actively studied. In order to solve the problems that occur when using zero valence iron, a technique of stabilizing arsenic by using ferrous iron and trivalent iron hydroxides generated by the oxidation of zero valence iron has been studied

In the previous studies, most of the minerals were synthesized for iron oxide / hydroxide and the adsorption efficiency for specific heavy metals was evaluated.

As a prior art for removing or treating arsenic contained in water, Korean Patent Laid-Open Publication No. 1998-34093 (published on October 22, 1996) discloses a water treatment method and a water treatment agent for removing arsenic. This water treatment method is a method in which water containing arsenic is paramagnetic. Ferromagnetic complex iron oxide.

As another prior art, Korean Patent Laid-Open No. 10-2006-43157 (Publication Date: May 05, 2006) discloses a method for removing arsenic from water. This arsenic removal method relates to a method of removing arsenic from water by contacting a strong base anion exchange resin containing a metal ion or a metal-containing ion with water.

As another prior art, Korean Patent Laid-Open No. 10-2011-58495 (Laid-open date: 2011.06.01) discloses a method for treating trivalent arsenic present in water. This treatment method is an oxidation step in which +5 is oxidized to +5 in arsenic in the form of trivalent in water, and +5 in the case of contaminated water that has undergone oxidation step by adsorbing arsenic.

As in the prior art, adsorbents used for the adsorption treatment of arsenic include active aluminum, gibbsite, fly ash, and manganese coating materials, but arsenic adsorption methods using zero valence iron and iron oxide / The removal effect is known to be the best.

Rebar slag contains a large amount of Al, Fe, Mn, Si, Mg oxide, Ca component, etc. Recently, heavy metals and arsenic can be removed by adsorption or coprecipitation. The arsenic adsorption method using zero-valent iron and iron oxide has proven to be highly effective in removing arsenic. Hematite (α-Fe2O3) is a typical iron (oxide) oxide widely distributed in nature. As primary minerals are exposed to the surface and weathered, secondary minerals are known to be the most stable iron oxide in thermodynamical form. Hematite has a relatively large specific surface area and is known to have an arsenic adsorption capacity similar to that of ferrihydrite and goethite. Techniques for recovering groundwater with arsenic include coprecipitation and precipitation, ion exchange, adsorption with activated alumina, reverse osmosis filtration, membrane filtration, and electrodialysis. However, these techniques have a disadvantage in that a large amount of sludge is generated or treated.

The current trend is that the adsorption treatment technology using adsorbent, which is a small-scale treatment facility, has less installation and operation cost than membrane and ion exchange treatment technology and is not much affected by ground water quality, and is applied to arsenic contaminated groundwater.

Previous studies have shown that minerals are amorphous and have a relatively small specific surface area, which is advantageous for arsenic adsorption. However, complex processes such as various materials and specific environments are required to produce pure iron oxide / hydroxide with these conditions There are disadvantages. In addition, an adsorbent capable of selectively adsorbing arsenic from water contaminated with various kinds of heavy metals has not been developed yet, and it is required to develop an adsorbent capable of selectively adsorbing arsenic from water contaminated with various kinds of heavy metals have.

. Korean Patent Publication No. 10-2006-43157 (published on May 15, 2006) . Korean Patent Publication No. 10-2006-43157 (published on May 15, 2006) . Korean Patent Publication No. 10-2011-58495 (Published Date: 2011.06.01)

It is an object of the present invention to provide an adsorbent comprising iron oxides capable of selectively removing arsenic from an aqueous solution containing various heavy metals.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to at least partially solve the problems in the conventional arts. It can be understood.

According to the present invention, there is provided a process for preparing a ferrous sulfate aqueous solution, comprising the steps of: a) dissolving ferrous sulfate in an aqueous hydrochloric acid solution to prepare an iron aqueous solution, dissolving 22-26 g of ferrous sulfate based on 1 L of 0.1 M hydrochloric acid aqueous solution, Producing; b) adjusting the pH of the aqueous solution of iron to be 4 - 14 using sodium hydroxide; And c) reacting the iron aqueous solution adjusted to have a pH of 4 to 14 for 30 minutes to 24 hours, and recovering the precipitated iron oxide as an adsorbent. Lt; / RTI >

The step c) further comprises washing the recovered precipitate with distilled water and drying the recovered precipitate.

The step c) is carried out at room temperature.

The step (b) is characterized in that the pH of the aqueous iron solution is adjusted to 5-7.

This object is achieved according to the present invention by an adsorbent for selective arsenic removal, characterized in that it is prepared by a process for preparing an adsorbent for selective arsenic removal and comprises iron oxides.

According to the present invention, it is possible to obtain an adsorbent composed of iron oxides having a low crystallinity and a high specific surface area by reacting an iron aqueous solution at room temperature for 1 hour at pH 6.0 to thereby obtain arsenic from water containing various kinds of heavy metals It is possible to provide an effect that can be adsorbed and removed. That is, the adsorbent according to the present invention is composed of the iron oxides synthesized after reacting the iron aqueous solution at room temperature for 1 hour at room temperature. Such iron oxides have a low crystallinity and a very high specific surface area, Since the re-dissolution rate after adsorption is very low, it can not be redissolved again after adsorption, so that it is possible to selectively adsorb and remove arsenic when various kinds of heavy metals are mixed.

FIG. 1 is a flow chart for explaining a method for producing an adsorbent for selective arsenic removal according to the present invention.
FIG. 2 is a photograph showing a precipitate as a red iron oxide adsorbent obtained according to the method for producing an adsorbent for selective arsenic removal according to the present invention.
3 to 8 are graphs and analysis results of the diffraction analysis of the iron-oxide precipitate obtained according to the method for producing an adsorbent for selective arsenic removal according to the present invention.
FIGS. 9 and 10 are graphs showing the adsorption ratios of the iridium oxide adsorbent obtained according to the method for producing an adsorbent for selective arsenic removal according to the present invention, according to time and pH.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, the well-known functions or constructions are not described in order to simplify the gist of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart for explaining a method for producing an adsorbent for selective arsenic removal according to the present invention; FIG.

As shown in FIG. 1, the method of preparing an adsorbent for selective arsenic removal according to the present invention comprises synthesizing an adsorbent composed of iron oxides capable of selectively adsorbing and removing arsenic in an aqueous solution contaminated with various kinds of heavy metals (S1) for preparing an iron aqueous solution by dissolving ferrous sulfate in an aqueous hydrochloric acid solution, and dissolving 22 to 26 g of ferrous sulfate based on 1 L of 0.1 M hydrochloric acid aqueous solution to prepare an iron aqueous solution; (S2) of adjusting the pH of the aqueous solution to 4 to 14 using sodium hydroxide, and a step (S2) of adjusting the pH of the aqueous solution of iron And a step (S3) of reacting the aqueous solution for 30 minutes to 24 hours and then recovering the precipitated iron oxide as an adsorbent.

This will be described more specifically.

a) Step

An iron aqueous solution is prepared by dissolving ferrous sulfate in an aqueous hydrochloric acid solution to prepare an iron aqueous solution, wherein 22-26 g of ferrous sulfate is dissolved based on 1 L of 0.1 M hydrochloric acid aqueous solution.

A 0.1 M hydrochloric acid aqueous solution is prepared by adding 8.84 ml of 35% hydrochloric acid in purity to 1 L of water.

22-26 g of ferrous sulfate is dissolved. Preferably, 24.9 g of ferrous sulfate is dissolved.

In this embodiment, ferrous sulfate was prepared by dissolving 22-26 g, preferably 24.9 g, of ferrous sulfate in an aqueous hydrochloric acid solution, but the present invention is not limited thereto. The concentration of hydrochloric acid in the aqueous hydrochloric acid solution and the dissolution amount of ferrous sulfate vary .

b) Step

When an iron aqueous solution is obtained by the above-described procedure, the pH of the aqueous solution of iron is adjusted to be 4 to 14 by using sodium hydroxide in the aqueous solution of iron (S2)

At this time, the pH of the iron aqueous solution is preferably adjusted to 6. This is because the adsorption rate of the adsorbent composed of the iron oxide obtained by the reaction at pH 6 is the highest.

c) Step

(3) The reaction time of the aqueous solution of iron is 1 hour, and the reaction time of the iron (III) and the iron (III) is 30 minutes to 24 hours. The reaction of the aqueous solution is preferably carried out at room temperature.

The reaction of the iron aqueous solution at room temperature for 30 minutes to 24 hours is intended to save time and energy. That is, the iron (II) oxide (goethite) synthesis has been conventionally recovered by reacting at 70 ° C. for 60 hours. However, in this case, not only the time and energy are consumed, but also the degree of crystallization is high and the heavy metal adsorption rate is very low. Therefore, in order to overcome this, in the present invention, an iron aqueous solution adjusted to pH 6 at room temperature is reacted for 1 hour to recover precipitated iron oxide as an adsorbent

The precipitate recovered in the above-mentioned process is washed five times with distilled water and then completely dried.

As described above, the adsorbent composed of the iron oxides obtained by adjusting the pH of the aqueous solution of iron at room temperature to 6.0 and synthesizing (reacting) it at room temperature for 1 hour can selectively adsorb and remove arsenic from water containing various kinds of heavy metals do.

The selective adsorbent preparation method for selective arsenic removal may be applied to a field where a technique for selectively removing a specific element is required when various kinds of metals are mixed, such as selective removal of radionuclides in seawater.

The results of the analysis and analysis of the precipitates obtained by the above procedure are as follows.

In the accompanying drawings, FIG. 2 shows a sample of the precipitate recovered by reacting at a pH of 4 to 14 and a reaction time of 1 to 24 hours, respectively.

3 to 8 show the diffraction analysis graph of the iron oxide and the SEM / EDS analysis results.

As shown in FIG. 2, the precipitate (sample) recovered after reacting at pH 4 and 6 for 1 hour and 24 hours to produce an adsorbent for selective arsenic removal according to the present invention has the following characteristics.

First, the precipitate has a pale yellowish brown color. As the pH and time are increased, iron oxide of black brown to black is produced.

3 to 8, X-ray diffraction analysis showed that the main constituent minerals of the synthesized iron oxide / hydroxide are Goethite, Lepidocrocite and Magnetite, and adsorbent synthesis There are differences in the kind and crystallinity of the minerals produced according to pH and time conditions for the following.

Here, the low crystallinity provides sufficient space for adsorbing arsenic, and the adsorption capacity is increased because the particle size is small and the specific surface area is large.

. The iron oxides synthesized at pH 4.0 are goethite, and the samples reacted for 24 hours than 1 hour have higher crystallinity.

. The iron oxides synthesized at pH 6.0 contain goethite and some redeposite, and the samples reacted for 24 hours have higher crystallinity.

. The iron oxides synthesized at pH 8.0 are mostly magnetite and reedocrocite and contain some goethite.

. The iron oxides synthesized at pH 10.0 contain some redeposite and goethite, mostly magnetite.

. The iron oxides synthesized at pH 12.0 contained a very small amount of lepidocrocite in the sample reacted for 1 hour, but it is almost composed of magnetite.

. The iron oxides synthesized at pH 14.0 consisted of magnetite in both 1 hour and 24 hour reaction.

Third, as the pH increases, the kinds of iron oxides synthesized are Goethite → Goethite + Lepidocrocite + Magnetite → Magnetite. As the reaction time becomes longer, The crystallinity of Goethite synthesized at the same pH increases.

. Heavy metal adsorption experiment

The heavy metal adsorption experiment was carried out using the adsorbent prepared by the method of preparing the adsorbent for selective arsenic removal according to the present invention.

The process is as follows.

1. Prepare heavy metals such as Cu, Cd, Pb, As, and Hg at concentrations of 20ppm and 40ppm using heavy metal standard solution and distilled water.

2. Add 0.2 g of iron oxide synthesized under the reaction conditions of pH 4, 6, 8, 12, 14 and 1 to 24 hours to 40 ml of each heavy metal solution prepared and shake for 2 hours.

3. After shaking, centrifuge and filter the supernatant using a 0.45 μm filter, and perform an atomic absorption spectrophotometer (AAS) analysis.

4. To determine the amount of resuspension, add 40 ml of distilled water to the remaining sediment after the adsorption test and shake for 1 hour.

5. After shaking, centrifuge the supernatant using a 0.45 μm filter and conduct an atomic absorption spectrophotometer (AAS) analysis.

. Evaluation of Heavy Metal Adsorption Efficiency of Iron Oxide

Concentration change and adsorption efficiency after heavy metal adsorption by iron oxide synthesized according to the present invention are as follows.

As shown in Tables 1 to 4 and 9 and 10 in the accompanying drawings, the adsorption efficiencies of Fe-hydroxide synthesized by 1 hour and 24 hour reaction were compared, The sorption efficiency of the recovered iron oxide was found to be 0.0% for Cd and 1.44% for Cu, and the adsorption efficiency of the recovered iron oxides after 24 hours was 1.38%, Pb 6.92%, Hg 0 and As 72.76% , Pb 4.17%, Hg 0.0%, As 78.06%.

The adsorption efficiency of the iron oxides recovered after 24 hours from the adsorption efficiency of Cd was 0.0 and the adsorption efficiency of Cd was 0.02, %, Cu 0.43%, Pb 81.99%, Hg 0.0%, As 32.44%.

The adsorption efficiency of the iron oxides recovered after 24 hours was found to be Cd 0.03, which was 1.73% for Cu, 66.31% for Pb, 37.61% for Hg 0 and As, %, Cu 1.44%, Pb 20.78%, Hg 0.0%, and As 40.53%.

The adsorption efficiency of the iron oxides recovered after 24 hours was found to be Cd 0.02, Pb 14.14%, Hg 0, and As 43.62%, while the adsorption efficiency of the synthetic iron oxide recovered after 1 hour at pH 10.0 was almost zero %, Cu 1.31%, Pb 13.66%, Hg 0.0% and As 41.48%.

The adsorption efficiency of the purified iron oxide recovered after 24 hours was found to be Cd 0.02, Pd 9.55%, Hg 0, and As 39.53%, respectively. %, Cu 2.08%, Pb 12.58%, Hg 0.0% and As 48.43%.

The adsorption efficiency of the iron oxides recovered after 24 hours was found to be Cd 0.02, Pb 23.38%, Hg 0, and As 55.95%, respectively. %, Cu 1.04%, Pb 12.90%, Hg 0.0%, As 77.94%.

. Elution rate evaluation

According to the present invention, in order to measure the amount of heavy metals adsorbed after adsorbing heavy metals by using iron oxides synthesized according to the present invention, a sample adsorbed heavy metals was measured by immersing the adsorbed heavy metals in distilled water. The results of leaching after adsorption by iron oxide synthesized at 1 hour and 24 hours show that the amount of heavy metals excluding As (arsenic) and Pb (lead) is very small because the amount adsorbed to synthetic iron oxide is small. However, As and Pb tend to adsorb a large amount in a synthesized sample at a specific pH value and reaction time.

In the case of As, a large amount is adsorbed in the samples synthesized at pH 6.0 for 1 hour and at pH 4.0 for 24 hours. In the case of Pb, adsorbs a large amount in samples synthesized at pH 8.0 for 1 hour and pH 6.0 for 24 hours. In the case of As adsorbed by iron oxide, the amount of re-dissolving is very small, but the adsorption rate of Pb is 81.99% but the amount of re-dissolving is 25%. It is thought that As is adsorbed in the crystal structure and can not be re-released, but Pb is easily re-eluted on the surface.

As described above, the iron oxide as an adsorbent capable of selectively adsorbing and removing arsenic from water containing various heavy metals can be prepared by using the synthesizer condition according to the present invention, that is, at a pH of 6 at room temperature, a reaction time of 1 hour It was found that the iron oxides can selectively remove and adsorb arsenic from water containing various heavy metals.

According to the results of X-ray diffraction analysis and SEM analysis, it was judged that the iron oxide recovered after pH 6 and 1 hour of reaction time had high arsenic adsorption ability because of low crystallinity and small particle size and large specific surface area.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is obvious to those who have. Accordingly, it should be understood that such modifications or alterations should not be understood individually from the technical spirit and viewpoint of the present invention, and that modified embodiments fall within the scope of the claims of the present invention.

S1: Iron solution preparation step
S2: pH adjustment step
S3: Step of obtaining iron oxide by reaction and precipitate recovery

Claims (5)

a) dissolving ferrous sulfate in an aqueous hydrochloric acid solution to prepare an iron aqueous solution, and dissolving 22 to 26 g of ferrous sulfate based on 1 L of a 0.1 M hydrochloric acid aqueous solution to prepare an iron aqueous solution;
b) adjusting the pH of the aqueous solution of iron to be 4 - 14 using sodium hydroxide; And
c) recovering the precipitated iron oxide as an adsorbent after the reaction in the iron aqueous solution adjusted to pH 4 - 14 for 30 minutes to 24 hours.
A method for producing an adsorbent for selective arsenic removal. The method according to claim 1,
The step c)
Washing the recovered precipitate with distilled water, and drying the recovered precipitate.
A method for producing an adsorbent for selective arsenic removal. The method according to claim 1,
The step c)
Characterized in that it is carried out at room temperature,
A method for producing an adsorbent for selective arsenic removal. 4. The method according to any one of claims 1 to 3,
The step b)
Characterized in that the pH of the aqueous iron solution is adjusted to 5-7,
A method for producing an adsorbent for selective arsenic removal. A method for producing an adsorbent for selective arsenic removal according to claim 4,
Adsorbent for selective arsenic removal.

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