WO2018216925A1

WO2018216925A1 - Method for preparing arsenic adsorbent, arsenic adsorbent prepared thereby, and method for removing arsenic using same arsenic adsorbent

Info

Publication number: WO2018216925A1
Application number: PCT/KR2018/005218
Authority: WO
Inventors: 장민
Original assignee: 주식회사 산하이앤씨
Priority date: 2017-05-26
Filing date: 2018-05-04
Publication date: 2018-11-29

Abstract

The present invention relates to a method for preparing an arsenic adsorbent wherein the arsenic adsorbent is prepared by mixing a magnesium compound and an iron compound, the method comprising step (a) for mixing a magnesium compound solution and an iron compound solution, wherein the magnesium compound is any one of MgSO4·7H2O or MgCl2, and the iron compound is any one of Fe2(SO4)3·5H2O or FeCl3.

Description

[Correction 10.05.2018 by Rule 26] Arsenic adsorbent manufacturing method, arsenic adsorbent manufactured by the method and arsenic removal method using the arsenic adsorbent

The invention according to synthetic methods Layered Double Hydroxide Preparation of arsenic sorbent for adsorbing an arsenic contained in water, relates to the arsenic removal method using an arsenic adsorbent and the arsenic sorbent prepared by a production method, the layered double hydroxide Mg ² ⁺ Fe ³ ⁺ or a metal cation and economical and environmentally friendly anion is Cl ^- or the like, or an invention relating to a process for producing arsenic adsorbent optimized around the SO ₄ ^2-.

Arsenic is the first group of carcinogens, and is known for its chemical stability, for the use of pesticides or herbicides, for artificial activities such as mining activities, or for the change in the geochemical stability of arsenic in underground rock due to changes in reduction-oxidation potential (REDOX). It is known to be eluted underwater due to a decrease or the like.

Arsenic contamination can extend to groundwater and surface water and poses serious problems for human and other living health. Prolonged consumption of arsenic-contaminated water can cause serious health problems, including skin lesions, liver cancer, and gastrointestinal damage.

Arsenic is a metalloid in the form of arsenite and arsenate. Trivalent is about 10 times more toxic than pentavalent arsenic. It is related.

As arsenic contamination is a worldwide phenomenon and can pose a number of health risks, there is an urgent need for highly effective and economical techniques to remove arsenic from water.

Although technologies such as oxidation, coagulation / agglomeration, adsorption, ion exchange and membranes have been developed to remove arsenic from contaminated water, adsorption is widely known to be a complex, economical and effective method.

1 is a layered double hydroxide (LDH) containing sulfate, a two-dimensional (2D) ionic layered compound. Such compounds are also known as hydrotalcite, and these compounds have a variety of brucite structures due to the availability of a wide range of compositions and methods of preparation.

LDH contains a positively charged metal hydroxide layer and an exchangeable anion (-) between the layers for charge neutrality, and chemically [M _1-x ²⁺ M _x ³ ⁺ (OH) ₂ ] ^x ⁺ And [(A) _{m / x} ^m- nH ₂ O] ^x- are composed of layers.

Divalent and trivalent metal cations are represented by M ²⁺ and M ³⁺ , respectively. These M ²⁺ and M ³⁺ species are used for the synthesis of LDH compounds, and the compound interlayer anions (A ^{m −} ) include NO ₂ ^3- , CO ₃ ^3- and the like. Water molecules are usually buried between the hydroxide layers during synthesis.

In general, the value of X varies from 0.20 to 0.33, and the M ²⁺ to M ³⁺ mole ratio is 2.0 to 4.0 with supercapacities, based on the excellent anion exchange capability of organic or inorganic anions. It is applied as an adsorbent in catalysts, drug delivery and water treatment, and has great potential due to its non-toxicity, low cost, high surface area, pore and possibility of functional chemicals tuning.

The prior art 1 discloses a method of removing arsenic in water using a layered double hydroxide. Korean Patent Registration No. 10-1185877 discloses a method of preparing LDH, an arsenic adsorbent, by mixing a Mn (NO ₃ ) ₂ solution with a Fe (NO ₃ ) ³ solution.

TABLE 1

[Table 1] shows the maximum adsorption amount of trivalent arsenic and pentavalent arsenic using LDH disclosed in Korean Patent Registration No. 10-1185877, which is the prior art 1, and shows the maximum adsorption amount of arsenic using Langmuir adsorption model. The calculated values are shown in a table.

Arsenic maximum adsorption amount of LDH prepared according to the prior art 1 is 13.725 (mg As / g LDH) for trivalent arsenic and 10.5 (mg As / g LDH) for pentavalent arsenic, but still increases the maximum adsorption amount of arsenic. There is a need for improved LDH.

It looks at the prior art 2 that discloses a method and apparatus for purifying heavy metals including arsenic contained in metal mine drainage. Korean Patent Registration No. 10-0968952 discloses a method of purifying metal mine drainage using coal mine drainage sludge (CMDS), specifically, the water discharged from the metal mine is coal mine drainage. By reacting with the sludge, the heavy metal contained in the metal mine effluent is fixed to the coal mine drainage sludge to purify the metal mine drainage.

However, the prior art 2 only suggests a method and apparatus for adsorbing arsenic using CMDS, and the adsorption effect of arsenic is unclear. Therefore, an adsorbent capable of increasing arsenic adsorption is still required.

(Patent Document 1) KR10-1185877 B

(Patent Document 2) KR10-0968952 B

It is an object of the present invention to provide an LDH manufacturing method capable of removing arsenic much more effectively than the LDH according to the related art, and an arsenic adsorbent prepared by the method. In particular, it is an object of the present invention to provide a method for producing an improved LDH having superior arsenic adsorption effects compared to the prior art.

Arsenic adsorbent manufacturing method according to the present invention to solve the above problems is, (a) comprises the step of mixing the magnesium compound solution and the solution of the iron compound, the magnesium compound is either of MgSO ₄ .7H ₂ O or MgCl ₂ and, and the one wherein the iron compound is any one of _{_{_{Fe 2 (SO 4) 3 .5H}}} 2 O , or FeCl _3.

Preferably, the magnesium compounds are MgSO ₄ and .7H ₂ O, wherein the iron compound is _{_{_{Fe 2 (SO 4) 3 .5H}}} 2 O.

Preferably, the magnesium compound is 240 to 250 parts by weight based on 100 parts by weight of the iron compound.

Preferably, the mole ratio of magnesium and iron in the mixture of step (a) is 2.2: 1 to 2.7: 1.

Preferably, (b) after step (a), maintaining the pH of the mixture solution produced in step (a) at 9 to 10; And (c) after step (b), further drying the solid produced from the mixture produced in step (b) at 90 to 110 ° C. for 10 to 24 hours.

Arsenic adsorbent according to the present invention includes an arsenic adsorbent prepared by the above-described manufacturing method.

Arsenic removal method according to the invention comprises the step of contacting the arsenic adsorbent prepared by the above-described method for producing arsenic adsorbent with arsenic-containing water.

Arsenic contained in the water by the above-mentioned problem solving means can be effectively removed far superior to the prior art. That is, the improved LDH produced by mixing the magnesium compound and the iron compound can remove a large amount of arsenic more effectively than the LDH according to the prior art.

In addition, by replacing the arsenic adsorbent according to the prior art with the LDH according to the present invention can be effectively removed arsenic in water.

1 is a diagram conceptually illustrating a layered double hydroxide in which sulfate is inserted.

Figure 2 is a graph showing the adsorption kinetics results for the arsenic pentavalent of the arsenic adsorbent LDH according to the present invention.

Figure 3 is a graph showing the adsorption kinetics results for the arsenic trivalent of the arsenic adsorbent LDH according to the present invention.

Figure 4 is a graph showing the adsorption isotherm results for the arsenic pentavalent of the arsenic adsorbent LDH according to the present invention.

Figure 5 is a graph showing the adsorption isotherm results for the arsenic trivalent of the arsenic adsorbent LDH according to the present invention.

Figure 6 is a graph showing the results of the adsorption isotherm comparison of the arsenic trivalent and pentavalent of the MSFS in the arsenic adsorbent LDH according to the present invention and CMDS of the prior art 2.

Hereinafter, preferred embodiments of the method according to the present invention will be described with reference to the accompanying drawings. In this process, the thickness of the lines or the size of the components shown in the drawings may be exaggerated for clarity and convenience of description. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to the intention or convention of a user or an operator. Therefore, the definitions of these terms should be made based on the contents throughout the specification.

1. a layered double hydroxide as an arsenic adsorbent ( LDH ) Manufacturing method

TABLE 2

Magnesium and iron chemicals are added to 100 mL of water with the weight shown in [Table 2] and dissolved by stirring at 150 to 500 rpm for about 30 minutes to 1 hour.

The pH of the solution is then adjusted to 10 using 1-10 M NaOH. After adjusting to pH 10, stirring is continued for 1 to 5 hours. After stirring, the solution is allowed to stand until no solid is left in the supernatant. After the supernatant is poured still, the solids are dried in a drying oven at 100 degrees for 10 to 24 hours.

After drying, the solids are washed with tap water using a washing mechanism with a sieve (mesh), but washed until the electrical conductivity of the washing water is 0 to 10 mS / cm.

2. Experimental method

2.1. Arsenic Trivalent and Pentavalent Adsorption Kinetic Experiments

In experiments to determine the kinetics rate constant for arsenic adsorption, 500 mL arsenic trivalent and 500 mL arsenic pentavalent solutions were placed in a 1 L Erlenmeyer flask at an initial concentration of 20 mg / L and performed without pH adjustment. At this time, the pH of the solution was 6.1 to 6.8 and there was no significant change in pH when the adsorbent was added. The shaking speed was 300 rpm and proceeded for 5 hours.

Samples were taken at predetermined time intervals and arsenic was analyzed by inductively coupled plasma emission spectroscopy (ICP-OES, Optima 5300V, Perkin Elmer). All kinetic data were derived from various factors using a pseudo-second order kinetic model.

2.2. Arsenic trivalent and pentavalent adsorption isotherm experiments

After preparing 50 mL of the solution dissolved in trivalent to

pentavalent arsenic

1, 2, 5, 8, 12, 16 and 20 mg / L, respectively, 0.01 g of an arsenic adsorbent according to the present invention was added thereto and shaken for 24 hours. After shaking, 10 mL of the suspension was filtered using a 0.45 μm pore filter, and the arsenic concentration of the filtrate was analyzed by ICP-OES. After analyzing the data, relevant parameter values were obtained using Langmuir and Freundlich model.

3. Experimental Results

3.1. Adsorption Kinetic Results for Arsenic Pentavalent of LDH, an Arsenic Adsorbent

TABLE 3

Table 3 and Figure 2 are the adsorption kinetics results of the arsenic pentavalent of the arsenic adsorbent LDH according to the present invention.

The equilibrium adsorption capacity (Qeq) is 69.2 mg / g MSFS, which is relatively higher than other media. The adsorption capacity sequence was found to be MSFS> MCFS> MSFC> MCFC. It can be seen that the ion exchange rate with arsenic pentavalent increases when sulfate enters the compound interlayer anion.

However, MSFS has lower initial sorption rate than MSFC or MCFS. This is because the sulfate in the LDH layer takes time for the diffusion required to sufficiently ion exchange with arsenic pentavalent.

3.2. Adsorption Kinetic Results for Arsenic Trivalent of LDH, an Arsenic Adsorbent

TABLE 4

Table 4 and FIG. 3 are adsorption kinetics results for the arsenic trivalent of the arsenic adsorbent LDH according to the present invention.

The equilibrium adsorption capacity (Qeq) was 52.3 mg / g, which was much higher than other media. The adsorption rates and capabilities of other media besides MSFS are similar. The adsorption capacity sequence is shown as MSFS> MCFS, MSFC, MCFC. Therefore, the adsorption efficiency for arsenic trivalent is high in MSFS similar to arsenic pentavalent.

Unlike arsenic pentavalent, arsenic trivalent is not ionized in water, so the adsorption mechanism of arsenic trivalent is related to the binding force of anions present in the layer. That is, since chloride has a higher binding force with a compound than sulfate, adsorption of arsenic trivalent has tended to be delayed.

3.3. Adsorption isotherm results for arsenic pentavalent of arsenic adsorbent LDH according to the present invention

TABLE 5

[Table 5] and Figure 4 is the adsorption isotherm results for the arsenic pentavalent of the arsenic adsorbent LDH according to the present invention.

MSFS has a much higher adsorption capacity than other media. The order of adsorption capacity was MSFS> MCFS> MSFC = MCFC, and MSFS was 44.4 mg / g at the maximum adsorption amount (Qmax) using the Langmuir model, about 1.7 to 2.5 times higher than other media. In particular, the maximum adsorption amount Qmax is 4.2 times higher than the maximum adsorption amount Qmax according to the prior art 1, which is 10.5 mg / g.

As a result of applying the isotherm model, the Langmuir model fits well with the MSFS, indicating that only sulphate is present in the adsorption layer, so that arsenic pentavalent is adsorbed in the form of ion exchange. .

However, for the other media, the Langmuir and Freundlich model results were similar. This is due to the heterogeneity caused by the formation of sulfate and chloride in the adsorption layer.

In the Freundlich model, K _F is an indicator of the adsorption capacity of the adsorbent, and 1 / n is the adsorption strength for the adsorption capacity. If 1 / n is less than 1, the adsorption proceeds chemically, but the lower the value, the higher the adsorption affinity. MSFS is suitable for removing Arsenic pentavalent when the K _F value is higher and 1 / n is relatively lower than other media.

3.4. Adsorption isotherm results for arsenic trivalent of arsenic adsorbent LDH according to the present invention

TABLE 6

[Table 6] and Figure 5 is the adsorption isotherm results for the arsenic trivalent of the arsenic adsorbent LDH according to the present invention.

Among the media, MSFS had higher adsorption capacity than other media. The order of adsorption capacity on the graph is MSFS> MSFC> MCFS = MCFC. However, the maximum adsorption amount (Qmax) using the Langmuir model showed similar results with 56.2 to 61.6 mg / g in all four media. However, the maximum adsorption amount shows a adsorption capacity of 4.0 to 4.5 times or more as compared with the maximum adsorption amount Qmax according to the prior art 1 which is 13.725 mg / g.

As a result of applying the Freundlich model, MSFS had a K _F of 16.23, which is higher than other media, and 1 / n was 0.55. Although MSFS is faster in arsenic trivalent removal than other media, the results show no significant difference from other media in adsorption after 24 hour shaking. This is because the charge) is neutral and similar exchange occurs with anions bound in the LDH layer.

3.5. Comparison of adsorption isotherms for arsenic trivalent and pentavalent of MSFS in LDH, an arsenic adsorbent, and CMDS, a conventional heavy metal adsorbent, according to the present invention

TABLE 7

[Table 7] and FIG. 6 are adsorption isotherm comparison results for arsenic trivalent and pentavalent of MSFS and CMDS in LDH, the arsenic adsorbent according to the present invention.

As a result, MSFS showed a maximum adsorption amount (Qmax) of 2.33 times for arsenic pentavalent and 1.6 times higher for arsenic trivalent than CMDS. In the case of MSFS, the model parameters were similar to those of the previous experiment, but the higher arsenic concentration (1 to 80 mg / L) resulted in higher Determination coefficient (R ² ) of the Freundlich model than Langmuir. . The reason seems to be that arsenic adsorption takes place in a multilayer form in the layer.

In the present specification, the present invention has been described with reference to the embodiments shown in the drawings so that those skilled in the art can easily understand and reproduce the present invention, which is merely exemplary, and those skilled in the art can make various modifications and equivalents from the embodiments of the present invention. It will be appreciated that embodiments are possible. Therefore, the protection scope of the present invention will be defined by the claims.

Claims

(a) mixing the magnesium compound solution with the iron compound solution to produce an arsenic adsorbent;

(b) injecting the arsenic adsorbent prepared in step (a) into water containing arsenic trivalent; And

(c) after step (b), the arsenic adsorbent in step (a) is introduced into water containing arsenic trivalent in step (b) and shaken for 23 to 25 hours,

The magnesium compounds and MgSO 4 .7H 2 O, and the iron compound is Fe 2 (SO 4) 3 .5H 2 O,

The magnesium compound is 240 to 250 parts by weight based on 100 parts by weight of the iron compound,

In the step (b), the arsenic trivalent is 0.5 to 10 parts by weight based on 100 parts by weight of the arsenic adsorbent is injected.