KR102389102B1 - Preparation method of arsenic adsorbent using iron-containing mine drainage - Google Patents

Abstract

The present invention relates to a method for producing an arsenic adsorbent capable of rapidly removing arsenic while having excellent strength by mixing liquid slaked lime, which forms a pozzolan reaction, and a liquid inorganic binder in acid drainage containing a large amount of iron.
The present invention relates to an iron-containing mine drainage storage process (S10) for storing the mine drainage having an iron content of 100 to 500 ppm to precipitate and remove solid foreign substances contained in the iron-containing mine drainage; An iron compound immersion process (S20) of supplying iron-containing mine drainage from which solid foreign substances have been removed to a sedimentation tank and adding and stirring liquid slaked lime (Ca(OH) ₂ ) to precipitate iron compounds present in the mine drainage as iron hydroxide; An inorganic binder addition process for pozzolan reaction in which an aluminum-based liquid inorganic binder inducing a pozzolan reaction is added to the reaction tank in which iron hydroxide is generated and stirred to generate iron hydroxide-inorganic binder precipitate (S30); A dehydration process (S40) of naturally dehydrating the iron hydroxide-inorganic binder deposits by gravity to remove moisture; It characterized in that it comprises an adsorbent molding and drying step (S50) of putting the precipitate dehydrated through the dehydration process into a mold of a predetermined shape, extruding it with an arsenic adsorbent in the form of pellets, and drying it.

Description

Preparation method of arsenic adsorbent using iron-containing mine drainage

The present invention relates to a method for producing an arsenic adsorbent capable of rapidly removing arsenic with excellent strength by mixing liquid slaked lime that forms a pozzolan reaction with a mineral acid drainage containing a large amount of iron and a liquid inorganic binder.

About 2,000 abandoned mines are scattered across the country, and a significant number of tailings and waste-rock generated from mine development are left without facilities to prevent pollution, such as installation of retaining walls. Along with the sluggishness of the domestic mining industry, environmental problems in the area around existing abandoned mines are continuously emerging. In Korea, as of 1998, there were 906 metal mines scattered across the country, of which 894, or 98.7% of the total, were closed or closed.

Leachate from abandoned mines differs from each other according to the characteristics of the deposit itself (the development of mineral species and ore bodies, the composition and production of ore and gangue minerals, geochemical environment, etc.) and the geological, geochemical, and hydrological environment of the vicinity. It shows different water quality characteristics, and if left unattended, it can become a factor of continuous environmental destruction as a semi-permanent source of pollution. Accordingly, it is urgent to develop appropriate technologies and prepare countermeasures for pollution reduction, along with a survey on the actual condition of water pollution caused by abandoned mines, and to improve the water quality of already polluted water systems (surface water and groundwater).

In addition, arsenic, a pollutant in abandoned metal mines, especially gold and silver mines, is one of the nitrogen group elements of group 15 of the periodic table, and is the 20th most distributed element among the constituents of the earth's surface, widely distributed in minerals, rocks, sediments, and soils. And unlike most other cationic metals, it exists as a polyatomic anion containing oxygen in soil solution. In addition, it is a metalloid element that changes into a different chemical species depending on pH and redox conditions, or exhibits different behaviors according to it, and is a highly toxic element (Ronald and William, 1982; Cullen and Reimer, 1989).

Arsenic has four oxidation states of ??3, 0, +3, and +5 depending on pH and electron activity (Eh). ₂ AsO ₃ ^- , HAsO ₃ ^2- and H ₂ AsO ₄ ^- , HAsO ₄ ^2- exists as an anion. In addition, organic arsenic MMAA (monometylarsonic acid) and DMAA (dimethylarsinic acid) are also found in nature (Xu et al., 1991). In general, inorganic arsenic is more toxic than organic arsenic, and As(III) is known to be more mobile and more toxic than As(V) (Ahmad et al., 1997; Buchet and Lauwerys, 1994). If you list them in the order of toxicity, As(III) > As(V) >> MMAA > DMAA (Thirumavukkarasu et al., 2002). It has been reported that when arsenic-contaminated groundwater is used as drinking water, the possibility of liver, kidney, lung, and skin cancer is high (Wang et al., 2002).

Also, as awareness of carcinogenicity of arsenic has emerged as an issue in the United States, the US Environmental Protection Agency (US EPA) has strengthened the arsenic limit in drinking water from 50 μg L ^-1 to 10 μg L ^-1 in 2001 (US EPA, 2001). In addition, the Agency for Toxic Substances and Disease Registry (ATSDR) within the U.S. Department of Health and Human Services (DHHS) publishes a ranking of hazardous substances every two years. This strong substance is listed as number one. Arsenic contamination is distributed all over the world to Asian regions such as India and Bangladesh, North and South America such as the United States, and European regions such as Germany (Smedley and Kinniburgh, 2002; Driehaus, 2002). In uncontaminated general groundwater, arsenic appears in the range of <0.5-10 μg L ^-1 , but there are areas where arsenic is naturally enriched at a level of 10 to 5,000 μg L ^-1 , and in areas affected by mining activities, etc. Concentrations up to 10,000 μg L ⁻¹ have been detected (Smedley and Kinniburgh, 2002).

USA (Welch et al., 2000), Mexico (Del Razo et al., 1990), Chile (Smith et al., 1998), Argentina (Bundschuh et al., 2004), Hungary (Varsanyi et al., 1991) ), China (Wang, 1984), Inner Mongolia (Smedley et al., 2003), Vietnam (Berg et al., 2001), Nepal, Cambodia (JICA & MRD, 2002), etc. The pollution patterns in West Bengal, India and Bangladesh (Ahmed et al., 2004) are the most severe. In addition, cases of natural arsenic contamination have recently been reported in Switzerland (Pfeifer et al., 2004) and Pakistan (Nickson et al., 2005), which had not been previously reported, and the effects of anthropogenic industrial and mining activities (Juillot et al. al., 1999; Charlet et al., 2001; Cappuyns et al., 2002), arsenic pollution has already appeared or continues to be discovered in almost all regions of the world. In Korea, arsenic accounts for 6.3% of groundwater pollution, and has the second highest pollution rate after TCE (Trichloroethylene) among specific harmful substances.

On the other hand, when mine drainage contains iron, which continuously pollutes water and soil, in a temporary coal mine or abandoned mine, sulfide minerals such as pyrite (FeS ₂ ) and white iron (FeS) exposed to the atmosphere react with oxygen and water. It is formed through oxidation, has a low pH, is acidic, and has a high content of metals such as sulfate, iron, aluminum, and manganese.

Iron contained in such mine drainage is largely treated with active treatment and passive treatment, settling into sludge, and then discharged, and the sludge is treated as waste, resulting in additional waste treatment costs.

Accordingly, the present inventors have developed a technology capable of reducing sludge emission while purifying the mine drainage by manufacturing an industrially usable arsenic adsorbent using the iron-containing mine drainage.

The problem to be solved by the present invention is that arsenic can be quickly removed with excellent strength by mixing liquid slaked lime (Ca(OH) ₂ ) that forms a pozzolan reaction in photo acid drainage containing a large amount of iron and a liquid inorganic binder. An object of the present invention is to provide a method for preparing an adsorbent.

The method for manufacturing an arsenic adsorbent using iron-containing mine drainage according to the present invention is an iron-containing mine drainage storage process ( S10) and; An iron compound immersion process (S20) of supplying iron-containing mine drainage from which solid foreign matter has been removed to a settling tank, and adding and stirring liquid slaked lime (Ca(OH) ₂ ) to precipitate iron compounds present in the mine drainage as iron hydroxide; An inorganic binder addition process for pozzolan reaction in which an aluminum-based liquid inorganic binder inducing a pozzolan reaction is added to the reaction tank in which iron hydroxide is produced and stirred to generate iron hydroxide-inorganic binder precipitate (S30); A dehydration process (S40) of naturally dehydrating the iron hydroxide-inorganic binder deposits by gravity to remove moisture; It characterized in that it comprises an adsorbent molding and drying step (S50) of putting the precipitate dehydrated through the dehydration process into a mold of a predetermined shape, extruding it with an arsenic adsorbent in the form of pellets, and drying it.

Preferably, the iron content of the mine drainage is characterized in that 100ppm or more.

Preferably, the iron content of the mine drainage is characterized in that 100 ~ 500ppm.

Preferably, liquid slaked lime (Ca(OH) ₂ ) is added so that the pH of the precipitation tank is maintained at 8-10.

Preferably, the liquid inorganic binder is a silicon-based inorganic binder or an aluminum-based inorganic binder.

Preferably, it is characterized in that the moisture content of the precipitate after the dehydration process is 80 to 90%.

The present invention has the effect of producing an arsenic adsorbent capable of adsorbing arsenic in a short time while having excellent strength from photoacid drainage containing a large amount of iron through the pozzolan reaction.

In addition, there is an advantage in that the arsenic adsorbent can be manufactured inexpensively by using Ca(OH) ₂ which is economical in terms of cost and mine drainage for wastewater treatment.

1 is a process diagram of a method for manufacturing an arsenic adsorbent using iron-containing mineral acid drainage according to the present invention.
2 is an isoelectric point graph for the arsenic adsorbent of Example and the arsenic adsorbent of Comparative Example according to the present invention.
3 is a graph of the arsenic adsorption rate for the arsenic adsorbent of Example and the arsenic adsorbent of Comparative Example according to the present invention.
4 is a graph of the removal rate for each adsorbent injection amount for the arsenic adsorbent of Examples and the arsenic adsorbent of Comparative Examples according to the present invention.

Hereinafter, the present invention will be described in detail.

The method for producing an arsenic adsorbent using iron-containing mineral acid drainage according to the present invention includes the iron-containing mineral acid drainage storage process (S10), the iron compound immersion process (S20), the pozzolan reaction inorganic binder addition process (S30), and the dehydration process (S40) , adsorbent molding and drying process (S50).

In the iron-containing mine drainage storage step (S10), iron-containing mine drainage containing 100 ppm or more, particularly preferably 100 to 500 ppm, is stored in a storage tank for a certain period of time, and solid foreign substances contained in the iron-containing mine drainage are precipitated and removed.

In the iron compound immersion process (S20), the iron compound present in the mineral acid drainage is supplied to the precipitation tank to the iron-containing mine drainage from which solid foreign substances have been removed, and liquid slaked lime (Ca(OH) ₂ ) is added and stirred to remove the iron compounds present in the mineral acid drainage. ₂ O ₃ , is precipitated with iron hydroxide such as Fe(OH) ₃ . At this time, the liquid slaked lime (Ca(OH) ₂ ) is preferably added so that the pH of the precipitation tank is maintained at 8-10. If the pH is less than 8, unreacted iron may be present in the mine drainage, and if the pH exceeds 10, there is a problem that a large amount of chemicals are required to neutralize the discharged water discharged from the reaction tank.

In the step of adding the inorganic binder for the pozzolan reaction (S30), a liquid inorganic binder that induces a pozzolan reaction is added to the reaction tank in which iron hydroxide is generated and stirred. In this case, the liquid inorganic binder is preferably an aluminum-based inorganic binder that can easily react with pozzolan. These inorganic binders induce a pozzolan reaction together with iron compounds, calcium, iron, etc., precipitated in the reaction tank.

The dehydration step (S40) removes moisture by naturally dehydrating the iron hydroxide-inorganic binder precipitate in the reaction tank by gravity. At this time, it is preferable that the moisture content of the precipitate is 80 to 90%. Moisture contained in these precipitates evaporates during molding to form porosity.

In the adsorbent molding and drying process (S50), the precipitate dehydrated through the dehydration process is put into a mold of a predetermined shape, extruded with an adsorbent in the form of pellets, and dried. Through these molding and drying processes, a pozzolan reaction is induced to increase the strength of the adsorbent, and when the moisture contained in the molding is evaporated, it has porosity, thereby improving the arsenic adsorption performance.

The adsorbent prepared from iron-containing mine drainage through this process can be used as an adsorbent having high arsenic adsorption capacity.

<Example>

About 20 L of mine drainage containing about 150 ppm of iron, where the sedimentation of solid foreign substances has been completed, is supplied to the reactor, and liquid slaked lime (Ca(OH) ₂ ) is added to maintain pH 8~9 (used about 9g) to contain iron. A precipitate was formed. Thereafter, 10 g of alumina, which is a liquid inorganic binder, was mixed and stirred and naturally dehydrated to produce an iron compound-inorganic binder precipitate having a moisture content of 80%. Then, the dehydrated iron compound and the inorganic binder were extruded into pellets with a mixture of inorganic binder-iron hydroxide and dried to prepare an arsenic adsorbent (ARS).

<Experimental Example 1>

<Equipotential point measurement>

The adsorbent (ARS) prepared in Examples was used, and as a comparative example, a hydroxide-based arsenic adsorbent (Granular Ferric Hydroxide (GFH); hereinafter referred to as 'Ref') was used, and each isoelectric point (pH _pzc ) is measured and shown in the graph of FIG. 1 .

As shown in FIG. 1 , it was confirmed that the adsorbent (ARS) of the example and the arsenic adsorbent (Ref) of the comparative example had isoelectric points (pH _pzc ) of 8.7 and 6.2, respectively. As such, since the surface of the arsenic adsorbent (ARS) of Example in the neutral region is positively charged, it can be confirmed that the arsenic adsorption performance for arsenic (V) compounds such as H ₂ AsO ₄ ^- and HAsO ₄ ^2- is excellent. there is. The surface of the arsenic adsorbent (Ref) of Comparative Example is negatively charged.

<Arsenic adsorption rate>

The adsorption rate test was performed on the adsorbent (ARS) prepared in Examples and the arsenic adsorbent (Ref) of Comparative Example using 1,000 ppm arsenic (V) standard solution, and is shown in the graph of FIG. 2 . The initial concentration of arsenic (V) was 30 mg/L, the adsorbent injection amount was 1 g/L, and the initial pH was 6.0.

As a result of confirming in FIG. 2, it can be seen that the adsorption rate of the arsenic adsorbent (ARS) of the Example is faster than the arsenic adsorbent (Ref) of the comparative example, and the time required to remove 50% of the initial arsenic concentration is 2.5 hours for the arsenic adsorbent (ARS) of the example , it was confirmed that the arsenic adsorbent (Ref) of the comparative example was 6.7 hours, and it was found that the arsenic adsorbent (ARS) of the example rapidly removed arsenic.

<Dissolution test>

In addition, the results of dissolution, which is one of the very important factors among the conditions for using the adsorbent, were confirmed.

As a result of the experiment, in the dissolution test of the iron component, the main component of the two adsorbents, the arsenic adsorbent (ARS) of the Example was below the detection limit, and the arsenic adsorbent (Ref) of the Comparative Example was at most 0.09 mg/L.

These results confirm that there is no problem in using the adsorbent as an adsorbent because it causes secondary pollutants to be generated by elution by the adsorbent when used as an adsorbent.

<Check the removal rate by arsenic adsorbent injection amount>

An adsorption experiment was performed using a 1,000 ppm arsenic (V) standard solution. The initial concentration of arsenic (V) was 10 mg/L, and the initial pH was 6. The arsenic removal rate was confirmed while varying the arsenic adsorbent injection amount from 0.1 g/L to 10.0 g/L, and is shown in the graph of FIG. 3 .

As shown in FIG. 3 , both the arsenic adsorbent (ARS) of the Example and the arsenic adsorbent (Ref) of the comparative example showed 100% arsenic removal rate at an injection amount of 1 g/L or more. This isothermal adsorption pattern is very similar to that of Langmuir isotherm, and when curve fitting (curve fitting) using Langmuir isotherm was applied, the adsorption amount was expected to be ARS=25.35mg/g and Ref=20.54mg/g.

As described above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited thereto, and the technical idea of the present invention and the following by those of ordinary skill in the art to which the present invention pertains Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

Claims (6)

an iron-containing mine drainage storage process (S10) of storing the mine drainage having an iron content of 100 to 500 ppm to precipitate and remove solid foreign substances contained in the iron-containing mine drainage;
An iron compound immersion process (S20) of supplying iron-containing mine drainage from which solid foreign substances have been removed to a sedimentation tank and adding and stirring liquid slaked lime (Ca(OH) ₂ ) to precipitate iron compounds present in the mine drainage as iron hydroxide;
An inorganic binder addition process for pozzolan reaction in which an aluminum-based liquid inorganic binder inducing a pozzolan reaction is added to the reaction tank in which iron hydroxide is produced and stirred to generate iron hydroxide-inorganic binder precipitate (S30);
A dehydration process (S40) of naturally dehydrating the iron hydroxide-inorganic binder deposits by gravity to remove moisture;
Arsenic adsorbent manufacturing using iron-containing mineral acid drainage, characterized in that it includes an adsorbent molding and drying step (S50) in which the precipitate dehydrated through the dehydration process is put into a mold of a predetermined shape, extruded with a pellet-shaped arsenic adsorbent, and dried Way.
delete delete The method according to claim 1, wherein the liquid slaked lime (Ca(OH) ₂ ) is added so that the pH of the precipitation tank is maintained at 8-10.
delete The method according to claim 1, wherein the water content of the precipitate after the dehydration process is 80 to 90%.

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