KR20190102896A - Manufacturing method of magnetic biochar for removing heavy metal and magnetic biochar manufactured therefrom and absorbent comprising of the biochar for removing heavy metal - Google Patents

Abstract

Disclosed is a method for manufacturing a magnetic biochar for removing heavy metals comprising: a first step of washing, drying and grinding kelp and preparing kelp powder; a second step of coating oxidized steel particles on the surface of kelp and magnetizing the same; and a third step of coating a chitosan layer to the surface of magnetic kelp. According to the present invention, an algae-based magnetic biochar containing chitosan is abundant in the active region due to the surface functional group so the adsorption and removal of heavy metals can be easily performed. In addition to the removal of heavy metals, the recovery of the heavy metals can be performed at the same time by using the magnetic method. The biochar and heavy metals can be recovered and reused.

Description

Manufacturing method of magnetic biocar for removing heavy metals, bio-car for removing heavy metals manufactured according to the above, and adsorbent for removing heavy metals comprising the same {Manufacturing method of magnetic biochar for removing heavy metal and magnetic biochar manufactured therefrom and absorbent comprising of the biochar for removing heavy metal}

The present invention relates to a method of manufacturing a magnetic bio tea for removing heavy metals, and more particularly, to a method of preparing a magnetic bio tea for removing heavy metals based on algae, which improves the adsorption effect of heavy metals and has an excellent magnetic recovery by using chitosan. The present invention relates to a manufactured magnetic bio-car for removing heavy metals and an adsorbent for removing heavy metals including the same.

As industrial development is accelerated and human activities are diversified, environmental pollution such as soil, air and water pollution caused by various pollutants is increasing. Especially in the case of water pollution, iron, copper, nickel, The problem of contamination by heavy metal-containing wastewater containing zinc, lead, cadmium and chromium is increasing.

Currently, ion exchange, activated carbon adsorption, membrane filtration, flocculation sedimentation, flotation treatment, electrochemical treatment, etc., are used to remove heavy metals from wastewater. Among the methods, activated carbon adsorption is disclosed in Korean Laid-Open Patent Publication No. 10-2016-0114883 to disclose a method of modifying the surface of a carbon material with iron oxide coating, which is currently being studied, and is effective in removing heavy metals and hardly decomposable harmful chemicals. to be. However, in the activated carbon adsorption method, it is difficult to supply raw materials such as palm, bamboo, sawdust, etc. and is produced through high temperature pyrolysis of 700 ℃ or more, and thus it is used as a method for removing heavy metals from waste water due to high energy consumption and high production cost. There is a limit to this.

Therefore, development of eco-friendly alternative adsorbents and the development of treatment technology for hardly decomposable substances including heavy metals using the same are required.

Biochar, also called biochar, is a solid carbon-rich material that is produced when biomass is pyrolyzed in an oxygen-free environment, where carbon sequestration, renewable energy, waste management, agricultural productivity improvement, It has recently attracted much attention for its important functions such as environmental restoration.

Moreover, algae biomass contains various minerals in seawater such as sodium, potassium, magnesium, calcium, and phosphorus, unlike woody biomass, so that algae bio teas prepared from them contain minerals, as well as minerals of seaweed minerals. It may contain minerals concentrated up to 2-4 times. Bio teas containing various minerals in seawater are expected to be useful as carriers for soil modifiers and adsorbents, unlike bio teas derived from other terrestrial biomass. However, algae biomass has been insufficiently studied compared to the expected use in various fields.

The present invention is to provide a method for producing a magnetic bio tea excellent in heavy metal removal effect by coating chitosan on the magnetic bio tea as a problem.

Another object of the present invention is to provide a magnetic biocar for removing heavy metals, which is manufactured by the method of manufacturing the magnetic biocar.

Another object of the present invention is to provide an adsorbent for removing heavy metals containing the magnetic biocar.

According to an aspect of the present invention for solving the above problems of the present invention,

A first step of preparing kelp powder by washing and drying the kelp;

A second step of coating iron oxide particles on the surface of the kelp to have a magnetic property; And

It provides a method of manufacturing a magnetic bio-car for removing heavy metals comprising a third step of coating a chitosan layer on the surface of the magnetic kelp.

According to another aspect of the present invention,

It provides a magnetic bio-car for removing heavy metals, characterized in that manufactured according to the manufacturing method.

According to another aspect of the present invention,

It provides a heavy metal removal adsorbent comprising the magnetic bio-car for removing the heavy metal.

According to the present invention, the algae-based magnetic bio-tea containing chitosan has an active area due to surface functional groups, which shows excellent adsorption performance, so that heavy metals can be easily adsorbed and removed. At the same time, there is an advantage that it is possible to recover and reuse bio tea and heavy metals.

1 shows a synthesis process of a magnetic bio-car manufactured according to an embodiment of the present invention.
Figure 2 shows an SEM image of the surface shape of the magnetic bio-car prepared in accordance with an embodiment of the present invention.
Figure 3 shows the FTIR spectrum of the magnetic bio-car prepared in accordance with an embodiment of the present invention.
Figure 4 (a) shows a magnetization curve expressing the magnetization value (emu / g) per g of bio tea against the magnetic strength (G) of the magnetic bio tea prepared according to an embodiment of the present invention, (b) Is the change in pH.
Figure 5 shows the copper adsorption amount for the iron oxide loading and the chitosan loading amount in accordance with an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

According to an aspect of the present invention, a first step of preparing a kelp powder by washing, drying and grinding kelp; A second step of coating iron oxide particles on the surface of the kelp to have a magnetic property; And a third step of coating a chitosan layer on the surface of the magnetic kelp.

Biochar, a carbon-based adsorbent, is attracting attention due to its low cost, biomass available from nature, and its advantages such as abundant carbon content and applicability to various environmental fields. Bio teas can be used to remove various pollutants such as organic pollutants and heavy metals due to their unique properties such as large surface area, high porosity and various mineral components.

Various types of bio-teas, such as peanut shells, sawdust, wastewater sludge, and seaweed, have been studied previously, and kelp, bamboo, and pine sawdust may be used. The superior copper removal efficiency of seaweed (Kashima) is due to the presence of unique structural and chemical functional groups that can adsorb heavy metal ions from the wastewater.

A first step of the present invention will be described. Washing and drying the kelp is a step of washing and drying kelp, a waste algae biomass discarded in aquaculture and harvesting, and preparing it for reuse as a bio-tea. Here, kelp may be used alone, but may be used with various seaweeds including 톳.

The step of preparing the kelp powder is such that the particle size is 0.05 to 3 mm, preferably 0.15 to 2.0 mm to improve the thermal decomposition reactivity of the kelp and increase the specific surface area.

Next, a process of pyrolyzing the kelp cut specifically for the particle size is carried out. After the kelp powder is injected into a pyrolysis furnace, it is heated at 400 to 700 ° C. at an rate of 3 to 10 ° C./min in an oxygen-free atmosphere, and pyrolyzed at 400 to 700 ° C. for 1 to 2.5 hours while maintaining the heating temperature. .

Specifically, the pyrolysis and cooling step may further include the step of flushing the pyrolysis furnace in which the kelp powder is injected with an inert gas before the temperature rise to the pyrolysis temperature, and pyrolysis to maintain the pyrolysis and cooling step in an oxygen-free atmosphere. During heating and cooling to temperature, an inert gas is introduced in an amount of 0.01 to 0.1 L / min per 1 g of the bio-tea base material to maintain an oxygen free atmosphere.

More specifically, in the pyrolysis and cooling step, the rate of increase to the pyrolysis temperature is preferably 5 to 10 ° C / min, and the pyrolysis temperature at this time is 500 to 700 ° C, more preferably 500 to 600 ° C It features. In addition, the magnetic bio-tea produced by the pyrolysis and cooling step is characterized in that the yield of 20 to 45%, preferably 25 to 40%.

A second step of the present invention will be described. Despite the advantages of biocar's good removal ability, the application is still limited because of its small particle size and low density, making it difficult to separate from aqueous solutions. As an effective solution, various reforming strategies have been applied to increase the adsorption site on the surface of the bio-car, which determines the adsorption capacity of heavy metals, or improve the adsorption performance of the bio-car by adding functional groups on the surface. Surface oxidation and the like can be attempted, and the bio tea can be modified using iron oxide particles as the magnetic agent to improve the separation (recovery) of the bio tea from the aqueous solution.

In the present invention, the kelp particles are characterized by coating the iron oxide particles to have a magnetic property. That is, the adsorbents can be sufficiently recovered from the aqueous solution using an external magnetic force. Therefore, according to the present invention can be characterized in that it can be effectively magnetically separated at the same time to adsorb the heavy metal excellently.

The use of an aqueous iron solution on the kelp particles to give magnetic (magnetic) properties to the kelp particles takes into account not only the adsorption of heavy metals but also the recovery of the adsorbent in the future. When the concentration of the aqueous iron solution is 0.05 mol / L may be 96% recovery.

Increasing the iron concentration in the manufacturing process can increase the adsorbent recovery. Most importantly, when the concentration of the aqueous iron solution is 0.05 mol / L, a recovery of 96% can be obtained for the bio-tea of the present invention. In general, at an iron aqueous solution concentration of 0.05 mo / L or more, the copper adsorption removal capability can be improved without lowering the recovery rate.

A third step of the present invention will be described. The present invention may include a third step of coating the chitosan layer on the magnetic kelp surface. Here, the chitosan-modified magnetic kelp bio-tea, which is an efficient adsorption material capable of simultaneously exhibiting high separation ability and heavy metal removal ability, is manufactured. Ultimately, it was found that it could be used for efficient heavy metal ion removal, which can be interpreted as a great possibility for wastewater treatment.

Chitosan coatings reduce the proportion of total mass of oxygen, while the proportion of nitrogen, hydrogen and carbon content is significantly increased. In particular, the nitrogen content of the chitosan-coated magnetic bio-tea according to the present invention is 1.4 times higher than the bio-tea nitrogen content without the chitosan-coated. This increase in the total nitrogen content can be said to improve the heavy metal adsorption performance by strengthening the active site of the surface of the chitosan modified bio-tea.

Chitosan is cheap, renewable, biodegradable, hydrophilic, non-toxic and abundant in nature. Therefore, chitosan has been used in industrial and biological applications, and related studies have identified chitosan as an excellent adsorbent for removing heavy metals in water. Good adsorption performance is due to the presence of effective functional groups on the surface, attracting ions from the wastewater.

In particular, chitosan can be said to be excellent in heavy metal adsorption due to the presence of amine groups capable of forming strong bonds with these ions. As a result, chitosan has been studied a lot as a surface modifier. However, poor porosity of chitosan and low recoverability from aqueous solution should be considered due to the possibility of secondary contamination when requiring heavy metal removal in water.

Therefore, by combining chitosan and magnetic bio-car as an adsorbent, it is possible to combine the advantages of both materials to improve the heavy metal removal capacity and recovery efficiency. More specifically, this binding can combine the advantages of chitosan, a chemical with a strong selective affinity for heavy metals, and the advantages of magnetic biotea for effective separation. This composite is economical, environmentally friendly and promising because it consists of cost-effective eco-friendly materials.

In the third step, magnetic kelp is preferably added to the chitosan solution and base solution is added until the pH reaches 9 and stored at room temperature. Specifically, the process of coating the chitosan layer on the surface of the magnetic kelp biocar is to dissolve chitosan in an aqueous solution of acetic acid of about 2 to 3% (v / v), and then add the magnetic kelp biocar prepared in the second step to the chitosan solution. Stir the mixture. Then, basic solution (eg, NaOH) is added to the mixed solution until the pH value reaches 9 as the optimum condition for the chitosan coating process. The mixed solution is then stored at room temperature for 12 hours, washed with deionized water to remove excess basic solution and completed by drying the particles sufficiently.

According to the present invention, the greater the content of chitosan, the better the removal efficiency of heavy metals, and the amount of chitosan can be appropriately adjusted for the adsorption and recovery of heavy metals. That is, as more chitosan is coated on the surface of the bio-car, the adsorption amount of the heavy metal increases. In the magnetic bio tea of the present invention, the content ratio of chitosan and bio tea may be 0.1 to 1.0 times, and preferably 0.6 times. When it exceeds 1.0 times, the chitosan may cover the pores of the bio-car, thereby lowering the adsorption power of the bio-car and making magnetic recovery difficult.

The magnetic bio-tea according to the present invention is characterized by having at least 80% adsorption and removal of heavy metals with a non-adsorption capacity of 4.0 to 20 mg heavy metals / g bio-tea when stirred with heavy metals for 10 to 40 minutes. More specifically, the magnetic kelp bio-tea of the present invention has a non-adsorption capacity of 4.0 to 20 mg heavy metal / g bio tea when stirred with copper, cadmium, or zinc for 10 to 40 minutes, thereby absorbing and removing at least 85% of heavy metals. Efficiency and in particular can exhibit significantly improved adsorption and removal efficiencies for copper.

Magnetic bio tea according to the present invention may vary the adsorption effect depending on the pH conditions. For example, at low pH levels, the surface of the adsorbent is positively charged such that copper ions (Cu ²⁺ ), which are positive ions, are electrostatically rejected, causing no adsorption and reducing adsorption capacity. On the other hand, at high pH, the copper adsorption capacity is improved, since hydroxide precipitation of OH ⁻ and Cu ²⁺ ions may be formed. Therefore, it is possible to apply the magnetic bio tea of the present invention by properly adjusting the pH in removing heavy metals. When the heavy metal is removed using the magnetic bio-car according to the present invention, particularly in the case of copper, when the pH is 6 to 11, the adsorption amount of copper ions may be 80 to 95%. In the case of a bio-tea not coated with chitosan, the adsorption amount of copper ions may be less than 80%.

As described above, the kelp bio-tea and the bio-tea according to the present invention can be easily removed as heavy metals, and are included as an adsorbent for removing heavy metals, and can be applied to waste water and contaminated soil.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited by Examples.

<Example>

Preparation of Magnetic Bio Tea

1 illustrates stepwise synthesis of a magnetic biocar according to an embodiment of the present invention. First, the raw kelp was washed, dried at room temperature overnight, and then pretreated by drying in an oven for 12 hours. The kelp was dried completely and ground to a sieve of 0.08 to 1.7 mm in diameter.

The second step is to coat the iron oxide particles with a magnetic preparation on the surface of the kelp prepared by pretreatment. That is, 30 g of kelp was continuously stirred vigorously for 30 minutes in 500 mL of various concentrations of FeCl ₃ · 6H ₂ O aqueous solution, and then the mixture was dried in a drying oven at 70 ° C. for 30 minutes, and the kelp was separated from the aqueous iron solution. The separated kelp was pyrolyzed under N ₂ flow conditions at a heating rate of 7 ° C./min for 2 hours at 500 ° C. in a furnace. Thereafter, the thermally decomposed magnetic bio tea (magnetic kelp bio tea KBm) was washed several times to remove impurities and then used in the experiment. Magnetic kelp biocar will be referred to as 'KBm _x ', where x represents the iron concentration.

Finally, a chitosan layer was coated on the surface of the magnetic kelp biocar. 3 g of chitosan was dissolved in 250 mL of 2% (v / v) acetic acid aqueous solution, and then 5 g of prepared magnetic kelp bio tea was added to the chitosan solution and the mixture was stirred for 30 minutes. Then, 1.2% NaOH was added to the mixed solution until the pH value reached 9 as the optimum condition for the chitosan coating process. The mixed solution was then stored at room temperature for 12 hours and washed with deionized water to remove excess NaOH. Finally, the particles were dried sufficiently to complete. The resulting chitosan modified magnetic biocar will be referred to as 'Chi-KBm'.

Bio Tea Evaluation and Analysis

In this example, the recovery ability of Chi-KBm was evaluated. Prepared materials were characterized by elemental analysis, specific surface area analysis (Brunauer Emmett-Teller. BET), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) analysis. The adsorption capacity of various heavy metals was also evaluated.

Property evaluation

The form and elemental composition of the prepared Chi-KBm were investigated by scanning electron microscope (SEM). In addition, the surface functional group of Chi-KBm was confirmed using the infrared spectroscopy (FTIR). The contents of elements C, H, O, N and S of Chi-KBm were investigated using an element analyzer. Surface properties were analyzed using XRD and XPS. Magnetic properties of biotea samples were evaluated through magnetization curves using VSM.

Adsorption test

0.5 g of adsorbent (KBm, Chi-KBm) prepared at room temperature was placed in 30 ml of 1000 mg / L Cu ²⁺ solution and allowed to react for 24 hours, after which the mixture was passed through a membrane filter (0.45 μm). To evaluate the effect of pH on copper adsorption solutions on KBm and Chi-KBm, various solutions with different pH values were prepared and tested. All experiments were performed at batch conditions at room temperature. In the aqueous solution filtered through the filter, the concentration of copper ions remaining unadsorbed by the bio-car was diluted with 2% nitric acid and measured using inductively coupled plasma (ICP). The adsorption capacity of the biocar to copper was calculated by the following equation.

Qe = (C0-Ce) V / m

C0 = initial concentration of copper ions, Ce = equilibrium concentration of copper ions (mg / L)

m = mass of adsorbent (bio) (g)

V = volume of solution (L)

Recovery experiment of bio tea using magnetic field approach

The recovery rates of KBm and Chi-KBm were investigated using an external magnetic field of various intensities. The experiment was performed as follows. First, 0.1 g of Chi-KBm was added to the vial and the total weight was recorded as W _a . Then, 10 ml of distilled water was added and stirred at 150 rpm for 1 hour. The neodymium magnet was then placed on the vial containing the mixture, which magnetically attracted the dispersed Chi-KBm particles. With the magnet attached, the mixture was poured out and the vial containing the discarded Chi-KBm was dried in a drying oven for one day. Finally the total weight was measured and recorded as W _b . Recovery rate (S) was calculated using the following formula.

S = (W _a -W _b ) / Wa × 100 (%)

Elemental composition

The elemental composition of KBm and Chi-KBm was examined as shown in Table 1. As a result, KBm and Chi-KBm both contained 60% or more carbon. However, in the recombined data, chitosan modifications have been shown to reduce the total mass ratio of oxygen, while the ratio of nitrogen, hydrogen and carbon content is significantly increased. In particular, the nitrogen content of Chi-KBm was 1.4 times higher than that of KBm. This increase in total nitrogen content is believed to be due to the introduction of a chitosan layer that strengthens the active site of the surface of the chitosan modified biocar.

X-ray photoelectron spectroscopy (XPS) analysis was performed to investigate the chemical composition of Chi-KBm before and after the adsorption experiment. Four significant peaks were seen in both samples: C1s (68.47%), O1s (21.27%), N 1s (2.13%), and iron γ-Fe ₂ O ₃ (0.46%). The main difference was the appearance of a copper peak (Cu ²⁺ ) after the adsorption process confirming the adsorption of Cu ^{2+ on} the Chi-KBm surface. All other peaks exhibited characteristics for magnetic bio-teas.

Bio Tea Surface area (m ² / g) Composition
(%, mole based) O / C
Molar ratio H / C
Molar ratio C / N
Molar ratio
C H O N S ¹ KB _m 0.97 5.36 2.05 1.72 0.22 0.09 0.32 0.38 24.36 ² Chi-KB _m 6.17 6.10 3.69 1.15 0.31 0.05 0.19 0.60 19.68

¹ KB _m : Magnetic kelp biochar

² Chi-KB _m : Chitosan-modified magnetic kelp biochar

Surface morphology

(A), (c), and (e) of FIG. 2 show SEM images of surface shapes of KB, KBm, and Chi-KBm, respectively. As shown in FIG. 2 (a), in the case of pure KB (Kashima Bio-Tea), the pore structure of the surface is hardly noticeable than KBm (FIG. 2 (c)) in which many pore channels are formed. The newly formed channel at KBm indicates that iron oxide was well coated on the modified kelp bio-car. On the other hand, the surface of Chi-KBm is smooth compared to the rough surface of KBm (Fig. 2 (e)). This smooth surface is due to the well coated chitosan layer on the Chi-KBm surface.

Chi-KBm formed a chitosan layer on its surface, which dramatically reduced the pore channel, blocking some of the pore channels of bio tea. Although the chitosan layer blocked some voids on the surface, as shown in Table 1, the total surface area increased by 6.4 times more than the conventional KBm for Chi-KBm. This phenomenon is negligible when compared to the amount of micro-pore generated after chitosan coating, the amount of macro-pore blocked (covered) by the chitosan layer. That is, the chitosan layer blocked some of the large pores, but it can be seen that a larger number of micropores formed on the surface of the bio-car. As a result, the total surface area of Chi-KBm was greatly increased.

(B), (d), and (f) of FIG. 2 show EDX results for KB, KBm, and Chi-KBm, respectively, according to an embodiment of the present invention. 2 (d) and (f) show multiple peaks related to various elements showing new peaks representing iron oxides in FIG. 2 (b).

These iron oxide peaks indicate that iron particles were well deposited on KBm and Chi-KBm surfaces. In addition, XRD characterization confirmed the deposition of two types of iron oxide magnetite (γ-Fe ₂ O ₃ ) and magnetite (Fe ₃ O ₄ ) on the surface of the modified magnetic kelp biocha and chitosan modified magnetic kelp biocha. It was. On the other hand, in the XRD results, a clear appearance of a new peak was observed at 2θ = 20 ° of Chi-KBm, which is due to the chitosan coating layer.

In addition, as shown in the illustration of Figure 2 (f), EDX mapping confirmed that the chitosan coating layer improves the surface properties by confirming the nitrogen components distributed on the Chi-KBm surface, C, O on the surface of the bio-car Together with other elements such as, and H atoms, new functional groups were formed.

Adsorbent Cu
absorption
(mg / g) Magnetic characteristics
Remarks Magnetic
shame
(emu / g) Magnetic
detach
(%) Chi-KB _{m -0.05} 19.88 7.15 93.84 The present invention Chi-KB _{m -0.025} 25.11 3.02 72.04 The present invention Iron oxide 17.08 - - (Huanget al., 2007) Magnetic Cu (II) ion imprinted composite 23.63 4.2 - (Ren et al., 2008) Starch- g -polyamidoxime / montomorillonite / Fe ₃ O ₄ nanocomposites 10.41 57.2 - (Mahdavinia et al., 2016) Amino-functionalized PAAcoated Fe ₃ O ₄ nanoparticles 12.43 63 - (Huang & Chen, 2009)

Surface functional group analysis and adsorption mechanism

FIG. 3A shows FTIR spectra of KBm and Chi-KBm according to an embodiment of the present invention.

Chi-KBm showed sharp peaks at 3400, 1394 and 1563 cm ⁻¹ compared to KBm unmodified with chitosan, which is attributable to the OH, —NH and CN functional groups, respectively, which are advantageous for the heavy metal adsorption process. These functional groups are presumably due to the chitosan layer coated on the surface of the biocar. Peaks at 560 and 576.8 cm ⁻¹ produced by Fe—O were observed in both KBm and Chi-KBm, confirming the presence of γ-Fe ₂ O ₃ particles in both biocars.

KBm, on the other hand, had strong peaks of 1580, 1450, 1100, 870 cm ⁻¹ , respectively, corresponding to C═O, C═C, CO, CH. The change in the new functional peak of Chi-KBm is noteworthy. In addition, the strong and sharp peaks at 1450 cm ⁻¹ (C = C) of KBm were significantly reduced and converted to very weak and broad peaks at Chi-KBm. The CH band of 780 cm ^-1 also shows the same trend. This result may be due to the interaction between chitosans such as C═O, C═C, CO and CH and amino, hydroxyl and carbonyl groups of the KBm group via hydrogen bonds or other chemical bonds.

The presence and type of functional group is very important because the functional group is directly related to heavy metal adsorption. The adsorption mechanism of copper ions on the biocar surface is largely classified into two categories (Fig. 3 (b)).

The first refers to physical adsorption, where a one-step reaction mechanism occurs through van der Waals forces that are inversely proportional to the distance between atoms or molecules (b (1) in FIG. 3). The second is the surface precipitation mechanism due to all the chemical adsorption occurring on the surface. It can occur through each individual mechanism, including ion exchange, surface compound formation, and coprecipitation. In the case of ion exchange (b (2) of FIG. 3), when exchangeable ions (eg, Na ⁺ , K ⁺ , Mg ^2+, etc.) are present on the surface of the bio-car, the heavy metals in the water are exchanged with the heavy metal ions in the aqueous solution. Removed. Surface complex formation is due to the electrostatic attraction between the surface functional groups of the biocar and heavy metal ions in water.

Positive or negatively charged functional groups on the surface, such as hydroxyl, carboxyl, ester or amine groups, attracted the oppositely charged heavy metal ions in water to form compounds through chemical bonds on the surface of the biocar (FIG. 3). B (3)). When several different ions or molecules in water are adsorbed together on the surface, this process is called co-precipitation (b (4) in FIG. 3). In the case of Chi-KBm, after the chitosan layer was introduced, various functional groups were added to the surface of the bio-car, and the mechanism of surface staining and co-precipitation was prominent.

Magnetic characteristics

FIG. 4A is a magnetization curve, which is an S-type graph representing the biocarbohydrate magnetization value (emu / g) versus magnetic strength (G) for KBm and Chi-KBm. Referring to Figure 4 (a), it can be confirmed that KBm and Chi-KBm are these strong magnetic materials, the saturation magnetization value of 7.45, 7.15 emu / g for KBm-0.05 and Chi-KBm-0.05, respectively, Magnetic force is used to indicate that the adsorbents are sufficiently recoverable from the aqueous solution.

In addition, the inserted drawings show that Chi-KBm can adsorb a heavy metal with excellent efficiency and can be effectively magnetically separated.

Effect of pH on Heavy Metal Adsorption

Figure 4 (b) shows the effect on the copper ion adsorption removal efficiency of the adsorbent KBm, Chi-KBm according to the change of the pH value according to an embodiment of the present invention. The copper adsorption capacity of Chi-KBm increased significantly as the pH value increased from 2 to 7.

As the pH value further increased, the amount of copper adsorption slightly increased. By removing the pH from 4.86 to 5.39 using Chi-KBm, the Cu removal efficiency increased from 46.60% to 90.14%. Maximum removal efficiency was 98% at pH 6.93. As a result, the optimal pH value can be concluded to be 6.93. On the other hand, the copper adsorption capacity of KBm gradually increased as the pH was increased from 2 to 12, and particularly, the copper adsorption capacity rapidly increased from 20.92% to 64.58% in the range of pH 4-5. A further increase in pH gradually increased the copper removal rate with the highest adsorption amount of 90.25% at pH 11.58.

At low pH levels, the surface of the adsorbent is positively charged such that copper ions (Cu ²⁺ ), which are positive ions, are electrostatically rejected and no further adsorption occurs, resulting in reduced adsorption capacity. On the other hand, at higher pH the copper adsorption capacity is improved, which can be explained by the formation of hydroxide precipitates of OH ⁻ and Cu ²⁺ ions.

Copper adsorption removal and recovery efficiency

FIG. 5 (a) shows the copper adsorption amount and the recovery rate due to the magnetic field for various iron oxide loads of KBm and Chi-KBm according to one embodiment of the present invention. Referring to Figure 5 (a), it can be divided into two ranges, the first range is a low iron load concentration (0 ~ 0.05 mol / L), the second range is a high iron load concentration (0.05 ~ 0.1 mol / L). In the range of low iron loading concentrations, the copper removal rate of KBm was greater than that of Chi-KBm (KBm and Chi-KBm respectively removed 60% and 48% copper from 0.01 mol / L iron load, respectively). .

In the low iron oxide loading range (0.05 mol / L or less), the effect of iron oxide on pore blocking is negligible. As a result, the adsorption mechanism by the pores (physical adsorption, b (1) in FIG. 3) is dominant in the KBm adsorption mechanism. On the other hand, the pore of Chi-KBm was negligibly blocked by iron oxide but blocked by an additional chitosan layer (see SEM in Fig. 2), and the active region was formed by various functional groups by the chitosan layer. . As a result, surface precipitation was dominant in the adsorption mechanism of Chi-KB.

However, the adsorption performance of high KBm compared to Chi-KBm in the range of low iron loading concentration is because the surface precipitation reaction that occurs mainly in Chi-KBm is a reversible reaction. Some adsorbed copper on the Chi-KBm surface may be redissolved through reversible reactions. KBm's main adsorption mechanism, the pore physical adsorption process, is irreversible and depends on the pore size.

In the range of high iron loading concentrations (greater than 0.05 mol / L), the copper removal rate in KBm decreased sharply to 3%, 20 times lower than the amount of copper adsorption without iron oxide coating. This was due to the reduction of pore size, the main factor affecting adsorption at KBm, whereas for Chi-KBm, the increase in iron loading concentration slightly reduced the copper removal rate, and the copper removal rate was 32% at 0.1 mol / L. This trend indicates that pore blocking by large amounts of iron oxide and thin chitosan layers did not significantly affect the overall copper adsorption performance. It was confirmed that the main factor for the adsorption of Chi-KBm is the surface functional group.

In contrast, the increase in the concentration of aqueous solution of iron in the manufacturing process resulted in an increase in recovery for both KBm and Chi-KBm. Most importantly, when the concentration of aqueous iron solution was 0.05 mol / L, 96% recovery was obtained for the two bio-teas.

Overall, the chitosan reforming process improved the ability to remove copper adsorption without reducing the recovery at iron concentrations above 0.05 mo / L. Thus, Chi-KBm-0.05 is regarded as the optimal adsorbent for good copper adsorption and recovery. For further comparison and optimization of the chitosan coating conditions, the adsorption amount of the chitosan coating amount from 0.1 to 1.0 g-chitosan / g-biocar was evaluated. According to the obtained result, it is confirmed that copper adsorption capacity increases as more chitosan is coated on the surface of the bio-car.

These results provide a new approach for the treatment of wastewater containing heavy metal ions. More specifically, the approach described herein demonstrates the success of chitosan modified magnetic kelp biocha (Chi-KBm) as an effective heavy metal adsorbent that can easily separate the adsorbent from water using an external magnetic field. The results obtained also show a significant improvement in both heavy metal ion removal and recovery as compared to previous studies as shown in Table 2.

Adsorption of Other Heavy Metal Ions

There are always many different heavy metal ions coexist in nature, including wastewater in nature. Thus, experiments were conducted to evaluate the adsorption performance of copper ions in the presence of other common metal ions. Various heavy metals were found to affect the adsorption capacity.

The removal efficiencies of Cu ²⁺ , Cd ²⁺ and Zn ²⁺ were 4.91, 4.81, 4.07 mg / g for KBm and 19.68, 6.94 and 4.13 mg / g for Chi-KBm, respectively. Cu ²⁺ removal capacity was highest compared to Cd ²⁺ and Zn ²⁺ removal capacity. This is likely due to the electronegativity of the metal ions. The electronegativity may be arranged in the order Cu ²⁺ (2.00)> Cd ²⁺ (1.69)> Zn ²⁺ (1.65). Metal ions with greater electronegativity can have a stronger attraction to the surface of the adsorbent. Cu ²⁺ had the highest electronegativity when compared to Cd ²⁺ and Zn ²⁺ , which resulted in strong selective adsorption of hydroxyl (-OH) and amino (-NH ₂ ) groups at Chi-KBm. It was possible. In addition, this adsorption tendency can be explained by the ion radius of the metal ion. It is reported that the smaller the ion diameter, the higher the adsorption capacity. Ion radii of metal ions are Cu ²⁺ (73 pm), Cd ²⁺ (95 pm), Zn ²⁺ (75 pm). This means that the trend of adsorption coincides with the order of electronegativity and ion radius size. Therefore, in our study, Cu ²⁺ ions with the largest electronegativity and the smallest ion radius showed the highest adsorption capacity, followed by Cd ^{2 +} and Zn ^{2 +} ions.

As mentioned above, although this invention was demonstrated by the limited Example, this invention is not limited by this and is described below by the person of ordinary skill in the art, and the following. Of course, various modifications and variations are possible within the scope of the claims.

Claims (11)

A first step of preparing kelp powder by washing and drying the kelp;
A second step of coating iron oxide particles on the surface of the kelp to have magnetic properties; And
The method of manufacturing a magnetic bio tea for removing heavy metals comprising a third step of coating a chitosan layer on the surface of the magnetic kelp.
The method of claim 1,
The bio-tea is characterized in that it has a non-adsorbing power of 4.0 to 20mg heavy metal / g bio-tea, heavy metal removal magnetic bio-tea manufacturing method.
The method of claim 1,
In the second step, the kelp powder is stirred in an aqueous iron solution, and separated therefrom, followed by pyrolysis at 400 to 700 ° C.
The method of claim 1,
In the third step, the magnetic kelp is added to the chitosan solution, and the base solution is added until the pH reaches 9, and the method for producing a magnetic bio tea for removing heavy metals, characterized in that stored at room temperature.
The method of claim 1,
The method of manufacturing a magnetic bio tea for removing heavy metals, characterized in that the first step is to add to the kelp to remove.
The method of claim 1,
The heavy metal is copper, cadmium or zinc manufacturing method of the magnetic bio-car for removing heavy metals, characterized in that.
The method of claim 3,
When the concentration of the aqueous iron solution is 0.05 mol / L The method of manufacturing a magnetic bio tea for removing heavy metals, characterized in that the recovery is 96%.
The method of manufacturing a bio-tea according to any one of claims 1 to 6, characterized in that the magnetic bio-car for removing heavy metals.
The method of claim 8,
Magnetic bio tea for removing heavy metals, characterized in that the content ratio of chitosan and bio tea in the bio tea is 0.1 to 1.0 times.
An adsorbent for removing heavy metals, comprising the magnetic biocar according to claim 8.
The method of claim 10,
When the pH is 6 to 11, the adsorbent amount of copper ions is 80 to 95%, characterized in that the adsorbent.

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