JP2010000465A - Heavy metal adsorbent and its preparing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adsorbent effectively adsorbing heavy metals such as cadmium from an extraction residue of Metroxylon sagu starch, as a raw material, of Metroxylon sagu which is raised in large quantities in tropical damp area and is promised as a food resource, and to provide a method for the same. <P>SOLUTION: In a method for preparing a heavy metal adsorbent which utilizes an esterified Metroxylon sagu extraction residue formed by carrying out esterification of Metroxylon sagu starch extraction residue as a main component, the esterification reaction includes a process of making a mixture of Metroxylon sagu starch extraction residue and a phosphoric esterified agent, and a process of adding an amine compound to the mixture generated in the above process to be heated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a heavy metal adsorbent. More specifically, the present invention relates to a heavy metal adsorbent using sago palm extract residue as a raw material and a method for producing the same.

Sago palm (Metroxylon sagu) grows in tropical wetlands where other crops are difficult to grow, and has the property of accumulating 200 to 400 kilograms of starch in the trunk (medulla) with its growth, and is used as a food resource ing. This sago palm starch is highly expected not only for economic development in tropical low-humidity regions where plant resources with economic advantages are extremely limited, but also as a future food problem. However, when the sago starch is extracted from the medulla, a large amount of starch extraction residue is generated. At present, this starch extraction residue is left as it is around the sago starch production plant and in the villages, not only deteriorating the natural landscape, but also the starch contained in the extraction residue decays and produces an unpleasant odor, etc. The disposal method is a big problem.

As an example of effectively utilizing a sago starch extraction residue, a biodegradable plastic composed of a sago starch extraction residue obtained by esterifying a sago palm extraction residue with an aliphatic esterifying agent such as natural oil and a plasticizer is disclosed (Patent Document) 1). However, the esterified sago palm starch extraction residue constituting the biodegradable plastic uses natural fats and oils as an esterifying agent, and the esterification requires about five times or more natural fats and oils relative to the sago palm starch extraction residues. Therefore, it is not preferable.

On the other hand, so-called heavy metal sewage such as cadmium and lead pollutes the environment and adversely affects the human body. Among the heavy metals mentioned above, cadmium toxicity has been reported in detail, and kidney damage, anemia, hypertension and itai-itai disease Cadmium has been shown to be the causative agent. Examples of methods for removing heavy metals in wastewater containing heavy metals include lime precipitation, ion exchange, activated carbon, membrane treatment, and electrolysis. However, in these methods, the adsorbent and other equipment used are expensive, so there is a problem as a method for removing heavy metals.

Many reports have been made of adsorbents using plant residues as raw materials for removing heavy metals (for example, Non-Patent Document 1). Non-Patent Document 1 discloses that a wood residue is used as a raw material, and a phosphate group is introduced into this to improve the adsorption ability of uranium, which is one of heavy metals, and other heavy metals. In the technique disclosed in Non-Patent Document 2, it is disclosed that introduction of a phosphate group into a wood residue can be performed by an esterification reaction.

Further, it is disclosed that a raw material used is cotton yarn, which is phosphorylated by a urea / phosphoric acid method to produce a cellulose phosphate material. It is shown that cadmium in the soil was adsorbed using this cellulose phosphate material (Non-patent Document 2).
However, the cadmium adsorption amount of the cellulose phosphate material is only about 20 mg per gram of the adsorbent, which is not sufficient for adsorbing a large amount of heavy metals. Moreover, since the raw material currently used is the cotton yarn marketed, it is not preferable from an economical viewpoint.

In addition, this patent applicant discloses the following technical literature as a publication in which the literature well-known invention relevant to this invention was described.
JP 2007-002142 A AMA Nada, NA El-Wakil, ML Hassan, AM Adel (2006): Differential adsorption of heavy metal ions by cotton stalk cation exchangers containing multiple functional groups, Journal of Applied Polymer Science, 101, 4124-4132 Naoki Harada, Makoto Suda, Yoko Saito, Katsumi Isozaki (“Adsorption Characteristics of Cadmium by Cellulose Phosphate Materials”, Japanese Soil Fertilizer Science Journal, 2007, Vol. 78, No. 1, pp. 89-91)

In view of the circumstances as described above, the problem of the present invention is to cultivate a large amount in a tropical low-humidity region, and to effectively adsorb heavy metals such as cadmium using sago palm starch extraction residue, which is promising as a food resource, as a raw material. It is in providing the adsorbent which can be performed, and its manufacturing method.

As a result of diligent research to solve the above-mentioned problems, the present inventors have phosphorylated sago starch extraction residue and used a specific amine as a catalyst, so that sago palm starch extraction residue is a heavy metal such as cadmium. The inventors have found that it can be suitably used as an adsorbent, and have completed the present invention.

The present invention is composed of the following technical matters. That is,
(1) A method for producing a heavy metal adsorbent mainly comprising an esterified sago palm starch extraction residue produced by esterifying the sago starch extraction residue, wherein the esterification reaction comprises a sago starch extraction residue and a phosphate ester. A method for producing a heavy metal adsorbent, comprising a step of using an agent as a mixture, and a step of adding an amine compound to the mixture produced in the step and heating the mixture.
(2) The mixture comprises 30% by weight to 50% by weight (dry weight) of sago starch extraction residue, 70% by weight to 50% by weight of the phosphoric acid esterifying agent, and the amine compound of the phosphoric acid esterifying agent. The method for producing a heavy metal adsorbent according to (1), wherein 1 to 3 equivalent parts are added to the weight.
(3) The method for producing a heavy metal adsorbent according to (2), wherein the phosphate esterifying agent is trichloride phosphate.
(4) The method for producing a heavy metal adsorbent according to (3), wherein the amine compound is tributylamine.
(5) A heavy metal adsorbent produced by the method according to any one of (1) to (4).
(6) The adsorbent according to (5), wherein the heavy metal is cadmium.
(7) The adsorbent according to (6), wherein the adsorbent is in the form of a pellet.

According to the present invention, it is possible to effectively utilize the sago palm extract residue that has been left as a pomace (waste), not the starch itself that can be used as food. Moreover, the heavy metal adsorbent of the present invention has an excellent heavy metal adsorption capacity and can efficiently adsorb various heavy metals including cadmium.

Hereinafter, embodiments of the present invention will be described in detail.

The method for producing a heavy metal adsorbent according to the present invention is characterized in that the sago starch extraction residue is esterified with a phosphoric acid esterifying agent, and the esterification reaction is further promoted by using a specific amine. is there. That is, cellulose and starch present in the sago starch extraction residue are crystallized by hydrogen bonds with each other and lack the ability to adsorb heavy metals. For this reason, in order to use the sago palm starch extraction residue as a heavy metal adsorbent, the cellulose constituting the sago palm extraction residue and the hydroxyl group present in the starch must be replaced with a less polar substituent that is less prone to hydrogen bonding. By this, heavy metal adsorptivity can be imparted. Such an esterified sago palm starch extraction residue is used as a heavy metal adsorbent.

The method for producing a heavy metal adsorbent is characterized in that a sago palm starch extraction residue and a phosphate esterifying agent are reacted to form a phosphate esterified sago palm starch extraction residue, which is used as a heavy metal adsorbent. First, as a sago palm starch extraction residue used as a raw material of the heavy metal adsorbent, a medullary residue after starch is extracted from a sago palm trunk of about 7 to 13 years old may be used. The method for extracting starch from sago palm is not particularly limited, but it is preferable to increase the surface area as much as possible in order to improve the reaction efficiency in the subsequent phosphoric esterification reaction. Therefore, it is preferable to use the extracted residue generated after sago palm is pulverized to a predetermined size. The degree of pulverization is not particularly limited as long as the subsequent esterification reaction proceeds, but in general, the major axis is preferably 1.0 to 30 mm, and particularly preferably 5 to 15 mm. If it is less than 1 mm, it is not preferable because it takes time to grind, and if it is 30 mm or more, it is not preferable from the viewpoint of handling. Further, the minor axis is preferably 0.1 to 3.0 mm, particularly preferably 0.5 to 2.0 mm. If it is less than 0.5 mm, it is not preferable because it takes time to grind, and if it is 2.0 mm or more, it is not preferable from the viewpoint of handling. Moreover, it is good also as a powder form.

In order to collect such sago palm extraction residue and use it as a heavy metal adsorbent, it is necessary to store a certain amount without rot. The sago palm extraction residue may be in a state containing moisture or in a dried state, but from the viewpoint of transportation and handling or the efficiency of the esterification reaction, a state in which moderate moisture has been removed is preferable. For example, it is preferable that 10 to 90% by weight of the sago palm is extracted. Further, from the viewpoint of preventing the sago palm extract residue from being spoiled during storage or transportation, it may be frozen or sun-dried.

The components of such sago palm extract residue vary depending on various conditions such as the production area and are not particularly limited, but generally 35 to 45% by weight of holocellulose and 25 of starch (starch). Those containing ˜35% by weight, 15 to 25% by weight of cellulose, and 3 to 8% by weight of lignin can be used. In addition, the sago palm extract residue contains resins such as terpenes and resins as impurities. In the present invention, it can be used as a raw material for an adsorbent of heavy metal without removing the impurities. If necessary, when removing the impurities, Soxhlet cooling is performed with an organic solvent such as an ethanol-benzene mixture (volume ratio 1: 2), an ethanol-hexane mixture (volume ratio 9: 1), or the like. It is also possible to perform extraction for 24 to 48 hours using a vessel.

Next, the phosphate esterifying agent for esterifying the sago starch extraction residue is not particularly limited as long as it can phosphate the cellulose and starch constituting the sago starch extraction residue, for example, , Phosphoric acid monochloride, phosphoric acid dichloride, phosphoric acid trichloride (compound name is described). Among the esterified compounds, phosphoric acid trichloride is preferable. The esterification reaction can also be carried out by sulfonation using sulfate or the like in addition to the phosphoric acid compound.

An esterification reaction when, for example, phosphoric acid trichloride is used as the phosphoric acid esterifying agent will be described. In the esterification reaction, the trichloride phosphate is considered to be ionized as shown by the following ionic reaction formula.

The ionization reaction generates active species PO ₃ ⁺ ions, which react with the cellulose constituting the sago palm starch extraction residue or the hydroxyl groups in the starch. On the other hand, in the above reaction, chloride ion Cl ⁻ is released, and as a result, hydrogen chloride HCl is generated. The generated hydrogen chloride HCl inhibits esterification. For this reason, in order to remove the generated hydrogen chloride HCl, an amine described later is used. By removing the generated hydrogen chloride HCl, the esterification reaction is promoted, and the phosphoric acid esterification of the sago palm starch extraction residue is further promoted. In addition to the phosphoric acid compound, sulfates and the like can be used as the esterifying agent. In addition, an aliphatic esterifying agent may be added to the said sago palm starch extraction residue at once, and may be gradually added and mixed on stirring conditions as needed.

An amine as a reaction accelerator refers to a compound represented by the following general formula. The amine as a reaction accelerator removes hydrogen chloride generated by the esterification reaction, shifts the chemical equilibrium in the esterification reaction to the right, and promotes the esterification reaction.

In said general formula, R1-R3 may be the same or different each independently, and represents a hydrogen atom, the C1-C6 alkyl group which may have a substituent, or an amino group. Since it is a thing, any of a primary amine, a secondary amine, and a tertiary amine may be sufficient. Among these amines, tertiary amines are preferable in view of the strength as a Lewis base. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group and the like.

Specific examples of the amine represented by the above general formula include trimethylamine, triethylamine, tripropylamine, tributylamine and the like. Among the amines, considering the electron donating effect of the alkyl group and the three-dimensional structure of the amine, the tertiary amines trimethylamine, triethylamine, tripropylamine, triallylamine, tributylamine, triethanolamine, triphenylamine, N, N -Diethylaniline, N, N-dimethyl-p-toluidine, N, N-dimethylethanolamine and the like are preferably used. Among the tertiary amines, tributylamine is preferable from the viewpoint of handling. In addition, the said amine as a reaction accelerator may be added to the said Sago palm starch extraction residue at once, and may be gradually added and mixed on stirring conditions as needed.

The method for producing a heavy metal adsorbent of the present invention is characterized in that the sago starch extraction residue and the phosphate esterifying agent are mixed in a predetermined ratio, and further, a predetermined amount of amine is added as a reaction accelerator. That is, 30% to 50% by weight of the sago starch extraction residue, 70% to 50% by weight of the phosphate esterifying agent, and 1 to 3 equivalent parts of the amine compound with respect to the weight of the phosphate esterifying agent. An esterification reaction is carried out by addition, and the resulting phosphoric acid esterified sago palm starch is extracted residue.

The phosphate esterifying agent is preferably 70% to 50% by weight, more preferably 40% to 45% by weight, based on 30% to 50% by weight of the sago starch extraction residue. On the other hand, the phosphoric acid esterifying agent is 60% by weight to 55% by weight. For the sago starch extraction residue, sufficient phosphate esterifying agent required for the ester reaction is necessary. From the viewpoint of accelerating the esterification reaction, the chloride ion generated with the phosphate esterification is sufficient. It is necessary to have an amine compound that only reacts with For example, when trichloride phosphate is used as the amine compound, three chloride ions are generated from one molecule of (POCl ₃ ), so the amine compound is 3 times the mole of the trichloride phosphate (in moles). Is required.

That is, it is preferable to add 1-3 parts by weight of the amine compound as the reaction accelerator with respect to the weight of the phosphate esterifying agent. If the amine compound is less than 1 equivalent, there is not sufficient amine that reacts with the chloride ion of hydrogen chloride produced by the esterification reaction, which is not preferable because the reaction is inhibited. On the other hand, if the amine exceeds 3 equivalents, side reactions and the like occur and it is not preferable from an economical viewpoint.

In the method for producing a heavy metal adsorbent of the present invention, first, the sago palm starch extraction residue is suspended in a solvent to obtain a reaction solution. The solvent that can be used is not particularly limited as long as it can uniformly diffuse the sago palm starch extraction residue as a raw material and does not swell the sago starch extraction residue as a plant residue. Therefore, it may be a low polarity solvent or a high polarity solvent. Examples of the low polarity solvent include hydrocarbons such as pentane, hexane, heptane, octane, cycloheptane, and cyclodecalin. Examples of highly polar solvents include dimethylformamide, acetonitrile, propionitrile, dimethylacetamide, dichloromethane, diethyl ether, tetrahydrofuran, dimethyl sulfoxide, acetone, methyl ethyl ketone, alcohols, N-methyl 2-pyrrolidone or 1,3. Examples thereof include dimethyl-2-imidazolidine, tetramethylurea, hexamethylphosphoric amide, N-methylacetamide and the like. In the present invention, these solvents may be used alone, or a mixed solution obtained by combining these solvents or a mixed solution with water may be used as a solvent.

Next, the reaction solution obtained by suspending the produced sago palm starch extraction residue in a solvent is heated at a predetermined temperature to perform an esterification reaction. When phosphoric acid is used as the esterifying agent, a phosphoric acid esterification reaction occurs. In the esterification reaction, a hydroxyl group present in cellulose or the like constituting the sago palm starch extraction residue can be converted to a phosphate ester group. In the esterification reaction, a predetermined amount of the above-described amine compound is further added. By adding an amine compound as the reaction accelerator, the esterification reaction is promoted, the sago palm starch extraction residue is phosphated, and a phosphate group is introduced into the sago palm starch extraction residue. By this reaction, the hydroxyl group originally possessed by the sago starch extraction residue is converted into a phosphate group, which can impart heavy metal adsorptivity.

The predetermined temperature is 50 ° C to 150 ° C, preferably 70 ° C to 100 ° C.
More preferably, it is 80 degreeC. When the heating temperature is less than 50 ° C., the reaction does not proceed sufficiently, which is not preferable. The reaction time is 1 hour to 4 hours, preferably 2 hours to 3 hours.

Furthermore, the sago palm starch extraction residue by which the phosphate esterification was carried out through a heating process produces | generates. In the heating step, the produced esterified sago palm starch extraction residue is extracted, washed and dried to obtain the heavy metal adsorbent of the present invention. In addition, completion of the said esterification reaction can be easily performed by confirming that the sago palm starch extraction residue changed from yellow before reaction to brown visually.

Finally, after the esterification reaction, it can be purified by extracting the esterified sago palm starch extraction residue present in the reaction system. The extraction conditions are not particularly limited, and for example, with stirring in an organic solvent such as an ethanol-benzene mixed solution (volume ratio 1: 2) or an ethanol-hexane mixed solution (volume ratio 9: 1). After pre-extraction for about 1 hour, a Soxhlet cooling extractor or the like can be used.

Thus, the esterified sago palm starch extraction residue is used as the heavy metal adsorbent of the present invention. The phosphorus content in the heavy metal adsorbent has a much higher phosphoric acid content than when no amine compound is used because an amine compound is used in the phosphoric esterification.

The heavy metal adsorbent of the present invention can be used in the form of powder or the like as it is, but it is desirable to use it by appropriately forming it as necessary. For example, in order to continuously recover heavy metals in sewage, it is preferable to form into pellets, and it is preferable to use what is molded into pellets in a column. If the adsorbent is in powder form, it is difficult to recover the adsorbent after recovering heavy metals in sewage, and when the column is packed and used, the powder adsorbent is clogged in the column. This makes it impossible to pass sewage.

In order to make pellets, adhesiveness is required as a raw material to some extent, so that the sago starch extraction residue as a raw material is not dried too much, and if necessary, a binder made of natural material such as gluten is added. Sometimes mixed. The sago starch extraction residue which is the raw material thus obtained is extruded from an extrusion die having a plurality of holes, cut into an appropriate length and pelletized. Although the specific shape of the pellet is not particularly limited, a columnar shape or a prismatic shape suitable for extrusion molding is preferable from the viewpoint of production efficiency. Further, the cross-sectional shape of the pellet need not be particularly limited. For example, a star shape or a triangle shape can be widely employed. Thus, since the heavy metal adsorbent of the present invention is in the form of pellets, it is easy to handle and convenient for measuring the amount used.

In the heavy metal adsorbent of the present invention, as long as it does not impair the purpose of the present invention, an antioxidant, a pigment, a coloring agent such as a dye, etc. Various additives can be appropriately added. The molding process can be performed by a known means such as calendar molding or press molding in addition to the above-described normal extrusion molding.

Next, a method for using the heavy metal adsorbent of the present invention will be described. The heavy metal adsorbent composed of the phosphate esterified sago palm starch extraction residue is mixed with and brought into contact with sewage, and mixed for a predetermined time, whereby the heavy metal in the sewage is recovered. And the adsorbent after collection | recovery is collect | recovered. From another point of view, the heavy metal adsorbent formed and processed into pellets is filled in the column, and the sewage is passed through the column, whereby the heavy metal in the sewage can be easily and easily recovered. Since the heavy metal adsorbent of the present invention can be used repeatedly as will be described later, the adsorbent in the column may be replaced when the adsorption capacity decreases after a predetermined number of uses.

As will be described later, the heavy metal adsorbent of the present invention is excellent in adsorption capacity and can be repeatedly used for desorption, re-adsorption, etc., so as described above, it can be used again as an adsorbent after use. it can.

Examples of components that can be adsorbed by the heavy metal adsorbent of the present invention include cadmium, zinc, copper, hexavalent chromium, lead, mercury, iron cobalt, nickel, manganese, etc. can do. Furthermore, dioxin, PCB, trihalomethane, humic acid, arsenic and the like can be adsorbed as components contained in the wastewater.

Hereinafter, although the present invention is explained using an example, the present invention is not limited to these at all.

Example 1
<Manufacture of heavy metal adsorbents>
Sago Palm Starch Extraction Residue In this example, the sago palm starch extraction residue used was extracted from the medulla of the sago palm sampled in Leyte Island, Philippines (2004), and after two additional starch extractions The product produced was dried. In this example, the sago palm starch extraction residue was applied to a pulverizer (Kiya Seisakusho Co., Ltd.) and powdered. Its properties are: color: yellow yellow orange (7.5YR8 / 3 [Revised Standard Sol Color Charts (reference value: Oyama et al., 2001)) composition: starch (67.1% (w / w), ingredients other than starch As for cellulose and lignin, cellulose is 29.6% (w / w) and lignin is 9.6% (w / w), respectively.)

Phosphoric esterification reaction The powder of the above sago starch extraction residue (5.0 g) was dissolved in a solvent. As a solvent, N, N-dimethylformamide (DMF) was used and suspended with 5.0 ml of the above-described sago palm starch extraction residue using 80 ml of solvent N, N-dimethylformamide (DMF). Next, 10 ml of phosphoric acid trichloride (POCl ₃ ) as a phosphoric acid esterifying agent and 40 ml of tributylamine for removing hydrogen chloride as a reaction accelerator are added to the above suspension, and 2. The reaction was performed for 0 hour. After completion of the reaction, the phosphate ester was washed using a Soxhlet extractor (ethanol-hexane volume ratio 9: 1), dried, and then used as a heavy metal adsorbent composed of phosphate esterified sago palm starch extraction residue. .

(Example 2)
<Quantification of phosphoric acid in heavy metal adsorbent>
The phosphoric acid content in the heavy metal adsorbent of the present invention produced in Example 1 was quantified. The quantitative method was performed according to the molybdenum blue method (Murphy and Riley, 1962). Specifically, (1) 0.2 g of a heavy metal adsorbent was decomposed by a microwave decomposition method using a nitric acid / hydrogen peroxide solution, and a volume of 100 ml was used as a sample solution. (2) 2.5 mol L ^-1 (245.2 g L ^-1 ) sulfuric acid solution 100 ml, 40 g L ^-1 ammonium molybdate solution 30 ml, 17.6 g L ^-1 ascorbic acid solution 60 ml, 0.27 g L ^-1 (1 mg Sb ml ⁻¹ ) Antimonyl potassium tartrate 10 ml was mixed with each other to prepare a coloring solution.
(3) A 0 to 2 mg L ⁻¹ potassium dihydrogen phosphate solution was prepared to obtain a phosphoric acid standard solution. (4) 10 ml of the sample solution or standard solution and 11 ml of pure water were mixed, several drops of p-nitrophenol were added, and aqueous ammonia (25%) was added until the solution became yellow (pH 7).
Then, 4 ml of coloring solution was added (25 ml in total), and after mixing, color was allowed to stand for 1 hour. (5) The absorbance of the colored solution was measured with a spectrophotometer at a wavelength of 890 nm.
(6) A calibration curve was created from the absorbance of the standard solution, and the phosphoric acid concentration in the sample solution was measured. From the phosphoric acid concentration, the phosphoric acid content (g kg-1) per unit weight of the heavy metal adsorbent was calculated. The results are shown in Table 3.

Example 3
<Measurement of maximum adsorption amount>
Suspend 0.05 g to 0.15 g of heavy metal adsorbent in 50 mg l ^-1 cadmium (Cd) solution (25 ml, pH 4.0), and shake and stir at 30 ° C for 1 hour to obtain cadmium (Cd) solution. Adsorption was performed. The concentration of the cadmium (Cd) solution before and after the adsorption test was measured with an atomic absorption photometer, and the equilibrium concentration (mg l ^-1 ) and the amount of adsorption (mg g ^-1 ) of cadmium (Cd) were calculated. The maximum adsorption amount was calculated from the equilibrium concentration and the adsorption amount using the Langmuir adsorption isotherm shown in the following formula. The results are shown in FIG.

As is clear from FIG. 1, the maximum adsorption amount of cadmium (Cd) is 25.2 mg / g.
It became.

(Example 4)
<Influence of contact time>
Suspend 0.2 g of heavy metal adsorbent in 50 mg l ^-1 cadmium (Cd) solution (25 ml) with pH adjusted to 4.0 at different contact times (10-90 min), respectively, in the adsorption of cadmium (Cd) The effect of contact time was evaluated. The results are shown in FIG. From FIG. 2, it was found that the adsorption equilibrium was reached within 10 minutes.

(Example 5)
<Hydrogen ion concentration (pH) characteristics>
Adopting cadmium as a heavy metal in sewage, making cadmium solution (concentration etc.),
This solution was used to test the adsorption properties. The adsorption test was specifically performed as follows. Suspend 0.2 g of heavy metal adsorbent in 50 mg l ^-1 cadmium solution (25 ml) with pH adjusted to 3.0, 3.5, 4.0, 5.0 and 6.0 respectively, stir and stir for 1.0 hour, then cadmium Adsorption of (Cd) was performed. The concentration of the cadmium (Cd) solution before and after the adsorption test was measured with an atomic absorption photometer (Z-5000, HITACHI), and the cadmium (Cd) adsorption amount was calculated from the concentration difference. The adsorption amount of cadmium (Cd) was calculated by the following formula. The results are shown in FIG. From FIG. 3, it was clarified that the heavy metal adsorbent of the present invention can adsorb cadmium (Cd) at a pH of 3.0 to 6.0. That is, it has been clarified that the adsorption of cadmium (Cd) is inhibited in the region where the pH is 2.0 or less.

(Example 6)
<Effect of electrolyte concentration>
Suspend 0.2 g of heavy metal adsorbent in 50 mg l ^-1 cadmium (Cd) solution (25 ml, pH 4.0) prepared with electrolyte solution (HNO ₃ nitrate) concentration of 0.01, 0.1 and 1.0 mol l ^-1 respectively. The mixture was turbid and stirred for 1.0 hour with shaking to evaluate the influence of the electrolyte concentration on the adsorption of cadmium (Cd). The results are shown in FIG. From FIG. 4, it is understood that the adsorption of cadmium (Cd) is inhibited by the increase in electrolyte.

(Example 7)
<Cadmium desorption and resorption test>
Cadmium was desorbed as follows. The adsorbed cadmium was desorbed using the heavy metal adsorbent in which cadmium (Cd) cadmium was adsorbed in Example 3. The heavy metal adsorbent adsorbed with cadmium (Cd) was added to 1.0 mol l ⁻¹ HNO ₃ solution (25 ml), and the mixture was shaken and stirred at 25 ° C. for 1 hour. After completion of shaking and stirring, the cadmium (Cd) concentration in the filtrate was measured with an atomic absorption photometer, and the desorption amount (mg g ⁻¹ ) of cadmium (Cd) was measured. The recovery rate (%) of cadmium (Cd) was calculated using the following formula.

Next, cadmium was adsorbed again in the same manner as in Example 3 using the adsorbent after desorption of cadmium. The desorbed heavy metal adsorbent (0.2 g) is air-dried, suspended again in 50 mg l ^-1 cadmium (Cd) solution (25 ml, pH), and shaken and stirred at 25 ° C for 1 hour. Cd) was adsorbed. The concentration of cadmium (Cd) in the solution before and after adsorption of cadmium (Cd) was measured with an atomic absorption photometer, and the amount of adsorption (mg / g) was calculated. Cadmium (Cd) adsorption / desorption operations were repeated three times. Cadmium (Cd) adsorption rate (%) was calculated using the following equation. The results are shown in Tables 1 and 2.

As is clear from Table 1, the cadmium (Cd) recovery rate in the cadmium (Cd) adsorption test was the first time (98.5%), the second time (79.5%), and the third time (54.1%).
It has become. That is, it has been clarified that the heavy metal adsorbent of the present invention can be repeatedly used as an adsorbent, although cadmium (Cd) adsorption is reduced by the desorption operation.

(Comparative Example 1)
A phosphate esterified sago palm starch extraction residue was produced in the same manner as in Example 1 except that tributylamine was not added as a reaction accelerator. The results are shown in FIG.

As is clear from FIG. 5, when no amine was added, the adsorption amount was low even when the equilibrium concentration of cadmium was increased, and the cadmium adsorption amount was significantly lower than when the amine was added.

In the heavy metal adsorbent produced by adding the amine of Example 1, the cadmium adsorption amount reached saturation as the equilibrium concentration increased, and it can be confirmed that the adsorption equilibrium was reached in the above figure. On the other hand, with respect to the heavy metal adsorbent to which the amine of Comparative Example 1 is not added, the adsorption amount increases linearly and gently even when the equilibrium concentration increases, and the adsorption equilibrium is not reached in FIG. That is, even when no amine is added, the phosphorylation reaction proceeds to some extent, but the degree is low, and it is understood that the performance of the produced heavy metal adsorbent is inferior.

The phosphoric acid content in Comparative Example 1 was measured in the same manner as in Example 1. Table 3 shows the results.
Shown in

When no amine was added (Comparative Example 1), the phosphoric acid content was about one-fourth that of the case where the amine was added (Example 1). That is, it has been clarified that by adding an amine during phosphorylation of the sago starch extraction residue, phosphorylation is promoted and the phosphorus content is increased.

Since the present invention is a manufacturing method that can provide a heavy metal material such as cadmium using sago palm starch extraction residue discarded in large quantities as waste, it can greatly contribute to the development of the environmental technology field.

It is the figure which showed the relationship between an equilibrium concentration and the largest adsorption amount. It is the figure which showed the relationship between contact time and the adsorption amount (mg / g) of cadmium. It is the figure which showed the relationship between pH of a solution, and the adsorption amount (mg / g) of cadmium. It is the figure which showed the relationship between the density | concentration of electrolyte solution, and the adsorption amount (mg / g) of cadmium. It is the figure which showed the relationship between the equilibrium density | concentration in the case where an amine is added, and the case where it does not add, and adsorption amount.

Claims (7)

A method for producing a heavy metal adsorbent mainly comprising an esterified sago palm starch extraction residue produced by esterifying the sago starch extraction residue, wherein the esterification reaction comprises a sago palm starch extraction residue and a phosphate esterifying agent. A method for producing a heavy metal adsorbent comprising a step of preparing a mixture, and a step of adding an amine compound to the mixture produced in the step and heating the mixture. The mixture comprises 30% to 50% by weight (dry weight) of sago starch extraction residue, 70% to 50% by weight of the phosphate esterifying agent, and the amine compound is based on the weight of the phosphate esterifying agent. 1 to 3 equivalent parts are added, The manufacturing method of the heavy metal adsorption material of Claim 1 characterized by the above-mentioned. The method for producing a heavy metal adsorbent according to claim 2, wherein the phosphate esterifying agent is trichloride phosphate. The method for producing a heavy metal adsorbent according to claim 3, wherein the amine compound is tributylamine. The heavy metal adsorbent manufactured by the method of any one of Claims 1-4. The adsorbent according to claim 5, wherein the heavy metal is cadmium. The adsorbent according to claim 6, wherein the adsorbent is in the form of a pellet.

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