JP2003225559A - Adsorbent made from plant biomass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for removing hazardous substances which can satisfy tight environmental regulations with an inexpensive adsorbent and simple operation. <P>SOLUTION: In this adsorbent, metal ions are carried on plant biomass mainly comprising cellulose and/or hemicellulose on which functional groups of an acidic phosphate ester are immobilized by reacting them with phosphoric acid. A preferable example as the plant biomass is a residue of squeezed orange. The adsorbent where a ferric ion is used as the carried metal ion is used for removing tervalent and pentavalent arsenic, pentavalent phosphorus, tervalent antimony, or tetravalent selenium. The adsorbent where a tetravalent cerium ion is used as the carried metal ion is used for removing a fluoride ion. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of removing harmful substances, and in particular, using a novel adsorbent, pentavalent phosphorus, trivalent antimony, tetravalent selenium from an aqueous solution,
The present invention relates to a technique for effectively adsorbing / removing (separating) trivalent and pentavalent arsenic or fluoride ions.

[0002]

2. Description of the Related Art Phosphorus, antimony, selenium, arsenic and the like exist in the environment as oxygen-bonded anions and oxoanions. Up to now, the removal of fluoride ions and oxoanions of these elements has been mainly carried out by the coagulation precipitation method. For example, in the removal of arsenic, many methods have been performed in which a large amount of iron powder is added to a treatment liquid containing arsenic to cause aggregation / precipitation. However, this method has a drawback in that a large amount of iron sludge, which has a high water content and is difficult to post-process, is generated. In addition, in the removal of fluoride ions, a method has been adopted in which lime is added and the calcium fluoride is separated as a precipitate. Although this method can remove fluoride ions to a large extent, it is difficult to meet the strict environmental standards expected in the future.

The ion exchange method and the adsorption method have been attracting attention as alternatives to the aggregation / precipitation method for removing these trace amounts of harmful substances existing in the environment. However, ordinary commercial ion exchange resins preferentially adsorb sulfide ions and sulfate ions present in a large amount in the environment rather than the above-mentioned oxo anions, and therefore these cannot be used for the above purpose.

Yoshida et al. Reported that arsenic and phosphorus can be effectively removed by using an adsorbent in which a ferric ion is adsorbed and supported on a chelate resin or a cation exchange resin ( Separation Science and Technology, 13
Vol., 173-184 (1978), Journal of Japan Society, 220- (1980)). In addition, Moriya reported that fluoride ions and selenium can be adsorbed and removed by using an adsorbent that adsorbs and supports aluminum and iron on a chelate resin (Journal of Japan Ion Exchange Society, Vol. 11, 10-). 12 (2000)). However, while these chelate resins and ion exchange resins are expensive,
The amount of metal ions supported per unit weight is not sufficient, and it is not suitable for removing a large amount of harmful substances. In addition, when the adsorption tower is filled with these resins and the treatment liquid is caused to flow, there is a problem that fine clogging due to fine solids in the liquid frequently causes smooth treatment.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a new technique capable of sufficiently clearing strict environmental regulations by a simple and simple operation using an inexpensive adsorbent in order to remove harmful substances. Let's take that issue.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that plant waste mainly composed of cellulose and hemicellulose, such as mandarin orange juice residue, which is an industrial waste. A gel-like substance that has been treated with phosphoric acid and has a functional group of phosphoric acid ester (acidic phosphoric acid ester) loaded with (bonded to) metal ions adsorbs various ions that are harmful substances and removes them. They found it useful and derived the present invention.

Thus, according to the present invention, the main component is cellulose and / or hemicellulose in which the functional group of the acidic phosphoric acid ester is immobilized by reacting with phosphoric acid, and metal ions are supported. An adsorbent is provided.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A solid adsorbent having a functional group of a phosphoric acid ester, a phosphonic acid ester, or a phosphinic acid ester, or a liquid extractant is strongly ferric ion, aluminum ion, tetravalent cerium ion, or the like. It is known to combine. In recent years, Mitsubishi Chemical Co., Ltd. has developed DIAION RSP-200, a chelate resin in which a functional group of phosphonic acid is immobilized on a matrix of polystyrene, and sells it as an adsorbent for iron and aluminum.

On the other hand, it is known that cellulose has three hydroxyl groups in one sugar chain unit, and these hydroxyl groups are converted into phosphoric acid ester by reacting with phosphoric acid. In the present invention, plant biomass mainly composed of polysaccharides such as cellulose and hemicellulose is phosphorylated by the same method, and ferric ion or tetravalent cerium ion is added to plant biomass composed of such phosphorylated ester. It is an adsorbent formed by strongly binding such as.

Thus, the present inventor has found that a phosphate ester of a plant biomass containing cellulose or hemicellulose as the main component and carrying ferric ion is a phosphate ion, an arsenate ion, an arsenite ion or a selenite ion. ,
It was found that it strongly adsorbs antimonite ion. It was also found that those carrying tetravalent cerium ions instead of ferric ions strongly adsorb fluoride ions.

As the plant biomass constituting the adsorbent for removing harmful substances of the present invention, any plant-derived biomass containing cellulose and / or hemicellulose as a main component can be used, but particularly preferable plant biomass. Is an orange juice residue. In addition to the citrus juice residue, used paper, seaweed (for example, kelp) residue, or the like can also be used.

To prepare the adsorbent of the present invention, plant biomass such as citrus juice residue is subjected to an appropriate pretreatment (see below), and then reacted with phosphoric acid to give hydroxyl groups of the cellulose or hemicellulose. And phosphoric acid ester are formed, and the functional group consisting of the phosphoric acid ester is immobilized in plant biomass. The phosphorylated esterification reaction is carried out according to a known method, for example, a phosphorylation treatment using urea as a catalyst is performed. The plant biomass composed of cellulose esterified with phosphoric acid (hemicellulose) is then immersed in an aqueous solution containing a metal ion to be supported so that the metal ion is adsorbed and supported (bonded) on the plant biomass via the phosphoric acid ester. Then, it is prepared as an adsorbent.

The plant biomass as a raw material is subjected to an appropriate pretreatment, if necessary, prior to the above-mentioned phosphoric acid esterification reaction and metal ion loading step. For example, when an adsorbent is prepared from citrus juice residue, it is made insoluble in water by a crosslinking reaction using epichlorohydrin and caustic soda.

If the adsorbent (adsorption gel) of the present invention prepared as described above is used, the harmful substance can be obtained by bringing it into contact with an aqueous solution containing the harmful substance (a simple batch operation as described later). Can be adsorbed and removed. In this case, there is a pH range suitable for adsorption / removal depending on each harmful substance.

For example, to adsorb and remove trivalent arsenic by using an adsorbent in which cellulose or hemicellulose of plant biomass such as citrus juice residue is phosphorylated and ferric ion is supported as metal ions. , PH is 7 ~
Adsorption is preferably carried out from an aqueous solution having a pH of 12, preferably 8 to 11. Similarly, in order to adsorb and remove tetravalent selenium, it is suitable to adsorb from an aqueous solution having a pH of 2 to 6, preferably a pH of 3 to 5. Similarly, adsorption of phosphorus
For removal, the pH is 1.5-5, preferably the pH is 2-
Adsorption from the aqueous solution of No. 4 is preferred. Similarly, 3
To adsorb and remove valent antimony, the pH is 2-1
Adsorption is preferably carried out from an aqueous solution having a pH of 0, preferably 5 to 8. Similarly, in order to adsorb and remove pentavalent arsenic, it is preferable to adsorb from an aqueous solution having a pH of 2 to 7, preferably a pH of 2 to 6.

Fluorine (fluoride ion) is adsorbed and removed using an adsorbent in which cellulose or hemicellulose of plant biomass such as mandarin orange juice residue is phosphorylated to carry tetravalent cerium ions as metal ions. In order to achieve this, it is preferable to perform adsorption from an aqueous solution having a pH of 3 to 5, preferably 3 to 4.

In the adsorption / removal or ion exchange operation using a solid adsorbent, the adsorbent or ion exchange resin is usually packed in a column, and the treatment liquid in question is passed through this column. In this case, the treatment liquid contains solid matter such as fine sand grains, which frequently causes a trouble of causing clogging in the column. After adsorption, an appropriate eluent is passed through the column to elute the adsorbent in question to regenerate the adsorbent and concentrate the adsorbent, but in actual operation, use of an eluent that greatly exceeds the theoretical amount is used. Are forced to. As described above, the ordinary adsorption / separation operation using a column requires a great deal of cost and causes troubles frequently.

On the other hand, when the adsorbent of the present invention is used, the plant biomass containing polysaccharides as the main component is easily incinerated. Therefore, after adsorbing, the plant biomass is dried and incinerated, and the adsorbed substance is ash or dust. It is more rational to concentrate and collect inside. From such an idea, the adsorption / separation operation using the adsorbent of the present invention can be performed by a simple patch operation using a tank and a stirring device. Thus, the adsorbent used in the present invention, which is a raw material of plant biomass, and the waste liquid are mixed and stirred, and then the adsorbent is removed by filtration to obtain a clean liquid in which the harmful anions are removed.

[0019]

EXAMPLES The following examples illustrate the embodiments of the present invention.
However, the present invention is not limited to these examples.
It is not something that will be done.Example 1 Method for producing adsorption gel The adsorption gel is manufactured, for example, by the following method. Orange
Wet crushed mandarin orange juice residue generated at the juice factory,
Vacuum-dried powder sample 20 with an average particle size of about 90 μm
g using 80% propyl alcohol aqueous solution
200m after vacuum-drying after removing oil and pigment components
l in dimethylsulfoxide (DMSO) at room temperature
It was stirred for 24 hours. 40 ml of epichlorohydrin in this liquid
Add drin, stir at room temperature for 2 hours, and then raise the temperature to 50 ° C.
Then add 3 ml of 5M caustic soda solution and stir for 5 hours
Then, the crosslinking reaction was carried out. Then to room temperature
Cooled with 70% aqueous propyl alcohol, and
Wash with 0.5 M aqueous hydrochloric acid until neutral.
No further vacuum dried.

After thoroughly washing the above dry powder with dimethylformamide (DMF), it was added to 200 ml of fresh dimethylformamide, and further 30 g of urea and 18 g of urea were added.
Phosphoric acid was added thereto, and the mixture was stirred at room temperature for 1 hour and at 150 ° C. for 2 hours to cause a reaction, whereby a phosphorylation treatment was performed. After cooling to room temperature, the powder after the reaction was collected by filtration and washed with propyl alcohol and a 0.1 M hydrochloric acid aqueous solution until neutral. Further, it was washed with distilled water and vacuum dried. The amount of phosphorus contained in this adsorbent was measured by a fluorescent X-ray analyzer to find that it was 1.15 per unit of sugar chain.
It was estimated to be mol.

The adsorbent gel was treated with various concentrations of ferric ion,
Alternatively, the mixture was shaken with an aqueous solution containing tetravalent cerium ions, and the relationship between the adsorption amount and the concentration (adsorption isotherm) was examined. The results shown in FIGS. 1 and 2 were obtained for ferric ions and tetravalent cerium ions, respectively. Was obtained. The adsorption amount increases with increasing concentration, but eventually reaches a certain value. When the maximum adsorption amount of these metal ions on the present adsorption gel was evaluated from this constant value, it was 3.7 for ferric ion and tetravalent cerium ion, respectively.
And a value of 1.7 mol / kg dry gel was obtained. Compared with the values of other commercially available chelate resins and ion exchange resins for ferric ion, this value is extremely large.

The dried adsorption gel (1.2 g) had a pH of 3.
Ferric acid was carried by loading 600 ml of an aqueous solution of 01 containing 15 mM ferric chloride and shaking at room temperature for 24 hours. Then, it was washed with distilled water, further dried under vacuum, and then subjected to an adsorption test. Similarly, tetravalent cerium ions were loaded in the following manner.
2.0 g of the above dry adsorption gel was used at a pH of 1.95 and 4.2
A tetravalent cerium ion having a concentration of mM was loaded. After that, it was washed with distilled water, further vacuum dried, and then subjected to an adsorption test.

[0023]Example 2 Antimony adsorption 15 ppm concentration of antimony chloride (II at various pH
15 ml of I) aqueous solution and 25 m of the above iron-supporting adsorption gel
g and g in an Erlenmeyer flask and shaker in a constant temperature water bath at 30 ° C.
Absorption of antimony by shaking with a mixer for 24 hours
I put on my clothes. The adsorptive gel also has good filtration characteristics.
If filtration is performed using Advantech A5 filter paper,
Mousse filtration results in a very clear filtrate
It was The concentration of antimony in the aqueous solution before and after adsorption was Shimadzu I
With the CPS5000 ICP atomic emission spectrometer,
The pH was measured by Orion 720 type pH meter.
It was The pH of the aqueous solution after adsorption and the anti-money by this adsorption gel
The relationship of the adsorption percentage of hydrogen is shown in FIG. Where the adsorption percentage
What is the ratio?
Percentage removed from liquid. Wide pH = 2-10
Adsorption of more than 80% was observed in the pH range, especially p
Adsorption close to 90% is achieved in the region of H = 5-8
It was

[0024]Example 3 Phosphorus adsorption Aqueous solution of phosphate at a concentration of 46 ppm at various pH 1
5 ml and 25 mg of the above-mentioned iron-supporting adsorption gel were mixed with a triangular flare.
Scoot and use a shaker in a constant temperature water bath at 30 ° C for 24:00
The phosphate ions were adsorbed by shaking and mixing.
The concentration of phosphate ion in the aqueous solution before and after adsorption is DIONEX
DX-120 type ion chromatograph manufactured by p
H was measured by Orion model 720 pH meter.
The pH of the aqueous solution after adsorption and the phosphate ion by this adsorption gel
The relationship with the adsorption percentage is shown in FIG. pH = 1.5-5
80% or more adsorption was observed in the region, especially pH = 2
In ~ 4, adsorption of 90% or more was achieved.

[0025]Example 4 Adsorption of pentavalent arsenic Arsenate with a concentration of 15 ppm as arsenic of various pH
15 ml of an aqueous solution containing iron and the above-mentioned iron-supporting adsorption gel 25 m
g and g in an Erlenmeyer flask and shaker in a constant temperature water bath at 30 ° C.
Absorption of arsenate ions by shaking with a mixer for 24 hours
I put on my clothes. The pH of the aqueous solution after adsorption and this adsorption gel
The relationship between the adsorption percentage of pentavalent arsenic is shown in FIG. pH =
Adsorption of 90% or more in a wide pH range of 2 to 6
Was made.

[0026]Example 5 Adsorption of trivalent arsenic 15 ppm concentration of arsenous-iodine as arsenic of various pH
15 ml of an aqueous solution containing iron and the above-mentioned iron-supporting adsorption gel 25
Transfer mg and mg to an Erlenmeyer flask and shake in a constant temperature water bath at 30 ° C.
Arsenite ion by shaking for 24 hours using a machine
Was adsorbed. PH of aqueous solution after adsorption and this adsorption gel
FIG. 6 shows the relationship of the adsorption percentage of trivalent arsenic according to. p
Adsorption of 80% or more was achieved at H = 8-11.

[0027]Example 6 Adsorption of tetravalent selenium Selenite concentration of 15ppm as selenium of various pH
15 ml of an aqueous solution containing acid ions and the above-mentioned iron-supported adsorption gel
25 mg and 25 ml of it in an Erlenmeyer flask and a constant temperature water bath at 30 °
Shaken for 24 hours using a shaker
Adsorption of nitrate ions was performed. The pH of the aqueous solution after adsorption
This figure shows the relationship between the adsorption percentage of tetravalent selenium on this adsorption gel.
7 shows. 80% or more adsorption reached at pH = 3-5
Was made.

[0028]Example 7 Fluorine adsorption Fluoride with a concentration of 15 ppm as selenium of various pH
15 ml of an aqueous solution containing ions and the above tetravalent cerium
Take 25 mg of the supported adsorption gel in an Erlenmeyer flask and
Shake for 24 hours using a shaker in a constant temperature water bath at 0 ° C.
The adsorption of fluorine ions was carried out by and. Water after adsorption
The relationship between the pH of the solution and the adsorption percentage of fluorine by this adsorption gel
The engagement is shown in FIG. 80% or more absorption at pH = 3-4
The clothes have been achieved.

[0029]Comparative Example 1 Using a phosphonic acid type chelate resin
Adsorption of trivalent antimony It is a phosphonic acid type chelating resin manufactured by Mitsubishi Chemical Corporation.
CRP-200 resin was loaded with ferric ions, 3
The adsorption test of high-value antimony was conducted. Bearing ferric ion
The holding was performed by the same method as described in Example 1. Well
The antimony adsorption method is also the same as the method described in Example 2.
Is. PH of aqueous solution after adsorption and trivalent by this adsorption gel
FIG. 9 shows the relationship of the adsorption percentage of antimony of. pH is
About 90% adsorption is observed in the area of 4 or less.
However, the adsorption drops sharply at pH higher than that.
There is.

[0030]Comparative Example 2 Trivalent Anne by Activated Alumina
Adsorption of Zimon Activated alumina manufactured by Sumitomo Chemical Co., Ltd. with a particle size of 1.8 mm
By the same method as described in Example 2 using KHD-12.
Trivalent antimony was adsorbed. Of the aqueous solution after adsorption
Of the pH and the adsorption ratio of trivalent antimony by this adsorption gel
The relationship is shown in FIG. CRP-200 shown in Comparative Example 1
Adsorption increases with increasing pH, as opposed to mold resins
It However, the adsorption is very low except when pH = 11.
Yes. Moreover, when using this adsorbent, the white turbidity in the filtrate
The formation of loid-like substances was observed.

[0031]Comparative Example 3 Absorption of fluorine by activated alumina
Wear Example 6 using the same activated alumina as described in Comparative Example 2.
Adsorption of fluorine was carried out by the same method as described above. adsorption
The pH of the aqueous solution after that and the adsorption of fluorine by this activated alumina
The relationship of the ratio is shown in FIG. 60 at pH = 6-7
% Adsorption is observed, but the tetravalent compounds shown in Example 6
Low adsorption compared to this adsorption gel supporting cerium
Yes. Moreover, in the same manner as in Comparative Example 2, white color was obtained in the filtrate after adsorption and filtration.
The formation of cloudy colloidal material was observed.

[0032]

As is clear from the above description, the adsorbent of the present invention can be manufactured at low cost by utilizing plant biomass such as citrus juice residue. If the adsorbent of the present invention is used, the harmful substances are adsorbed very efficiently by a simple operation of bringing an aqueous solution containing the harmful substances into contact with the adsorbent of the present invention in a batch system.
Can be removed.

[Brief description of drawings]

FIG. 1 shows the relationship between the adsorption amount and the concentration of ferric ions carried by the adsorbent of the present invention.

FIG. 2 shows the relationship between the adsorption amount and the concentration of tetravalent cerium ions carried by the adsorbent of the present invention.

[Fig. 3] pH of the aqueous solution when antimony is adsorbed and removed from the aqueous solution containing antimony by using the adsorbent of the present invention prepared from citrus juice residue
2 is a graph showing the adsorption percentage (vertical axis) of antimony removed from the aqueous solution.

FIG. 4 shows the pH (horizontal axis) of an aqueous solution when antimony is adsorbed and removed from an aqueous solution containing phosphorus using the adsorbent of the present invention prepared by using citrus juice residue as a raw material and the removal from the aqueous solution. It is a graph which shows the adsorption percentage (vertical axis) of the performed phosphorus.

FIG. 5: pH of the aqueous solution when antimony is adsorbed / removed from an aqueous solution containing pentavalent arsenic using the adsorbent of the present invention prepared by using citrus juice residue as a raw material (horizontal axis)
3 is a graph showing the adsorption percentage (vertical axis) of arsenic removed from the aqueous solution.

[Fig. 6] pH of the aqueous solution when antimony is adsorbed and removed from the aqueous solution containing trivalent arsenic using the adsorbent of the present invention prepared by using citrus juice residue as a raw material (horizontal axis).
3 is a graph showing the adsorption percentage (vertical axis) of arsenic removed from the aqueous solution.

FIG. 7: pH (horizontal axis) and aqueous solution of an aqueous solution when antimony is adsorbed and removed from an aqueous solution containing tetravalent selenium by using the adsorbent of the present invention prepared by using citrus juice residue It is a graph which shows the adsorption percentage (vertical axis) of selenium removed from the inside.

FIG. 8: pH of the aqueous solution (abscissa) and removal from the aqueous solution when antimony is adsorbed and removed from the aqueous solution containing fluorine using the adsorbent of the present invention prepared from the citrus juice residue It is a graph which shows the adsorption percentage (vertical axis) of the produced fluorine.

FIG. 9 is a DIA carrying ferric ions for a comparative example.
In a graph showing the pH of the aqueous solution (horizontal axis) and the adsorption percentage of the antimony removed from the aqueous solution (vertical axis) when antimony was adsorbed and removed from the aqueous solution containing antimony using ION CRP-200 resin as an adsorbent. is there.

FIG. 10 shows the pH (horizontal axis) of the aqueous solution when antimony is adsorbed and removed from the aqueous solution containing antimony using activated alumina as an adsorbent and the adsorption percentage of antimony removed from the aqueous solution (longitudinal direction). (Axis) is a graph showing.

FIG. 11: pH (horizontal axis) of the aqueous solution when antimony was adsorbed and removed from the aqueous solution containing fluorine using activated alumina as an adsorbent for the comparative example and the adsorption percentage of the fluorine removed from the aqueous solution (longitudinal axis). (Axis) is a graph showing.

   ─────────────────────────────────────────────────── ─── Continued front page    (71) Applicant 500287352             Sanso Micron Co., Ltd.             21-12 Uenoshiba-cho, Sakai City, Osaka Prefecture (72) Inventor Victory Inoue             19-21 Kago, Honjo-cho, Saga City, Saga Prefecture (72) Inventor Gimire Kedarnato             1 Saga University International Exchange Meeting, Honjo-cho, Saga City, Saga Prefecture             Hall (72) Inventor Kenjiro Makino             2-517-57 Sakuragaoka, Nobeoka City, Miyazaki Prefecture F-term (reference) 4D024 AA04 AB11 AB12 AB16 BA14                       BA19 BB01 BB08 BC04 CA06                       DB03                 4G066 AA02B AA50A AB19B AC02A                       AC02C AC35C AE10B AE19C                       BA36 CA21 CA32 CA41 CA46                       DA08 FA03 FA12 FA38

Claims (4)

[Claims] 1. An adsorbent characterized by supporting a metal ion on a plant biomass mainly composed of cellulose and / or hemicellulose in which a functional group of an acidic phosphoric acid ester is immobilized by reacting with phosphoric acid. 2. The adsorbent according to claim 1, wherein the plant biomass containing cellulose and / or hemicellulose as a main component is citrus juice residue. 3. A metal ion to be carried is ferric ion, which is used for removing trivalent and pentavalent arsenic, pentavalent phosphorus, trivalent antimony, or tetravalent selenium. The adsorbent according to claim 1 or 2. 4. The adsorbent according to claim 1, wherein the metal ion to be supported is a tetravalent cerium ion, which is used for removing fluoride ions.