JP2008095072A - Polymer useful as scavenger for noble metal ion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer provided with a chelate ligande in a molecule and a scavenger for a noble metal ion containing the polymer. <P>SOLUTION: A polymer is made by making chitosan molecules shown by a formula crosslinked and a scavenger for a noble metal contains the polymer. (In the formula, R1, R2 or R3 shows respectively independently a crosslinkable group which is coordinatable to the noble metal ion or hydorgen). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a noble metal ion scavenger and a noble metal ion recovery method using the same.

  The amount of sludge generated from plating companies in the Kyushu area was about 3,000 tons / year, and it became clear that the industrial waste treatment costs of about 100 million yen / year were incurred. In particular, noble metals such as gold, palladium and platinum are often drained due to their dilute concentration even though they are contained in trace amounts in the plating waste liquid.

  On the other hand, in Miyazaki Prefecture, which has many primary industries, a large amount of biomass waste (such as citrus fruit juice, salmon and shrimp shells) is generated from agriculture, fishery and food processing industries. Now that ocean dumping is no longer possible, the development of treatment technology and effective utilization technology has become an urgent issue. In particular, research on the effective use of chitosan obtained from shells of crustaceans such as shrimp and crabs is underway in many fields.

  The present inventors have found and announced that chitosan has high selectivity for specific metal ions and has a considerably large amount of saturated adsorption [Chem, Lett. p. 1281 (1988)]. This excellent property is considered to be due to (1) high hydrophilicity, (2) flexible skeletal structure and (3) presence of many active amino groups possessed by natural polysaccharide chitosan. As described above, chitosan has excellent metal ion adsorption characteristics not found in commercially available chelate resins, and has an advantage that it can be obtained at low cost because the starting material is waste from the biomass industry. However, adsorption of noble metal or heavy metal ions by chitosan occurs in an acidic but relatively high pH region. Therefore, when treating an acid leachate having a very low pH, an alkali is added to adjust the pH. There was a difficulty that had to be adjusted. In order to solve this problem, many chitosan derivatives were synthesized, and the adsorptivity of metal ions was studied. However, when a functional group having a chelate-forming ability is introduced for the purpose of effectively collecting metal ions, there arises a problem that the chitosan derivative is dissolved in an acidic solution.

  Therefore, an attempt has been made to crosslink the chitosan derivative having a functional group introduced therein to make the resin insoluble in an acidic solution. However, the functional group is crushed by the crosslinking reaction, resulting in a problem that the exchange capacity is greatly reduced.

  In order to solve this problem, the present inventors have completed the invention described in JP-A-6-227813. In the invention described in JP-A-6-227813, the amino group of glucosamine constituting chitosan is first reacted with an aldehyde derivative containing a pyridine ring or a thiophene ring to form a Schiff base to protect the amino group. Crosslinking between chitosan molecules with epichlorohydrin and then reducing the Schiff base with sodium tetraborohydride to form a crosslinked polymer having a pyridine ring or a thiophene ring, which is a functional group having chelating ability It relates to a method of synthesis. The polymer according to the invention described in Japanese Patent Application Laid-Open No. 6-227813 has a chitosan molecular skeleton having a crosslinked structure, so that it does not dissolve in an acidic solution suitable for adsorption of noble metal ions, and has a functional group having a chelating ability. Since they are bonded, noble metal ions can be adsorbed efficiently.

Japanese Patent Laid-Open No. 6-227813 Japanese Patent Laid-Open No. 2004-2582 Japanese Patent No. 3235283 Chem, Lett. p. 1281 (1988)

  As described above, the polymer described in JP-A-6-227813 has excellent properties, but the production process of this polymer includes a step of forming a cross-linking, a step of introducing a chelating coordination group, There was a problem that it was complicated to include.

  Accordingly, an object of the present invention is to provide a chitosan derivative polymer having a crosslinked structure and having a chelate ligand, which can be easily produced.

  The present inventors have found that the above object can be achieved by carrying out the cross-linking step of the chitosan molecule and the introduction step of the chelate ligand together, and have completed the present invention.

The present invention includes the following inventions.
(1) A polymer having a structure in which chitosan molecules are cross-linked by a cross-linking group containing a coordinating group capable of coordinating with a noble metal ion.
(2) Formula (I) as glucosamine (repeating unit) constituting chitosan:

（式中、Ｒ_１、Ｒ_２又はＲ_３は、それぞれ独立に、貴金属イオンに配位可能な配位基を含有する架橋基を形成しているか、或いは水素であり、ただしＲ_１、Ｒ_２及びＲ_３が同時に水素であることはなく、
前記架橋基を形成するＲ_１、Ｒ_２又はＲ_３は、それぞれ独立に、同一又は異なるキトサン分子を構成する他のグルコサミンのＲ_１、Ｒ_２又はＲ_３と一緒になって貴金属イオンに配位可能な配位基を含有する架橋基を形成しており、
前記架橋基の少なくとも１つは、異なるキトサン分子間に形成された架橋基である）
で表されるグルコサミン誘導体（繰り返し単位）を含有する、（１）記載のポリマー。

(Wherein R ₁ , R ₂ or R ₃ independently form a bridging group containing a coordinating group capable of coordinating to a noble metal ion or are hydrogen, provided that R ₁ , R ₂ And R ₃ are not simultaneously hydrogen,
R ₁ , R ₂ or R ₃ forming the bridging group independently coordinate to a noble metal ion together with other glucosamine R ₁ , R ₂ or R ₃ constituting the same or different chitosan molecule. Forming a bridging group containing possible coordinating groups,
At least one of the bridging groups is a bridging group formed between different chitosan molecules)
The polymer as described in (1) containing the glucosamine derivative (repeating unit) represented by these.

(3) The polymer according to (1) or (2), wherein the number of atoms other than hydrogen in the bridging group is 4 to 30.
(4) The polymer according to any one of (1) to (3), wherein the coordination group is a coordination group containing a sulfur atom or a nitrogen atom.
(5) The bridging group has the formula (II):

（式中、Ｘ又はＹは、それぞれ独立に、Ｓ、ＮＨ又はＯであり、ただしＸ及びＹが同時にＯであることはなく、
ｍ又はｎは、それぞれ独立に、１以上の整数であり、
＊印は結合位置を示す）
で表される部分構造を含む、（４）記載のポリマー。

Wherein X or Y are each independently S, NH or O, provided that X and Y are not O at the same time,
m or n each independently represents an integer of 1 or more,
(* Indicates the coupling position)
The polymer of (4) description including the partial structure represented by these.

(6) A method for producing a polymer having a structure in which chitosan molecules are cross-linked by a cross-linking group containing a coordinating group capable of coordinating to a noble metal ion, the amino group of glucosamine constituting chitosan on the 6-position carbon The hydroxyl group on the 3-position carbon and / or the hydroxyl group on the 3-position carbon is converted into a reactive group, and the converted chitosan has at least two functional groups capable of binding to the reactive group and is coordinated with a noble metal ion. A method comprising reacting a compound containing a possible coordinating group to crosslink between chitosan molecules.
(7) A noble metal ion scavenger containing the polymer according to any one of (1) to (5).
(8) A noble metal ion recovery method using the noble metal ion scavenger described in (7) as an adsorbent in an acidic solution.

(9) A method for producing fine particles containing a polymer having a structure in which chitosan molecules are cross-linked by a cross-linking group containing a coordinating group capable of coordinating to a noble metal ion,
An O / W / O emulsion having a first aqueous solution in which chitosan is dissolved as an aqueous phase, 1) a second aqueous solution having an osmotic pressure higher than that of the first aqueous solution, and / or 2) the second aqueous solution being water. A chitosan concentration step of concentrating chitosan in the aqueous phase comprising the first aqueous solution by mixing with a W / O emulsion as a phase, and if necessary, in the first aqueous solution after the concentration step A chitosan fine particle preparation step further comprising an insolubilization step for insolubilizing chitosan; and the chitosan fine particles obtained by the chitosan fine particle preparation step, the amino group of glucosamine constituting the chitosan in the fine particles, and the hydroxyl group on the 6-position carbon And / or a hydroxyl group on the 3-position carbon is converted into a reactive group, and the chitosan after the conversion has at least two functional groups capable of binding to the reactive group, and is noble. Crosslinking step of the compound containing a coordinating capable coordinating groups genus ions reacted performs processing to crosslink between chitosan molecules,
Said method.

(10) The method according to (9), wherein the number of atoms other than hydrogen in the bridging group is 4 to 30.
(11) The method according to (9) or (10), wherein the coordination group is a coordination group containing a sulfur atom or a nitrogen atom.
(12) The bridging group has the formula (II):

（式中、Ｘ又はＹは、それぞれ独立に、Ｓ、ＮＨ又はＯであり、ただしＸ及びＹが同時にＯであることはなく、
ｍ又はｎは、それぞれ独立に、１以上の整数であり、
＊印は結合位置を示す）
で表される部分構造を含む、（１１）記載の方法。

Wherein X or Y are each independently S, NH or O, provided that X and Y are not O at the same time,
m or n each independently represents an integer of 1 or more,
(* Indicates the coupling position)
The method of (11) description including the partial structure represented by these.

(13) A polymer produced by the method according to any one of (9) to (12), having a structure in which chitosan molecules are cross-linked by a cross-linking group containing a coordinating group capable of coordinating to a noble metal ion. Contains fine particles.
(14) A precious metal ion scavenger containing the fine particles according to (13).
(15) A noble metal ion recovery method using the noble metal ion scavenger described in (14) as an adsorbent in an acidic solution.
(16) The method for recovering noble metal ions according to (15), wherein an acidic solution containing noble metal ions is passed through a column packed with the precious metal ion scavenger according to (14).

  The polymer of the present invention can be produced by a simple method in which the introduction of a chelate ligand and the crosslinking reaction are performed in a common process.

(Chitosan)
The molecular weight and the like of chitosan used as a raw material for the polymer of the present invention are not particularly limited.
The shape of chitosan as a raw material is not particularly limited, and may be a powder shape or a spherical fine particle shape. Spherical chitosan fine particles can be produced, for example, by the technique described in JP-A No. 2004-2582.

(Crosslinking group)
The polymer of the present invention is characterized in that chitosan molecules are cross-linked by a cross-linking group containing a coordinating group capable of coordinating to a noble metal ion.

In the polymer of the present invention, glucosamine bonded to a crosslinking group formed between chitosan molecules has a structure of a glucosamine derivative of the above formula (I). Since the hydroxyl group on the 3-position carbon of glucosamine is less reactive than the amino group and the hydroxyl group on the 6-position carbon, R ₃ is present as a glucosamine derivative represented by formula (I) in the polymer of the present invention. What is primarily hydrogen is included. In the polymer of the present invention, as glucosamine constituting chitosan, in addition to the glucosamine derivative of the above formula (I), normal glucosamine having no crosslinking group, or all glucosamines in the same molecule between the glucosamines in the same molecule. A glucosamine derivative or the like having the same structure as that of the above formula (I) except that it is formed can be included.

  Examples of the “coordinating group capable of coordinating with a noble metal ion” include, but are not limited to, a coordinating group containing a sulfur atom, a nitrogen atom, and a combination thereof as a ligand. By using these coordination groups, noble metal ions can be adsorbed with high selectivity.

  It is preferable that two ligands are contained in one bridging group and the bridging group functions as a bidentate chelate ligand.

  The length of the bridging group is not particularly limited, but usually the number of atoms other than hydrogen is preferably 4-30, more preferably 4-20, and 6-12. Particularly preferred.

The crosslinking group preferably has a partial structure represented by the above formula (II). In the formula (II), n or m are each independently an integer of 1 or more, n is preferably an integer of 2 to 4, and m is preferably an integer of 1 to 4. For example, as a specific coordinating _{groups, -NHCH 2 CH 2 NH -,} - HNCH 2 CH 2 NH 2, -SCH 2 CH 2 NH -, - SCH 2 CH 2 S -, - HNCH 2 CH 2 SH, - _{HNCH 2 CH 2 S -, -} SCH 2 CH 2 SCH 2 CH 2 NHCH 2 CH 2 N -, - (NHCH 2 CH 2 N) m -, - (NHCH 2 CH 2 S) m -, - (SCH 2 CH ₂ S) m-, or _{even, - (NH- (CH 2)} n-NH) m -, - (NH- (CH 2) n-S) m -, - (S- (CH 2) n-S _{) m -, - OCH 2 CH} 2 NH -, - OCH 2 CH 2 NH 2, -SCH 2 CH 2 O -, - OCH 2 CH 2 SH, -HNCH 2 CH 2 O -, - SCH 2 CH 2 SCH 2 _{CH 2 NHCH 2 CH 2 O -} , - ( _{CH 2 CH 2 NH) m -} , - (NHCH 2 CH 2 S) m -, - (SCH 2 CH 2 S) m-, or _{even, - (NH- (CH 2)} n-NH) m -, - _{(NH- (CH 2) n-} S) m -, - (S- (CH 2) n-S) m -, - (O- (CH 2) n-NH) m -, - (O- (CH ₂ ) n-S) m- (wherein n or m is as defined above for formula (II)).

  In the examples of the present specification, a crosslinking group represented by the following formula (III) or (IV) is employed as a crosslinking group, but the present invention is not limited to these.

（式中、＊印は式（I）のＲ_１が結合する窒素原子、Ｒ_２が結合する酸素原子又はＲ_３が結合する酸素原子への結合位置を示す）

(In the formula, * indicates a bonding position to the nitrogen atom to which R ₁ of formula (I) is bonded, the oxygen atom to which R ₂ is bonded, or the oxygen atom to which R ₃ is bonded)

(Method for producing polymer)
The present invention also relates to a method for producing the polymer. This method converts the amino group of glucosamine constituting the chitosan, the hydroxyl group on the 6-position carbon, and / or the hydroxyl group on the 3-position carbon to a reactive group, and binds the reactive group to the chitosan after the conversion. It is characterized by reacting a compound containing at least two possible functional groups and a coordinating group capable of coordinating with a noble metal ion to crosslink between chitosan molecules. Since the hydroxyl group on the 3-position carbon of glucosamine is less reactive than the amino group and the hydroxyl group on the 6-position carbon, in the production of the polymer of the present invention, mainly on the amino group and / or the 6-position carbon of glucosamine. The hydroxyl group is converted to a reactive group and becomes a base point for bonding of the crosslinking group.

FIG. 1 shows a reaction scheme of one embodiment of this method. In this embodiment, formic acid is used to convert an amino group to a reactive group —N═CH ₂ , and then has two —SH groups that are functional groups capable of binding to the reactive group, and A 1,2-ethanedithiol having a sulfur atom, which is a ligand that can be applied to a noble metal ion, is added and reacted to crosslink between chitosan molecules. In the present specification, EDTC means a chitosan derivative crosslinked with 1,2-ethanedithiol.

  FIG. 2 shows a reaction scheme of another embodiment of the present method. In this embodiment, epichlorohydrin is used to convert the amino group and hydroxyl group of glucosamine to the reactive groups 2,3-epoxypropylamino group and 2,3-epoxypropyloxyl group, and then the reactivity 1,2-ethanedithiol having a sulfur atom as a ligand capable of binding to two groups and having a —SH group, which is a functional group that can be bonded to a group, and reacting between the chitosan molecules Crosslink. Although not shown in FIG. 2 because it is complicated, a form in which N and O are bridged may also exist. There may also be a form in which one end of the bridging group is O-bonded on the 3-position carbon and the other end is bound to the amino group of another glucosamine, O on the 6-position carbon, or O on the 3-position carbon. In the present specification, EDTSC means a chitosan derivative crosslinked with 1,2-ethanedithiol through epichlorohydrin.

  As a compound that can be converted to a crosslinking group, in addition to 1,2-ethanedithiol, halogen compounds having the above coordination group represented by formula (II), dihalogen compounds, aldehyde compounds, dialdehyde compounds, epoxy compounds, And diepoxy compounds, but are not limited thereto.

(Polymer shape)
The polymer of the present invention can take various shapes, for example, a powder shape or a spherical fine particle shape. When chitosan fine particles are used as raw materials, the produced polymer of the present invention can also be in the form of fine particles. Regardless of the shape of the raw material chitosan, the produced polymer of the present invention can be processed into fine particles by the technique described in, for example, JP-A No. 2004-2582.

(Precious metal ion recovery method)
The polymer of the present invention can be used as a precious metal ion scavenger. The polymer of the present invention can be used, for example, for the purpose of selectively collecting a noble metal from a waste solution such as a plating waste liquid containing a trace amount of noble metal ions, an electronic component / electronic device, or a waste catalyst.

  The polymer of the present invention exhibits a high adsorption rate for gold (III), palladium (II) and platinum (IV).

The recovery of the noble metal using the polymer of the present invention is preferably performed in an acidic solution. If the pH of the acidic solution is 1 or more, an adsorption rate of 100% is achieved. Moreover, an adsorption rate of 80% or more is achieved even in the vicinity of ³ mol / dm ³ where industrially important hydrochloric acid concentration is high. Thus, the polymer of the present invention can adsorb noble metals efficiently even in a strongly acidic solution.

  The polymer of the present invention adsorbing a noble metal can be easily regenerated and reused with a thiourea solution containing thiourea or hydrochloric acid.

(Superporous fine particles of the polymer of the present invention)
The present invention also relates to a method for producing fine particles containing the polymer, and fine particles produced by the method. The microparticles provided by this embodiment of the present invention are superporous microparticles having through holes in the particles.

The method for producing fine particles of the present invention comprises:
An O / W / O emulsion having a first aqueous solution in which chitosan is dissolved as an aqueous phase, 1) a second aqueous solution having an osmotic pressure higher than that of the first aqueous solution, and / or 2) the second aqueous solution being water. A chitosan concentration step of concentrating chitosan in the aqueous phase composed of the first aqueous solution by mixing with a W / O emulsion as a phase, and if necessary, in the first aqueous solution after the concentration step A chitosan fine particle preparation step further comprising an insolubilization step for insolubilizing chitosan; and the chitosan fine particles obtained by the chitosan fine particle preparation step, the amino group of glucosamine constituting the chitosan in the fine particles, and the hydroxyl group on the 6-position carbon And / or a hydroxyl group on the 3-position carbon is converted into a reactive group, and the chitosan after the conversion has at least two functional groups capable of binding to the reactive group, and is noble. Crosslinking step of the compound containing a coordinating capable coordinating groups genus ions reacted performs processing to crosslink between chitosan molecules,
It is characterized by including. The method for producing fine particles of the present invention is a modification of the method for producing fine particles described in JP-A No. 2004-2582.

The features of this method are described in detail below.
(1) Water phase and oil phase of O / W / O emulsion a) Water phase As the water phase in the above O / W / O emulsion, an aqueous solution containing chitosan (first aqueous solution) is used.

  As the solvent for preparing the first aqueous solution, water can be usually used, and various aqueous solutions can also be used as the solvent.

  Since chitosan can be dissolved in an acid, the first aqueous solution may be dissolved, for example, by dissolving chitosan in an acid aqueous solution or suspending chitosan in water and then dropping the acid.

  The acid is not limited as long as the chitosan used can be dissolved in water. For example, adipic acid, acetic acid, propionic acid, butyric acid, L-ascorbic acid, acrylic acid, citric acid, maleic acid, lactic acid, In addition to organic acids such as malic acid, inorganic acids such as hydrochloric acid and boric acid can be used. In the present invention, among these, a weak acid is particularly preferable.

  The concentration of chitosan in the first aqueous solution is not particularly limited, but is usually about 1 to 15% by weight, preferably 6 to 12% by weight.

  Moreover, you may add an additive suitably to 1st aqueous solution as needed. The additive is not limited as long as it does not insolubilize dissolved chitosan. For example, osmotic pressure regulators such as NaCl, glucose, lactose, glycerin, sucrose fatty acid ester, monoglycerin fatty acid ester, diglycerin fatty acid ester, polyglyceric acid fatty acid ester, polyoxyethylene / sorbitan surfactant, lecithin, poly Examples include aqueous emulsifiers such as oxyethylene hydrogenated castor oil surfactants. The amount of the osmotic pressure adjusting agent used can be appropriately determined according to the desired osmotic pressure. The amount of the aqueous emulsifier used is not limited, and can usually be about 0.01 to 10% by weight.

b) Oil phase The oil phase constitutes the inner and outer oil phases of the O / W / O emulsion.

  As the oil agent in the oil phase, any oil phase oils, oils, petroleum oils, organic solvents, synthetic oils and the like may be used as long as they are used as oil phases such as known O / W / O emulsions. . You may use these by 1 type (s) or 2 or more types. In particular, when it is necessary to remove the oil agent during particle recovery, it is preferable to use an organic solvent such as toluene or benzene in addition to a petroleum oil agent such as hexane having a low boiling point.

  Moreover, you may add additives, such as an emulsifier (oil-based emulsifier), to an oil phase as needed. As the oily emulsifier, sucrose fatty acid ester, polyglycerin fatty acid ester, polyglycerin condensed ricinoleic acid ester, sorbitan surfactant, lecithin, polyoxyethylene hydrogenated castor oil surfactant and the like can be used. The addition amount of the oil emulsifier may be appropriately set according to the type of the oil emulsifier to be used and the like, but may be usually in the range of 0.5 to 10% by weight.

(2) Preparation of O / W / O Emulsion In the present invention, an O / W / O emulsion can be prepared using the aqueous phase and the oil phase.

  When preparing an O / W / O emulsion, first, an oil agent is added to the first aqueous solution, and an O / W emulsion is prepared by emulsifying so that the oil agent is dispersed in the continuous phase of the first aqueous solution. The emulsification method for preparing the W / O emulsion is not particularly limited, and a stirring method, a mixing method using a homomixer, a membrane emulsification method using a porous membrane, and the like can be used. The membrane emulsification method is desirable when it is desired to make the particle sizes uniform, but the method using a homomixer is desirable from an industrial point of view otherwise.

  An additive such as an aqueous emulsifier is appropriately added to the first aqueous solution, and the volume ratio of the oil agent in the O / W emulsion may be set to 0.1 to 70% by volume, preferably 10 to 50% by volume.

  An O / W / O emulsion can be obtained by dispersing the O / W emulsion thus obtained in a continuous oil phase. The emulsification method is not particularly limited, and a stirring method, a mixing method using a homomixer, a membrane emulsification method using a porous membrane, and the like can be used. The membrane emulsification method is desirable when it is desired to make the particle sizes uniform, but the method using a homomixer is desirable from an industrial point of view otherwise.

  The volume ratio of the dispersed phase (O / W emulsion) at this time may be set to about 0.1 to 70% by volume, preferably 10 to 50% by volume in the O / W / O emulsion.

(3) Concentration step In the method of the present invention, the O / W / O emulsion, 1) a second aqueous solution having an osmotic pressure higher than the osmotic pressure of the first aqueous solution, and / or 2) the second aqueous solution in an aqueous phase By mixing the W / O emulsion, the chitosan in the aqueous phase composed of the first aqueous solution is dehydrated and concentrated using the osmotic pressure difference between the first aqueous solution and the second aqueous solution. Fine particles of chitosan are formed in the first aqueous solution by dehydration and concentration. When fine particles are not formed, the insolubilization step described later can be further performed to form fine particles.

  Dehydration and concentration can also be performed by heating, vacuum heating, etc., but since the oil agent used has a low boiling point and it is difficult to precisely control the amount of dehydration, the osmotic pressure of the first aqueous solution By mixing a second aqueous solution having a high osmotic pressure and / or a W / O emulsion in which the second aqueous solution is an aqueous phase (dispersed phase), the osmotic pressure difference becomes a driving force in the state of the mixed emulsion (mixture). The water is taken from the dispersed water droplets of low osmotic pressure, and the chitosan of the first aqueous solution is concentrated.

  Moreover, although the viscosity of the water phase containing chitosan becomes high by the said concentration, the viscosity of a water phase has a great influence on the shape and dispersibility of the particle | grains formed by the insolubilization process mentioned later. That is, the higher the concentration ratio and the higher the viscosity due to gelation, the smaller the deformation of the water phase particles, and the closer the shape to a sphere and the more dispersible.

As the second aqueous solution, an osmotic pressure adjusting agent dissolved in water can be used. There is no limitation on the type of the osmotic pressure adjusting agent as long as it is a substance capable of producing a high osmotic pressure. For example, NaCl, inorganic salts CaCl _2, etc., glucose, saccharides sucrose such as glycerin.

  The concentration of the second aqueous solution may be adjusted so as to have an osmotic pressure higher than that of the first aqueous solution. Specifically, the concentration of the second aqueous solution can be set in advance based on the desired concentration rate.

  Here, the concentration rate ε% is that the osmotic pressure of the first aqueous solution is Πa, the volume of the aqueous phase is Va, the osmotic pressure of the second aqueous solution is Πb, and the volume of the aqueous phase is Vb. If the equilibrium osmotic pressure when the osmotic pressures are equal is Πe, it can be estimated by the following equation.

  Since chitosan is a polymer, it usually has a small amount of dissolution and generally has low osmotic pressure. Therefore, in the method of the present invention, a second aqueous solution having a higher osmotic pressure may be prepared.

  Generally, the porosity of the fine particles obtained can be controlled by adjusting the concentration rate.

  In the present invention, in addition to using the second aqueous solution as it is, a W / O emulsion having the second aqueous solution as an aqueous phase can be used alone or together with the second aqueous solution. The W / O emulsion should be prepared in the same manner as the W / O emulsion prepared in advance when preparing the O / W / O emulsion, except that the second aqueous solution is used as the aqueous phase. Can do.

(4) Insolubilization treatment When chitosan fine particles are not formed in the concentration step, a substance (insolubilized substance) capable of insolubilizing (or solidifying) chitosan is further added to the mixture obtained in the concentration step. To form fine particles.

  The insolubilizing substance is not limited as long as it dissolves (precipitates) dissolved chitosan, and can be appropriately selected. In general, hydroxides such as alkali metals and alkaline earth metals; inorganic acid salts (chlorides, carbonates, etc.) such as alkali metals, alkaline earth metals, transition metals, and ammonium salts Alternatively, two or more kinds may be adopted as appropriate.

  The insolubilizing substance is preferably added in the form of an aqueous solution of the substance or a W / O emulsion having the aqueous solution as an aqueous phase.

  The addition amount or concentration of the insolubilizing substance (when the aqueous solution is used) may be an amount sufficient to insolubilize the chitosan used. Therefore, it can be set as appropriate according to the concentration of chitosan used.

  In particular, in the insolubilization step, the osmotic pressure of the aqueous solution of the insolubilizing substance can be appropriately changed according to the purpose. That is, (i) when the osmotic pressure is set equal to the equilibrium osmotic pressure e, the high-viscosity particles of chitosan are insolubilized as they are. (Ii) When it is set higher than Πe, the high viscosity particles are insolubilized while being further dehydrated. (Iii) When set lower than Πe, water is taken in and insolubilized while swelling. Thus, the particle diameter, shape, porosity and the like of the particles can be arbitrarily controlled also by the osmotic pressure of the insolubilizing solution. The osmotic pressure can be appropriately changed depending on the concentration of the aqueous solution. Similar control can be carried out by changing the amount of the aqueous solution or W / O emulsion added.

(5) Recovery of chitosan fine particles In the chitosan fine particle preparation step of the present invention, the mixture obtained in the concentration step or insolubilization treatment can be used as chitosan fine particles as they are, but the oil phase is removed and washed as necessary. You may collect it after doing. Thereby, the solidified chitosan particles can be recovered. The oil phase removal method, the washing method, and the like may be performed according to known methods as long as the properties of the fine particles are not affected. For example, if the mixed emulsion that has been insolubilized is subjected to solid-liquid separation by filtration or the like, and the resulting solid content is washed with alcohol and then dried, chitosan fine particles can be recovered as solidified particles. Moreover, you may implement the process of removing the oil phase which forms the cavity inside microparticles | fine-particles as needed. For example, the oil phase can be removed by a submerged drying method, a freeze drying method, or the like.

(6) Crosslinking step The chitosan fine particles obtained in the chitosan fine particle preparation step are cross-linked between chitosan molecules constituting the fine particles by a crosslinking group containing a coordination group capable of coordinating to a noble metal ion. Apply. Crosslinking can be carried out according to the procedure described in “Method for producing polymer” described above.

(7) Features of crosslinked chitosan fine particles Fine particles containing a polymer having a structure in which chitosan molecules are cross-linked by a crosslinking group containing a coordination group capable of coordinating to a noble metal ion, produced according to the present invention, are SEM photographs. As is apparent from the results of the pore distribution and the particle size distribution, these are superporous fine particles having through holes having a pore diameter of 2 to 6 μm. Moreover, the porosity is as large as 70-80% or more, and the average particle size is a true sphere having a size of about 150 μm.

  The solution containing the substance to be adsorbed can rapidly pass through the fine particles of the present invention. Therefore, by collecting the fine particles of the present invention in a column or the like as a noble metal ion scavenger and passing a solution containing the noble metal ions, it is possible to quickly recover and remove the noble metal ions.

1. 1 g (6.2 mmol) of EDTC synthetic chitosan fine particles were dispersed in 100 ml of a distilled water: DMF = 1: 9 mixed solution in a three-necked flask, and 5.3 g (62 mmol) of 35% formaldehyde was added dropwise at 60 ° C. under a nitrogen atmosphere. Stirring was carried out over time. After completion of the reaction, the mixture was filtered and washed with ethanol.

  The obtained fine particles were dispersed in 60 ml of DMF in a three-necked flask, 4.3 g (62 mmol) of 1,2-ethanedithiol was added dropwise, and the mixture was stirred at room temperature for 48 hours in a nitrogen atmosphere. After completion of the reaction, the mixture was filtered, washed with ethanol, distilled water and an aqueous sodium hydroxide solution, and dried under reduced pressure at 50 ° C.

2. 1 g (6.2 mmol) of EDTSC synthetic chitosan fine particles are dispersed in a mixed solution of 15 ml of DMF and 25 ml of epichlorohydrin in a three-necked flask, added with 25 ml of 3 mol dm ^-3 sodium hydroxide solution and stirred at 60 ° C for 2 hours with heating. went. After completion of the reaction, the mixture was filtered and washed with ethanol many times.

  The obtained fine particles are dispersed in 50 ml of DMF in a three-necked flask, 4.3 g (62 mmol) of 1,2-ethanedithiol and 1.9 g (18.6 mmol) of triethylamine are added dropwise, and the mixture is stirred at room temperature in a nitrogen atmosphere for 48 hours. It was. After completion of the reaction, the mixture was filtered, washed with ethanol, distilled water and an aqueous sodium hydroxide solution, and dried under reduced pressure at 50 ° C.

3. Synthesis of cross-linked chitosan 10 g (62 mmol) of chitosan fine particles were dispersed in 500 g of distilled water, and 10 g of acetic acid was added to dissolve the chitosan. While stirring the chitosan acetic acid solution at 50 ° C., 63 g (620 mmol) of benzaldehyde was added dropwise. The gelled chitosan was washed with acetone and dried under reduced pressure at 50 ° C.

The obtained chitosan was dispersed in a mixed solution of 150 ml of DMF and 150 ml of epichlorohydrin in a three-necked flask, 150 ml of 0.5 mol dm ^-3 sodium hydroxide solution was added, and the mixture was heated and stirred at 50 ° C for 24 hours. After completion of the reaction, the mixture was filtered, washed with ethanol, distilled water, hydrochloric acid solution and aqueous sodium hydroxide solution, and dried under reduced pressure at 50 ° C.

4). Relationship between adsorption rate of palladium (II) and gold (III) and hydrochloric acid concentration The adsorption rate of palladium (II) and gold (III) by EDTC and EDTSC prepared above was measured under various hydrochloric acid concentration conditions. For comparison, the adsorption rate of the crosslinked chitosan prepared above was also measured.

All experiments were performed by the batch method. The chloride salt of the metal ions dissolved in any hydrochloric acid concentration was the initial concentration of the metal and 1 m mol dm ^-3. 0.05 g of resin was added to 15 ml of each solution and shaken for 24 hours in a 30 ° C. constant temperature bath. Quantification of metal ions before and after equilibration was measured using an atomic absorption photometer. In evaluating the adsorption characteristics, the adsorption rate% was defined as follows.
Adsorption rate (Adsorption)% = (Co−Ce) / Co × 100
Co: Metal initial concentration [m mol dm ^-3 ]
Ce: Metal equilibrium concentration [m mol dm ^-3 ]
The results are shown in FIG. 3 (EDTC and crosslinked chitosan) and FIG. 4 (EDTSC and crosslinked chitosan). The adsorption rate of Pd (II) and Au (III) by cross-linked chitosan decreased rapidly with increasing hydrochloric acid concentration. On the other hand, EDTC and EDTSC did not show a rapid decrease like crosslinked chitosan, and showed a high adsorption rate even in a high hydrochloric acid concentration region.

5. Relationship between adsorption rate of various metal ions and hydrochloric acid concentration The adsorption rate of various metal ions by EDTC and EDTSC prepared above was measured under various hydrochloric acid concentration conditions.

All experiments were performed by the batch method. The chloride salt of the metal ions dissolved in any hydrochloric acid concentration was the initial concentration of the metal and 1 m mol dm ^-3. 0.05 g of resin was added to 15 ml of each solution and shaken for 24 hours in a 30 ° C. constant temperature bath. Quantification of metal ions before and after equilibration was measured using an atomic absorption photometer. In evaluating the adsorption characteristics, the adsorption rate% was defined as follows.
Adsorption rate (Adsorption)% = (Co−Ce) / Co × 100
Co: Metal initial concentration [m mol dm ^-3 ]
Ce: Metal equilibrium concentration [m mol dm ^-3 ]
The adsorption result of EDTC is shown in FIG. 5, and the adsorption result of EDTSC is shown in FIG.

  Both EDTC and EDTSC showed high adsorption rates for noble metals (palladium (II), gold (III) and platinum (IV)). On the other hand, heavy metals (copper (II), nickel (II), cadmium (II), iron (II), cobalt (II) and zinc (II)) were hardly adsorbed in the total hydrochloric acid concentration region. From this, it is considered that selective separation of noble metal from heavy metal is possible.

6). All the desorption experiments of palladium (II) adsorbed on the polymer were conducted by the batch method. The chloride salt of palladium ion was dissolved in 0.1 mol dm ^-3 hydrochloric acid solution to make the initial concentration of palladium ion 1 mMol dm ^-3 . 0.05 g of resin was added to 10 ml of the solution, and the mixture was shaken in a 30 ° C. constant temperature bath for 24 hours. After shaking, filtration was performed, and 15 ml of various desorption solutions were added to the obtained resin, and the mixture was shaken again in a thermostat at 30 ° C. for 24 hours. The metal ions before and after equilibration and the metal ions in the desorption solution after desorption were measured using an atomic absorption photometer. In evaluating the adsorption characteristics, the desorption rate (%) was defined by the following equation.
Desorption% = (Cd × 0.015) / ((Co−Ce) × 0.010) × 100
Co: Metal initial concentration [m mol dm ^-3 ]
Ce: Metal equilibrium concentration [m mol dm ^-3 ]
Cd: Metal concentration in desorption solution [m mol dm ^-3 ]
The results are shown in Table 1.

  It was found that EDTSC adsorbed with palladium (II) can be easily regenerated by using thiourea and a mixed solution of thiourea and hydrochloric acid and can be used repeatedly. Here, the result of EDTSC is shown, but the result of EDTC is almost the same.

1. Synthesis experiment of adsorbent
1.1 Preparation of Superporous Chitosan Fine Particles (OWOC) FIG. 7 shows a preparation scheme of ultraporous chitosan fine particles (OWOC) prepared from an O / W / O emulsion containing a chitosan aqueous solution as an aqueous phase. 16.4 g of chitosan was dispersed in 250 ml of distilled water, and 8.1 g of adipic acid and 5.4 g of Tween 60 were added to prepare a 6 wt% chitosan aqueous solution. 50 ml of hexane was added to the chitosan aqueous solution, and the mixture was stirred for 10 minutes at 17500 rpm using a homogenizer to prepare a chitosan O / W emulsion. In a separable flask with a water jacket, slowly add the chitosan O / W emulsion to 500 ml of 2 wt% tetraglycerin condensed ricinoleate (TGCR) hexane solution while stirring and stir at 20 ° C, 250 rpm for 2 hours. An O / W / O emulsion was prepared. On the other hand, a high-concentration sodium chloride W / O emulsion was prepared by emulsifying 230 ml of a 15 wt% sodium chloride aqueous solution in 250 ml of a 2 wt% TGCR hexane solution. The prepared sodium chloride W / O emulsion was slowly added to the stirring chitosan O / W / O emulsion and stirred at 20 ° C. and 250 rpm for about 12 hours. Here, chitosan in the chitosan O / W / O emulsion is concentrated by the oil phase movement of water using the osmotic pressure difference between the high concentration sodium chloride W / O emulsion and the chitosan O / W / O emulsion as a driving force. Filtration, washing with ethanol, and subsequent drying yielded OWOC.

1.2 Preparation of 1,2-ethanedithiol-immobilized chitosan (EDTSC) via a spacer The synthesis scheme of 1,2-ethanedithiol-immobilized chitosan (EDTSC) via a spacer is as shown in FIG. Disperse 7.7 g (47.9 mmol) of OWOC in a mixed solution of 50 ml of DMF and 100 ml of epichlorohydrin in a three-necked flask, add 100 ml of 3 mol dm ^-3 sodium hydroxide solution, and heat and stir at 60 ° C for 2 hours. went. After the reaction, it was filtered and washed with ethanol. The obtained intermediate was dispersed in 100 ml of DMF in a three-necked flask, 1,2-ethanedithiol 45.1 g (479.0 mmol) and triethylamine 14.5 g (143.7 mmol) were added, and the mixture was stirred at room temperature for 48 hours under a nitrogen atmosphere. . After the reaction, it was filtered and washed with ethanol, distilled water, hydrochloric acid solution and sodium hydroxide solution. EDTSC was obtained by drying.

2. Adsorption experiment
2.1 Adsorption equilibrium experiments All adsorption experiments were performed by the batch method. The chloride salt of each metal ion was dissolved in various hydrochloric acid solutions, and the initial concentration of each metal ion was 1 mmol dm ⁻³ . 0.05 g of chitosan derivative was added to 15 ml of each solution in a 30 ml sample tube and shaken in a 30 ° C. constant temperature bath for 24 hours. The hydrochloric acid concentration after equilibration was determined by neutralization titration. The metal ion concentration before and after the equilibrium was measured using an ICP emission analyzer (SHIMADZU ICPS = 7000). In evaluating the adsorption characteristics, the adsorption rate% and the adsorption amount q _e were defined by the following equations.
Adsorption rate (Adsorption)% = {(C _init −C _e ) / C _init } × 100
Adsorption amount q _e = (Cinit−Ce) × 15/1000 / w
C _init : Initial metal ion concentration [mmol dm ^-3 ]
C _e : equilibrium metal ion concentration [mmol dm ⁻³ ]
w: Resin amount [g]

2.2 Adsorption rate experiment
In a 303 K thermostat, 0.1 g of EDTSC was added to a 200 ml tall beaker, and 2 ml of various hydrochloric acid solutions were added to impregnate the adsorbent with the hydrochloric acid solution. The chloride salt of palladium (II) was dissolved in various hydrochloric acid solutions, so that the initial concentration of palladium (II) ions was 0.25 mmol dm ⁻³ . After the temperature of 100 ml of the palladium (II) solution was adjusted to 303 K, it was added to a tall beaker and stirred at a constant rotational speed using a stirring blade. The time when the palladium (II) solution was added was set as the reaction start (t = 0), and 1 ml of the solution was collected at regular intervals. At this time, since this reaction experiment was performed in a state where the concentration was kept constant, an initial concentration of palladium (II) solution was added in the amount collected. The amount of palladium (II) adsorbed by EDTSC was determined from the mass balance (C _init -C _t [mmol dm ^-3 ]). In order to evaluate the adsorption rate, a pseudo first-order rate constant k ₁ of the initial rate was derived from the pseudo first-order rate equation. The pseudo first order velocity equation is shown below.
ln (C _t / C _init ) = − k ₁ t
C _t : Metal ion concentration at time t [mmol dm ⁻³ ]
C _init : Initial metal ion concentration [mmol dm ⁻³ ]
t: Time [sec]

2.3 Adsorption rate experiment About 0.05 g of EDTSC was packed in a glass column with a column jacket (inner diameter 0.3 cm, length 10 cm). The chloride salt of palladium (II) was dissolved in a 0.1 mol dm ^-3 hydrochloric acid solution to adjust the initial concentration of palladium (II) ions to 0.1 mmol dm ^-3 . A palladium (II) solution was fed at a constant temperature and a constant flow rate using a dual pump (FLOM KP-12), and the outflow solution was collected every hour using a fraction collector (EYELA DC-1200).

3. Results and discussion The results of the above experiment and discussions on the results obtained are shown below. The symbols used in this specification and drawings have the meanings shown in the following table.

3.1 Evaluation of EDTSC shape characteristics
A SEM photograph of EDTSC is shown in FIG. From the surface and cross-sectional photographs, EDTSC was confirmed to be superporous chitosan fine particles with large through-holes. It is considered that an inner oil phase having a large droplet diameter is formed by coalescence of the inner oil phase droplets in the O / W / O emulsion, thereby forming a large through hole. The pore structure of EDTSC was analyzed using a mercury porosimeter (SHIMADZU micromeritics PORE SIZER 9320). The pore distribution of EDTSC is shown in FIG. From the pore distribution, EDTSC was found to have uniform large pores with a diameter of 2-6 μm. Since this diameter almost coincides with the value measured from the cross-sectional SEM photograph, the obtained pore distribution is considered to be highly reliable. The effect of the large pores is considered to increase the adsorption rate, and can be expected to be used as an adsorbent for perfusion chromatography. The particle size distribution of EDTSC was measured using an optical microscope (OLYMPUS) equipped with a personal computer microscope dedicated camera (Carton Optical Co., Ltd. XP9507). The particle size distribution is shown in FIG. EDTSC was polydispersed and the average particle diameter was 142.8 μm.

A simple determination of sulfur atoms contained in EDTSC was performed using a wavelength dispersive X-ray fluorescence analyzer (Rigaku Denki Kogyo Co., Ltd. System 3270E). As a result, the sulfur content of EDTSC was 1.84 mol kg ⁻¹ , and thus the content of dithioether (—S— (C ₂ H ₄ ) —S—) was 0.92 mol kg ⁻¹ . The thiol group was quantified by the Ellman method. From the results, the amount of thiol groups contained in EDTSC was a very small value of 3.6 × 10 ⁻³ mol kg ⁻¹ . Therefore, it is considered that the sulfur atom exists almost as a thioether. This suggests that EDTSC achieves ligand introduction and crosslinking simultaneously.

3.2 Adsorption selectivity from hydrochloric acid solution by EDTSC
EDTSC shows the results of adsorption of each metal ion from hydrochloric acid solution by EDTSC. EDTSC showed high adsorption rate for precious metals such as palladium (II), gold (III) and platinum (IV) in the total hydrochloric acid concentration region. . On the other hand, copper (II), nickel (II), cadmium (II), iron (III), cobalt (II) and zinc (II), which are base metals, were hardly adsorbed by EDTSC in the total hydrochloric acid concentration region. These results suggest that EDTSC can selectively adsorb and separate noble metal ions from a solution containing a large amount of base metal.

3.3 Adsorption isotherm of palladium (II) by EDTSC The adsorption isotherm of palladium (II) by EDTSC at each temperature was measured. The results are shown in FIG. From the results, all adsorption isotherms were plotted based on the Langmuir equation, respectively, and the saturated adsorption amount (q _m ) and Langmuir constant (K _L ) of palladium (II) were determined from the obtained straight lines. The results are shown in Table 3. The saturated adsorption amount and Langmuir constant were almost equal at all temperatures. The saturated adsorption amount of palladium (II) by EDTSC was 2.4 mol kg ^-1 , and the Langmuir constant was confirmed to decrease slightly with increasing temperature.

We investigated how enthalpy and entropy are involved in the adsorption of palladium (II). Assuming that enthalpy is constant regardless of temperature, free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) can be calculated by the following equations. T is the temperature [T] and R is the gas constant [JK ⁻¹ mol ⁻¹ ].

  ΔH was derived from the slope of the straight line obtained from equation (1), and ΔG and ΔS were derived from equations (2) and (3), respectively. The obtained results are shown in Table 3, respectively. From these thermodynamic parameters, it is considered that the adsorption of palladium (II) by EDTSC from hydrochloric acid solution is almost dominated by entropy. Therefore, the adsorption mechanism of palladium (II) by EDTSC is considered to be due to the formation of a stable 5-membered ring chelate complex by chelate adsorption by dithioether possessed by EDTSC.

3.4 Adsorption rate of palladium (II) from hydrochloric acid solution by EDTSC First , the effect of chloride ion concentration on the adsorption rate when hydrogen ion concentration was constant was investigated. Fig. 13 shows the effect of chloride ion concentration on the pseudo-first order rate constant. In the low chloride ion concentration region, the influence of chloride ion on the pseudo first-order rate constant was hardly observed. However, in the high chloride ion concentration region, the pseudo first-order rate constant decreased with increasing chloride ion concentration. A straight line with a slope of -1 was obtained from the decrease.

  FIG. 14 shows the influence of the hydrogen ion concentration on the pseudo first-order rate constant. In the low chloride ion concentration region and the high chloride ion concentration region, the influence of hydrogen ions on the pseudo first-order rate constant was hardly observed. From this result, it became clear that hydrogen ions are not involved in the adsorption rate of palladium (II) by EDTSC.

  FIG. 15 shows the influence of the stirring speed on the pseudo first-order rate constant. In the high hydrochloric acid concentration region, the influence of the stirring speed on the pseudo first-order rate constant was hardly confirmed. On the other hand, in the low hydrochloric acid concentration region, the influence of the stirring speed appeared remarkably, and the pseudo first-order rate constant increased with the increase of the stirring speed.

  From the above results, it was clarified that the pseudo first-order rate constant depends on the stirring speed in the low hydrochloric acid concentration region, and shows the −1st order dependency with the increase in chloride ion concentration in the high hydrochloric acid concentration region. From this, it is considered that the adsorption of palladium (II) by EDTSC from a hydrochloric acid solution becomes the rate of mass transfer in the fluid boundary film in the low hydrochloric acid concentration region and the reaction rate in the high hydrochloric acid concentration region.

  Based on the dependence of chloride ion concentration on the quasi-first-order rate constant, the rate-limiting step of the adsorption reaction was considered as follows.

一方、塩化物溶液中のパラジウム(II)イオンは以下のように錯体を形成する。

On the other hand, palladium (II) ions in the chloride solution form a complex as follows.

Here, β _i is the total stability constant of chloride ion and palladium (II) ion, β ₁ = 10 ^4.7 [kmol m ⁻³ ] ⁻¹ , β ₂ = 10 ^7.7 [kmol m ⁻³ ] ^{− 2} , β ₃ = 10 ^10.3 [kmol m ⁻³ ] ⁻³ and β ₄ = 10 ^11.9 [kmol m ⁻³ ] ⁻⁴ .

  From the above equilibrium relationship, equation (1) can be expressed as follows.

擬定常状態を仮定すると流体境膜内の物質移動速度J_MはR₀と等しい。

Assuming a quasi-steady state, the mass transfer rate J _M in the fluid film is equal to R ₀ .

初速度R₀を溶液中のバルク相におけるパラジウム(II)イオン濃度についての擬一次式と仮定すると、擬一次速度定数k₁[s^-1]は

Assuming that the initial rate R ₀ is a quasi-linear equation for the concentration of palladium (II) ions in the bulk phase in solution, the quasi-first-order rate constant k ₁ [s ^-1 ] is

From the experimental results shown in Fig. 13, the reaction rate constant k _R = 0.25 [s ^-1 ] and the mass transfer capacity coefficient a _p k _M = 0.80 × 10 ^-2 [s ^-1 ] are obtained by the nonlinear least squares method. It was. The calculation lines and experimental points based on Equation (4) are shown in FIGS. 13 and 14 at the same time. Since the calculated line was in good agreement with the experimental point, the adsorption of palladium (II) by EDTSC from hydrochloric acid solution controlled the mass transfer rate in the fluid film in the low hydrochloric acid concentration region, and the reaction in the high hydrochloric acid concentration region. It became clear that it was rate limiting. Therefore, it was confirmed that the diffusion resistance in the particle decreased due to the large through hole, and the adsorption rate increased.

3.5 Construction of palladium (II) fast recovery system using EDTSC packed column Fig. 16 shows the adsorption breakthrough curves at each space velocity. When Q _S = 111 hour ^-1 , it was possible to treat a very large amount of palladium (II) solution, about 1800 times the bed volume. Usually, the space velocity in stationary phase adsorption is often performed at about 0.5-10 hour ^-1 . Compared with this, it can be seen that EDTSC can perform very rapid chromatographic separation. The total exchange capacity q _m at Q _S = 111 hour ^-1 was obtained by integration on the figure, and as a result, q _m = 1.68 mol kg ^-1 . This indicates that adsorption and concentration are sufficiently performed at a space velocity 10 to 100 times that of the conventional method as described above.

FIG. 17 shows the result of recovering palladium (II) from a palladium (II) saturated EDTSC packed column using a thiourea solution. When a 0.1 mol dm ^-3 thiourea solution was used at Q _S = 112 hour ^-1 , a very high concentration was possible, approximately 160 times that of the palladium (II) solution, despite the very high flow rate. . The desorption rate was 96%.

4. Conclusion It was shown that the superporous chitosan derivative EDTSC is capable of selective adsorption separation of the precious metals palladium (II), gold (III) and platinum (IV). It was clarified that the adsorption rate of palladium (II) by EDTSC showed a rapid adsorption rate due to the reduced diffusion resistance in the particles due to the effect of large pores. It was shown that it can be used as an adsorbent for perfusion chromatography due to the difference from the rate limiting step of the conventional porous adsorbent. EDTSC packed columns can be used for very fast and highly selective palladium (II) chromatographic separation due to its high adsorption rate, and the adsorption-separated palladium (II) is concentrated and recovered to a very high concentration. It became clear that we could do it.

FIG. 2 shows a reaction scheme for preparing EDTC from chitosan. FIG. 2 shows a reaction scheme for preparing EDTSC from chitosan. It is the figure which compared the adsorption rate of palladium (II) and gold (III) by EDTC with bridge | crosslinking chitosan in each hydrochloric acid concentration. It is the figure which compared the adsorption rate of palladium (II) and gold (III) by EDTSC in each hydrochloric acid concentration with bridged chitosan. It is the figure which compared the adsorption rate of the various metal ions by EDTC in each hydrochloric acid concentration with crosslinked chitosan. It is the figure which compared the adsorption rate of various metal ions by EDTSC in each hydrochloric acid density | concentration with bridge | crosslinking chitosan. It is a figure which shows the preparation scheme of a superporous chitosan microparticle (OWOC). It is a scanning electron microscope image of 1,2-ethanedithiol-immobilized chitosan (EDTSC) through a spacer ((a) is the surface of the fine particle, (b) is the cross section of the fine particle). It is a figure which shows the pore distribution of EDTSC. It is a figure which shows the particle size distribution of EDTSC. Number of measured particles = 700. It is a figure which shows the adsorption | suction result of each metal ion from the hydrochloric acid solution of each density | concentration by EDTSC. Is a graph showing measurement results of the adsorption isotherm of palladium (II) at each temperature from 0.1 mol / dm ³ hydrochloric acid solution by EDTSC. It is a figure which shows the influence of the chloride ion density | concentration which acts on a pseudo primary rate constant. It is a figure which shows the influence of the hydrogen ion density | concentration which acts on a quasi first-order rate constant. It is a figure which shows the influence of the stirring speed which acts on a pseudo primary rate constant. It is a figure which shows the adsorption breakthrough curve of palladium (II) on EDTSC in each space velocity. It is a figure which shows the collection | recovery result of palladium (II) from a palladium (II) saturated EDTSC packed column.

Claims (16)

  A polymer having a structure in which chitosan molecules are cross-linked by a cross-linking group containing a coordinating group capable of coordinating with a noble metal ion. Formula (I) as glucosamine constituting chitosan:

(Wherein R ₁ , R ₂ or R ₃ independently form a bridging group containing a coordinating group capable of coordinating to a noble metal ion or are hydrogen, provided that R ₁ , R ₂ And R ₃ are not simultaneously hydrogen,
R ₁ , R ₂ or R ₃ forming the bridging group independently coordinate to a noble metal ion together with other glucosamine R ₁ , R ₂ or R ₃ constituting the same or different chitosan molecule. Forming a bridging group containing possible coordinating groups,
At least one of the bridging groups is a bridging group formed between different chitosan molecules)
The polymer of Claim 1 containing the glucosamine derivative represented by these.   The polymer according to claim 1 or 2, wherein the number of atoms other than hydrogen in the bridging group is 4 to 30.   The polymer according to any one of claims 1 to 3, wherein the coordination group is a coordination group containing a sulfur atom or a nitrogen atom. The bridging group has the formula (II):

Wherein X or Y are each independently S, NH or O, provided that X and Y are not O at the same time,
m or n each independently represents an integer of 1 or more,
(* Indicates the coupling position)
The polymer of Claim 4 containing the partial structure represented by these.   A method for producing a polymer having a structure in which chitosan molecules are cross-linked by a cross-linking group containing a coordinating group capable of coordinating with a noble metal ion, the amino group of glucosamine constituting the chitosan, a hydroxyl group on the 6-position carbon, And / or a hydroxyl group on the 3-position carbon is converted to a reactive group, and the converted chitosan has at least two functional groups capable of binding to the reactive group and can be coordinated to a noble metal ion. A process comprising reacting a compound containing a coordinating group to crosslink between chitosan molecules.   A noble metal ion scavenger containing the polymer according to any one of claims 1 to 5.   A precious metal ion recovery method using the precious metal ion scavenger according to claim 7 as an adsorbent in an acidic solution. A method for producing fine particles containing a polymer having a structure in which chitosan molecules are cross-linked by a cross-linking group containing a coordinating group capable of coordinating to a noble metal ion,
An O / W / O emulsion having a first aqueous solution in which chitosan is dissolved as an aqueous phase, 1) a second aqueous solution having an osmotic pressure higher than that of the first aqueous solution, and / or 2) the second aqueous solution being water. A chitosan concentration step of concentrating chitosan in the aqueous phase comprising the first aqueous solution by mixing with a W / O emulsion as a phase, and if necessary, in the first aqueous solution after the concentration step A chitosan fine particle preparation step further comprising an insolubilization step for insolubilizing chitosan; and the chitosan fine particles obtained by the chitosan fine particle preparation step, the amino group of glucosamine constituting the chitosan in the fine particles, and the hydroxyl group on the 6-position carbon And / or a hydroxyl group on the 3-position carbon is converted into a reactive group, and the chitosan after the conversion has at least two functional groups capable of binding to the reactive group, and is noble. Crosslinking step of the compound containing a coordinating capable coordinating groups genus ions reacted performs processing to crosslink between chitosan molecules,
Said method.   The method according to claim 9, wherein the number of atoms other than hydrogen in the bridging group is 4 to 30.   The method according to claim 9 or 10, wherein the coordination group is a coordination group containing a sulfur atom or a nitrogen atom. The bridging group has the formula (II):

Wherein X or Y are each independently S, NH or O, provided that X and Y are not O at the same time,
m or n each independently represents an integer of 1 or more,
(* Indicates the coupling position)
The method of Claim 11 containing the partial structure represented by these.   Fine particles containing a polymer produced by the method according to any one of claims 9 to 12 and having a structure in which chitosan molecules are cross-linked by a cross-linking group containing a coordinating group capable of coordinating to a noble metal ion.   A noble metal ion scavenger containing the fine particles according to claim 13.   A noble metal ion recovery method using the noble metal ion scavenger according to claim 14 as an adsorbent in an acidic solution.   The noble metal ion recovery method according to claim 15, wherein an acidic solution containing the noble metal ions is passed through a column packed with the noble metal ion scavenger according to claim 14.

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