CA1196618A - Metal extraction from solution and immobilized chelating agents used therefor - Google Patents
Metal extraction from solution and immobilized chelating agents used thereforInfo
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Abstract
METAL EXTRACTION FROM SOLUTION AND
IMMOBILIZED CHELATING AGENTS USED THEREFOR
ABSTRACT
What is disclosed are novel metal chelating agents which are bonded to inorganic substrates to immobilize them. An example of such a metal chelating agent is (CH3O)3Si(CH2)3NH(CH2CH2NH)2(CH2)3Si(OCH3). An example of an inorganic substrate is a silica gel.
IMMOBILIZED CHELATING AGENTS USED THEREFOR
ABSTRACT
What is disclosed are novel metal chelating agents which are bonded to inorganic substrates to immobilize them. An example of such a metal chelating agent is (CH3O)3Si(CH2)3NH(CH2CH2NH)2(CH2)3Si(OCH3). An example of an inorganic substrate is a silica gel.
Description
"~
6~i~
MI~TAL EXTRACTION FROM SOLUTIO~ AND
I.~lOB:l:LlZED CHELATING AGENllS USED THEREFOR
~ he present invention deals with new and novel chelating agents which can be immobilized on inorganic solids and used to chelate metals from solution.
It is well known in th~ art to treat ino~ganic solids with hydrolyzable organosilanes to bond the organo-silanes to the inorganic solid surfaces. For example, British patent 1,530,039 published Oc~ober 25, 1978, and assigned to the British Petroleum Company Limited, shows the use of polyamines bonded to inorganic solids by the use of an organosilane coupling agent. The organosilane coupling agent is described preferably as alpha-chloropropyl-trimethoxysilane and the polyamine as N(CH2CH2NH2)3. Leyden, et. al., Anal. ChemO, 47(a), pp.
1612 to 1617, August 1975, shows the use of aminoalkyltrimethoxysilanes as treatments for silica geL
to give a silica having aminoalkylsilyl groups on the surface which are subsequently derivatized to the corresponding dithiocarbamate to give chelating groups on the surace of the silica.
Plueddemann, U.S. Patent 4,071,546, issued January 31, 1978, prepared carboxymethyl containing polyaminosiloxanes which were bonded to siliceous supports which were subsequently used as metal chelating agents and Hancock et. al., in U.S. Patent 4,203,952, lssued May 20, i 15~0, and assigned to the British Petroleum Company, shows the use of silane co~pling agents to bond various amine functional chelating compounds to inorganic solids.
5. D. Schucker et. al., in ~.S. Patent No.
3,335,03Q, issued ~ay 27, 1975, shows the use of si1ane coupling agents to immobilize certain chelatin~ agents on f~
inorganic solids. Specifically, the compound 8-hydroxy quinoline is shown as one of the chelating agents that can be bound to inorganic solids by th~ir method.
Finally~ the inventor in this application, E. P.
Plueddemann, has disclosed in United States Patent No.
4,379,931, issued April 12, 1983, that 8-hydroxyquinoline chelating agents could be bonded by novel means to the surface of inorganic solids which result in new immobilized chelating substances which have durability on the inorganic solid sub~
strate thereby giving the chelating agent extended chelating capacity.
Percolation of dilute heavy metal ion solutions through silylated silica has been used as an analytical method for concentrating the metal ion for estimation by X-ray fluores-cence tD. E. Leyden, M. L. Steele and B. B~ Jablonski, Anal.
Chem. Acta 100 549 (1978)). In these methods, ami.ne func-tional silanes were used to bond chelating agents to the silica surface~ Materials such as (CH3CM2O)3Si(CH2)3NE12 (CH3O~3si~c~2)3N~c~l2)2N~2 have been pre-ferred silylating agents and these materials give almost quanti-tative yields when used as chelating agents themselves. Capa city for metal ions is proportional to surface area of the fil-ler. These hydrolyzed hydrophilic silanes when deposited under mild conditions on siliceous surfaces are not tightly bonded to the surface through the surface silanols. Siloxane bonds formed between the coupling agent and the siliceous surface are hydrolyzable and if the hydrolyzed hydrophilic silane is a ~onomer or an uncrosslinked oligomer, the coupling agent is ~isplaced relatively easily from the surface~ Crosslinking such monomers or oligomers while on a silica surface, such as by heating, is not a useful method of impartinq durability to the t.reated surface since for the metal ion remova~
~.
~3--application, the reactivity with the metal ions is reduced or lost.
The hydrophilic diamine group on a silica surrace becomes even more hydrophilic in acid solutions such as are used to elute metais from chelate-silylated surfaces.
FurthPr, as it has already been pointed out by Schucker, supra, inorganic solid substrates for immobilization oE the chela~ing agents are preferred over that of organic carriers because the inorsanic carriers are ~iologically stable; they do not tend to swell or shrink with changing conditions of pH and, such compositions can be sterilized without degradation Isee Column 2, line 15 et seq. of Schucker~O
It would thus appPar that it would be desirabla to have the stability of the inorganic substrates and a chelating agent which has enhanced durability and strong chelating properties over that of the above discussed prior art materials.
It is one object of this invention to provide novel silicon-containing chelating agents whic~h are useful for removing heavy metal ions from solutions.
It is another object of this inventlon to provide immobilized chelating agents which have d~rability in use.
These and other objects will become obvious after consideration of the following disclosure and claims.
In one aspect, this invention deals with a method for preparing an immobilized chelating agent. The chelating agent is immobilized by reacting an organo-functional silane, as a bis compound, with an inorganic substrate. Thus, this invention deals with a method for preparing an immobilized chelating agent which comprises treating an inorganic solid substrate with a silylating agent which is a compound of the formula (ROj3siQNHlcH2cH2NH3xQsi(oR)3 where x has a value of 2, 3, or 4, R is a methyl, ethyl, propyl or butyl radical and is propylene or butylene.
It should be noted that the general formula contemplates very few specific compounds. I'he polyamine precursors for the bis silanes are commercial products and are obt.ainable from many sources one o~ which is The Dow Chemical Co., Midland, Michigan, USA. The materials can be purchased under the names of diethylenetriamine, triethylenetet.ramine and tetraethylenepentamine.
It should be noted that these materials ~re not pure amines by virtue of the methods by which they are m~nufactured. For purposes of this invention, the inventor means to include commercial polyamines, such as those named above, even though it is recognized that such amines are not pure~ For example, it is known from the sales literature that tetraethylenepentamine is composed of the following:
"~, ~AJOR COMPONENTS: ~
H2N~CH2CH2NH)2 C~l2CH2~ 2 2 ? 2 2 ~_~2 ~_~
~_~ 2 2 ~_J
H2NtCH2CH2N )3-CH2CH2NH2
6~i~
MI~TAL EXTRACTION FROM SOLUTIO~ AND
I.~lOB:l:LlZED CHELATING AGENllS USED THEREFOR
~ he present invention deals with new and novel chelating agents which can be immobilized on inorganic solids and used to chelate metals from solution.
It is well known in th~ art to treat ino~ganic solids with hydrolyzable organosilanes to bond the organo-silanes to the inorganic solid surfaces. For example, British patent 1,530,039 published Oc~ober 25, 1978, and assigned to the British Petroleum Company Limited, shows the use of polyamines bonded to inorganic solids by the use of an organosilane coupling agent. The organosilane coupling agent is described preferably as alpha-chloropropyl-trimethoxysilane and the polyamine as N(CH2CH2NH2)3. Leyden, et. al., Anal. ChemO, 47(a), pp.
1612 to 1617, August 1975, shows the use of aminoalkyltrimethoxysilanes as treatments for silica geL
to give a silica having aminoalkylsilyl groups on the surface which are subsequently derivatized to the corresponding dithiocarbamate to give chelating groups on the surace of the silica.
Plueddemann, U.S. Patent 4,071,546, issued January 31, 1978, prepared carboxymethyl containing polyaminosiloxanes which were bonded to siliceous supports which were subsequently used as metal chelating agents and Hancock et. al., in U.S. Patent 4,203,952, lssued May 20, i 15~0, and assigned to the British Petroleum Company, shows the use of silane co~pling agents to bond various amine functional chelating compounds to inorganic solids.
5. D. Schucker et. al., in ~.S. Patent No.
3,335,03Q, issued ~ay 27, 1975, shows the use of si1ane coupling agents to immobilize certain chelatin~ agents on f~
inorganic solids. Specifically, the compound 8-hydroxy quinoline is shown as one of the chelating agents that can be bound to inorganic solids by th~ir method.
Finally~ the inventor in this application, E. P.
Plueddemann, has disclosed in United States Patent No.
4,379,931, issued April 12, 1983, that 8-hydroxyquinoline chelating agents could be bonded by novel means to the surface of inorganic solids which result in new immobilized chelating substances which have durability on the inorganic solid sub~
strate thereby giving the chelating agent extended chelating capacity.
Percolation of dilute heavy metal ion solutions through silylated silica has been used as an analytical method for concentrating the metal ion for estimation by X-ray fluores-cence tD. E. Leyden, M. L. Steele and B. B~ Jablonski, Anal.
Chem. Acta 100 549 (1978)). In these methods, ami.ne func-tional silanes were used to bond chelating agents to the silica surface~ Materials such as (CH3CM2O)3Si(CH2)3NE12 (CH3O~3si~c~2)3N~c~l2)2N~2 have been pre-ferred silylating agents and these materials give almost quanti-tative yields when used as chelating agents themselves. Capa city for metal ions is proportional to surface area of the fil-ler. These hydrolyzed hydrophilic silanes when deposited under mild conditions on siliceous surfaces are not tightly bonded to the surface through the surface silanols. Siloxane bonds formed between the coupling agent and the siliceous surface are hydrolyzable and if the hydrolyzed hydrophilic silane is a ~onomer or an uncrosslinked oligomer, the coupling agent is ~isplaced relatively easily from the surface~ Crosslinking such monomers or oligomers while on a silica surface, such as by heating, is not a useful method of impartinq durability to the t.reated surface since for the metal ion remova~
~.
~3--application, the reactivity with the metal ions is reduced or lost.
The hydrophilic diamine group on a silica surrace becomes even more hydrophilic in acid solutions such as are used to elute metais from chelate-silylated surfaces.
FurthPr, as it has already been pointed out by Schucker, supra, inorganic solid substrates for immobilization oE the chela~ing agents are preferred over that of organic carriers because the inorsanic carriers are ~iologically stable; they do not tend to swell or shrink with changing conditions of pH and, such compositions can be sterilized without degradation Isee Column 2, line 15 et seq. of Schucker~O
It would thus appPar that it would be desirabla to have the stability of the inorganic substrates and a chelating agent which has enhanced durability and strong chelating properties over that of the above discussed prior art materials.
It is one object of this invention to provide novel silicon-containing chelating agents whic~h are useful for removing heavy metal ions from solutions.
It is another object of this inventlon to provide immobilized chelating agents which have d~rability in use.
These and other objects will become obvious after consideration of the following disclosure and claims.
In one aspect, this invention deals with a method for preparing an immobilized chelating agent. The chelating agent is immobilized by reacting an organo-functional silane, as a bis compound, with an inorganic substrate. Thus, this invention deals with a method for preparing an immobilized chelating agent which comprises treating an inorganic solid substrate with a silylating agent which is a compound of the formula (ROj3siQNHlcH2cH2NH3xQsi(oR)3 where x has a value of 2, 3, or 4, R is a methyl, ethyl, propyl or butyl radical and is propylene or butylene.
It should be noted that the general formula contemplates very few specific compounds. I'he polyamine precursors for the bis silanes are commercial products and are obt.ainable from many sources one o~ which is The Dow Chemical Co., Midland, Michigan, USA. The materials can be purchased under the names of diethylenetriamine, triethylenetet.ramine and tetraethylenepentamine.
It should be noted that these materials ~re not pure amines by virtue of the methods by which they are m~nufactured. For purposes of this invention, the inventor means to include commercial polyamines, such as those named above, even though it is recognized that such amines are not pure~ For example, it is known from the sales literature that tetraethylenepentamine is composed of the following:
"~, ~AJOR COMPONENTS: ~
H2N~CH2CH2NH)2 C~l2CH2~ 2 2 ? 2 2 ~_~2 ~_~
~_~ 2 2 ~_J
H2NtCH2CH2N )3-CH2CH2NH2
2 ~_~C~2N~_~NcEI2cH2NHcH2cH2NH2 20 H2N~_~ C 2 2 2 2 2 2 2 (5 isomers) 16 AMINE CONTENT: ~NMeg./g mgO XOH/g Primary ~nine 13.8 9.9 530 Secondary Amine 14~410.3 577 Tertiary Amine 5.5 3.9 220 _ . _ Total Basic N 33.7 24.1 1327 AVEE~GE MOLECULAR WEIGHT = 201 g/mol.
The polyamines are reacted with chloroalkyl~
silanes in order to prepare the bis silane compounds of this invention.
Thus, for example, chloropropyltrimethoxYsllane is reacted with the polyamine in a ratio of at least two moles o chloropropyl to one mole of polyamine (i.e. two equivalents of -NH2).
2(CH30)3Si(CH2)3Cl + H2N(CH2CH2NH)3-CH~C~NH2-~CH3O~3Si(CE~2)3NH(CH2CH2NH)4(CH2)3Si(oCH3)3- This general reaction is known from Dvo.rak, Mojmir, et. al. in Czechslovakian Patent Number 177,563 (March 15, 1979) (CA
91:108695y) except that the disclosure therein teaches a 1:1 mole ratio of al.'~ylchloro compound to the polyamine (2 equi,alents-NE~2) (CH (CH ) O~ SiCH Cl -~ tetraethylenepentamine >
The polyamines are reacted with chloroalkyl~
silanes in order to prepare the bis silane compounds of this invention.
Thus, for example, chloropropyltrimethoxYsllane is reacted with the polyamine in a ratio of at least two moles o chloropropyl to one mole of polyamine (i.e. two equivalents of -NH2).
2(CH30)3Si(CH2)3Cl + H2N(CH2CH2NH)3-CH~C~NH2-~CH3O~3Si(CE~2)3NH(CH2CH2NH)4(CH2)3Si(oCH3)3- This general reaction is known from Dvo.rak, Mojmir, et. al. in Czechslovakian Patent Number 177,563 (March 15, 1979) (CA
91:108695y) except that the disclosure therein teaches a 1:1 mole ratio of al.'~ylchloro compound to the polyamine (2 equi,alents-NE~2) (CH (CH ) O~ SiCH Cl -~ tetraethylenepentamine >
3 2 3 3 ~ 90-100C, 5 hrs.
For purposes of this invention, the value of x is 2, 3, or 4 and R is selected from the radicals methyl, ethyl, propyl and butyl. Most preferred is the methyl group.
Q is a linking group selected from propylene and butylene. Contemplated within the scope of the Q group are the iso derivatives and the preferred iso derivative is -C~2CHCH2-.
For purposes of this invention, the crude product is generally used to treat the inorganic solid substrate and the water -found on such substrates hydroly~es the trialkoxy groups, in situ/ during the substrate treatment.
The method is carried out by simply mixing the bis silanes of this invention with the inorganic solid, usually in a water-insoluble solvent, and war~ing to a boiling stage for 1-2 hours. The concentration of the organosilicon compound in the treatlng solution i.s usually one-half to about five weight percent. The object is to cap all available hydroxyl groups on the surface with the organosilicon compound. As is obvious, therefore, the inorganic solids that are useful in this invention are those which have hydroxyl groups on their surfaces.
Further, such inorganic solids must ~é insoluble in water and solvents (although they should be dispersable therein) since applications for such materials within the scope of this inventior. are in various aqueous and solvent solutions. Examples of such inorganic solids are alumina, bentonite~ sand, glass, silicas and silica gels. It i5 preferred for purposes of this invention that the inorganic solid be finely divided. Finely divided for purposes of this invention means any particulate matexial having an average diameter of less than lO mm. The treated inorganic solid is then filtered to remove tne liquid portions and washed with fresh solvent and thereafter dried in an air circulating oven.
Thus, this invention also contempla~es a product which is an immobilized chelating agent bound to an inorganic solid which is prepared by treat~ng an inorganic solid substrate wlth a sllylating agent which is a compound of the formula (RO)3SiQ~H~C~2CH2NH)~QSi(OR)3 where x has a value of 2, 3, or 4, R is a methyl, ethyl, propyl or butyl radical and Q is propylene or butylene.
In addition, this invention contemplates a method of removing heavy metal ions from solution which method comprises contacting a solution containing heavy metal ions with a silylated substrate prepared by treating an inorganic solid substrate with a silylating agen-t which is a compound of the formula (Ro)3SiQNH~CH2CH2NH)XQSi~oR)3 where x has a value of 2, 3, or 4, R is a methyl, ethyl, propyl or butyl radical and Q is propylene or butylene.
The chelating product is ready for use after drying and it can be stored in this manner. When used, the dried product is typically re-dispersed in the metal containing solution that is to be treated. Typically, this treatment is carried out at room temperature but it can also be ca~-ried out at hlgher temperatures. The pH or the treating solution may have to be adjusted in order to maximize the chelating capability of the product. A pH of 6.5 to 7.5 is considered to be advantageous for most applications.
The chelating substrate does not have infinite activity because the metal ions are removed from the metal ion solution relative to the amount of chelate available and this in turn is dependent on the amount of the chelate bound to the inoxganic solid which i5 in turn dependent on the surface area of the inorganic solid and the number of hydroxyl groups available for coupling with the alkoxv-silyl groups of the inventive bis silanes. Further, the extent to which metal ion solution can be cleaned of metal ions is proportionate to the amount of treated substrate that comes in contact with metal ions. It, therefore, becomes advantageous in most applications to utilize, glass or plastic columns packed with the finely divided treated chelating substrate and pass the solution to be treated through such columns. However, batch treatments can be used with the chelating substrates of this invention.
When the substrate loses its activity for removing metals it may be discarded or the substrate may be reactivated by the use of mineral acid. One such method xequires contacting the metal chelated substrate with an aqueous acid solution such as HNO3, follo~ed by separation of the aqueous acid solution from the substrate. The metal can then be recovered or discarded as desired.
Heavy metal ions contemplated within this invention are the transition elements (series 3b, 4b, 5b, 6b, 7b, 3b, and lb of the periodic table) and the zinc family (series 2b of the periodic table). Especially contemplated within the scope of this invention are the lanthanides and actinldes. This 1nvention is especially useful for removal of the more commonly used metals such as copper, platinum, nickel, gold, s lver, and iron.
The following examples are shown to illustrat2 the invention and are not intended to define the scope thereof.
Example l Bis-trimethoxysilylpropyltriethylenete~ramine (TETA) In this reaction, the amine precursor acts as its own HC1 acceptor.
Into a 500 ml, 3-necked round-bottomed glass flask were weighed 75 gms (0.5 moles) of co~mercial triethylenetetramine, 200 gms. ~1.0 moles) of (CH30)3Si(CH2)3Cl and 25 gms. of CH30H. The flask; was equipped with a mo~or driven stirrer, thermome-ter and reflux condenser. The reaction mass was heated to reflux and when the stirrer was stopped there was observed two layers. CH30H, lO0 gms., was added ~o give a homogeneous material. The reaction mass was heated overnight (about 16 hrs.l at reflux. Upon cooling, a titration for Cl showed about 0.88 equivalents o the Cl . The reaction was heated at reflux for an additional 8 hours after about 250 gms. of CH30H had been added. The reaction was essentially complete at this time. The crude reactlon product gave a hazy solution in water and in alcohols but it ga~e a clear solution in dilute acetic acid.
Example ~
Bis-trimethoxysilylpropyltetraethylene pentamine (TEPA) In a reaction flask, equipped as ln example l, I there was placed 20 gms. (0.1 mole plus 10~ mole excess) of tetraethylenepentamine, 40 gms. (0.2 moles) of digtilled (C~30)3si(CH2)3Cl and 40 gms- of CH30H- This mixture was refluxed (about 65C~ for 3 hours where a titration showed O.Q7 equiv. of Cl . The reaction was continued a~ reflux for an additional 21 hours whereupon ~9~
the xeaction mass titrated at 0.19 equivO of Cl . A crude sample of this material (10 weight %) gave an initial ha~y solution in acidic water or basic water but the material cleared within about 30 minutes to give stable solutions.
Example 3 Bis-trimethoxysilylpropyldiethylene triamine (DETA~
In a manner similar to the above examples, a bis trimethoxysilylpropyldiethylenetriamine was prepared. The precursor amine was about 95~ pure linear material.
Example 4 Bis-trimethoxysilylpropylethylene diamine (EDA) In a manner similar to that shown in examples l and 2 above~ 44 gmsO of (CH3)3si(cH2)3~H~cH2)2NH2 and 40 gms. of (CH30)3Si(CH2)3Cl were mixed together and warmed to 140C whereupon the reaction exothermed to 200C. The reaction mass was heated at 140C for about 2 hours and then cooled and diluted using 168 gms. of CH30H. After removal of HCl as an ethylenediamine salt, the crude product was distilled to recover a center cut boiling at 160C at 0.5 mm Hg, d425-1.048, ND25=1.4462.
Note that this material does not fall within the scope of the instant invention but is included as a comparison to show that it is not useful as a chelatlng agent when immobilized on a solid substrate.
Example 5 The materials from the examples above were evaluated as immobilized chelating agents for heavy metals.
A silica gel, Davison grade 62 was use~ in this evaluation~ Grade 62 is available commerciallv from Davison, a division of W. R. Grace Co., 10 East Baltlmore St., Baltimore, MD . This material has a pore volume of 1.15 cc/gms; average pore diameter of 140 Angstroms;
surface area of 340 M2/gm. and a mesh size of 60-200 (U.S.
Standard Mesh).
Small portions of the silica gel and the bis silanes were mixed together and warmed to a gentle boil for 1 hour. The silanes were used as 2% solutions in toluene. The treated silica was recovered by ~iltration and washed with fresh toluene and then dried for 2 hours in a 60C air-convection oven.
Five gram portions of treated silica were mixed with 50 ml of 1 weight % Cu++ ~chloride) solution and adjusted to pH 7 with ammoniaO After mixing for 15 minutes, the treated silica was filtered and washed 10 times with deionized water. The washed silica was then stirred with 30 ml. of 1 weight % HNO3 for 30 minutes. A
portion of the HNO3 was analyzed for Cu++ by atomic absorption. The acid eluted silica was rinsed with water and stored under water/ as shown in the table below. This was one cycle. The treated silica was th~n recycled with more copper solution. Cycles were repeated after 1, 4, and 45 days storage in water. Copper capacity is reported as ppm Cu++ in the 30 ml nitric acid solution. Copper concentration of 1000 ppm is equivalent to a capacity of Ool milliequiva]ents of copper per gram of silica. Copper capacities are shown in Table I.
TABLE I
Copper Capacity of Silylated Silica Gel Cu~+ in HN03 Acid Rinse (ppm~
Trea~ment on 2nd Cycle 3rd Cycle % Retention After Silica Gel1st Cycle l Day Later 4 Days Later 3rd Cycle Untreated Si~ica 114 50 51 *EDA 113 20 20 17.7 r)ETA 1590 910 740 46.5 TETA I025 625 475(1) 46.3 @~
TEPA 538 356 270 50.2 *(CH30~3Si(cH2)3N~cH2)2N 2 338 260 23.6 ~(CI130)3Si~cH2)3Nll(c~2j2 2 * , blended with (CH30)3Si(cH2)2si~oc~3)3 525 235 180 34.3 *Outside scope of invention, (1) After 45 days (4th cycle) = 260 ppm Cu++
comparison samples (2~ After 45 d~ys (4th cycle] = 62 ppm Cu++
For purposes of this invention, the value of x is 2, 3, or 4 and R is selected from the radicals methyl, ethyl, propyl and butyl. Most preferred is the methyl group.
Q is a linking group selected from propylene and butylene. Contemplated within the scope of the Q group are the iso derivatives and the preferred iso derivative is -C~2CHCH2-.
For purposes of this invention, the crude product is generally used to treat the inorganic solid substrate and the water -found on such substrates hydroly~es the trialkoxy groups, in situ/ during the substrate treatment.
The method is carried out by simply mixing the bis silanes of this invention with the inorganic solid, usually in a water-insoluble solvent, and war~ing to a boiling stage for 1-2 hours. The concentration of the organosilicon compound in the treatlng solution i.s usually one-half to about five weight percent. The object is to cap all available hydroxyl groups on the surface with the organosilicon compound. As is obvious, therefore, the inorganic solids that are useful in this invention are those which have hydroxyl groups on their surfaces.
Further, such inorganic solids must ~é insoluble in water and solvents (although they should be dispersable therein) since applications for such materials within the scope of this inventior. are in various aqueous and solvent solutions. Examples of such inorganic solids are alumina, bentonite~ sand, glass, silicas and silica gels. It i5 preferred for purposes of this invention that the inorganic solid be finely divided. Finely divided for purposes of this invention means any particulate matexial having an average diameter of less than lO mm. The treated inorganic solid is then filtered to remove tne liquid portions and washed with fresh solvent and thereafter dried in an air circulating oven.
Thus, this invention also contempla~es a product which is an immobilized chelating agent bound to an inorganic solid which is prepared by treat~ng an inorganic solid substrate wlth a sllylating agent which is a compound of the formula (RO)3SiQ~H~C~2CH2NH)~QSi(OR)3 where x has a value of 2, 3, or 4, R is a methyl, ethyl, propyl or butyl radical and Q is propylene or butylene.
In addition, this invention contemplates a method of removing heavy metal ions from solution which method comprises contacting a solution containing heavy metal ions with a silylated substrate prepared by treating an inorganic solid substrate with a silylating agen-t which is a compound of the formula (Ro)3SiQNH~CH2CH2NH)XQSi~oR)3 where x has a value of 2, 3, or 4, R is a methyl, ethyl, propyl or butyl radical and Q is propylene or butylene.
The chelating product is ready for use after drying and it can be stored in this manner. When used, the dried product is typically re-dispersed in the metal containing solution that is to be treated. Typically, this treatment is carried out at room temperature but it can also be ca~-ried out at hlgher temperatures. The pH or the treating solution may have to be adjusted in order to maximize the chelating capability of the product. A pH of 6.5 to 7.5 is considered to be advantageous for most applications.
The chelating substrate does not have infinite activity because the metal ions are removed from the metal ion solution relative to the amount of chelate available and this in turn is dependent on the amount of the chelate bound to the inoxganic solid which i5 in turn dependent on the surface area of the inorganic solid and the number of hydroxyl groups available for coupling with the alkoxv-silyl groups of the inventive bis silanes. Further, the extent to which metal ion solution can be cleaned of metal ions is proportionate to the amount of treated substrate that comes in contact with metal ions. It, therefore, becomes advantageous in most applications to utilize, glass or plastic columns packed with the finely divided treated chelating substrate and pass the solution to be treated through such columns. However, batch treatments can be used with the chelating substrates of this invention.
When the substrate loses its activity for removing metals it may be discarded or the substrate may be reactivated by the use of mineral acid. One such method xequires contacting the metal chelated substrate with an aqueous acid solution such as HNO3, follo~ed by separation of the aqueous acid solution from the substrate. The metal can then be recovered or discarded as desired.
Heavy metal ions contemplated within this invention are the transition elements (series 3b, 4b, 5b, 6b, 7b, 3b, and lb of the periodic table) and the zinc family (series 2b of the periodic table). Especially contemplated within the scope of this invention are the lanthanides and actinldes. This 1nvention is especially useful for removal of the more commonly used metals such as copper, platinum, nickel, gold, s lver, and iron.
The following examples are shown to illustrat2 the invention and are not intended to define the scope thereof.
Example l Bis-trimethoxysilylpropyltriethylenete~ramine (TETA) In this reaction, the amine precursor acts as its own HC1 acceptor.
Into a 500 ml, 3-necked round-bottomed glass flask were weighed 75 gms (0.5 moles) of co~mercial triethylenetetramine, 200 gms. ~1.0 moles) of (CH30)3Si(CH2)3Cl and 25 gms. of CH30H. The flask; was equipped with a mo~or driven stirrer, thermome-ter and reflux condenser. The reaction mass was heated to reflux and when the stirrer was stopped there was observed two layers. CH30H, lO0 gms., was added ~o give a homogeneous material. The reaction mass was heated overnight (about 16 hrs.l at reflux. Upon cooling, a titration for Cl showed about 0.88 equivalents o the Cl . The reaction was heated at reflux for an additional 8 hours after about 250 gms. of CH30H had been added. The reaction was essentially complete at this time. The crude reactlon product gave a hazy solution in water and in alcohols but it ga~e a clear solution in dilute acetic acid.
Example ~
Bis-trimethoxysilylpropyltetraethylene pentamine (TEPA) In a reaction flask, equipped as ln example l, I there was placed 20 gms. (0.1 mole plus 10~ mole excess) of tetraethylenepentamine, 40 gms. (0.2 moles) of digtilled (C~30)3si(CH2)3Cl and 40 gms- of CH30H- This mixture was refluxed (about 65C~ for 3 hours where a titration showed O.Q7 equiv. of Cl . The reaction was continued a~ reflux for an additional 21 hours whereupon ~9~
the xeaction mass titrated at 0.19 equivO of Cl . A crude sample of this material (10 weight %) gave an initial ha~y solution in acidic water or basic water but the material cleared within about 30 minutes to give stable solutions.
Example 3 Bis-trimethoxysilylpropyldiethylene triamine (DETA~
In a manner similar to the above examples, a bis trimethoxysilylpropyldiethylenetriamine was prepared. The precursor amine was about 95~ pure linear material.
Example 4 Bis-trimethoxysilylpropylethylene diamine (EDA) In a manner similar to that shown in examples l and 2 above~ 44 gmsO of (CH3)3si(cH2)3~H~cH2)2NH2 and 40 gms. of (CH30)3Si(CH2)3Cl were mixed together and warmed to 140C whereupon the reaction exothermed to 200C. The reaction mass was heated at 140C for about 2 hours and then cooled and diluted using 168 gms. of CH30H. After removal of HCl as an ethylenediamine salt, the crude product was distilled to recover a center cut boiling at 160C at 0.5 mm Hg, d425-1.048, ND25=1.4462.
Note that this material does not fall within the scope of the instant invention but is included as a comparison to show that it is not useful as a chelatlng agent when immobilized on a solid substrate.
Example 5 The materials from the examples above were evaluated as immobilized chelating agents for heavy metals.
A silica gel, Davison grade 62 was use~ in this evaluation~ Grade 62 is available commerciallv from Davison, a division of W. R. Grace Co., 10 East Baltlmore St., Baltimore, MD . This material has a pore volume of 1.15 cc/gms; average pore diameter of 140 Angstroms;
surface area of 340 M2/gm. and a mesh size of 60-200 (U.S.
Standard Mesh).
Small portions of the silica gel and the bis silanes were mixed together and warmed to a gentle boil for 1 hour. The silanes were used as 2% solutions in toluene. The treated silica was recovered by ~iltration and washed with fresh toluene and then dried for 2 hours in a 60C air-convection oven.
Five gram portions of treated silica were mixed with 50 ml of 1 weight % Cu++ ~chloride) solution and adjusted to pH 7 with ammoniaO After mixing for 15 minutes, the treated silica was filtered and washed 10 times with deionized water. The washed silica was then stirred with 30 ml. of 1 weight % HNO3 for 30 minutes. A
portion of the HNO3 was analyzed for Cu++ by atomic absorption. The acid eluted silica was rinsed with water and stored under water/ as shown in the table below. This was one cycle. The treated silica was th~n recycled with more copper solution. Cycles were repeated after 1, 4, and 45 days storage in water. Copper capacity is reported as ppm Cu++ in the 30 ml nitric acid solution. Copper concentration of 1000 ppm is equivalent to a capacity of Ool milliequiva]ents of copper per gram of silica. Copper capacities are shown in Table I.
TABLE I
Copper Capacity of Silylated Silica Gel Cu~+ in HN03 Acid Rinse (ppm~
Trea~ment on 2nd Cycle 3rd Cycle % Retention After Silica Gel1st Cycle l Day Later 4 Days Later 3rd Cycle Untreated Si~ica 114 50 51 *EDA 113 20 20 17.7 r)ETA 1590 910 740 46.5 TETA I025 625 475(1) 46.3 @~
TEPA 538 356 270 50.2 *(CH30~3Si(cH2)3N~cH2)2N 2 338 260 23.6 ~(CI130)3Si~cH2)3Nll(c~2j2 2 * , blended with (CH30)3Si(cH2)2si~oc~3)3 525 235 180 34.3 *Outside scope of invention, (1) After 45 days (4th cycle) = 260 ppm Cu++
comparison samples (2~ After 45 d~ys (4th cycle] = 62 ppm Cu++
Claims (16)
1. A method for preparing an immobilized chelating agent which comprises treating an inorganic solid substrate with a silylating agent which is a compound of the formula (RO)3SiQNH(CH2CH2NH)xQSi(OR)3 where x has a value of 2, 3, or 4, R is a methyl, ethyl, propyl or butyl radical and Q
is propylene or butylene.
is propylene or butylene.
2. A method as claimed in claim 1 wherein x is 2.
3. A method as claimed in claim 1 wherein x is 3.
4. A method as claimed in claim 1 wherein x is 4.
5. A method as claimed in claim 1 wherein the substrate is siliceous mineral and the treating compound is (CH3OO)3Si-(CH2)3NH(CH2CH2NH)x(CH2)3Si(OCH3)3.
6. A method of removing heavy metal ions from solution which method comprises contacting a solution containing heavy metal ions with an inorganic solid substrate which has been treated with a silylating agent which is a compound of the for-mula (RO)3SiQNH(CH2CH2NH)xQSi(OR)3 where x has a value of 2, 3, or 4, R is a methyl, ethyl, propyl or butyl radi-cal and Q is propylene or butylene.
7. A method as claimed in claim 6 wherein x is 2.
8. A method as claimed in claim 6 wherein x is 3.
9. A method as claimed in claim 6 wherein x is 4.
10. A method as claimed in claim 6 wherein the substrate is siliceous mineral and the treating compound is (CH3O)3Si-(CH2)3NH(CH2CH2NH)x(CH2)3Si(OCH3)3.
11. A method as claimed in claim 10 wherein the solution is aqueous.
12. A method as claimed in claim 6 wherein the heavy metal ions are transition metal ions.
13. A method as claimed in claim 12 wherein the transit tion metal ions are selected from the group consisting of lan-thanides and actinides.
14. A method as claimed in claim 12 wherein the transition metal ions are selected from the group consisting of copper, iron, cobalt, nickel, molybdenum, rhodium, silver, platinum, gold, manganese, titanium and uranium.
15. The product produced by the method of claim 1, 2 or 3.
16. The product produced by the method of claim 4 or 5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000421543A CA1196618A (en) | 1983-02-14 | 1983-02-14 | Metal extraction from solution and immobilized chelating agents used therefor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000421543A CA1196618A (en) | 1983-02-14 | 1983-02-14 | Metal extraction from solution and immobilized chelating agents used therefor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1196618A true CA1196618A (en) | 1985-11-12 |
Family
ID=4124566
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000421543A Expired CA1196618A (en) | 1983-02-14 | 1983-02-14 | Metal extraction from solution and immobilized chelating agents used therefor |
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| Country | Link |
|---|---|
| CA (1) | CA1196618A (en) |
-
1983
- 1983-02-14 CA CA000421543A patent/CA1196618A/en not_active Expired
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