Catalyst – solid sorbent – or support therefor: product or process – Solid sorbent – Organic
Reexamination Certificate
1999-06-11
2002-01-15
Hendrickson, Stuart L. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Solid sorbent
Organic
C210S198200, C502S404000, C427S412200
Reexamination Certificate
active
06339039
ABSTRACT:
The present invention relates to a hydrogel product for adsorption where a non-water-soluble support matrix is cross-linked to polymers which give rise to an in water swellable adsorbent. As support matrix, an organic polymer or a combination of such, e.g. polysaccharide such as agar, cellulose, starch etc., protein and components of protein and polysaccharide.
The present invention aims for achieving an improved adsorbent which selectively binds different materials, preferably metals.
Further, the invention aims for an adsorbent which can be regenerated with required, powerful means without causing the adsorbent to be non-usable, e.g. loses its form, is e.g. eluated or treated with 20% H
2
SO
4
.
Further the invention aims for an adsorbent which effectively may bind and concentrate poisonous compounds and which is cheap enough for making an economically harmless rendering possible of such materials through e.g. dumping.
Further the invention aims for an adsorbent which makes economically recycling of small amounts of valuable metals possible, from large quantities of waste.
These aims and further advantages are obtained with the adsorbent according to the invention which in its most common embodiment is built upon a support matrix consisting of polysaccharide to which different polymers have been cross-linked with other cross-linking agents. The support matrix may also consist of protein or a mixture of protein and polysaccharide.
A polysaccharide such as agarose and cellulose may be interpreted as thread-shaped molecules consisting of monomeric units containing several hydroxyl groups and internal and external ether bonds (acetal bonds), which taken together give the polysaccharide affinity to water (it is said to be hydrophilic). Such polymers form in water swellabe gels with hydroxyls as targets for substitution.
Alkylation of the hydroxyls calls generally for a strong alkaline environment. The present invention relates to a product in which adjacent amino groups have been incorporated into the matrix. These amino groups may be alkylated under less drastic conditions (lower alkalinity than the hydroxyls).
The amino groups are part of polyalkylene imines (which actually ought to be called polyalkylene amines) which first are coupled to the polysaccharide. This can be done at a high pH e.g. 13-14. If an oligoethylene imine or polyethylene imine is selected the amino group density will be higher than the hydroxyl density in the original gel network which is an advantage for the production of the product.
U.S. Pat. No. 4,144,190, 1979 (Bowes et al.) has disclosed a polysaccharide adsorbent produced from a polysaccharide and a nitrogen containing polymer which is possible to acetylate with a cross-linking substance. Steinmann et al. (Talarta, vol 41, No 10, p 1707-1713) synthesized a similar metal adsorbent from agarose and polyethylene imine. The metal ions Co
2+
, Ni
2+
, Cu
2+
, Zn
2+
, Cd
2+
and UO
2
2+
were studied. Our adsorbent differs from these metal adsorbents through that the carbohydrate/protein component (the support matrix) may be hydrolysed with a strong acid without causing the product to change shape macroscopically. This component may also be decomposed through oxidation with saturated sodium periodate solution. Where the gel thus retains its form despite these drastic treatments. If the product is produced in the form of particles, these may after acid treatment be packed in beds which allow high filtration velocities. These characteristics are acquired through coupling together soluble polymer with a carbohydrate-polyamine complex in a non-soluble (gel) form with a cross-linking reagent.
G. P. Royer and his group of scientists describe (J.Am.Chem.Soc. 99, 1977, p. 6141-42 (1977J.Org.Chem., 45 (1980) 2269) how an inorganic core in the form of aluminium hydroxide gel is treated with polyethylene imine followed by glutaraldehyde and reaction of the “Schiff” product with sodium boron hydride. The aluminium hydroxide is thereafter dissolved with hydrochloric acid. The differences between this product and the product according to the present invention are, among other things, the following:
1. We use organic polymer preferably polysaccharide and/or protein as support matrix or core material.
2. At least two, often many layers of polyethylene imine are coupled together between themselves and with the support matrix. The difference becomes particularly evident when the polymer former is a low molecular alkylene amine as e.g. tetraethylene pentamine (TEPA). Here the cross-linker may outweigh the polyethylene imine component in the end product.
3. After hydrolytic destruction (degradation) of the polysaccharide and/or the protein, an acid- and base stable residue remains from this (i.e. the support matrix) which may be manipulated chemically (e.g. be substituted). This is not the case with an inorganic core; thus no substitutable remainder is obtained with the invention according to Royer et al. This is an advantage when the polyalkylene amine product becomes hydrophilized with this remainder, most of which ought to have structure —X—O—CH
2
—CHOH—CH
2
OH and —X—O—CH
2
—CH
2
—OH where X is a cross-linking structure which has arisen during the coupling. Thus, we have after the acid treatment a stable product with both NH
2
, NH-groups and OH-groups of which any may be activated and substituted (with the same or different substituents). Even after acid treatment, followed by periodate treatment and final reduction with sodium boron hydride, a polyethylene imine complex remains with attached residues of polysaccharides. These residues should mainly have the structures —CH
2
—CHOH—CH
2
OH, and —CH
2
—CH
2
—OH with the cross-link to the polyethylene imine still there. These structures are to be regarded as a glycerol ether and a glycol ether, respectively and therefore it makes the product more hydrophilic and biocompatible (and thus more lenient to biological material). The glycerol and the glycol residues may be activated and thereafter substituted. As a higher pH is required for the activation of an aliphatic hydroxyl than an amine, polyamine and alcohol components may independently be activated and substituted. You may therefore substitute the polyamine with a metal chelating agent and the alcohol groups with another group, e.g. an aromatic, substance and thus obtain an adsorbent with double functions. Thus, a such adsorbent may be produced which is resistant to either a strong acid or base.
4. In the invention according to Royer et al, an inorganic core material is included and the polyethylene imine is not coupled to this through chemical combination, but the contact is through physical adsorption and through filling of canals and pores with polyethylene imine (PEI) before cross-linking. The efficiency of the capillary penetration may be questioned. According to the present invention the time for contact between the polyamine and the activated solid phase may be fiery long. All permeably available canals and pores with active groups may then react with penetrating polymer and there be fixed. Thus the contacting between reacting components is totally different.
Thus our adsorbent according to the present invention differs from these above mentioned prior art metal adsorbents through, among other things, that the carbohydrate/protein component (support matrix) may undergo drastic treatments without the product macroscopically changing shape. If then the product is produced in the form of particles, these may after treatment be packed in beds which allow high filtration velocities.
Thus, we have achieved a new adsorbent which overcomes earlier known stability problems in metal adsorbents. Furthermore we may use higher filtration velocities when Losing the present invention, which may be a great advantage in e.g. large scale processes.
SUMMARY OF THE INVENTION
The present invention relates to a hydrogel product for adsorption purposes consisting of an in water non-soluble support matrix and cross-linked polymers, characterized by that the
Ersson Bo
Porath Jerker
Hendrickson Stuart L.
Young & Thompson
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