Liquid purification or separation – Processes – Ion exchange or selective sorption
Patent
1998-04-17
2000-10-31
Cintins, Ivars
Liquid purification or separation
Processes
Ion exchange or selective sorption
210682, 210688, 502401, B01D 1500, B01J 2022
Patent
active
061397520
DESCRIPTION:
BRIEF SUMMARY
This invention relates to compositions of matter and more particularly to ligand-bearing compounds and to the use thereof in removing molecules and ions from solution.
The use of ligands for removing ions and molecules from solution is well known. In particular, it is known to use various ligands to remove metal ions from the aqueous solutions obtained in the hydrometallurgical recovery of metals by treating metal ores with acids. In some cases, a ligand is used to extract valuable metal ions selectively from solution in the form of a metal-ligand complex which is then subjected to further treatment to recover the desired metal from the complex. In other cases, a ligand is used to extract contaminant metal ions selectively from a solution containing a more valuable metal, the solution then being further treated to recover the valuable metal in pure form.
Ligands may also be used for the selective removal of metal ions from water supplies or from waste solutions to permit safe disposal.
In many cases, the ligand is a solvent-soluble organic compound such as an o-hydroxyaryloxime, a .beta.-diketone, a hydroxyamic acid or an ester of various phosphorus oxy-acids and is used in the form of a solution in a water-immiscible organic solvent such as kerosene. In other cases, a ligand material is physically or chemically attached to a solid support material which may be organic or inorganic in nature.
In U.S. Pat. No. 5,182,251, there is described a method for the removal and concentration of certain metal ions from a multiple ion source by bringing the source solution into contact with a compound comprising an aminoalkylphosphonic acid containing ligand covalently bonded through an organic spacer silicon grouping to a solid inorganic support. However, in the course of studies resulting in the present invention, such supported compounds were found to be poor extractants under highly acidic conditions.
U.S. Pat. No. 5,190,161 teaches the use for metal extraction of thiophenols and thioalkyl carboxylates bonded via the thio moiety and an organic spacer group to silica, but discloses that such compounds do not preferentially extract more highly charged ions over less highly charged ions.
It has now been found that materials in which a phosphonic acid or phosphonic acid ester ligand group is bonded through a thioether residue and a silicon atom to a solid inorganic support are extremely effective in selectively removing metal ions from solution even under highly acidic conditions and which in certain embodiments can selectively extract more highly charged cations from aqueous solutions also containing less highly charged cations. Furthermore, the complexed metal ions may easily be stripped from the supported ligand material using simple techniques.
Accordingly, the invention provides a composition of matter in which a phosphonic acid or phosphonic acid ester group is linked through a thioether residue to a silicon atom which is further covalently bonded to a solid inorganic support.
The compounds of the invention may typically be represented by the Formula (1): ##STR1## wherein: Z represents a solid inorganic support; each of X and Y, independently, represents Cl, Br, I, optionally substituted lower alkyl, optionally substituted lower alkoxy, a group of the formula Z--O-- or a group of the formula: ##STR2## wherein: each of W and U represents an organic spacer group; ##STR3## and A represents H or optionally substituted hydrocarbyl.
As examples of solid inorganic supports which may be represented by Z, there may be mentioned hydrophilic inorganic supports such as silica-based materials, for example silica gel, sand, quartz, silicates, glass, glass fibres and clays and other oxides that can be reacted with a silane, for example alumina, such as .gamma.-alumina, zirconia, titania and nickel oxide.
As examples of lower alkyl and lower alkoxy groups which may be represented by X and Y, there may be mentioned groups having from 1 to 6 carbon atoms, especially methoxy groups.
As examples of organic spacer groups which may be
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Kadlec et al: "Separation of Uin and Multivalent Cations and Selective De-ionisation by a Phosphonic Cation Exchanger", Journal of Applied Chemistry & Biotechnology, vol. 23, No. 1, Jan. 1973, pp. 41-50, XP002011730, see pp. 41-43.
Atkinson Ian Murray
Lindoy Leonard Francis
Tasker Peter Anthony
Thorp Derek
Cintins Ivars
Zeneca Limited
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