Adsorption method and ligands

1. A method for testing the appropriateness of a cation-exchanger for removing a substance from a liquid, said method comprising the steps:

(a) providing a library which comprises

(i) one or more cation-exchangers to be tested (exchangers 1, 2, 3, 4 . . . n; n=an integer>0) each of which cation-exchangers differs with respect to kind of ligand (ligands 1, 2, 3, 4 . . . n), and

(ii) one or more reference cation-exchangers having reference ligands, wherein the support matrix and the substitution degree are essentially the same in the exchangers 1, 2, 3, 4 . . . n and in the reference cation-exchanger;

(b) determining the breakthrough capacity of exchanger 1 for the substance at predetermined conditions;

(c) determining the breakthrough capacity of the reference cation-exchanger for the substance at the same conditions as in step (b);

(d) concluding from the relation between the breakthrough capacities obtained in steps (b) and (c), if cation-exchanger 1 is appropriate to use for removing the substance; and

(e) repeating steps (b), (c) and (d) for at least one of the exchangers 2, 3, 4 . . . n.

2. The method of claim 1 , wherein step (e) is performed in parallel with or subsequent to steps (b), (c) and (d) for exchanger 1.

3. The method of claim 1 , wherein the predetermined conditions in steps (b) and (c) include that the ionic strength is above the ionic strength of a water solution that is 0.3 M in NaCl.

4. The method of claim 1 , wherein the breakthrough capacity determined for a tested cation-exchanger that is larger than the breakthrough capacity for the reference cation-exchanger is taken as an indication that the cation-exchanger or ligand is appropriate to use for removing the substance.

5. In a method for removing a positively charged substance from an aqueous liquid(l) containing said substance by contacting the liquid with a cation-exchanger(1) under conditions permitting binding of said substance to said cation-exchanger(1), optionally followed by a subsequent desorption of said substance, the improvement comprising selecting said cation-exchanger to be capable of

(a) binding said substance by cation-exchange in an aqueous liquid reference(II) at an ionic strength corresponding to 0.3M NaCl and

(b) permitting a break through capacity for said substance>200% of the break-through capacity of said substance for a reference cation-exchanger(2) containing sulphopropyl groups —CH 2 CH 2 CH 2 SO 2 O—,

wherein the cation-exchanger includes a plurality of cation exchange ligands having the formula

—D—X″

where

(c) X″ is a cation-exchange group selected from the group consisting of sulphonate (—SO 3 − /—SO 3 H) sulphate(—OSO 3 − /—OSO 3 H), carboxylate(—COO − /—COOH), phosphate(—OPO 3 2− /OPO 3 H − /—OPO 3 H 2 ) and phosphonate(—PO 3 2− /—PO 3 − H/—PO 3 H 2 ), and

(d) D is an organic group including an organic chain D′ linking X″ to the support matrix, and said organic chain D′ includes a thioether sulphur at a distance of 1–7 atoms from the cation-exchange group (X′) and only non-aromatic carbons,

and wherein D′ includes an amide group(—CONH—, —NHCO—, —N(OCR)—, —SO 2 NH—, —NHSO 2 —, —N(SO 2 R)—), an ether, an ester, or a hydrogen-binding group projecting from D′ selected from the group consisting of

(i) oxygens in

(i.1) —CO—, —SO— or —SO2-where the carbon and sulphur are part of D′;

(i.2) alcoholic or phenolic hydroxy that bind directly to a carbon in D′;

(i.3) nitro (—NO 2 ) which is attached to a carbon which is part of A′, and amine oxide(NO), where represents three single bonds and the nitrogen is part of A′

(ii) halogens which are bound to a carbon in D′, such as fluoro, chloro, bromo or iodo with preference for fluoro; and

(iii) sp and sp 2 -hybridised carbons directly attached to an sp- and sp 2 -hybridised carbon, respectively, which is part of D′.