**2. Application of ion exchangers of various types in recovery of platinum metal ions from secondary sources**

Small amounts of noble elements in nature and constant impoverishment of their natural resources result in significant importance of physicochemical methods used for platinum metal ions recovery from secondary resources e.g. worn car exhaust gas convertor, chemical catalysts, stomatology alloys as well as waste waters and waters of refinery origin. Noble metals recovery from such raw materials requires individual approach and application of selective methods of their removal. Moreover, worse quality of these raw materials makes removal of pure noble metals more difficult. Determination of noble metals, particularly platinum ones in the above-mentioned materials, geological samples and synthetic mixtures together with other elements is of significant importance nowadays. Liquid–solid phase extraction (SPE) has some advantages compared to liquid–liquid extraction. Among others, it is faster, cheaper, uses small amounts of reagents and above all its automatization is easier. Moreover, its simple performance and high enrichment coefficients decide about its common laboratory application. SPE uses solid sorbents which should be characterized by not only high capacity towards metal ions under determination but also large selectivity and suitable sorption and desorption kinetics.

Synthetic ion exchange resins are widely applied in platinum metal ions enrichments. Among them of particular interest are cation exchangers, chelating ion exchangers and anion exchang‐ ers of different basicity of functional groups. Ion exchange selectivity depends on the kind and number of functional groups of ion exchanger as well as cross-linking and composition of external electrolyte solution composition from which concentration proceeds. Of these types of ion exchangers, the most effective are monofunctional ones, which ensure the same strength of bonding ions with the ion exchanger surface due to the presence of one type of groups which does not make equilibrium establishment difficult. Complexity of platinum carrying samples for enrichment makes it necessary to separate a component under determination due to large interference of components present in the analyte. In the chloride systems, ion exchange enables platinum metal ions separation not only from their mixtures but also from other metals. In the hydrogen chloride acid solutions, most platinum metal ions are present in the form of anion chloride complexes; therefore they are retained by strongly basic anion exchangers. Anion exchangers enable selective removal of platinum metal ions from solutions of other metals; however, there appear some problems with their elution due to strong sorption of platinum metal ions. It can often occur that recovery is not quantitative or rendered difficult. Such situation arises because of stable ion pairs formation between anionic complexes and the quaternary ammonium groups of the anion exchanger. Reduction of noble metal ions can proceed in the ion exchanger phase which also affects incomplete recovery. Some difficulties with determination can result from different behaviour of new and 'old' solutions which is connected with the hydrolysis process in the solution. This reflects mainly to rhodium or iridium chloride complexes because they have the greatest tendency towards hydrolysis. Using cation exchangers, rare earth elements, transient metals as well as alkali metals and alkaline earth family form weakly anionic or stable cationic complexes therefore they are retained on the cation exchange deposit whereas platinum metals go through the column not being retained by the cation exchangers making separation of the above-mentioned metal ions possible.

polyacids, polybases or both polyacids and polybases (polyampholyte, amphoteric ion exchangers). Those which exchange cations are called *cation exchangers* and those which exchange anions are called *anion exchangers*. Generally, those exchanging ions are called *ion exchangers*. Some ion exchangers prepared by modification of various types of substances, particularly natural ones, besides capability of exchanging ions exhibit distinct sorption properties [1–5]. The cation exchangers occurring most frequently possess functional groups such as -SO3H, -COOH and -OH, whereas the anion exchangers possess the primary, secon‐ dary and tertiary amine ones and quaternary ammonium ones, quaternary phosphate ones and tertiary sulfone ones. Selective (chelating) ion exchangers and those strongly basic and weakly basic of the polymerization type of the functional trimethylammonium (type 1) and dimethylhydroxyethylammonium (type 2) groups are most widely applied in exchange chromatography. Their affinity mostly depends on the structure, size and change of anion exchanger. Type of functional groups in ion exchangers is decisive about the character of

Besides the general division of ion exchange materials due to the material (organic and inorganic) the skeleton is built, there are many others whose classification is based on the methods of preparation, type of functional groups and skeleton structure. There is still another basis of ion exchangers division conditioned by historical development of this area, i.e.

**2. Application of ion exchangers of various types in recovery of platinum**

Small amounts of noble elements in nature and constant impoverishment of their natural resources result in significant importance of physicochemical methods used for platinum metal ions recovery from secondary resources e.g. worn car exhaust gas convertor, chemical catalysts, stomatology alloys as well as waste waters and waters of refinery origin. Noble metals recovery from such raw materials requires individual approach and application of selective methods of their removal. Moreover, worse quality of these raw materials makes removal of pure noble metals more difficult. Determination of noble metals, particularly platinum ones in the above-mentioned materials, geological samples and synthetic mixtures together with other elements is of significant importance nowadays. Liquid–solid phase extraction (SPE) has some advantages compared to liquid–liquid extraction. Among others, it is faster, cheaper, uses small amounts of reagents and above all its automatization is easier. Moreover, its simple performance and high enrichment coefficients decide about its common laboratory application. SPE uses solid sorbents which should be characterized by not only high capacity towards metal ions under determination but also large selectivity and suitable

Synthetic ion exchange resins are widely applied in platinum metal ions enrichments. Among them of particular interest are cation exchangers, chelating ion exchangers and anion exchang‐

according to their origin – natural, semi-synthetic and synthetic [1–5].

exchange reaction and its applicability.

4 Ion Exchange - Studies and Applications

**metal ions from secondary sources**

sorption and desorption kinetics.
