## 1 Introduction  
Ion exchangers are used for purifying water, including in the treatment of water for conventional and nuclear power plants [1, 2]. Many treatment and disposal strategies for reducing the environmental hazard arising from the generation of waste resins (some of which are radioactive waste) have been considered [3, 4, 5]. One of the ways of dealing with spent ion exchangers is their thermal decomposition, including incineration and pyrolysis, whereby the volume of the ion exchanger wastes is reduced and they acquire a more stable form for deposition in the environment [6, 7, 8, 9, 10, 11, 12]. Pyrolysis of ion-exchange resins yields porous carbon beads [13, 14] usable for desulfurization of fuels [15], hydrogen storage [16], CO\({}_{2}\) capture [17, 18], sorption of heavy metal ions [19], benzene [20] and also in catalysis [21]. Ion exchangers containing dispersed inorganic fine particles, mostly of FeOOH [22, 23] and also MnO\({}_{2}\)[24] and ZrO\({}_{2}\)[25, 26] in their polymeric phase, are composite materials (called hybrid ion exchangers, HIXs) that offer properties and application opportunities not exhibited separately by the polymeric host materials or inorganic particles alone. Their polymeric-inorganic structure offers a synergy often aided by the Donnan membrane principle (in sorption processes the ions with charge similar to the functional groups are excluded from entering in the exchange phase while the ions with charge opposite to the functional groups tend to concentrate inside the exchanger phase [27]. HIXs show better properties, especially excellent sorptivity and selectivity in many reactions of environmental significance, than the parent resins [28]. They are used to remove such target contaminants as heavy metals, metalloids (especially arsenic), (inorganic ligands, fluoride, chlorophenols and pesticides, from water through sorption and redox processes [29]. A thermal analysis, comprising thermogravimetry (TG) and derivative thermogravimetry (DTG), needs to be carried out to identify the effect of the deposit on the thermal decomposition of the ion exchangers (the host materials). Recently we have undertaken in-depth studies into the thermal decomposition of HIXs. So far the studies have concentrated on anion exchangers containing particles of hydrated iron oxide (FeOOH) [30] and different cupric compounds (CuO, Cu(OH)\({}_{2}\) and Cu\({}_{4}\)(OH)\({}_{6}\)SO\({}_{4}\)) in their porous matrix [31]. In comparison with the pure resins, the particles have been found to: (a) lower the incineration end temperature while raising the pyrolysis end temperature, (b) change the temperature ranges of the individual ion exchanger decomposition stages, (c) react with the char arising from organic matter (the anion exchanger) in the course of pyrolysis. Thanks to this latter property, stemming from the chemical structure of the inorganic phase (more precisely from its reducibility), it was possible to obtain more char than from the pyrolysis of the pure resin, and the char contained the chemically transformed (reduced when possible) inorganic phase [31]. Consequently, the pyrolysis of a HIX containing FeOOH yielded a carbonaceous material with Fe\({}_{3}\)O\({}_{4}\)[30], the pyrolysis of a HIX containing Cu\({}_{4}\)(OH)\({}_{6}\)SO\({}_{4}\) (brochantite) yielded a carbonaceous material with Cu\({}_{2}\)S and the pyrolysis of a HIX containing CuO yielded a carbonaceous material with metallic copper [31]. This means that by pyrolyzing HIXs one can obtain unconventional and potentially usable carbon char-inorganic particle composites with a designable chemical composition.