# Application of Modern Research Methods for the Physicochemical Characterization of Ion Exchangers
## 1 Introduction
### Ion Exchangers Advantages and Applications  
The ion exchange process similar to adsorption (with the contribution of ions) plays an important role in the water treatment to enable recycling of such waters and reduces the demand for freshwater resources. This is still the only practicable option with full and part flow for treatment of ammoniated and microbiological wastewaters [35; 36; 37; 38; 39; 40; 41]. The main advantages of ion exchange are the recovery of valuable substances, selectivity, reduced sludge formation and compliance with the discharge specifications compared to the other methods such as chemical precipitation, adsorption, membrane filtration, coagulation-flocculation and floatation as the materials belonging to active charcoals, zeolites, hybrid materials, MOFs, etc. [42; 43; 44].  
Among them, of significant importance are those connected with effective sorption of metal ions from acidic solutions with the complex matrix, selective sorption of the specific group of metal ions such as alkali, alkali earth, heavy metal or lanthanide ions. In many cases with high sorption capacity, several sorption/desorption cycles and not large ecological footprint are found [45; 46; 47; 48; 49; 50; 51; 52; 53]. Ion exchangers in the weakly acidic forms are also useful in food production, proteins purification, colour removal from cane sugar syrupts to make white sugar as well as to purify antibiotics and other pharmaceuticals [54; 55; 56; 57].  
The resins are also used as active ingredients in drug formulations for pills disintegration, taste-masking, controlled or extended-release, stabilization as well as for drug isolation or purification. The drug-resin complex can be used in the suspension or isolated as a dry, solid, free-flowing, stable compound. The drug is released from the resinate upon exposure to physiological fluids [45; 46].  
Physical characterization of ion exchangers can be made by means of different methods. In the presented paper the optical profilometry and the X-ray photoelectron spectroscopy were used to characterize the commercially available ion exchangers Dowex M 4195, Amberlite IRA 743 and Purolite Arsen \(\mathrm{X^{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{ \mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{ \mathrm{ \mathrm{   }}}}}}}{}}}{}}}{}}}}}}\) before and after the sorption of Cu(II) or As(V). These two methods are rarely used together to characterize ion exchangers. Finding the relation between the compositional differences, topography, shape, inclination, edges, or physical differences, etc., and the type of elements, their oxidation state and binding energy is very useful for prediction of mechanism sorption of different adsorbents. In order to examine the internal structure, the beads were cut using an ultramicrotome and then imaged, e.g., using a high resolution scanning electron microscope. For describing the distribution of elements before and after the sorption process the profiles were registered and the roughness parameters were determined. This type of research on microgeometry and roughness analysis of cut beads of the Dowex M 4195, Amberlite IRA 743 and Purolite Arsen \(\mathrm{X^{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{ \mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{ \mathrm{ \mathrm{ }}}}}}}}}}}}}}}}}}\) ion exchangers were not described in the literature.