# Adsorption of Ag (I) Ions at the Zirconium Phosphate/KNO3 Aqueous Solution Interface
## 1 Introduction  
Silver ions are characterized by antibacterial properties as well as low toxicity to humans. Although known from antiquity, the antibacterial properties of Ag\({}^{+}\) ions, have been appreciated in recent years due to the increasing resistance of bacteria to antibiotics [1]. Owing to this property, silver ions, silver nanoparticles (AgNps), and silver antibacterial agents are used to treat various infections [2; 3]. Among the silver antibacterial agents, in addition to the AgNPs deposited on nanofibers, there were obtained other inorganic silver carriers, such as zeolites, phosphates, titanium dioxide, activated carbon, montmorillonite, and MoS\({}_{2}\)[4; 5].  
Crystalline zirconium phosphates, having a two-dimensional layered structure, as well as those in the amorphous state exhibit ion exchange properties and are characterized by large thermal, chemical, included in the acidic media, and radiolytic stability [6; 7]. It was shown that, owing to these properties, zirconium phosphates can be widely applied in materials chemistry and based on them it is possible to obtain catalysts, drug delivery carriers, or adsorbents for purifying water from pollutants. The studies of zirconium phosphate doping with Ag ions as a result of NaZrP ion exchange proved that the obtained silver zirconium phosphate is characterized by antibacterial properties against _Escherichia coli_ and _Staphylococcus aureus_[4]. The antibacterial activity against _Escherichia coli_ was demonstrated by the samples of titanium zirconium phosphate on which Ag\({}^{+}\) ions were adsorbed [8]. Besides, the Ag-containing zirconium phosphate synthesized by the ion-exchange procedure was studied as an effective oxidation catalyst [9; 10; 11], photocatalyst [12; 13; 14], and adsorbent for dye removal from aqueous media [15]. Therefore, the investigations of silver cations sorption on zirconium phosphate is important from the point of view of the preparation of these materials. It should be noted that there is only a limited amount of research onthis issue [4; 8; 16]. At the same time, the influence of the porous structure of ZrP on the Ag\({}^{+}\) sorption has not been studied at all. Thus, modification of zirconium, titanium, and tin phosphates under hydrothermal conditions (using conventional hydrothermal, microwave, and mechanochemical treatments) demonstrates wide possibilities for controlling the parameters of the porous structure, surface structure and, as a result, their adsorption characteristics [7; 17; 18; 19]. Therefore, it is important from the scientific and applied points of view to study the features of these types of treatment for phosphates and the relationship between the physicochemical characteristics, and the adsorption properties of phosphates was established, including in relation to Ag\({}^{+}\) ions. Based on this, the synthesis of the Ag-containing materials can be improved.  
The studies of Ag\({}^{+}\) ion adsorption using the zirconium phosphate samples will allow determining the conditions for removing \({}^{110\mathrm{m}}\mathrm{A}\mathrm{g}\) radioisotope ions from the nuclear liquid waste in order to purify these waters. Another aspect of the research is to obtain a material that, on one hand, will be characterized by great antibacterial activity and, on the other hand, will be chemically and thermally stable.  
This paper presented the results of the studies on adsorption of Ag\({}^{+}\) ions as a function of pH in the amorphous zirconium phosphate samples previously subjected to the hydrothermal, mechanical, and microwave modifications in order to vary the parameters of the porous structure and surface design and its adsorption activity with respect to Ag\({}^{+}\). The discussion on the activity of the groups on the surface of the modified zirconium phosphate samples was held based on the FTIR spectra.