# Adsorption of Ag (I) Ions at the Zirconium Phosphate/KNO3 Aqueous Solution Interface
## 2 Materials and Methods
### Physicochemical Methods of Investigations  
The details of the procedure used for physicochemical characteristics determination are described in ref. [17]. In order to measure nitrogen adsorption/desorption based on  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Preparation Conditions** & **Sample Designation** & **Specific Surface Area (m\({}^{2}\)/g)** & **Adsorbent Mass (g)** & **Adsorbent Surface m\({}^{2}\)** \\ \hline Initial precipitated & Initial & 195 & 0.1283 & 25.0 \\ \hline HTT 150 \({}^{\circ}\)C Aerogel & Xero & 278 & 0.0899 & 25.0 \\ \hline HTT 150 \({}^{\circ}\)C Gel & Gel HTT & 450 & 0.0556 & 25.0 \\ \hline MWT 230 \({}^{\circ}\)C xerogel & MWT Xero & 234 & 0.1068 & 25.0 \\ \hline MWT 230 \({}^{\circ}\)C gel & MWT Gel & 319 & 0.0784 & 25.0 \\ \hline MChT 500 rpm gel & MChT Gel & 406 & 0.0616 & 25.0 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The specific surface area of the zirconium phosphate samples, the weight of the sample used in the adsorption tests and the surface area of the sample.  
the obtained adsorption isotherms, the analyzer ASAP 2405N (\"Micromerities Instrument Corp.\", Norcross, GA, USA) was used. The specific surface area and porosity of the tested zirconium phosphate samples were determined; the details of the procedure are discussed in ref. [17]. The FTIR spectrum of the tested samples was recorded with a Nicolet 8700A FTIR spectrometer in the wavelength range 4000-400 cm\({}^{-1}\). All samples were also examined using the diffractometer Philips PW 1830 (Amsterdam, The Netherlands) with CuK\(\alpha\)-radiation (\(\lambda\) = 0.15406 nm) for the crystal structure characterization.  
Measurements of the of silver ions adsorption at the interface of the zirconium phosphate sample/0.001 mol/dm\({}^{3}\) KNO\({}_{3}\) solution interface + Ag\({}^{+}\) ions with the concentrations of 1, 10, and 100 umol/dm\({}^{3}\), respectively, were made by means of the method of radioactivity loss from the solution using a measuring system also in the potentiometric titration. Nitrogen, purified from CO\({}_{2}\), was passed through the measuring system consisting of a Teflon vessel, propeller stirrer, glass electrode, and calomel electrode. Then, 50 cm\({}^{3}\) of the electrolyte solution was placed in a Teflon vessel, and then the solution containing the radioactive isotope \({}^{110m}\)Ag\({}^{+}\) was added. From the solution prepared in this way, zero samples with the volume of 0.1 cm\({}^{3}\) were taken, and then the weighed amount of zirconium phosphate precipitate was added. The resulting suspension was vigorously stirred, and at the time of equilibrium, 0.5 cm\({}^{3}\) samples of the suspension were taken which were then centrifuged. From each of the centrifuged samples, 0.1 cm\({}^{3}\) of the supernatant solution was taken twice and placed on the filter paper, thus creating sources for radioactivity measurements using the Beckman Gamma 5500B automatic scintillation counter (Brea, CA, USA). The modification procedure changed the surface specific area which affects the adsorption results. Moreover, the amount of the adsorbent was selected so that each adsorbent contacted with the same surface of the Ag\({}^{+}\) solution (Table 1).  
The density of the ion sorption (A\({}_{\rm Ag}\)) on the zirconium phosphate surface was calculated from the changes in radioactivity before and after the adsorption using the formula:  
\[{\rm A}_{\rm Ag}=\frac{c_{0}V}{mS_{w}}\bigg{(}1-\frac{N_{r}}{N_{0}}\bigg{)}\]  
and  
\[c_{r}=c_{0}\frac{N_{r}}{N_{0}}\]  
where:  
\(c_{0}\)--the Ag\({}^{+}\) initial concentration (mol/dm\({}^{3}\))  
\(V\)--the volume of the solution (dm\({}^{3}\))  
\(m\)--the adsorbent mass (g)  
\(S_{w}\)--the specific surface area (m\({}^{2}\)/g)  
\(N_{r}\)--the number of counts from the source taken during the adsorption,  
\(N_{0}\)--the number of counts from the source taken before adsorption,  
\(c_{r}\)--the Ag\({}^{+}\) equilibrium concentration (mol/dm\({}^{3}\))