## 3 Results and Discussion  
### Adsorbent Characterization  
In this work, polyolefine wax and phenol-formaldehyde resin were selected as the carbon precursors. The addition of phenol-formaldehyde resin to polyolefine wax, used in the precursor mixture and treatment with sulfuric acid, aims to incorporate a reactive structure in the carbon matrix, capable of inducing polymerization and polycondensation reactions, that will facilitate the solidification of the mixture. The resulting solid product was carbonized and submitted to steam activation to produce a suitable porous adsorbent. Inserting oxygen in the carbon precursor leads to the formation of oxygen containing structures on the surface of the final product, confirmed by elemental analysis (Table 1). The analysis is performed three times and the average was taken. The X-ray diffraction pattern of the synthesized nanoporous carbon is shown in Figure 1. Two intense and considerably narrow peaks located at 24.5\({}^{\circ}\) and 43.5\({}^{\circ}\) are detected, corresponding to the (0 0 2) and (1 0 0) reflexes of crystalline graphite. These peaks corroborate the presence of porous network, associated with the typical microcrystal turbostratic structure of carbon materials. Porosity has strong effect on the adsorption properties of activated carbon. The pore structure of obtained activated carbon was investigated by N\({}_{2}\) gas adsorption. Textural characterization was carried out by measuring the N\({}_{2}\) adsorption isotherms at \(-196\)\({}^{\circ}\)C. The nitrogen adsorption isotherms of the activated carbon are presented in Figure 2a. Analysis of nitrogen adsorption data indicates that the activated carbon obtained from polymer waste and phenol-formaldehyde resin has a high surface area (S\({}_{\text{BET}}\)) and a well-developed pore structure (Figure 2b). The part of the isotherms in the range of the relatively lower pressures has a steep increase with a tendency for saturation, which is typical for microporous adsorbents. The N\({}_{2}\) adsorption isotherms obtained correspond to IV type according to Brunauer classification at low pressure. The main textural parameters of the prepared carbon, obtained from the analysis of the nitrogen adsorption isotherms, are compiled in Table 2. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Specific Surface** & **Total Pore Volume** & **Micropore** & **Mesopore Volume** \\  & **Area S\({}_{\text{BET}}\)**, **m\({}^{2}\)/g** & **V\({}_{\text{total}}\)**, **cm\({}^{2}\)/g** & **Volume V\({}_{\text{micro}}\)**, & **V\({}_{\text{meso}}\)**, **cm\({}^{2}\)/g** & **V\({}_{\text{meso}}\)**, **cm\({}^{2}\)/g** \\ \hline AC & 885 & 0.59 & 0.38 & 0.15 \\ \hline \hline \end{tabular} Note: Accuracy: surface area—0.5 m\({}^{2}\)/g: pore volume—0.01 cm\({}^{3}\)/g.  
\end{table} 
Table 2: Textural characteristics of activated carbon. Figure 1: XRD pattern of obtained activated carbon (accuracy 0.5%). According to IUPAC classification, the isotherm is of IV type, with hysteresis of H4 type, characteristic for micro-mesoporous material. Type H4 hysteresis is also often associated with narrow slit pores. Our results show that using the precursor mixture of polyolefin wax and phenol-formaldehyde resin (containing oxygen) leads to activated carbon with a high surface area. The pore volume analysis shows that this activated carbon has prevailing content of micropores. The surface functionalities are characterized by the Boehm titration (Table 3). Data shows that the surface chemistry of carbon comprises carbonyl and small amount of carboxyl, carboxyl in lactone like structures and phenolic functionalities, and a considerably high content of carbonyl groups, which render a basic character to the adsorbent. The synthesized carbon also displays strong alkaline character, as inferred from the pH value. Along with the incorporation of acidic surface groups (due to the treatment with a sulfuric acid), a moderate amount of basic groups is detected, which determine the basic character of the surface.