## 4 Discussion and Conclusions  
In this paper, the sorption properties of two types of silica gels enriched with carbon nanotubes were investigated. It was proved that the granulation of silica gels affects the magnitude of their sorption capacity. SEM-EDS investigations showed that the materials used are of high purity and that they differ significantly in particle shape. The SG2 material has a rounded shape, while SG1 has irregular shapes with sharp edges. From the vapor sorption research, the shape of the silica gel, and thus the size of the \(SSA_{BET}\) specific surface area can influence the vapor adsorption-desorption processes. Although for both silica gels similar values of the total sorption capacity were obtained at the same temperatures, the surface structure parameters were already significantly different in value. As the study shows, the temperature and relative humidity of water vapor at an ambient pressure are the dominant factors affecting the range and rapidity of adsorption. At the same temperature, water vapor uptake increases rapidly with relative humidity. At the same humidity, although the water vapor concentration increases significantly with temperature, the water vapor uptake decreases slightly with increasing temperature, resulting in an adverse effect of temperature. Water vapor adsorption decreases rapidly with the temperature at the same water vapor concentration. The effect of temperature on the process in pure silica gels was not clear. In mixtures, worse sorption capacity parameters were obtained at higher temperatures. The efficiency of devices using physical adsorption depends primarily on the parameters of heat and mass transport in the adsorbent bed in the form of working vapor, which must first be obtained from a specific source. An important factor determining the efficiency of the process is the thermophysical properties of the substances used in the process. The scope of the expected application and design of the device depends on the parameters of the vapor that can be obtained under given environmental conditions. Analyses of sorption equilibrium points provide information about the sorption capacity of the adsorbent at different relative pressures or adsorbate concentrations, which is very useful for the selection of adsorbent or optimal process parameters. As can be seen from the presented results, the use of a mixture of silica gels and multi-walled nanotubes can influence the parameters of water vapor sorption in adsorption chillers. The addition of CNTs can change the sorption capacity values of the bed. The addition of 10 wt.% CNTs resulted in a decrease in the sorption capacity in mixtures. Closures of the desorption curve were obtained, which may indicate the ease of the adsorption-desorption cycle. The ratio of sorption capacities \(Q_{SG1/CNT}/Q_{SG1}\) was below 1 in the whole range of tested pressures 0-0.1 MPa. For the SG2/CNT mixture, the ratio \(Q_{SG2/CNT}/Q_{SG2}\) in the pressure of 0.1 MPa was also below 1. Only at 333 K and the range of 10% \(<\) RH \(<\) 60% this ratio was above 1. These results indicate the unfavorable applications of CNTs in the context of sorption. This is due to the hydrophobic properties of the tested CNTs. This is confirmed by SEM-EDS analysis, proving the purity of the nanotubes used. The presence of functional groups, both carboxyl (-COOH) and hydroxyl (-OH), is undesirable for industrial use. These functional groups block the pores of the nanotube surface and can adsorb water due to their more hydrophilic nature. The specific characteristics of CNTs related to electrical conductivity and mechanical properties, make this material nevertheless interesting for applications related to sorption as a function of temperature and pressure.