# Activated Carbons as Effective Adsorbents of Non-Steroidal Anti-Inflammatory Drugs
## 5 Conclusions  
Studies on the adsorption of sodium salts of non-steroidal anti-inflammatory drugs were carried out. The adsorption equilibrium studies were conducted at 15, 25, and 35 \({}^{\circ}\)C, while adsorption kinetics were studied at 25 and 35 \({}^{\circ}\)C.  
The largest amount (adsorption value ranging from 0.61 to 0.98 mmol/g) and rate (half-time in a range from 286.7 to 355.9 min) of adsorption were demonstrated in the presence of naproxen sodium. Moreover, the lowest adsorption amount was observed in the system with ibuprofen sodium (adsorption value ranging from 0.26 to 0.45 mmol/g), and the slowest kinetics was recorded for diclofenac sodium (half-time in a range from 902.9 to 1562.4 min). This is the effect of different solubility and various molecular structures of the studied pharmaceuticals. Additionally, a strong influence of temperature on the adsorption of sodium salts of non-steroidal anti-inflammatory drugs was demonstrated. Higher adsorption amounts and rates were recorded at higher temperatures. This effect is the result of increased dehydration of both adsorbate molecules and adsorbent grains, which facilitates diffusion into the porous structure of the carbon material. The values of thermodynamic parameters confirmed the endothermic nature of naproxen sodium (\(\Delta\)H\({}^{\circ}\)15-35\({}^{\circ}\)C = 26.41 kJ/mol), ibuprofen sodium (\(\Delta\)H\({}^{\circ}\)15-35\({}^{\circ}\)C = 22.73 kJ/mol), and diclofenac sodium (\(\Delta\)H\({}^{\circ}\)15-35\({}^{\circ}\)C = 21.61 kJ/mol) adsorption on GAC activated carbon. Additionally, it has been shown that the adsorption of pharmaceuticals is physisorption (\(\Delta\)H < 40 kJ/mol and 0 < \(\Delta\)G\({}^{\circ}\)NPX\({}_{\text{-}}\)15\({}^{\circ}\)C = \(-\)0.10 kJ/mol, \(\Delta\)G\({}^{\circ}\)NPX\({}_{\text{-}}\)25\({}^{\circ}\)C = \(-\)0.73 kJ/mol, \(\Delta\)G\({}^{\circ}\)NPX\({}_{\text{-}}\)35\({}^{\circ}\)C = \(-\)1.62 kJ/mol, \(\Delta\)G\({}^{\circ}\)BP\({}_{\text{-}}\)15\({}^{\circ}\)C = \(-\)2.66 kJ/mol, \(\Delta\)G\({}^{\circ}\)BP\({}_{\text{-}}\)25\({}^{\circ}\)C = \(-\)3.07 kJ/mol, \(\Delta\)G\({}^{\circ}\)BP\({}_{\text{-}}\)35\({}^{\circ}\)C = \(-\)3.97 kJ/mol, \(\Delta\)G\({}^{\circ}\)D\({}_{\text{-}}\)15\({}^{\circ}\)C = \(-\)1.98 kJ/mol, \(\Delta\)G\({}^{\circ}\)D\({}_{\text{-}}\)25\({}^{\circ}\)C = \(-\)2.72 kJ/mol, \(\Delta\)G\({}^{\circ}\)D\({}_{\text{-}}\)35\({}^{\circ}\)C = \(-\)3.25 kJ/mol < 20 kJ/mol). The adsorption equilibrium data were analyzed using the generalized Langmuir equation. However, only for D/GAC_25 \({}^{\circ}\)C the full form of the GL equation correctly describes the behavior of this system. In other cases, simplifications of the GL isotherm were used: the Toth isotherm (IBP/GAC_15 \({}^{\circ}\)C, IBP/GAC_25 \({}^{\circ}\)C, IBP/GAC_35 \({}^{\circ}\)C) and the generalized Freundlich isotherm (D/GAC_15 \({}^{\circ}\)C, D/GAC_35 \({}^{\circ}\)C, NPX/GAC_15 \({}^{\circ}\)C, NPX/GAC_25 \({}^{\circ}\)C, NPX/GAC_35 \({}^{\circ}\)C). In practice, this means that medium heterogeneity effects were observed in the experimental systems. The adsorption rate data were analyzed using numerous adsorption kinetics equations. The best fitting quality was obtained for the multi-exponential equation (0.335% < SD(c)/co < 0.720% and 9.4 \(\times\) 10\({}^{-5}\) < 1 - R\({}^{2}\) < 4.9 \(\times\) 10\({}^{-4}\)) and good for the fractal-like MOE equation (0.520% < SD(c)/co < 0.879% and 2.2 \(\times\) 10\({}^{-4}\) < 1 - R\({}^{2}\) < 6.0 \(\times\) 10\({}^{-4}\)). The analysis of the estimated parameters showed that the adsorption processes of naproxen sodium, ibuprofen sodium, and diclofenac sodium on GAC activated carbon proceeds approximately with first-order kinetics. Moreover, for activated carbon samples after adsorption of the tested pharmaceuticals, compared to pure carbon material, lower resistance to high temperatures and a decrease in zeta potential were observed.