# Ibuprofen Removal by Aluminum-Modified Activated Carbon (AC@Al) Derived from Coconut Shells
## 4 Conclusions  
In this study, the application of hybrid, porous aluminum-modified coconut-shell-derived activated carbon (AC@Al) was evaluated for the removal of Ibuprofen (NSAID) from pharmaceutical wastewaters. The results showed that at pH 2.0 \(\pm\) 0.1, a removal rate of around 99% was achieved when 0.8 g/L of AC@Al was added. Additionally, at pH 2.0, which is less than pH\({}_{\text{Pzc}}\) (5.72), the positively charged surface of AC@Al probably attracted negatively charged Ibuprofen molecules due to protonation and electrostatic repulsion. Langmuir, Freundlich, Sips and Redlich-Peterson isotherm models were applied to evaluate the adsorption. It was found that all isotherm models fit the adsorption well according to R\({}^{2}\) values, so the adsorption mechanism is a mixture that does not follow an ideal and exclusive monolayer adsorption. The PSO kinetic model was found to best fit the adsorption procedure, demonstrating that the adsorption of IBU onto AC@Al is close to chemisorption. The Langmuir maximum adsorption capacity was determined to be extremely high, reaching 2053 mg/g. According to kinetics calculations, equilibrium was reached at 90 min. Thermodynamics calculations showed that the adsorption was endothermic in nature (\(\Delta H^{0}\)= 42.9 kJ/mol) and spontaneous (\(\Delta G^{0}\) < 0) at all temperatures. The positive value of \(\Delta S^{0}\) (0.1722 kJ/mol-K) indicated that there was an increase in the random interaction between the solid and liquid interfaces. In conclusion, AC@Al as an adsorbent was effectively regenerated and reused for five cycles in the removal of IBU from pharmaceutical wastewater.  
Conceptualization, A.K.T., G.Z.K. and I.A.K.; methodology, A.K.T., G.Z.K. and I.A.K.; validation, A.K.T., G.Z.K. and I.A.K.; formal analysis, N.M., A.K.T., G.Z.K. and I.A.K.; investigation, N.M., A.K.T., G.Z.K. and I.A.K.; resources, N.M., A.K.T., G.Z.K. and I.A.K.; data curation, N.M. and A.K.T.; writing--original draft preparation, N.M. and A.K.T.; writing--review and editing. N.M., A.K.T., G.Z.K. and I.A.K.; visualization, A.K.T., G.Z.K. and I.A.K.; supervision, A.K.T., G.Z.K. and I.A.K. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** All data analyzed during this study are included in this published article.  
Figure 7: Adsorption of IBU onto AC@Al for 5 adsorption–desorption cycles after regeneration at alkatic pH using 0.1 M NaOH treatment; IBU C\({}_{\text{o}}\) = 100 mg/L, dose = 0.8 g/L, pH = 2.0 \(\pm\) 0.1, t = 1.5 h.  
**Acknowledgments:** We acknowledge support of this work by the project \"Advanced Nanostructured Materials for Sustainable Growth: Green Energy Production/Storage, Energy Saving and Environmental Remediation\" (TAEDR-0535821), which is implemented under the action \"Flagship actions in interdisciplinary scientific fields with a special focus on the productive fabric\" (ID 16618), Greece 2.0-National Recovery and Resilience Fund and funded by European Union NextGenerationEU.  
**Conflicts of Interest:** The authors declare no conflicts of interest.