## 4 Conclusions  
This study underscores the potential of bentonite-based materials as effective and sustainable adsorbents for removing contaminants from pharmaceutical effluents, aligning with the United Nations' 2030 Agenda, specifically SDG 12 on Responsible Consumption and Production. Among the tested adsorbents, acid-treated bentonite exhibited enhanced adsorption capacity compared to its natural form. Notably, BA1 demonstrated similar adsorption performance to BA2.5, an adsorbent subjected to acid treatment with 2.5 mol\(\cdot\)L\({}^{-1}\) HCl, while requiring a lower acid concentration. This reduction minimizes reagent consumption and waste generation while maintaining high removal efficiency. Advanced characterization techniques, including XPS, XRF, EDS, SEM, and TEM, revealed a silicon- and aluminum-rich composition. Acid treatment significantly improved \begin{table}
\begin{tabular}{c c c c c c} \hline
**Clay Mineral** & **Isotherm** & **Kinetics** & **Time (min)** & **Removal (\%)** & **Author** \\ \hline
25\% In\({}_{2}\)O\({}_{3}\)/Halloyite & Freundlich & Pseudo-second order & 1440 & 88.3 & [36] \\ Carbon–Cu composite & Langmuir & Pseudo-second order & 120 & 75 & [37] \\ Bentonite & Langmuir & Pseudo-second order & 1440 & - & [9] \\ Orange biocarbon & Langmuir & Pseudo-second order & 16 & 57.69 & [38] \\ Magnetic bentonite/CMC & Langmuir & Pseudo-second order & 120 & 96 & [39] \\ \hline \end{tabular}
\end{table} 
Table 4: _Cont._  
Figure 12: Reuse of BN and BA1 adsorbents after drug adsorption. surface properties, increasing surface area and functional group availability. The reuse analysis demonstrates that BA1 maintained high removal efficiency over multiple cycles, indicating its robustness and suitability for continuous wastewater treatment applications. Kinetic studies confirmed that optimal adsorption conditions for BA1 were achieved within 30 min using 0.30 g of adsorbent, following a pseudo-second-order kinetic model and Freundlich isotherm, suggesting a mixed adsorption mechanism involving chemisorption and physisorption. These modifications not only enhanced the adsorption of pharmaceutical contaminants, such as tetracycline hydrochloride, but also demonstrated the versatility of bentonite in addressing diverse industrial and environmental challenges. Overall, this work highlights bentonite as a readily available, eco-friendly material with significant potential for sustainable applications in the pharmaceutical industry, particularly in the development of reusable, high-efficiency adsorbents. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app15063372/s1](https://www.mdpi.com/article/10.3390/app15063372/s1)]([https://www.mdpi.com/article/10.3390/app15063372/s1](https://www.mdpi.com/article/10.3390/app15063372/s1)), Figure S1. Maximum adsorptive capacity of BN and BA1 adsorbents as a function of time for the adsorption TC. Table S1: Kinetic data related to the BN adsorbent; Table S2: Kinetic data related to the BA1 adsorbent  
A.P. : conceptualization, methodology, experimental operation, data analysis, visualization, investigation, writing--original draft. A.F. : investigation, data analysis, writing--review and editing. A.C.: conceptualization, methodology, visualization, investigation, writing--review and editing. M.S. : conceptualization, methodology, visualization, investigation, writing--review and editing. H.M.: conceptualization, methodology, data analysis, writing--original draft, writing--review and editing. E.R.-C.: writing--review and editing, discussion, data analysis, funding, resources. D.B.-P.: writing--review and editing, discussion, data analysis. L.d.C. : conceptualization, resources, methodology, project administration, supervision, writing--review and editing. All authors have read and agreed to the published version of the manuscript.