Removal of active pharmaceutical compounds in Primalan and Diane using pumpkin biochar: synthesis, characterization, and adsorption study

Abstract

This investigation aims to apply the adsorption process to eliminate mequitazine and ethinylestradiol, the active molecules of Primalan and Diane, respectively, from aqueous solutions, utilizing biochar synthesized from pumpkin fruits (PB-500). The results revealed that the obtained adsorbent possessed a notable specific surface area, contributing to removal efficiencies of 66.61% and 62.37% for mequitazine and ethinylestradiol, respectively. The sludge recovered under equilibrium conditions was also characterized to facilitate comparison of biochar properties before and after adsorption. Several models were employed to analyze the adsorption kinetics and isotherms, showing that the pseudo-second-order model offers the optimal representation for the kinetic behavior. Both the Sips and Freundlich models accurately described the isotherm data. On the other hand, the adsorption on PB-500 was clearly affected by the variation in solution pH. The PB-500 variation test indicated that the optimum adsorbent concentration was around 0.8 g L⁻¹, where the removal yields were 67% for mequitazine and 65.16% for ethinylestradiol. Thermodynamic studies indicated that the adsorption was exothermic for both pollutants. Consequently, it can be inferred that pumpkin-biochar serves as an effective adsorbent for eliminating mequitazine and ethinylestradiol from water.