Evaluation of novel activated carbons from chichá-do-cerrado (Sterculia striata St. Hil. et Naud) fruit shells on metformin adsorption and treatment of a synthetic mixture

Abstract

Chichá-do-cerrado (Sterculia Striata St. Hil. et Naud) is a Brazilian native plant whose nuts have interesting nutritional value. However, the fruit shells (CH) have never been evaluated for potential uses. This study aimed to characterize the biochar (BC–CH) and the activated carbons synthesized by chemical (K–CH) and physical (C–CH) processes. The activated carbons were evaluated on metformin adsorption and treatment of a synthetic mixture. Pyrolysis increased the carbon content and the H/C ratio indicated higher aromatization for C–CH. BC–CH presented low surface area, which was increased mainly with KOH activation (1273.6 m2 g−1). FTIR demonstrated the degradation of lignocellulosic compounds and zeta potential inferred a higher number of oxygenated groups for C–CH. Regarding the adsorption studies, the kinetics demonstrated an equilibrium time of 60 min and the isotherm resulted in a maximum experimental adsorption capacity of 33.75 and 45.50 mg L−1 for C–CH and K–CH, respectively. Interestingly, C–CH presented the highest removal percentage of the synthetic mixture, indicating the role of Cu (II) interactions and synergistic effects. In summary, it was verified the potential of the adsorbents in wastewater treatment, and the importance of evaluating the composition of the aqueous matrix, which can alter the adsorption mechanisms.