Removal of enalapril maleate drug from industry waters using activated biochar prepared from Butia capitata seed. Kinetics, equilibrium, thermodynamic, and DFT calculations

Abstract

Porous biochar was fabricated from Butia capitata (Bc) seed, which was used to uptake enalapril maleate from synthetic wastewater. Activated biochars were fabricated by blending Bc and ZnCl2 at 1:1 (BcB-1.0) or 1:1.5 (BcB-1.5) proportions and furtherly pyrolyzed at 600 °C. The elemental analysis, Boehm titration, hydrophobic balance ratio, FTIR, TGA, and N2 isotherm characterized the carbon-based materials. They presented a hydrophilic behavior with diverse polar groups on their surface. BcB-1 and BcB-1.5 biochars have a total pore volume of 0.392 and 0.492 cm3 g−1 and a surface area of 1267 and 1520 m2/g, respectively. The kinetics and isothermal data were adequately adjusted to the fractal-like pseudo-second-order and Liu models. The employment of BcB-1.0 and BcB-1.5 for treating synthetic wastewater containing high levels of pollutants had elevated efficiency in their removals (up to 99.06%). We also conducted a DFT computational study, density functional theory (DFT), to examine the interactions between enalapril and a graphitic domain of biochar by using these calculations, the most stable configuration presented interaction energy of −88.7 kJ mol−1 implies a face-to-face π–π stacking interaction involving the enalapril phenyl segment and an aromatic ring of the graphitic domain, as well as London dispersion arising from the proximity of ethoxy/pyrrolidine to biochar carbon atoms, with interatomic distances of 3.31 Å for the former and 3.60 Å /3.48 Å for the latter. Also, the DFT calculations agreed with the thermodynamic data calculated from the isotherms (283–318 K).