Production of porous activated carbons from Caesalpinia ferrea seed pod wastes: Highly efficient removal of captopril from aqueous solutions

Porous activated carbons (ACs) prepared from a lignocellulosic waste, Caesalpinia ferrea seed pod wastes (CF) were utilised for removing captopril pharmaceutical from synthetic hospital effluents and aqueous effluents. Chemical activation using ZnCl2 was performed. It was utilised the following proportions CF-Biomass: ZnCl2 (1: 0.5, 1:1 and 1:1.5, obtaining CFAC.0.5, CFAC.1.0, and CFAC.1.5 activated carbons. These mixtures were pyrolysed at 600 °C in a conventional furnace. The ACs were characterised by FTIR, hydrophobic/hydrophilic ratio (HI), CHN/O elemental analysis, Boehm titration, surface areas (SBET), total pore volumes, and pore size distribution. These analyses show that the ACs presents several functional groups on AC surfaces and there is a predominance of hydrophilic surfaces. All the activated carbons prepared presented surface area 1050-1480 m2 g−1. Regarding the adsorption process, the kinetics data were fitted to General-order kinetic model and equilibrium of adsorption data were well represented by and Liu isotherm model. The maximum adsorption capacity of 535.5 mg g−1 was obtained at 25 °C for the sample CFAC.1.5. The thermodynamic studies have shown that the adsorption process of captopril is spontaneous and favourable. The employment of the ACs for treating simulated effluents, with different emerging contaminants, showed an excellent removal (up to 97.67%). This result is evidence that Caesalpinia ferrea seed pod wastes were a high-efficiency precursor for AC preparation and that such activated carbons could be used for treating hospital effluents containing pharmaceuticals.