Efficient adsorptive removal of Congo Red dye using activated carbon derived from Spathodea campanulata flowers

Addressing the environmental threat posed by dye-contaminated wastewater, this study presents the development of a high-performance activated carbon (SCAC) synthesized from Spathodea campanulata flowers for the efficient removal of Congo Red (CR) dye from aqueous systems. Chemical activation using orthophosphoric acid (H3PO4) at a relatively low temperature (400 ℃) yielded a mesoporous carbon with a high BET surface area of 986.41 m2/g and a pore volume of 0.8797 cc/g, outperforming many floral biomass-based activated carbons reported in the literature. Comprehensive characterization using FESEM, EDS, FTIR, XRD, and XPS confirmed the formation of a porous structure with abundant oxygen-rich functional groups, favorable for dye adsorption. Batch adsorption experiments revealed that the process was highly effective at pH 7.0 and 303 K, fitting best to the Langmuir isotherm model with a maximum adsorption capacity (qm) of 59.27 mg/g. Kinetic analysis followed a pseudo-second-order model, indicating chemisorption, supported by thermodynamic data showing endothermic and spontaneous behavior (ΔH° = 42.48 kJ/mol, ΔG° < 0). Methanol was identified as the optimal desorbing agent, and SCAC demonstrated excellent regeneration potential with a marginal reduction of only 43.49 % in adsorption capacity after six cycles. In tests with real water matrices, SCAC demonstrated significantly higher removal efficiency in natural waters than control, suggesting enhanced adsorption in complex matrices. These findings underscore the practical applicability of SCAC in real-world wastewater treatment, offering a promising solution for large-scale industrial applications.