Adsorptive removal of Basic Red 46 by raw corn cob: Optimization using response surface methodology, kinetic modeling, and thermodynamic analysis

Dye-bearing water represents a serious and current drawback that concerns the entire society.An efficient and growing alternative for its treatment is the use of unconventional adsorbents.This work evaluated the adsorption of basic red 46 dye (BR46) onto raw corn cob (CC) using statistical tools.Particularly, a 2 3 factorial design, a steepest ascent approach and an orthogonal central composite surface design were performed, obtaining an optimized process and the interaction between its factors.A removal of 98.1% under a dosage of 5.5 g L -1 , initial BR46 concentration of 16.6 mg L -1 and contact time of 201.9 min was achieved.The assessment of the equilibrium and kinetics of the BR46-CC system showed the best fit with pseudo-second-order kinetics with R 2 = 0.94, while for equilibrium, a better fit was observed with the Redlich-Peterson isotherm, with R 2 = 0.99.Thermodynamic parameters proved a spontaneous and exothermic process, with an average Gibbs free energy of -10.0 kJ mol -1 and enthalpy of -27.2 kJ mol -1 .The entropy of -54.7 J mol -1 K -1 suggests a reduction in the vibrational capacity of the molecules involved in the process.Furthermore, chemical oxygen demand was evaluated to verify the improvement in water quality after the adsorption process, obtaining a 29% reduction in organic load.These findings highlight the potential of corn cob as a promissory and non-conventional adsorbent for environmental remediation of dye-contaminated water bodies.