Bromophenol blue adsorption onto maize cob-derived activated carbon: process optimization, kinetic modeling, and isotherm studies

The release of synthetic dyes into wastewater poses serious environmental and health risks, necessitating efficient and low-cost treatment solutions. This study investigates the adsorption performance of maize cob-derived activated carbon for bromophenol blue removal, integrating adsorbent characterization, process optimization, and mechanistic modeling. Activated carbon produced via phosphoric acid activation and thermochemical carbonization was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy, which confirmed the development of functionalized surfaces and well-defined porosity. A Box–Behnken design was applied to optimize agitation speed, dye concentration, contact time, and adsorbent dosage, achieving a maximum removal efficiency of 99.95% under optimal conditions. Kinetic modeling showed that the pseudo-second-order model best described the adsorption process ( = 0.9983), indicating chemisorption as the rate-controlling mechanism. Equilibrium data were most consistent with the Temkin isotherm ( = 0.9722), suggesting adsorption on energetically heterogeneous surfaces with a gradual decrease in adsorption energy as coverage increased. Overall, the results demonstrate that maize cob–derived activated carbon is an effective, sustainable adsorbent for dye remediation and highlight its potential for application in wastewater treatment systems. Keywords: Bromophenol blue, Maize cob-derived activated carbon, Pseudo-second-order kinetic model, Response surface methodology, Temkin isotherm model The release of synthetic dyes into wastewater poses serious environmental and health risks, necessitating efficient and low-cost treatment solutions. This study investigates the adsorption performance of maize cob-derived activated carbon for bromophenol blue removal, integrating adsorbent characterization, process optimization, and mechanistic modeling. Activated carbon produced via phosphoric acid activation and thermochemical carbonization was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy, which confirmed the development of functionalized surfaces and well-defined porosity. A Box–Behnken design was applied to optimize agitation speed, dye concentration, contact time, and adsorbent dosage, achieving a maximum removal efficiency of 99.95% under optimal conditions. Kinetic modeling showed that the pseudo-second-order model best described the adsorption process ( = 0.9983), indicating chemisorption as the rate-controlling mechanism. Equilibrium data were most consistent with the Temkin isotherm ( = 0.9722), suggesting adsorption on energetically heterogeneous surfaces with a gradual decrease in adsorption energy as coverage increased. Overall, the results demonstrate that maize cob–derived activated carbon is an effective, sustainable adsorbent for dye remediation and highlight its potential for application in wastewater treatment systems.