Carbon nanomaterials from cassava rhizome for efficient toluene removal from aqueous solutions: Continuous adsorption studies using local and global optimization

• Cassava-derived carbon adsorbs toluene from water effectively. • Adsorption capacity optimized using RSM and GRG techniques. • Local optimization achieved 211.051 mg/g adsorption capacity. • Global optimization improved capacity to 211.517 mg/g. This study explores cassava rhizome-derived carbon nanomaterials for continuous toluene adsorption from water. The research focuses on their preparation, characterization, and adsorption capacity through continuous adsorption studies. Optimization was performed using response surface methodology (RSM) and generalized reduced gradient (GRG) to determine ideal conditions. RSM optimization yielded a maximum adsorption capacity of 211.051 mg/g at a flow rate of 20.69 mL/min, bed height of 9.85 cm, initial toluene concentration of 94.50 ppm, and contact time of 207.83 min, with a desirability value of 1.000. GRG further improved the capacity to 211.517 mg/g under optimized conditions of 20.80 mL/min flow rate, 10.71 cm bed height, 97.60 ppm initial toluene concentration, and 210.31 min contact time. These results highlight the potential of cassava rhizome-derived carbon nanomaterials as effective adsorbents for toluene removal from aqueous solutions.