Development of methacrylamide/methylmethacrylate copolymer modified biomass-carbon for superior Congo red adsorption: Leveraging RSM and machine learning for optimization and mechanistic insights

Abstract

This study reports the synthesis and performance evaluation of a novel adsorbent composite, PMMGCF, developed from Arabian date palm leaves and modified with a methacrylamide (MAAm) and methyl methacrylate (MMA) copolymer for enhanced Congo Red (CR) dye removal from water. Structural and surface characterizations using BET, TGA, XRD, FTIR, SEM, and zeta potential analyses confirmed that polymer modification significantly increased porosity, thermal stability, and surface reactivity. The PMMGCF exhibited a maximum adsorption capacity of 411.71 mg/g, outperforming the unmodified green carbon fiber (GCF). Response Surface Methodology (RSM) with Central Composite Design (CCD) identified solution pH, adsorbent dosage, and initial CR concentration as significant parameters, with a reduced quadratic model achieving an R² of 0.9755. Kinetic analysis indicated chemisorption-driven uptake following the Elovich and pseudo-second-order models (R² = 0.9899 and 0.983). The Langmuir isotherm provided the best fit (R² = 0.973), indicating monolayer adsorption. Thermodynamic analysis revealed the process to be spontaneous and endothermic (ΔH° = 34.58 kJ/mol; ΔG° = −5.11 kJ/mol at 318 K). Additionally, machine learning models were employed to predict adsorption capacity, with the Gaussian Process Regressor achieving the highest accuracy (R² = 0.96; RMSE = 0.06), demonstrating the potential of data-driven approaches for adsorption system optimization. These findings establish PMMGCF as a high-capacity, scalable adsorbent suitable for industrial wastewater treatment applications.