Modification of Non-Activated Carbon from Rubber Fruit Shells with 3-(Aminopropyl)-Triethoxysilane and Its Adsorption Study on Coomassie Brilliant Blue and Methylene Blue in Solution

This study involved modifying carbon derived from rubber fruit shells, referred to as nAC-RFs, without activation. The modification process utilized a silane agent known as 3-Aminopropyl-Triethoxysilane (APTES), resulting in the formation of nAC-RFs-S. To confirm the successful modification, the adsorbent underwent characterization using an Infrared Spectrometer (IR) to identify functional groups and Scanning Electron Microscopy-Energy Dispersive-X-ray (SEM–EDX) to analyze surface morphology and constituent elements. The adsorption capacity of nAC-RFs-S was evaluated through batch adsorption experiments involving Coomassie Brilliant Blue (CBB) dye (anionic) and Methylene Blue (MB) dye (cationic). The optimal conditions for CBB and MB adsorption on both nAC-RFs and nAC-RFs-S were found to be pH 5, a contact time of 90 min, and a temperature of 27 °C. The adsorption kinetics of CBB and MB onto nAC-RFs and nAC-RFs-S followed the pseudo-second-order kinetic model. The pseudo-second-order rate constants ( k 2 ) for CBB were 2.674 × 10 –3 and 0.185 × 10 –3 (g/mg·min) for nAC-RFs and nAC-RFs-S, respectively, while for MB, the corresponding values were 2.735 × 10 –3 and 0.415 × 10 –3 (g/mg·min). CBB adsorption tended to conform to the Freundlich adsorption isotherm model on nAC-RFs, whereas, on nAC-RFs-S, it tended to align with the Langmuir adsorption isotherm model. For MB, both nAC-RFs and nAC-RFs-S exhibited adsorption tendencies that followed the Freundlich isotherm model. The nAC-RFs-S adsorbent demonstrated remarkable effectiveness in adsorbing CBB and MB in solution, with the ability to be reused for up to three cycles while maintaining an adsorption percentage exceeding 80%. Consequently, the nAC-RFs-S adsorbent holds promise as an advantageous and efficient solution for combating water pollution caused by toxic chemicals like synthetic dyes.