This study investigates the enhanced adsorption of methylene blue (MB) dye on functionalized multi-walled carbon nanotubes (MWCNT-S), which are modified with benzenesulfonate groups. The functionalized MWCNT-S showed improved dispersibility in water and higher adsorption capacity compared to pristine MWCNT. Adsorption kinetic studies revealed a rapid process, with MWCNT-S demonstrating a significantly higher adsorption rate than both unfunctionalized MWCNT and activated carbon. The adsorption capacity of MWCNT-S was more than doubled compared to pristine MWCNT, attributed to increased surface area and electrostatic interactions between the cationic MB and anionic sulfonate groups. The material also exhibited reversibility, allowing for regeneration through competition with salts, with a 75% regeneration capacity achieved using 1 M NaCl. The study also evaluated the effects of pH, ionic strength, and temperature on adsorption, finding that MWCNT-S performed well under various conditions. The results indicate that functionalized MWCNT-S is a promising adsorbent for dye removal from wastewater due to its high efficiency, fast kinetics, and regeneration potential.This study investigates the enhanced adsorption of methylene blue (MB) dye on functionalized multi-walled carbon nanotubes (MWCNT-S), which are modified with benzenesulfonate groups. The functionalized MWCNT-S showed improved dispersibility in water and higher adsorption capacity compared to pristine MWCNT. Adsorption kinetic studies revealed a rapid process, with MWCNT-S demonstrating a significantly higher adsorption rate than both unfunctionalized MWCNT and activated carbon. The adsorption capacity of MWCNT-S was more than doubled compared to pristine MWCNT, attributed to increased surface area and electrostatic interactions between the cationic MB and anionic sulfonate groups. The material also exhibited reversibility, allowing for regeneration through competition with salts, with a 75% regeneration capacity achieved using 1 M NaCl. The study also evaluated the effects of pH, ionic strength, and temperature on adsorption, finding that MWCNT-S performed well under various conditions. The results indicate that functionalized MWCNT-S is a promising adsorbent for dye removal from wastewater due to its high efficiency, fast kinetics, and regeneration potential.