•CMC/kC/AMMT composite beads were developed for the adsorption of MB dye.•The adsorption process has been conducted under different adsorption conditions.•CMC/kC/AMMT composite beads adsorb more MB dye than plain CMC and kC beads.•Results have been tested by using isotherm and classical kinetic models.•CMC/kC/AMMT composite beads were successfully reused for five adsorption-desorption cycles. In the present study, new composite beads based on carboxymethyl cellulose (CMC)/k-carrageenan (kC)/activated montmorillonite (AMMT) were prepared for adsorptive removal of cationic methylene blue (MB) as a dye model. The structure and morphology of the composite beads were investigated by FT-IR and SEM, while the thermal properties were tested using TGA. Factors affecting the removal percent of MB such as CMC/kC/AMMT ratios, initial MB concentration, pH medium, adsorbent dosage, solution temperature, and agitation speed were also explored. Results demonstrated that MB removal (%) exceeded 92% after 120 min using CMC/kC/AMMT (1:1:0.4 ratio) compared to 69% in case of free AMMT beads. Moreover, data obtained from isotherm studies were fitted well to Langmuir model (R2=0.999), and the kinetics of adsorption followed pseudo-second order model. Finally, the composite beads showed good reusability for MB dye removal with high efficiency. Results obtained from this study suggest that the prepared composite beads could be applied effectively for removing cationic dyes from aqueous solutions.