Synthesis of CarAlg/MMt nanocomposite hydrogels and adsorption of cationic crystal violet

•CarAlg nanocomposites from binary mixture of kappa-carrageenan and sodium alginate.•Introduction of montmorillonite nanoclay in CarAlg hydrogel as nanoclay.•Evaluation of CarAlg/MMt nanocomposites to remove crystal violet dye.•Maximum dye adsorption capacity of nanocomposites was obtained 88.8mgg−1.•Improvement of dye adsorption at acidic media by introducing of kappa-carrageenan. CarAlg/MMt nanocomposite hydrogels composed of kappa-carrageenan (Car) and sodium alginate (Alg) biopolymers were synthesized by incorporation of sodium montmorillonite (Na-MMt) nanoclay. Acrylamide (AAm), methylenebisacrylamide (MBA), and ammonium persulfate (APS) were used as monomer, crosslinker, and initiator, respectively. The structure and morphology of nanocomposites were characterized by XRD, SEM, and TEM techniques. The XRD results showed exfoliated MMt nanoclay and exfoliation of MMt was confirmed by TEM graph. The resulting nanocomposites were evaluated to remove cationic crystal violet (CV) dye from water. According to data, the adsorption capacity of nanocomposites was enhanced as the clay content was increased. The experimental data were analyzed according to both Langmuir and Freundlich models and experimental maximum adsorption capacity was obtained 88.8mgg−1. By studying the effect of pH on the dye adsorption capacity of nanocomposites, it was revealed that the adsorption capacity of nanocomposites was enhanced at acidic pHs as the Na-MMt nanoclay and kappa-carrageenan components were increased.