Synthesis and characterization of alginate-polyacrylic acid/multiwalled carbon nanotubes composite with efficient removal for nigrosine dye

The current study detailed the efficacy of a simply prepared alginate-polyacrylic acid/functionalized multiwalled carbon nanotubes (Alg-PAA/f-MWCNTs) composite for adsorption of nigrosine dye (acid black II) from aqueous environments. Firstly, preparation of the Alg-PAA/f-MWCNTs composite was achieved via gamma radiation-induced template polymerization of AA onto the Alg/f-MWCNTs surface. The maximum grafting efficiency (GE%) of AA onto the surface of Alg/f-MWCNTs was ~ 82% under the optimized conditions: (2.5 wt% Alg, 30 wt% AA, 0.5 wt% f-MWCNTs, 0.6 wt% N,N'-methylenebisacrylamide (NMBA), and irradiation dose ~ 20 kGy). The structural characteristics, thermal features as well as the morphological appearance of the Alg-PAA/f-MWCNTs composite were validated using different analyses including FTIR, TGA, DTA, XRD and SEM. Additionally, the composite exhibited uniform particle size distribution (~150.7 nm), point of zero charge at pH = 6.28, and negative Zeta potentials of a minimum at pH = 2. The adsorption batch experiments showed good adsorption capacity for the nigrosine dye from their aqueous media with adsorption efficiency up to 83% using the batch technique at pH = 2.0 for 420 min. The adsorption of nigrosine dye onto Alg-PAA/f-MWCNTs is favorable thermodynamically, obeying the Freundlich isotherm model and controlled by a chemisorption mechanism. Additionally, the composite showed a good regeneration ability up to five times with almost the same removal of ~80%. The results demonstrated that the Alg-PAA/f-MWCNTs composite could be a promising candidate for the removal of nigrosine dye from industrial aqueous environments.