Green preparation of polydopamine-modified multiwalled carbon nanotube/calcium alginate composite aerogels for effective adsorption of methylene blue

Polydopamine-modified multiwalled carbon nanotube/calcium alginate (P-CNTs/CA) aerogel was greenly prepared. The synthesis method of the P-CNTs/CA aerogel was evaluated for its environmental friendliness. SEM, FT-IR, Raman, TGA, BET, XPS, and Zeta potential characterized the P-CNTs/CA aerogel. Batch adsorption experiments were conducted to assess the adsorption efficacy of the P-CNTs/CA aerogel on methylene blue (MB). The results demonstrated that the maximum theoretical adsorption capacity of the P-CNTs/CA aerogel for MB was 506.12 mg center dot g(-1). The adsorption kinetics analysis indicated that the adsorption of MB by the P-CNTs/CA aerogel was more consistent with the pseudo-second-order model. The adsorption isotherm analysis demonstrated that the Sips model exhibited the most accurate fit to the experimental data. The adsorption thermodynamics showed that the adsorption process was spontaneous and heat-absorbing. The adsorption mechanism of MB adsorption by P-CNTs/CA aerogel was analyzed graphically by the density functional theory (DFT) and independent gradient model (IGM), which revealed the involvement of hydrogen bonding, electrostatic, and dispersive interactions. In parallel, the distribution of adsorption forces was analyzed using isosurfaces. Adsorption desorption experiment showed that the P-CNTs/CA aerogel maintained 79 % removal capacity after six adsorption cycles.