Chitosan films modified with glow discharge plasma in aqueous solution of pyrrole and its evaluation in the removal of red dye no. 2

In this work, the elasticity, morphology and chemical structure of chitosan-glycerol-EDGE films treated with glow discharge plasma (GDP), in an aqueous pyrrole solution for the removal of red dye No. 2, were studied. The treatment of the films with plasma was accomplished supplying 1.57 kV voltage with a current of 0.74 A, while the working frequency was 5.54 kHz. The exposure times of the films to the plasma were 20, 40, and 60 min. Results showed that the stress-strain mechanical properties for an untreated film was 2.6 N with an elongation of 17 mm, while for the treated film was 66 N with an elongation of 6 mm; thus, improving its mechanical properties. The adsorption capacity of films, treated during 40 min at pH close to neutral using a mass of 15 mg, was qe = 757 mg/g. The morphology of the film before its treatment showed a smooth surface; while after treatment, some pores were observed, probably produced by the impact of pyrrole ions onto the surface of the film. The FTIR analysis allowed to identify the functional groups before and after films treatment; it showed a reduction of -OH groups that belongs to chitosan, and the presence of N-H, C-N, and C=C groups, which corresponds to the aromatic ring of the polypyrrole molecule.

Keywords: thin film chitosan-glycerol-polypyrrole, azo dyes, adsorption, glow discharge plasma.