Effective photocatalytic and antibacterial nanomembranes from a GO-grafted dapsone-incorporated chitosan/gelatin blend for enhancing the removal of toxic dyes from wastewater

Abstract

Organic dyes, such as Eriochrome Black T (EBT) and methyl green (MG), are widely used in the textile industry, leading to their accumulation in the environment. Thus, the present study aimed to synthesise functional graphene oxide-grafted dapsone (GOgD), which was incorporated into a chitosan/gelatin (CGe) blend at different dosages (10%, 20%, and 30%) for the preparation of nanomembranes. A series of techniques and tests, including FT-IR spectroscopy, XRD, Raman spectroscopy, SEM, and mechanical and antibacterial property analyses, were applied for the characterization of functional GOgD and nanomembranes. Moreover, ultraviolet and visible light irradiations were used to evaluate the photocatalytic degradation of the EBT and MG dyes. The data revealed that optimum mechanical properties were found for CGe–GOgD 20%, with a value of ∼85 MPa, compared with the unfilled blend (61.35 MPa). However, the CGe–GOgD 30% nanomembrane exhibited the best photocatalytic activity for the degradation of EBT at pH 5.0 and that of MG at pH 8.0, with degradation efficiencies of 90.8% and 97.9% under visible light and 83% and 90% under UV light, respectively. The kinetics of degradation for both dyes showed pseudo-first-order kinetics. The mechanism involved the production of the highly oxidizing species ˙OH and ˙O₂⁻ upon light irradiation, which initiated the dye degradation process, generating CO₂ and H₂O as the reaction byproducts, with complete degradation until 120 min. The photocatalyst can be regenerated and reused three times, which decreases the cost of operation. The final impact on the antibacterial activities of the nanomembranes was also investigated, and the data revealed their strong antibacterial properties against E. coli and S. aureus with different inhibitory zone diameters ranging from 21 to 34 mm, as compared with the pristine matrix. In addition to the sustainable environmental benefits of the prepared CGe–GOgD 30% nanomembrane due to the degradation of harmful organic dyes, a strong antibacterial activity was observed, highlighting its wider environmental significance and promising applications in several ecological domains.