Bi-model cationic dye adsorption by native and surface-modified Trichoderma asperellum BPL MBT1 biomass: From fermentation waste to value-added biosorbent

In this study, we aimed to assess the possible reusability of native and surface-modified waste biomass of a novel ascomycetes fungi Trichoderma asperellum BPL MBT1 for the adsorption of triphenylmethane dyes. Spent biomass obtained from fermentation medium has been applied in the uptake of model cationic dyes viz., crystal violet and malachite green. Optimization of experimental parameters by batch mode studies revealed that dye adsorption is influenced by medium pH time, initial concentration of dyes, and adsorbent dosage. It was observed that pH 10 was optimum for cationic dye adsorption. Further, the adsorption process obeyed the bi-model (Langmuir–Freundlich model) isotherm and adhered to pseudo-second-order kinetics. The involvement of ion exchange as the dominant mechanism of dye adsorption was indicated by the mean free energy obtained from Dubinin–Radushkevich isotherm. Cellular morphology and the involved functional groups were studied by scanning electron microscopy and Fourier transform infrared spectroscopy that revealed the presence of carbon and oxygen containing groups on the surface. Maximum desorption efficiency was achieved using a 0.1 M solution of HCl and the stability of the biosorbent was confirmed through reusability analysis. Our results confirm the applicability of both native and surface-modified T. asperellum BPL MBT1 biomass as a potential biosorbent for the sustainable wastewater treatment and safe dye disposal. [Display omitted] •Reusable biosorption potential of cationic dyes by T. asperellum was assesed.•Biosorption obeyed hybrid isotherm and fits with the pseudo-second-order kinetics.•Biosorption was controlled by ion exchange mechanism.•Autoclaved biomass of T. asperellum was effective in the removal of dyes.•Successful conversion of spent biomass into value-added adsorbent.