Fungal Waste-Biomasses as Potential Low-Cost Biosorbents for Decolorization of Textile Wastewaters

The biosorption potential of three fungal waste-biomasses (Acremonium strictum, Acremonium sp. and Penicillium sp.) from pharmaceutical companies was compared with that of a selected biomass (Cunninghamella elegans), already proven to be very effective in dye biosorption. Among the waste-biomasses, A. strictum was the most efficient (decolorization percentage up to 90% within 30 min) with regard to three simulated dye baths; nevertheless it was less active than C. elegans which was able to produce a quick and substantial decolorization of all the simulated dye baths (up to 97% within 30 min). The biomasses of A. strictum and C. elegans were then tested for the treatment of nine real exhausted dye baths. A. strictum was effective at acidic or neutral pH, whereas C. elegans confirmed its high efficiency and versatility towards exhausted dye baths characterised by different classes of dyes (acid, disperse, vat, reactive) and variation in pH and ionic strength. Finally, the effect of pH on the biosorption process was evaluated to provide a realistic estimation of the validity of the laboratory results in an industrial setting. The C. elegans biomass was highly effective from pH 3 to pH 11 (for amounts of adsorbed dye up to 1054 and 667 mg of dye g−1 biomass dry weight, respectively); thus, this biomass can be considered an excellent and exceptionally versatile biosorbent material.