Eco-friendly removal of disperse dyes from polyester

Abstract

The frequent contamination to the environment posed by synthetic dyes and chemical auxiliaries is persistently growing concern in almost industrialized countries. Industrial effluent is hazardous to environment by several respects especially in terms of pH, dissolved oxygen (DO) and other water quality parameters. Various standardized chemical methods for the treatment of industrial effluents are available but increased research efforts have been focused to substitute the chemical methods by eco-friendly biological treatments. The present work has been directed to contribute in the same replacing chemical treatment for the washing and degradation of surplus disperse dye from the dyed polyester fabric (reduction clearance) with an eco-friendly approach based on white rot fungi (biological clearance). The present work was designed to evaluate the ability of four indigenous strains of white rot fungi (WRF), including Pleurotus ostreatus IBL-02, Ganoderma lucidum IBL-05, Trametes versicolor IBL-04 and Schizophyllum commune IBL-06 for the removal and degradation of surplus disperse dye, Foron Rubine RD-GFL 200, from dyed polyester fabrics in Kirk’s basal medium (Biological Clearing). Color strength (%) and washing fastness results were considered to evaluate the comparison between biological clearing and chemical clearing. In initial screening, Ganoderma leucidum demonstrated better clearing performance as compared to other WRF as well as standard chemical treatment, after an incubation time of 10 days, at 4.5 pH and 30°C temperature. Physical factors such as pH, temperature and incubation period were optimized by Response Surface methodology to explore the better viability of biological process. Effectiveness of nitrogen and carbon additives, low molecular mass mediators and metal ions on biological clearing were also studied. The optimal biological clearing was achieved in 135 hours of incubation period, at 6 pH, 35°C temperature and in a medium containing Glucose (additional carbon source), NH4H2PO4 (additional nitrogen source), MnSO4 (mediator) and ZnSO4 (metal ion). The potential influences of ligninolytic enzymes such as LiP, MnP and Laccase secreted during each biological process were also investigated and found positively correlated to the enhancements in the biological process. The best optimized set of conditions was further investigated for the biological clearing of polyester fabric dyed with two more disperse dyes Foron Brilliant Yellow S-6GL and Foron Blue E-BL 150 which survived the superior efficiency of biological treatment. In short, biological clearing treatment may prove much superior in context to quality of fabric and safety of environment.