Utilization of montmorillonite in biostoning process as a strategy for effluent reuse

BACKGROUND Biostoning using cellulase is a process used in place of the traditional stone‐washing of denim. This process guarantees a more controlled removal of the Indigo blue dye from the cotton fibers, giving an aged‐look and softness to denim. However, it also causes backstaining and generates a high volume of colored effluent. In this context, this work evaluated the possibility to reuse the effluent from the biostoning process combined with montmorillonite addition. It is an attractive and sustainable alternative to the conventional process. RESULTS In this study, four biostoning processes were conducted and the results showed that the moment of the montmorillonite addition affected the washing effects. Clay addition after 40 min of beginning of the process provided washing effects on denim similar to those obtained by traditional biostoning and the highest effluent discoloration percentage (above 96%). Moreover, due to Indigo dye adsorption, the clay addition reduced the backstaining. The results also showed the that washing effects obtained after two consecutive reuses were not significantly different from those obtained with fresh water. CONCLUSION Adding montmorillonite to biostoning led to a discolor effluent that can be used in repeated processing. Overall, the utilization of clay in the process can be considered a promising alternative to reduce water consumption and environmental impacts without compromising the washing effects. © 2020 Society of Chemical Industry (SCI)