Flax processing waste – A low-cost, potential biosorbent for treatment of heavy metal, dye and organic matter contaminated industrial wastewater

A huge quantity of dye and heavy metal contaminated wastewater is generated from the textile industries every year all over the world. Additionally, water retting of flax fibre in sub-tropical humid climate also produces bulk amount of wastewater. Extraction of flax fibre from stem produces a large quantity of flax processing waste mainly composed of broken shives. A potential and cost-effective biosorbent can be formulated using these flax processing wastes to remediate the wastewater. However, no such previous studies were conducted to evaluate its potentiality as a biosorbent in detail. Keeping such a wide research-gap in mind, this study was done to explore the potentiality of almost freely available flax processing waste as a biosorbent. The present study demonstrated the efficient adsorption of heavy metals like adsorption of zinc (Zn), lead (Pb), and copper (Cu) as well as reduction of dyes viz. malachite green (MG), methylene blue (MB) and Congo red (CR) from contaminated wastewater treated with flax-biosorbent. Calculated maximum adsorption capacity values were obtained as 8.32, 13.35, and 7.12 mg g−1 for Cu, Pb, and Zn, correspondingly; and 163.9, 94.3 and 85.5 mg g−1 for MB, MG, and CR, respectively. Such values strongly indicate the higher adsorption competence of the flax-waste based biosorbent. The optimum pH ranged from 5.0 to 7.0 concerning heavy metal-adsorption on this biosorbent, while, the optimal pH for the removal of dyes was ranged from 6.5 to 6.7. The adsorption kinetics for heavy metals and dyes followed the pseudo-second-order path. Significant improvements of flax-retting wastewater were also found after treating it with flax-biosorbent at the rate of 2 g L−1. All these results strongly depict the potentiality of flax processing waste as a low-cost biosorbent to treat industrial wastewater as well as the leftover flax retting water. Thus, this technology might be a breakthrough to ensure cleaner production and sustainable development goals.