Sustainable metal recovery from bio-leach liquor using extracellular polymeric substances (EPS) produced by cyanobacteria Synechocystis sp. IMMT47

Abstract

Sustainable recovery of valuable metals from primary and secondary wastes are essential for circular economy and critical metal conservation. In this study, a bio-based ecofriendly method for metal recovery is demonstrated using a natural biopolymer, extracellular polymeric substance (EPS) produced by the cyanobacteria Synechocystis sp. IMMT47. EPS, was used to recover manganese and iron from low-pH leach liquor derived from bioleaching of polymetallic nodules (PMNs). The influence of pH, EPS dosage, and metal concentration on recovery efficiency was evaluated. High recovery rates of manganese (85.18%) and iron (99.73%) were achieved even at low pH of 2, eliminating the need for neutralization-a major cost and environmental constraint in conventional hydrometallurgy. This study is first to report application of cyanobacterial EPS for direct metal recovery under acidic conditions, offering a sustainable and low-impact alternative to traditional chemical processes such as precipitation and solvent extraction. This approach aligns with green extraction technologies and zero-waste resource management principles.