Hydrometallurgical Recovery and Complexation of Zn and Mn from Spent Batteries for Micronutrient Fertilizer Development: Leaching Optimization and Characterization

Spent primary batteries pose significant environmental challenges, while agricultural systems increasingly demand sustainable micronutrient fertilizers to address widespread zinc and manganese deficiencies in crops. This study aims to develop a facile synthesis method for producing chelated micronutrient fertilizers (Na<inf>2</inf>Zn-EDTA and Na<inf>2</inf>Mn-EDTA) from spent primary batteries via selective metal recovery and complexation. The recovery of Zn and Mn leaching parameters was optimized using response surface methodology. The proposed approach involved the sequential leaching of black mass from dismantled batteries to extract zinc and manganese, followed by conversion to EDTA complexes. Comprehensive characterization was performed using XRD, FTIR, SEM, EDX, AAS, TG-DTA, and UV-Visible spectroscopy to evaluate the synthesized products. Results revealed highly crystalline chelated fertilizers with substantial metal contents of 13.3 w/w Zn and 12.7 w/w Mn, exhibiting high purity. Pot trials using Capsicum frutescens demonstrated promising fertilizer efficacy, with the mixed treatment achieving a 43 increase in plant height compared to control groups over 77 days. This research successfully demonstrates the conversion of electronic waste into high-quality agricultural inputs, providing dual environmental benefits through waste valorization and sustainable fertilizer production. © The Minerals, Metals & Materials Society 2025.