A Fully Green Process Based on Recycled Primary Zn–C Battery and Natural Lemon Extract for Highly Efficient, Salt Tolerant, and Multi‐Use Desalination

Solar evaporation for seawater desalination requires solar absorber materials with high solar‐to‐thermal conversion efficiency, good heat retention ability, and salt tolerance. The material purity standards for the stated purpose are not very stringent; hence, recycled materials can potentially address both the issues of affordability and functionality concurrently. In this work, we demonstrate that recycled battery waste (BW) material from spent primary Zn–C batteries (which are commonly used in many household applications and thrown away), after being treated with squeezed real Lemon extract (BWLx), renders very impressive solar desalination evaporation rate of 4.02 ± 0.16 kg m ⁻² h ⁻¹ under 1 sun irradiation in 3.5 wt.% (or even higher concentration) saline water, with excellent stability for multiple uses. The BW material mainly comprises ZnMn ₂ O ₄ spinel phase with carbon, with a small amount of Zn ₅ (OH) ₈ Cl ₂ H ₂ O (simonkolleite). Importantly, lemon extract treatment of BW improves the performance significantly, and it works much better than citric acid treatment which is attributed to enhanced heat retention by its constituents. Thorough characterizations of the materials using multiple techniques and also the evaporation process reveal the mechanistic aspects responsible for impressive performance.