From waste to resource: Evaluation of zinc compounds recovered from spent batteries as antimicrobial additives for paints with photoactivity potential

Abstract

The recovery of valuable compounds from spent alkaline batteries offers a promising pathway for reducing hazardous waste while enabling the development of functional materials for advanced applications. In this work, zinc-based compounds obtained through a hydrometallurgical route were transformed into antimicrobial and photoactive additives for water-based architectural coatings. Calcination yielded nanostructured ZnO-rich solids, while sulfur incorporation further modified defect chemistry and surface composition, as confirmed by XRD, FTIR, UV–Vis, SEM/EDS and TEM analyses. These structural changes strongly impacted on functional perfor mance. Paints formulated with the recovered materials exhibited significant antimicrobial activity, with inhibition zone diameters reaching 30.2 ± 1.0 mm against P. commune and 27.6 ± 1.9 mm against S. aureus for the WC-Zn samples. Sulfur-modified materials enhanced photoactivity, enabling up to 58% photodegradation of Rhodamine B under UV irradiation and producing measurable color shifts in paint films (ΔE values up to 2.49). The results demonstrate that battery-derived zinc compounds can be engineered into multifunctional coating additives displaying both antimicrobial and photoactive behavior, representing a viable circular-economy strategy for the development of sustainable and high-performance bioactive paints.