Recycling Industrial Waste: Ferritization Products for Zn²⁺ Removal from Wastewater

This study presents a sustainable approach to recycling exhausted etching solutions through ferritization, using various activation methods and aeration rates. The process transforms industrial waste into valuable magnetic sorbents, supporting circular economy principles. Structural and chemical analysis of the ferritization products revealed the formation of ferromagnetic crystalline phases, including lepidocrocite (ɣ-FeOOH), ferrooxygite (δ-FeOOH), and magnetite (Fe₃O₄). Increasing the aeration rate and use of ultrasound treatment enhances Fe₃O₄ content and iron ion removal efficiency. The adsorption capacity of the recycled materials for Zn²⁺ removal was assessed under different pH conditions using mechanical mixing and ultrasound treatment. The highest level of Zn²⁺ removal (92.0%) was achieved at pH 8 with ultrasound-activated sorbents containing 61.3% δ-FeOOH and 38.7% Fe₃O₄. At pH 10, magnetite-based sorbents achieved over 98.9% Zn²⁺ removal, enabling the treated water’s reuse in industrial rinsing processes. Electron microscopy and X-ray fluorescence confirmed the presence of fine, spherical magnetite and zinc ferrite particles. These findings underscore the potential of ferritization-based recycling as an eco-friendly and efficient strategy for heavy metal removal from galvanic wastewater.