Green-Synthesized Ag/Zn Nanocomposites from Chlorella vulgaris Polar Extract: Sustainable Photocatalytic Water Remediation and Kinetic Modeling

Zedda, Federico;Atzori, Federico;Casu, Silvia;Sidorowicz, Agnieszka;Fais, Giacomo;Desogus, Francesco;Licheri, Roberta;Porcu, Stefania;Cao, Giacomo;Lutzu, Giovanni Antonio;Concas, Alessandro

2026-01-01

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Abstract

The growing demand for sustainable water treatment technologies requires photocatalysts that combine low environmental impact, energy efficiency, and mechanistic robustness. In this work, (Formula presented.) nanocomposites were green-synthesized using Chlorella vulgaris polar extract as a bio-mediated reducing and stabilizing agent, eliminating hazardous reagents and high-energy processing steps. Structural characterization (XRD, FTIR, SEM, UV–Vis) confirmed the coexistence of crystalline wurtzite (Formula presented.) with metallic (Formula presented.) and (Formula presented.) phases. Photocatalytic activity was evaluated through Congo Red degradation under a sequential dark–light protocol, enabling clear separation of adsorption and photoactivated pathways. During the (Formula presented.) dark stage, removal remained limited ((Formula presented.)), consistent with adsorption–desorption equilibration. Upon UV irradiation, a distinct kinetic transition occurred, leading to final removal efficiencies of (Formula presented.) after (Formula presented.). Notably, performance remained stable across the investigated photon flux range, indicating operation beyond a strictly photon-limited regime and highlighting an intrinsically energy-resilient catalytic response. A mechanistic kinetic model integrating reversible adsorption with light-dependent degradation accurately reproduced all experimental profiles ((Formula presented.)) and successfully predicted an independent dark-control experiment without additional fitting. By coupling green synthesis with quantitative kinetic validation, this study proposes a sustainability-oriented framework for designing photocatalysts that align low-impact fabrication with energy-conscious water remediation.