Green synthesis of zinc oxide nanoparticles from Pistia stratiotes for triclosan degradation in greywater

Abstract

Triclosan is a widely used antimicrobial compound commonly incorporated into personal care products, raising significant environmental concerns because of its persistence and toxicity in greywater systems. This research examined the photocatalytic degradation of triclosan in artificial bathroom greywater using zinc oxide nanoparticles that were synthesized using a green method with Pistia stratiotes extract. The nanoparticles were synthesized using a precipitation process and characterized through ultraviolet–visible spectroscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, atomic force microscopy and Raman spectroscopy. The tests confirmed their crystalline structure, spherical morphology (30–87 nm), and surface functionalization by phytochemicals. Photocatalytic experiments were carried out under UV light, optimizing parameters such as pH (5–9), catalyst dosage (0.05–0.20 g), and triclosan concentration (1–20 mg/L) through response surface methodology utilizing a face-centred central composite design. The optimal conditions for degradation were a pH of 7, a catalyst loading of 0.125 g, and initial triclosan concentration of 10.5 mg/L, which led to a peak degradation efficiency of 94.63%. Kinetic modelling indicated that the degradation of triclosan adhered to a pseudo-first-order model, exhibiting a strong correlation coefficient of 0.9862 and a rate constant of 0.0318 min⁻ 1 . The Langmuir–Hinshelwood model demonstrated notable linearity, evidenced by a correlation coefficient of 0.9651, suggesting that surface-mediated interaction played a crucial role in the photocatalytic degradation process.

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