Synthesis of CdS and ZnS to enhance the photocatalytic degradation of fluoroquinolone antibiotics and textile dye

This study presents CdS and ZnS nanoparticles as multifunctional photocatalysts for simultaneous degradation of fluoroquinolone antibiotics (ciprofloxacin and levofloxacin) and Congo red dye with concurrent antimicrobial activity under visible-light irradiation. Nanoparticles synthesized via chemical precipitation exhibited cubic zinc-blende structures with crystallite sizes of 2.1 -2.6 nm (CdS) and 23.5-31.3 nm (ZnS), confirmed by XRD analysis. FTIR spectroscopy revealed metal-sulfur lattice vibrations at 632 cm-1 (Cd-S) and 650 cm-1 (Zn-S), while EDX confirmed stoichiometric composition (CdS: 75.01 wt% Cd, 24.99 wt% S). Williamson-Hall analysis indicated microstrain values of 1.98-7.77 × 10-3 for CdS and 4.42-5.89 × 10-2 for ZnS, suggesting moderate lattice distortion. CdS demonstrated superior photocatalytic performance attributed to its optimal bandgap and point of zero charge (PZC ≈ 6.0), achieving near-complete degradation of target pollutants through enhanced reactive oxygen species generation. Antimicrobial assays revealed CdS exhibited broad-spectrum activity against S.aureus (9.3±0.36 mm) and S.abony (8.3±0.42 mm), while ZnS showed limited activity only against S.abony (9.5±0.50 mm). Both materials remained inactive against L. monocytogenes, E. coli and Candida albicans (<6 mm). The superior multifunctional performance of CdS, combining efficient visible-light photocatalysis with selective antimicrobial activity, establishes it as a promising single-material solution for next-generation water treatment systems addressing pharmaceutical contamination and microbial threats in aquatic environments.