Green laser-ablated CdS nanoparticles in aloe vera medium: structural, optical, electrochemical, and synergistic photocatalytic–adsorptive performance for pentachlorophenol degradation

According to the principles of green chemistry, this work presents a sustainable way to produce cadmium sulfide (CdS) nanoparticles using laser liquid ablation (LLA) in a natural Aloe vera medium. TEM and FE-SEM revealed nearly spherical particles of about 40 nm with a uniform distribution. In comparison, XRD analysis verified a mixed cubic–hexagonal crystalline phase with an average crystallite size of 28.5 nm. The prepared nanoparticles' purity was confirmed by EDX. Photoluminescence spectra showed both near-band-edge emission and defect-related states, indicating dual recombination pathways important to photocatalysis, and optical investigations showed a direct band gap of 2.5 eV. Pentachlorophenol (10 ppm), a persistent organic pollutant, was photocatalytically degraded in 120 min with 98% removal and 97% mineralization using CdS nanoparticles (0.01 g/100 mL) exposed to direct sunlight (1200 W.m⁻²). Adsorption fitted both the Langmuir and the Freundlich models (R² = 0.997), indicating multilayer adsorption on heterogeneous surfaces, while thermodynamic analysis confirmed spontaneity (ΔG < 0) and an endothermic, physisorption-driven process. With current densities of 23 and 15 mA.cm⁻² and low resistance values (Rs = 0.7 Ω.cm² Rct = 4.1 Ω.cm²), photoelectrochemical measurements showed effective charge separation. These results illustrate the ability of CdS nanoparticles to act as materials for environmentally sustainable water purification.