This study presents an advanced poly(3-hydroxybutyrate)-g-poly(2-ethyl oxazoline) (PHB-pEtOx) nanocomposite embedded with ZnO nanoparticles, engineered for efficient adsorption of Malachite Green (MG) dye from aqueous solutions. The incorporation of ZnO enhances adsorption efficiency through its high surface area and reactive properties. Comprehensive characterization using FT-IR, SEM-EDX, DSC, and 1H NMR confirmed the successful synthesis and structural integrity of the nanocomposite. The proposed approach has a limit of detection of 0.45 mu g/L and indicates a high-level capability for monolayer adsorption of 198 mg/g, with 98.7 % adsorption efficiency, a significant improvement over unmodified matrices. Kinetic modeling revealed that the adsorption process aligns closely with a pseudo-second-order model, while data fit well with Langmuir isotherm model, suggesting monolayer adsorption on a homogeneous surface. Thermodynamic parameters, including a negative Delta G degrees (-3.85 KJ/mol) and positive Delta H degrees (5.10 KJ/mol), suggested adsorption process is spontaneous and endothermic. The nanocomposite's performance was validated in practical applications using a solid-phase microextraction (SPME) system, achieving removal rates of 98.3 % from wastewater, 99.1 % from potable water, and 99.4 % from river water. These results underscore the potential of the PHB-pEtOx/ZnO nanocomposite as an effective solution for water treatment and environmental remediation, with strong scalability for broader applications.