Eco-friendly alginate/PCL-TiO2 hybrid biocomposites: Preparation, properties, and methylene blue photodegradation

• Eco-friendly hybrid biocomposites were successfully synthesized using alginate, PCL, and TiO 2 fillers through an environmentally friendly method. • The addition of TiO 2 increased the crystallinity and thermal stability of the biocomposites, while slightly decreasing mechanical strength. • The biocomposites exhibited effective photocatalytic degradation of methylene blue, indicated by a color change from blue to transparent after 24 h of irradiation. • The hybrid biocomposite can be separated and recycled without any external intervention, making it environmentally friendly and cost-effective. The study focuses on developing an environmentally friendly method for synthesizing hybrid biocomposites using sodium alginate, polycaprolactone (PCL), and TiO 2 fillers. The eco-friendly alginate/PCL-TiO 2 hybrid biocomposites were prepared using a Rheomixer Polylab OS. Various characterization techniques, including XRD, FT-IR, UTM, DSC, TGA, biodegradation testing, and methylene blue photodegradation, were employed to evaluate the properties of the composites. XRD analysis of the composites PA, PA-Ti1, PA-Ti3, and PA-Ti5 revealed an orthorhombic to tetragonal semicrystalline structure after added TiO 2 . FT-IR spectroscopy show sharp peak at 1721 cm⁻¹ represents C = O vibration, while characteristic C H stretching vibrations of PCL are evident at 2800–2900 cm -1 . Furthermore, Ti-O-Ti bond appears at wave number 668.48 cm −1 and Ti-O-C appears at 1054.69 cm −1 . The addition of TiO 2 slightly reduced mechanical properties. TiO 2 influence the compound mechanical performance, with a decrease in elastic modulus and corresponding increase in elongation at break with increasing TiO 2 content. DSC analysis revealed that the composites with TiO 2 displayed a single melting peak slightly above 50 °C, with a significant increase in ∆Hm with TiO 2 content. TGA results showed that all samples exhibited two stages of decomposition. The first stage, occurring around 200 °C and the second stage, observed above 300 °C. The PA composite showed a mass reduction from 0.058 g to 0.052 g, similar to PA-Ti1 and PA-Ti3. However, PA-Ti5 composite showed a smaller mass reduction. Methylene blue solutions containing PA-Ti1, PA-Ti3, and PA-Ti5 composites exhibited a color change from blue to transparent after 24 h of irradiation, indicating MB degradation.