PVDF/ZnO composite films for photocatalysis: A comparative study of solution mixing and melt blending methods

Heterogeneous photocatalysis represents a solution for several environmental problems. However, achieving photocatalyst separation from reaction media on a large scale remains a challenge, one that might be overcome by the immobilization of photocatalysts into supports. To this end, composites of polyvinylidene fluoride and zinc oxide (ZnO) were prepared by three different techniques: solution mixing (SM) followed by Nonsolvent Induced Phase Separation; and melt blending at both low- and high-shear rates (LS and HS) in a rheometer and mixing chamber, respectively, to compare the resultant morphology in photocatalysis. Photocatalytic efficiency was assessed by methylene blue (MB) discoloration in a batch reactor liquid phase and by resazurin (RZ) reduction. The changes promoted by nanoparticle inclusion, processing conditions and UV effect were demonstrated by FTIR-ATR, XRD, DSC, and SEM. Results showed that ZnO incorporation was successful under all processing conditions, providing effective photocatalytic composites. However, samples prepared by SM had a twofold increase in discoloration efficiency and fourfold increase in surface photoactivity, when compared with LS or HS-produced samples, explained by its higher porosity of 88% [+ or -] 1.3%. The covering of the photocatalyst surface was also evident on SEM analysis for melt blended samples, further contributing to reduction in their photocatalytic activity. KEYWORDS blending, catalysis, composites, films, mixing, phase separation
1 | INTRODUCTION Heterogeneous photocatalysis, an Advanced Oxidation Process, has attracted much attention for the synthesis of chemical compounds and environmental remediation, mainly as an alternative for resolving a number [...]