Copper (II) phthalocyanines immobilized on alumina and encapsulated inside zeolite-X and their applications in photocatalytic degradation of cyanide: A comparative study

Copper phthalocyanine (CuPc) complexes either deposited on alumina (CuPc/Al); synthesized by sol–gel, or encapsulated inside zeolite-X (CuPc/ZX) while in situ synthesis were characterized by X-ray diffraction (XRD), DSC, FT-IR, diffuse reflectance UV–vis, dynamic light scattering and N2 adsorption techniques. These materials were tested for photocatalytic oxidation of cyanide in comparison with ZX and CuPc free complex. Unlike the case on Al, CuPc was accommodated inside ZX, as confirmed from lattice parameter increment (from 25.101 of ZX to 25.250 Å of CuPc/ZX) and decreasing both SBET and pore volume (705 m2/g, 0.550 cm3/g) as compared to the neat zeolite (837 m2/g, 0.684 cm3/g). Bending modes vibrations of δC–H showed bands at 1041 and 970 cm−1 for CuPc/Al where CuPc/ZX did not, suggesting that these bonds are formed while CuPc vibrating on the former. Contrarily, they are restricted in the latter proposing accommodation of the complex inside zeolite cages as emphasized from ΔS values that showed marked decrease in disorderness (−29 J/mol K) compared with CuPc (−13 J/mol K). In accordance, Q band revealed a red shift from 614 to 632 nm. A very strong photo-oxidation capability of oxidizing CN− was exhibited for the encapsulated complex (CuPc/ZX; 100% removal in 1 h; rate constant = 0.1 min−1) comprehending the importance of electron transfer reactions within ZX to external surfaces, and the zeolite framework that seems participating efficiently in the electron transfer process.

The oxidation of CN− that follows first order rate kinetics exhibited remarkable activity on CuPc/ZX (0.1 min−1) compared with other catalysts emphasizing the dependence of the electronic transition on zeolite structure.Figure optionsDownload as PowerPoint slide