Chain Reduction of CHCl₃ Photocatalyzed by SPEEK/PVA Films Swollen in Air-Saturated HCO₂Na Solutions

Abstract

Thin cross-linked films containing sulfonated poly(ether etherketone), SPEEK, and poly(vinyl alcohol), PVA, served as efficient photocatalysts for the reduction of CHCl3 when swollen in air-saturated solutions of formate buffers were photolyzed with 350 nm photons. The phototransformation generated CH2Cl2, CO2 and Cl− as products. The utilization of the continuous extraction method coupled with in situ potentiometry enabled kinetic determinations of the reaction progress. Quantum yields of halide ion formation, ϕ(Cl−), larger than 1 were obtained in the presence of air. These findings, together with the occurrence of a post-irradiation Cl− formation, indicated that the photoreduction took place via a chain process. Reductions photoinitiated by swollen films exhibited ϕ(Cl−) values between 3 and 20 times higher than the reactions induced in solutions containing the two polymers. Also, the dependencies of ϕ(Cl−) on CHCl3 or HCO2− concentration diverged significantly from the trends observed using solutions. Most findings are consistent with the occurrence of a reaction mechanism involving SPEEK radicals, •CO2− and •CHCl2 as chain carriers.

Keywords

• photoreduction
• photocatalyst
• CHCl₃
• chain reaction
• SPEEK
• cross-linked polymer film