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

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.