Photoreduction of Chlorinated Organic Pollutants Using Solutions or Films of a Polymeric System via a Free Radical Mechanism
Type of DegreePhD Dissertation
Chemistry and Biochemistry
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Efficient reduction of chlorinated organics took place upon exposure to 350 nm photons in aqueous solutions containing sulfonated poly(ether etherketone), SPEEK, and either poly(vinyl alcohol), PVA, or HCO2H/HCO2- buffers. Chloride ions together with H+ were photogenerated and the rate of Cl- formation, r(Cl-), was a linear function of time. The efficiency of the photoreaction increased in air-free solutions, since oxygen is a scavenger of the reducing species, SPEEK•. Using formate buffers as H-atom donors not only generated Cl- as a reaction product but also induced reductions at least 10 times faster than in the presence of PVA. Differences in obtained quantum yield, Φ(Cl-), were also noticed when SPEEK samples were prepared from poly(ether etherketone) precursors supplied by Evonik (called E-SPEEK) or Victrex (known as V-SPEEK) or Solvay (known as S-SPEEK). Efficiency for the reduction of the chlorinated organics increases more than 20 fold using SPEEK/PVA film as a reducing system instead of aqueous SPEEK/PVA solution. Drastic Φ(Cl-) increases were noticed in neutral solutions and at pH = 7.3 the quantum yield reached maximum values exceeding one irrespective of the nature of SPEEK. The dependence of r(Cl-) on (I0)1/2, I0 = light intensity, and the occurrence of post-irradiation formation of Cl- via reduction of CCl4/CHCl3 in the dark are further evidence that the photoreaction proceeded via a chain process.