Photodegradation of Carbamazepine and Acridine with 165-200 nm Radiation from a Microcavity-Plasma VUV Phosphor Lamp

A longstanding obstacle to the application of vacuum ultraviolet (VUV) radiation for advanced water treatment is the absence of efficient, affordable, and powerful lamps. A custom Xe₂ microcavity plasma (McP) lamp with an internal phosphor film, generating broadband emission in the 165-200 nm interval, is presented here as an optical source for the degradation of dissolved contaminants. The performance of this lamp was evaluated by comparing measured photodegradation rates for carbamazepine (CBZ, a model compound) with corresponding data obtained with a conventional 254/185 nm Hg lamp. While the oxidant production rate was lower for the McP lamp, it was found to be more effective in photodegrading CBZ for a given energy dosage absorbed by the water. The McP lamp also produced higher concentrations of the byproduct acridine (ARD) but normalization to effective fluence exposure reveals it produced and removed ARD more efficiently than did the Hg lamp. The flat form factor and ability to produce output powers >10 W from a 100 cm² aperture make the McP lamp promising for photochemical water treatment. Although its emission spectrum is not currently optimized, the data indicate that the lamp spectrum can be engineered to efficiently photodegrade a wide range of challenging water pollutants.