Pilot-plant photomineralization of dichloromethane and tetrachloroethene in aqueous solution, by photocatalytic membranes immobilizing titanium dioxide and photopromoters

Franco Gianturco, Luca Vianelli, Luca Tatti, Fabrizio Rota, Paolo Bruzzi, Laura Rivas, Ignazio Renato Bellobono, Michele Bianchi, Herbert Muntau

Research output: Contribution to journalArticlepeer-review

Abstract

The TiO2-mediated photomineralization of 5.0 x 10-6-5.0 x 10-7 M aqueous solutions of dichloromethane (DCM), tetrachloroethene (PCE), and mono-, di-, and trichloroethanoic acids (MCEA, DCEA, and TCEA respectively) was studied at 296 ± 2 K, using PHOTOPERM® CPP/313 membranes containing immobilized 30 ± 3 wt.% TiO2, and, in some of the runs with PCE, 7 wt.% of photocatalytic promoters based on Co(III), V(V) and Fe(III) organometallic compounds. Disappearance of both substrate and total organic carbon (TOC) was examined, as well as chloride ion formation. The apparent reaction order being unit in the range of concentration considered, half times for these three kinetic processes have been measured in a PHOTOPERM® WW membrane module, fitted with 1 m2 of membrane, with an absorbed radiating power of 31 W, and saturated with air. With PCE, the marked decrease of rate (to 1/25) with decreasing O2 concentration (to 2-3 ppm), and the positive effects of promoters or of applying an anodic bias (enhancement of rate up to about 3/1) were ascertained. The role of oxygen as scavenger for photogenerated electrons is much preferable to that of adsorbed substrate to scavenge these conduction band electrons, both to explain the efficient action of photopromoters as oxidant scavengers or oxygen transporters, and redox processes involving formation of chlorinated intermediates, such as DCEA, during radical reactions, as TOC disappearance from DCEA, MCEA, and TCEA proceeds at a much slower rate than that experimentally observed for PCE.

Original languageEnglish
Pages (from-to)1531-1542
Number of pages12
JournalChemosphere
Volume33
Issue number8
DOIs
Publication statusPublished - Oct 1996

ASJC Scopus subject areas

  • Environmental Chemistry
  • Environmental Science(all)

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