Pilot-plant-scale photodegradation of phenol in aqueous solution by photocatalytic membranes immobilizing titanium dioxide (PHOTOPERM® process)

The TiO2-mediated photodegradation of phenol was studied at 298 ± 2 K or at 315 ± 5 K (with the ratio between the hydrogen peroxide added and the stoichiometric amount (N) in the range 0 – 3), using PHOTOPERM® CPP/313 membranes containing immobilized 30 ± 3 wt.% TiO 2. The rate of photodegradation was studied as a function of: i) initial concentration of substrate (8.76x10−6 − 0.01 M), ii) flow rate (0.4 – 5 m3/h),iii) apparent (geometrical) membrane surface (30 – 190 cm2/cm of central axis of radiation field), iv) kind of radiation source (low and high pressure mercury arc lamps, with fixed or variable radiant power, in the absorption range of semiconductor, of 31 W and 136–680 W respectively), v) radiation intensity. Disappearance of both phenol and total organic carbon (TOC) was examined. The operations of two pilot-plants, differing in range of flow rates, and membrane arrangement, are critically compared. The apparent reaction orders as a function of concentration are also compared and discussed, on the basis of kinetic parameters resulting from both pilot-plant- and laboratory-scale experience. Advantages of the membrane process are highlighted.