Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

PP-IV-8electrolyte solution is fed to the cathode,whereas the condensate water is fed tothe anodes. The electrokinetic tests werecarried out under a constant direct currentwith current density of about 5 mA/cm 2 .At this point the treated water is rich ofoxygen and can be either fed back to the Fig.1. cell exploded scheme. CF: condensate feed;A: anode; T: turbulence promoter; CM: cationicreservoirs or undergo the photocatalytic membrane, C: cathode; EF: electrolytic feed.treatment to reach lower TOC values.The photocatalytic reactor can be operated either as a trickle bed reactor or as a thin film one.In this reactor, the working length of the UV lamp can be regulated. Continuous analysis ofthe treated solutions was accomplished through suitable probes meanwhile measuring the pHvalue to get an idea of the acid concentration by oxidation reaction.Results and DiscussionSeveral runs were performed to determine the TOC concentration, nitrate and nitrite,ammonia and pH and conductivity evolution during the regenerative treatments. The TOCdecrease after 1 hr of treatment from 190 ppm to 46 ppm when a pH equal to 3 is reached dueto formation of organic acids, which have to be considered as rather refractory to furtherelectrooxidation and thus require photocatalysis.Several tests have been performed with cationic (CM) and anionic membrane (AM) for acomparison. When the CM is used, ammonia is generated from nitrogen organic contaminantsin the acidic environment; it is then converted into ammonium ions, which reach the cathodiccompartment via electro-migration ionic, where the local basic lead once again to ammoniaformation and removal as gas. Conversely, AMs forced only nitrate and nitrite ions to movetowards the cathode side, where they are concentrated. However, the benefit of CMs issomehow reduced by the lower electrical conductivity of the treated solution.Since NASA potable water TOC specification is below 500 ppb, a second photocatalyticstep would be required and possibly favored by the fact that space UV emissions are strong.AcknowledgementsThe financial support of Alenia Space and Regione Piemonte is gratefully acknowledged.References1. A.F. Behrend Jr., R.D. MacElroy, & R.P. Reysa, SP-873, SAE International, Warrendale, PA, (1991).2. R. Andreozzi, V. Caprio, A. Insola, & R. Marotta, Catalysis Today, 53, 51-59 (1999).3. C. Comminelis & A. De Battisti, J. Chem. Phys., 93, 673-679, (1996).411