Catalytic membrane reactor based on Pd-Sn supported on nanocarbons for the reduction of nitrate in water

Abstract

This work studies the reduction of NO3- in water using a catalytic membrane reactor in flow-through configuration (FTCMR) for enhanced control of H2 availability and generation of NH4+. The catalytic membrane was prepared with metal catalysts supported on carbon materials with different structural and physicochemical properties (graphite, carbon nanofibers, reduced graphene oxide, activated carbon and carbon black). The catalysts were firstly tested in a batch reactor for screening and assessing influence of regime control on activity and selectivity. Pd-Sn catalysts showed higher production of NH4+ under chemical control than Pd-Cu ones, but equivalent performance was reached for Pd-Sn supported on carbon nanofibers and carbon black in conditions of H2 mass transfer control. Catalytic membranes were prepared with Pd-Sn catalyst according to higher impact of H2 availability in NH4+ generation. FTCMR was less selective to NH4+ compared to the batch reactor due to better control of H2 mass transfer. Reduction of NH4+ generation was achieved at the expense of activity due to lower availability of H2. However, membranes based on Pd-Sn supported on carbon nanofibers and carbon black were able to operate at higher H2 concentration with low selectivity to NH4+, making possible the use of membrane reactors at advantageous conditions.