Nitrite removal from water by catalytic hydrogenation in a Pd-CNTs/Al2O3hollow fiber membrane reactor

Abstract

BACKGROUND Nitrite contaminants in groundwater endanger public health since they may cause many diseases such as blue baby syndrome, cancer and hypertension. In this work, novel Pd-CNTs/Al2O3 catalytic hollow fiber membranes for aqueous nitrite hydrogenation reduction were fabricated by the deposition of carbon nanotubes (CNTs) and Pd nanoparticles inside porous Al2O3 hollow fibers. A hollow fiber membrane reactor was assembled for nitrite removal from water by catalytic hydrogenation reduction. RESULTS Experimental results indicated that the nitrite hydrogenation rate was highly dependent on hydrogen dissolution in water and adsorption on the catalyst. The nitrite removal increased with increasing H2 partial pressure to balance the nitrite solution, but the influence became very marginal as it approached 1.0 atm. The oxygen in the gas feed lowered the nitrite removal due to the reaction with dissolved hydrogen over the Pd-catalyst. Compared with the conventional diffusion operation of the membrane reactor, the ‘flow-through’ operation resulted in higher nitrite removals due to the intensified mass transfer rate. CONCLUSION The nitrites in water can be completely removed using the Pd-CNTs/Al2O3 membrane reactor with flow-through operation. The denitrification should be operated at around 25°C for large reaction kinetics, which is determined by both the temperature and the hydrogen solubility in water. © 2015 Society of Chemical Industry