Abstract
Porous Al2O3 hollow fiber membranes have been fabricated via a phase inversion – sintering technique. Pd-loaded carbon nanotubes (CNTs) are formed inside the hollow fibre wall by the catalytic decomposition of methane over Fe particles, followed by impregnation and reduction with hydrogen to form catalytic hollow fibre membranes. Hydrophobic modification of the hollow fibres is conducted by gas permeable polymeric coating. The resultant hollow fibre membranes exhibit highly catalytic activity to the hydrogenation reduction of nitrites in aqueous solution. Hollow fibre membrane reactors are assembled for nitrite hydrogenation by pumping nitrite solution into the tube side and introducing hydrogen countercurrently to the shell side of the reactor. The nitrite removal in the hollow fibre membrane reactors increases with the operation temperature and the hydrogen feed concentration at lower hydrogen partial pressures, but less influenced by the hydrogen feed concentration when it is higher than 50%. A higher nitrite concentration favors the nitrite hydrogenation reaction but lowers the nitrite removal efficiency.
Highlights
The removal of nitrites (NO2-) and nitrates (NO3-) from water is environmentally important since these contaminants can cause cancer extremely harmful to human health [1, 2]
In order to overcome these shortcomings, a catalytic hydrogenation reduction route has been developed in which the nitrite ions are converted on a noble-metal solid catalyst to nitrogen (N2) and/or ammonia as a byproduct at ambient temperature [3]
Porous Al2O3 ceramic hollow fiber membranes deposited with carbon nano-tubes (CNTs) as the solid catalyst carrier were fabricated for hydrogenation reduction of nitrites in water
Summary
The removal of nitrites (NO2-) and nitrates (NO3-) from water is environmentally important since these contaminants can cause cancer extremely harmful to human health [1, 2]. In order to overcome these shortcomings, a catalytic hydrogenation reduction route has been developed in which the nitrite ions are converted on a noble-metal solid catalyst to nitrogen (N2) and/or ammonia as a byproduct at ambient temperature [3]. This reaction system has fast kinetics and is generally limited by the internal diffusion in catalysts. Thereby, an effective contact between the gas-liquid reactants and the solid catalyst is established It can be operated by pumping the dissolved reactants through the catalytic membrane, a very short contact time can be achieved. Journal of Membrane and Separation Technology, 2014, Vol 3, No 3 147 and liquid phases minimizing the mass transfer limitations [8, 9]
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