Zero valent nano-sized iron/clinoptilolite modified with zero valent copper for reductive nitrate removal

Nitrates constitute one of the main toxic contaminants of groundwater. On the other hand, groundwater may be considered anoxic (oxygen concentration less than 9 μg L−1). This fact justifies the use of nano zero valent metals for nitrate removal. In such conditions, zero valent metals are quite stable against oxidation due to the very low level of dissolved oxygen concentration. It has been shown that the performance of zero valent iron coated clinoptilolite zeolite for the reduction of nitrate anion in un-buffered conditions may be enhanced by coating small amounts of Cu0 onto the freshly prepared Fe0/zeolite composite. An optimum loading of Cu0 exists for which the rate of nitrate removal is maximal. For this optimal composition, the nitrite anion production curve with time passes through a maximum. Nitrite production, however, is slightly higher for the Cu modified zeolite. It has been shown that the nitrate removal process is only slightly dependent on the initial solution pH. In the temperature range of 20–60 °C, the process is controlled by both the liquid phase mass transfer and intrinsic reaction rate resistances. FESEM analysis of the zero valent metal/zeolite composite showed that upon the metal reduction reaction, an egg-shell distribution of zero valent metal in the zeolite agglomerate particle is produced.

Nitrate removal kinetics for the Cu modified zero valent iron/clinoptilolite zeolite composite.Figure optionsDownload high-quality image (87 K)Download as PowerPoint slideHighlights
► Nitrate removal with a modified Fe0/clinoptilolite composite.
► Inclusion of Cu0 enhances significantly the removal kinetics.
► An optimum Cu loading exits.
► We show an egg-shell distribution of zero valent metal for the zeolite agglomerate.