Enhanced removal of nitrate by a novel composite: Nanoscale zero valent iron supported on pillared clay

The nanoscale zero valent iron supported on pillared clay (NZVI/PILC) was prepared, and used for nitrate removal with the objective of enhanced efficiency. The composite NZVI/PILC was characterized by transmission electron microscope (TEM), X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET). Good dispersion of NZVI particles (ca. 30–70 nm) in the clay phase was observed. The removal efficiency of nitrate by this composite was investigated, and compared with commercial iron powder and NZVI containing the same amount of iron. Results showed nitrate could be completely removed by NZVI/PILC within 120 min. This efficiency was not only much higher than that (62.3%) by NZVI alone, but also superior to the sum (71.5%) of reduction by NZVI plus adsorption (9.19%) by PILC. The kinetic studies indicated that the rate of nitrate removal was positively related to the adsorption. So we suggested that the adsorption of nitrate by PILC enhanced the mass transfer of nitrate from solution to iron surface, therefore accelerated the reduction rate. The end-products of nitrate reduction by NZVI/PILC were identified as ammonium and nitrogen gas, implying NZVI/PILC may help cut down the total nitrogen amount in water.

► The pillared clay (PILC) as the carrier can prevent NZVI from aggregation.
► NZVI/PILC composite has higher efficiency on removing nitrate than NZVI.
► The adsorption of nitrate by PILC enhanced the mass transfer of nitrate from solution to iron surface, therefore accelerated the reduction rate.