Kinetics of reductive denitrification by nanoscale zero-valent iron

Zero-valent iron powder (Fe-0) has been determined to be potentially useful for the removal of nitrate in the water environment. This research is aime d at subjecting the kinetics of denitrification by nanoscale Fe-0 to an ana lysis of factors affecting the chemical denitrification of nitrate, Nanosca le iron particles with a diameter in the range of 1-100 nm, which are chara cterized by the large BET specific surface area to mass ratio (31.4 m(2)/g) , removed mostly 50, 100, 200, and 400 mg/l of nitrate within a period of 3 0 min with little intermediates. Compared with microscale (75-150 mu m) Fe- 0, endproduct is not ammonia but N-2 gas. Kinetics analysis from batch stud ies revealed that the denitrification reaction with nanoscale Fe-0 appeared to be a pseudo first-order with respect to substrate and the observed reac tion rate constant (k(obs)) varied with iron content at a relatively low de gree of application. The effects of mixing intensity (rpm) on the denitrifi cation rate suggest that the denitrification appears to be coupled with oxi dative dissolution of iron through a largely mass transport-limited surface reaction (<40 rpm). (C) 2000 Elsevier Science Ltd. All rights reserved.