טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentFux Inbal
SubjectRemoval of Nitrate from Drinking Water by Ion Exchange
Followed by nZVI-Based Reduction and
Electrooxidation of the Ammonia Product
to N2(g)
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Ori Lahav
Dr. Liat Birnhack
Full Thesis textFull thesis text - English Version


Abstract

Ion-exchange (IX) is common for separating NO3- from drinking water. From both cost and environmental perspectives, the IX regeneration brine must be recycled, via nitrate reduction to N2(g). Nano zero-valent iron (nZVI) reduces nitrate efficiently to ammonia, under brine conditions. However, to be sustainable, the formed ammonia should be oxidized. Accordingly, a new process was developed, comprising IX separation, nZVI-based nitrate removal from the IX regeneration brine, followed by indirect ammonia electro-oxidation. The aim was to convert nitrate to N2(g) while allowing repeated usage of the NaCl brine for multiple IX cycles. All process steps were experimentally examined, and shown feasible: nitrate was efficiently separated using IX, which was subsequently regenerated with the treated/recovered NaCl brine. The nitrate released to the brine reacted with nZVI, generating ammonia and Fe(II). Fresh nZVI particles were reproduced from the resulting brine, which contained Fe(II), Na, Cl- and ammonia. The ammonia in the nZVI production procedure filtrate was indirectly electro-oxidized to N2(g) at the inherent high Cl- concentration, which prepared the brine for the next IX regeneration cycle. The dominant reaction between nZVI and NO3- was described best (Wilcoxon test) by 4Fe(s)?3-?4Fe242O, and proceeded at >5 mmol l-1 min-1 at room temperature and 3<pH<5.