This study has investigated how to simultaneously remove
both heavy metals (Cu, Mn, and Zn) and natural organic matters (NOM; humic acid and fulvic acid)
from river water using potassium ferrate (K2FeO4), a multipurpose chemical acting as oxidant,
disinfectant, and coagulant. In water sample including each 0.1 mM heavy metal, its removal
efficiency ranged 28-99% for Cu, 22-73% for Mn, and 18-100% for Zn at the ferrate(VI) doses of
0.03-0.7 mM (as Fe). The removal efficiency of each heavy metal increased with increasing pH,
whereas an overall temperature did not make any special effect on the reaction between the heavy
metal and ferrate(VI). A high efficiency was achieved on the simultaneous treatment of heavy
metals (0.1 mM) and NOM (10 mg/l) at the ferrate(VI) doses of 0.03-0.7 mM (as Fe): 87-100% (Cu),
31-81% (Mn), 11-100% (Zn), and 33-86% (NOM). In the single heavy metal solution, the optimum
ferrate dose for treating 0.1 mM Cu or Mn was 0.1 mM (as Fe), while that for treating 0.1 mM Zn
was 0.3 mM (as Fe). In the mixture of three heavy metals and NOM, on the other hand, 0.5 mM (as
Fe) ferrate(VI) was determined as an optimum dose for removing both 0.1 mM heavy metals (Cu, Mn,
and Zn) and 10 mg/l NOM. Prior to the addition of ferrate(VI) into the solution of heavy metals
and NOM (HA or FA), complexes were formed by the reaction between divalent cations of heavy
metals and negatively charged functional groups of NOM, enhancing the removal of both heavy
metals and NOM by ferrate(VI).