Impact of selected solution factors on arsenate and arsenite removal by nanoiron particles.
BACKGROUND
The nano-scale zero-valent iron (NZVI) was used for the removal of arsenite (As(III)) and arsenate (As(V)) in aqueous solution. Batch experiments were conducted to investigate the effects of initial pH, initial arsenic concentration, dissolved oxygen (DO), and ratio of As(III)/As(V) on arsenic removal.


METHODS
The NZVI synthesized by using NaBH4 and FeCl3 was put into use right after its synthesis. The arsenic treatment system of recirculation mode consists of a reactor with a liquid volume of 4.4 L, which provides dual function of reactants reaction and particles settling in one unit.


CONCLUSIONS
Consequently, the pseudo-first order rate equations can be used to describe the removal kinetics for As(V) at pH 4 and 7, while the pseudo-second order reaction was observed for As(V) at pH 9 and As(III) at all pH's studied. Arsenic removal rates of both As(V) and As(III) were lower in the system with lower DO. The rate of As(III) removal decreased with the increase of its initial concentration. In contrast, the removal rate of As(V) still remained significantly high as its initial concentration increased.


CONCLUSIONS
This study reveals that low pH and high DO will favor arsenic removal. With the mixture of As(III) and As(V), the total arsenic was removed faster than solution containing As(III) or As(V) alone. In addition, the mixture with higher fraction of As(V) resulted in higher arsenic removal.
Department of Chemical Engineering, Faculty of Engineering, Thammasat University, Pathumthani, Thailand.
Visanu
V
Tanboonchuy
Jia-Chin
JC
Hsu
Nurak
N
Grisdanurak
Chih-Hsiang
CH
Liao
D001149:Arsenates / Q000302:isolation & purification*; D001151:Arsenic / Q000302:isolation & purification; D018053:Arsenites / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D014877:Water Pollution, Chemical / Q000032:analysis; D018508:Water Purification / Q000379:methods
D001149:Arsenates; D018053:Arsenites; D014874:Water Pollutants, Chemical; D007501:Iron; C015001:arsenite; D001151:Arsenic; C025657:arsenic acid; D010100:Oxygen
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