94
Tecnología y Ciencias del Agua
, vol. VIII, núm. 2, marzo-abril de 2017, pp. 93-103
Song & Song,
Kinetics and influential factors of nanoscale iron-facilitated nitrate-nitrogen removal
•
ISSN 2007-2422
reverse osmosis, biological treatment, and
chemical reduction. The repeated regeneration
processes that occur during ion exchange and
reverse osmosis produce secondary pollution.
Likewise, biological treatment entails numer-
ous operation and management requirements,
including a sufficient carbon source. Compared
to ion exchange, reverse osmosis, and biologi-
cal treatment, the chemical reduction has many
advantages, such as rapid reaction rates. In ad-
dition, the chemical reduction does not cause
secondary pollution, is not difficult to perform
and is suitable for the treatment of small and
distributed areas (Chen & Wu, 2009; Fan, Guan,
Ma, &Ai, 2009). Kinetics and corrosion products
of aqueous nitrate reduction by iron powder
without reaction conditions control (
Journal of
Environmental Sciences
, 2009, 21, 1028-1035).
Since the 1990s, numerous studies concern-
ing the removal of nitrate-nitrogen pollution
from surface water using nanoscale iron as an
adsorbent and reductant have been conducted
(Song & Song, 2015; Chen & Wu, 2009; Fan
et
al
., 2009; Cheng, Muftikian, Fernando, & Korte,
1997; Huang, Wang, & Chiu, 1998; Choe, Chang,
Hwang, & Khim, 2000; Lien & Zhang, 2001;
Ponder, Darab, & Mallouk, 2000). Nanoscale
iron has a large surface area (Liou, Lo, & Lin,
2005; Philips & Laura, 1992; Siantar, Schreier,
Chou, & Reinhard, 1996; Wang & Zhang, 1997;
Kanel, Manning, Charlet, & Choi, 2005; Yuan &
Lien, 2006; Lien, Jhuo, & Chen, 2007; Tratnyek,
Johnson, & Scherer, 1996), good surface adsorp-
tion, and strong reduction capabilities (Murphy,
1991). Previous studies have shown that 4 g/L
of nanoscale iron can efficiently and effectively
remove 30-120 mg/l of nitrate nitrogen. In one
study, Seunghee Choe (Seunghee, Howard, &
Li, 2004) investigated the effects of pH on the
reaction rate of nitrate nitrogen in a nanoscale
iron removal solution. The results indicated that
nitrate nitrogen can be removed entirely under
acidic conditions. In another study, Liou (Liou
et al
., 2005) studied the effects of temperature on
the reaction rate of nitrate nitrogen as well as the
nitrate removal efficiency of nanoscale iron. Fur-
thermore, Chunming (Chunm & Robert, 2004)
investigated the influential factors and reaction
products of nanoscale iron-facilitated nitrate-
nitrogen removal in different acidic solutions.
In all of these studies, the influential factors and
nitrate-nitrogen removal efficiency of nanoscale
iron were investigated using relatively large
amounts of nanoscale iron. In this study, the
influential factors and nitrate-nitrogen removal
efficiency of small amounts of nanoscale iron
are analyzed in order to facilitate the efficiency
of nitrate removal in practical applications. In
addition, the reaction kinetics of the removal
process were studied in order to develop a
kinetic equation that effectively describes the
reaction rate and activation energy of nanoscale
iron-facilitated nitrate-nitrogen removal and,
thereby, provides a theoretical basis for the
application of nanoscale iron technology to the
treatment of wastewater.
Materials and methods
Instruments and reagents
The reagents used for the purposes of this study
included KNO
3
(analytical reagent grade, A.R.),
FeSO
4
·7H
2
O (A.R.), NaOH (A.R.), KBH
4
(A.R.),
absolute ethyl alcohol (A.R.), polyethylene gly-
col (A.R.), and reduced iron powder (200 mesh).
In addition, the D/MAX-2500 X-ray diffrac-
tometer (Japan), Philips EM400ST transmission
electron microscope, 752N UV-Vis spectropho-
tometer, DJIC-100 electric mixer, Formal1025
anaerobic operation box, THZ-82B
air bath
constant-temperature-oscillator, JW-04 nitrogen
adsorption surface area tester, and Delta-320 pH
meter were used to conduct the experiments
(Song & Song, 2015).
All of the glassware was immersed in 10%
(volume fraction) HNO3 for 48 hours and then
rinsed with tap water and deionized water
several times before use.
Preparation and characterization of the
nanoscale iron
At room temperature, a 1.6 mol/l NaBH
4
so-
lution was added drop by drop to the same
