Nitrate removal from aqueous solutions by
magnetic cationic hydrogel: Effect of electrostatic
adsorption and mechanism
Q5
Q4
Junyi Li
1
, Shuoxun Dong
2,*
, Yili Wang
1,**
, Xiaomin Dou
1
, Haotian Hao
3
1
College of Environmental Science and Engineering, Beijing Key Lab for Source Control Technology of Water
Pollution, Beijing Forestry University, Beijing, 100083, China
2
Center for Water and Ecology, State Key Joint Laboratory of Environment Simulation and Pollution Control, School
of Environment, Tsinghua University, Beijing, 100084, China
3
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
article info
Article history:
Received 28 October 2019
Received in revised form
30 January 2020
Accepted 31 January 2020
Available online xxx
Keywords:
Adsorption
Nitrate removal
Low concentration
Electrical stern layer
Magnetic cationic hydrogel
abstract
Excessive nitrate (NO
3
) is among the most problematic surface water and groundwater
pollutants. In this study, a type of magnetic cationic hydrogel (MCH) is employed for NO
3
adsorption and well characterized herein. Its adsorption capacity is considerably pH-
dependent and achieves the optimal adsorption (maximum NO
3
-adsorption capacity is
95.88 ± 1.24 mg/g) when the pH level is 5.2e8.8. The fitting result using the homogeneous
surface diffusion model indicates that the surface/film diffusion controls the adsorption
rate, and NO
3
approaches the center of MCH particles within 30 min. The diffusion coef-
ficient (D
s
) and external mass transfer coefficient (k
F
) in the liquid phase are
1.15 10
6
cm
2
/min and 4.5 10
6
cm/min, respectively. The MCH is employed to treat
surface water that contains 10 mg/L of NO
3
, and it is found that the optimal magnetic
separation time is 1.6 min. The high-efficiency mass transfer and magnetic separation of
MCH during the adsorptioneregeneration process favors its application in surface water
treatment. Furthermore, the study of the mechanism involved reveals that both eN
þ
(CH
3
)
3
groups and NO
3
are convoluted in adsorption via electrostatic interactions. It is further
found that ion exchange between NO
3
and chlorine occurs.
© 2020 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sci-
ences. Published by Elsevier B.V.
Introduction
Nitrate-polluted surface water and groundwater are ubiqui-
tous in India, China, and Spain (Han et al., 2016; Ahada and
Suthar, 2018; Arauzo et al., 2019). In recent years, the
presence of elevated nitrate levels in water caused by exces-
sive fertilizer use and uncontrolled wastewater discharge has
become a critical environmental problem because it leads to
water pollution (Han et al., 2016). Elevated nitrate intake is
also expected to detrimentally affect the health of aquatic
biota, livestock, and humans (Manjunath and Kumar, 2018;
* Corresponding author.
** Q8 Corresponding author.
E-mail addresses: dongshuoxun@163.com (S. Dong), wangyilimail@126.com (Y. Wang).
Available online at www.sciencedirect.com
ScienceDirect
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journal of environmental sciences xxx (xxxx) xxx
JES1997_proof ■ 12 February 2020 ■ 1/12
https://doi.org/10.1016/j.jes.2020.01.029
1001-0742/© 2020 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.
Please cite this article as: Li, J et al., Nitrate removal from aqueous solutions by magnetic cationic hydrogel: Effect of electrostatic
adsorption and mechanism, Journal of Environmental Sciences, https://doi.org/10.1016/j.jes.2020.01.029