Advanced Materials Research
ISSN: 1662-8985, Vols. 383-390, pp 947-952
doi:10.4028/www.scientific.net/AMR.383-390.947
© 2012 Trans Tech Publications, Switzerland
Online: 2011-11-22
A Study on Ammonia Nitrogen, Phosphorus and Organic Pollutants
Removal of Zeolites by Salt Modification
Hai Lin, Zhiying Zhao, Leyong Jiang and Wei Wei
School of Civil and Environmental Engineering, University of Science and Technology Beijing,
Beijing, China
[email protected]
Keywords: Zeolites, Salt Modification, Ammonia Nitrogen, Phosphorus, Reclaimed Water.
Abstract. In this study, the zeolites were treated by NaCl and FeCl3 as an active agent, combined
with calcination modification. We studied the ammonia nitrogen (NH3-N) and phosphorus (P)
removal of the modified zeolites. The results showed that concentration of NaCl and FeCl3 affected
NH3-N and P removal of Secondary sewage effluent greatly. The optimal concentrations of NaCl
and FeCl3 were 2.0% and 0.4%. At this condition, the NH3-N and P removal rate of zeolites reached
the peak. Application experiments revealed that NH3-N removal rate reached 80.9%, P removal rate
reached 83.4%, and COD removal rate reached 96.0%, when the dosage of modified zeolites was
3.0g/L and adsorption duration was 2h for Secondary sewage effluent with 6.0mg/L NH3-N
concentration and 1.5mg/L P concentration. After the treatment, the NH3-N and P concentration met
Reclaimed Water Quality Standards. The adsorption capability of modified zeolites was better when
the pH ranged from 3 to 6. The reason of using NaCl+FeCl3 was that Na+ could exchange the
NH3-N in the effluent; Fe3+was able to combine with PO43- in the sewage and formed precipitate;
and Fe3+ could also oxidize the organic pollutants.
Introduction
China is a country of water shortage. With the accelerated process of urbanization, the condition of
urban water shortage is getting worse. At the same time, the reclaimed water has been paid more
attention, and has become an important second water source. The reuse of reclaimed water
improves the utilization of city resources, and has significant environmental benefits and economic
benefits [1]. However, there still exists a certain amount of pollutants in the sewage effluents. The
COD, nitrogen and phosphorus remaining in the treated wastewater still affect the use of reclaimed
wastewater, especially nitrogen and phosphorus. In the water polluted by N and P, Algal blooms,
and dissolved oxygen drops, which have serious impact on living things in the water [2]. Currently,
eutrophication is the major water pollution problem of lakes, reservoirs, and oceans, and researches
of advanced wastewater treatment are carried out both at home and abroad [3-5].
Zeolite is a kind of mineral material, in which there is a plenty of inner cavity and subtle channel.
As a result, it has large adsorption surface area. In recent years, more and more scholars are studying
on using zeolite as an adsorbent [6]. Concerning about the high concentrations of nitrogen,
phosphorus, COD and other pollutants in municipal secondary treated sewage effluent, which cannot
meet the standard of reclaimed water, we study the pollutant adsorption of zeolites treated by salt
modification, in order to explore new fields of advanced treatment of municipal sewage.
Experimental Material and Method
Experimental Material. The zeolites used in this study were produced by Jiekun Zeolite New
Technology Processing Co., Ltd in Xuanhua, Hebei Province. The zeolites were about 76-154µm.
The main components of zeolites were shown in Table 1. FeCl3, NaCl, NH4Cl, NaOH, KH2PO4 and
HCl were of analytical grade. HZQ-F160 temperature oscillation incubator, DHG-9053A electric
constant temperature drying oven, WFZ-UV-2000 UV visible spectrophotometer, pH meter 320 and
SX-10-13-type box resistance furnace were used in the experiments.
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans
Tech Publications, www.ttp.net. (ID: 130.203.136.75, Pennsylvania State University, University Park, USA-16/05/16,23:24:52)
948
Manufacturing Science and Technology, ICMST2011
The indicators of simulation wastewater were ammonia nitrogen (NH3-N) of 6 mg/L, total
phosphorus (TP) of 1.5 mg/L, COD of 60 mg/L.
TABLE 1 COMPOSITION OF ZEOLITE[%]
SiO2
Al2O3
Fe2O3
CaO
MgO
K2O
Na2O
LOI
79.06
16.23
0.46
0.63
0.80
1.80
0.7
0.5
Experimental Method. NaCl and FeCl3 were used to modify zeolites in the study. Na+ was able to
exchange NH3-N in the wastewater. On the other hand, Fe3+ had the ability to remove P and COD.
Modification Experiments
a) NaCl modification. Different concentrations of NaCl (1.0%, 2.0%, 3.0%, 4.0%, 5.0%) were
used to modify the zeolites. The solid-to-liquid ratio (S/L) was 1/50[g/mL]. Stirring in the oscillator
for 2h, the zeolites were washed, dried, heated at 500℃, and cooled in a closed container. Using the
modified zeolites for adsorption experiments, the experiment studied on the impact of different NaCl
concentrations on the removal of ammonia nitrogen.
b) FeCl3 modification. The experiment was carried out at the best NaCl concentration, combined
with different FeCl3 concentration (0.2%, 0.4%., 0.6%, 0.8%, 1.0%, 2.0%, 4.0%) for 1.0h, in order to
know the influence of FeCl3 concentration on ammonia nitrogen and phosphorus removal.
Adsorption Application Experiments
a) The effect of different dosages. Different dosage (1.0g/L, 2g/L, 3g/L, 4.0g/L, 5.0g/L) were
adopted to treat the simulated sewage.
b) The effect of adsorption time. Using the best dosage, the adsorption experiments were carried
out for different time (0.5h, 1.0h, 2.0h, 3.0h, 5.0h).
c) The effect of pH value. The adsorption experiments were carried out at different pH value (3, 4,
5, 6, 7, 8, 9), under the condition of the best dosage and adsorption time.
Results and Discussion
Modification experiments
NaCl Modification The NH3-N adsorption ability of NaCl modified zeolites was shown in
Figure 1. In this experiment, the adsorption material dosage was 2.0 g/L. As shown in Figure 1, the
NH3-N adsorption ability was dramatically enhanced and was varied by the change of NaCl
concentration. When NaCl concentration was 5.0%, the removal rate was the highest. The removal
rate of NH3-N reached 84.1%, residual NH3-N concentration was 0.8mg/L, and adsorptive capacity
was 2.5mg/g. Concerning about the preparation costs and the adsorptive capacity, 2.0% NaCl was
chosen as optimal concentration.
Fig. 1 Influence of NaCl concentration on NH3-N removal
Modified by NaCl, Ca2+ and Mg2+ would be exchange by Na+. As a result, the content of Ca2+ and
Mg2+ would be reduced. On the other side, the order of zeolites adsorptive ability was
K+>NH4+>Na+>Ca2+>Mg2+ [7, 8]. So increasing of Na+ content could enhance its adsorptive ability
of NH3-N.
Advanced Materials Research Vols. 383-390
949
FeCl3 Modification In this experiment, Fe3+ was introduced to boost P removal of zeolites. The
dosage was 1.5 g/L. As could be seen from Figure 2, when FeCl3 concentration was 0.4%, P
removal was the best. In that way, P removal rate was 68.1%, and the residual P concentration was
0.48 mg/L. When FeCl3 concentration was lower than 0.4%, P removal rate increased with the
concentration increasing. When FeCl3 concentration was higher than 0.4%, P removal rate
decreased with the concentration decreasing.
The higher the concentration of Fe3+ was, the more Fe3+ would change to Fe2O3. Meanwhile,
excessive Fe2O3 would make the internal pore of zeolite blocked, which meant adsorptive surface
area reduced and adsorptive ability decreased. Therefore, 0.4% of FeCl3 concentration is optimal.
Fig 2 Influence of FeCl3 concentration on P removal
P adsorption of modified zeolites included two aspects. One was adsorption of the active sites in
the zeolites, and the other was Fe3+, which had the ability to form precipitation with PO4-3 [9]. The
chemical equation was:
Fe3++HnPO4-(3-n)＝FePO4↓+nH+
(1)
From the experiment above, the effect of adsorptive active sites was quite limit. It was Fe3+,
which played an important role in removing P.
Adsorption Application Experiments
Effect of the Dosage The dosage of absorbent directly determined the treatment effect of
absorbent material and processing costs.
As could be seen from Figure 3, with the increasing of dosage, P removal rate increased. When
the dosage was 3.0 g/L, residual content of phosphorus reached the setting target, less than 0.2mg/L.
When the dosage was more than 3.0 g/L, P removal rate increased a little.
Fig 3 Influence of Dosage of modified zeolites on P removal
As could be seen from Figure 4, the regularity of NH3-N removal almost the same with P
removal. With the increasing of dosage, NH3-N removal increased. When the dosage was 2.0g/L,
residual content of NH3-N reached the setting target, less than 1.0mg/L.
950
Manufacturing Science and Technology, ICMST2011
Fig 4 Influence of Dosage of modified zeolites on NH3-N removal
Summarily, in order to meet targets of both P and NH3-N removal, the optimal dosage was 3.0g/L
to treat the simulated wastewater of 6.0mg/L NH3-N concentration and 1.5mg/L P concentration.
Effect of Adsorption Time In this experiment, the dosage was 3g/L.
It was showed in Figure 5 and Figure 6 that with time increasing, the removal rate of both P and
NH3-N increased. When the adsorption time was longer than 2h, the residual P and NH3-N
concentration tended to stabilize. Comparing the adsorption velocity of P and NH3-N, the former was
faster.
Fig 6 Influence of adsorption time on NH3-N
Fig 5 Influence of adsorption time on P
removal
removal
Effect of pH In practice, for different pH values, the results of adsorbent treatment varied. This
experiment selected 7 different pH values.
Figure 7 reflected the influence of different pH values on P removal. As could be read in Figure 7,
P removal rate was much higher when pH was 3-6 than that when pH was 7-9.
The phosphorus resident in the secondary municipal sewage effluent was mainly in the form of
PO43-. After modified by FeCl3, Fe3+ finally changed into hydrous ferric oxides. When the simulated
water was acidic, Fe3+ was more active, and formed precipitation with PO43-. The precipitation
deposited on the zeolites surface, so the content of P in water reduced [9].
Fig 7 Influence of pH of simulated
wastewater on P removal
Fig 8 Influence of pH of
wastewater on NH3-N removal
simulated
Advanced Materials Research Vols. 383-390
951
Figure 8 reflected the influence of different pH values on NH3-N removal. Similarly, NH3-N
removal rate was much higher when pH was 3-6 than that when pH was 7-9. When pH value was 6,
the NH3-N removal rate was 77.0%, which was the best removal rate. When pH value was 9, the
NH3-N removal rate was 55.9%, which was the worst removal rate. The reason was there was a
chemical equilibrium:
ΝΗ4++Η2Ο
ΝΗ3•Η2Ο
(2)
In alkaline condition, the NH3-N remaining in the wastewater was in the form of NH3·H2O.
Therefore it was more difficult to adsorb NH3-N. When the pH was 3-6, the NH3-N remaining in the
wastewater was in the form of NH4+, which was much easier to adsorb [10].
The ensuing experiment was using the zeolites modified by salt and calcination to treat the
secondary sewage effluent (sampled from Gaobeidian sewage treatment plant in Beijing). The results
were listed in Table 2.
Because Fe3+ had the ability to oxidize the organic pollutants, the modified zeolite could also
remove the COD in the wastewater.
Table 2 Results of modifies zeolites applied in secondary sewage effluent
Zeolites modified by
FeCl3+NaCl
Raw zeolites
Pollutant Index
Sewage effluent
untreated
[mg/L]
P
NH3-N
COD
0.83
4.4
11.5
Residual content
[mg/L]
Removal rate
[%]
Residual content
[mg/L]
Removal rate
[%]
0.67
2.1
8.08
22.9
52.3
29.7
0.138
0.84
0.46
83.4
80.9
96.0
Summary
(1) The conclusion of modification experiments: the optimal NaCl and FeCl3 concentrations were
2% and 0.4%. Under optimal condition, P removal rate was 68.1%, which was 3.0 times more than
that of raw zeolites, and NH3-N removal rate was 83.0%, which was 44.2% more than that of raw
zeolites.
(2) The absorption application experiments revealed that the optimal dosage of modified zeolites
was 3g/L and adsorption duration was 2h for Secondary sewage effluent with 6.0mg/L NH3-N
concentration and 1.5mg/L P concentration. The practical application experiments results showed
that the adsorptive ability of zeolites was enhanced greatly after salt and calcination modification.
(3) The mechanisms of pollutants removal by NaCl and FeCl3 modification: NH3-N removal
mechanism was based on the ion exchange ability of Na+; P removal mechanism was based on that
Fe3+ could form precipitation with PO43- in the wastewater; COD removal mechanism was Fe3+ was
an oxidant, which could oxidize the organic pollutant.
Acknowledgment
We are thankful to Gaobeidian sewage treatment plant for providing the water samples, to the
laboratory of School of Civil and Environmental Engineering, University of Science and
Technology Beijing for providing the experimental instruments.
952
Manufacturing Science and Technology, ICMST2011
References
[1]
Wang Dinghui, On the reclaimed water. Journal of Qinghai Environment, 2009(3):132~135.
[2]
V.H. Smith, Eutrophication. Encyclopedia of Inland Waters, 2009, Pages 61-73.
[3]
C.J. Mena-Duran, M.R. Sun Kou, T. Lopez, J.A. Azamar-Barrios, D.H. Aguilar, M.I.
Domı´nguez, J.A. Odriozola, P. Quintana. Nitrate removal using natural clays modified by
acid thermoactivation. Applied Surface Science, 2007(253): 5762~5766.
[4]
Hengpeng Ye, Fanzhong Chen, Yanqing Sheng, Guoying Sheng, Jiamo Fu. Adsorption of
phosphate from aqueous solution onto modified palygorskites. Separation and Purification
Technology 2006 (50): 283~290.
[5]
Gideon Oron, Leonid Gillerman, Nissan Buriakovsky, Amos Bick, Moti Gargir, Yonthan
Dolan, Yossi Manor, Ludmilla Katz, Josef Hagin. Membrane technology for advanced
wastewater reclamation for sustainable agriculture production. Desalination 2008(218):
170~180.
[6]
M. Rozic, S.Cerjan-Stefanovic, S. Kurajica, V. Vancina, E. Hodzic. Ammoniacal nitrogen
removal from waer by treatment with clay and zeolites. Elsevier Science 2000,
34(14):3675~3681.
[7]
Y.-F.Wang, F. Lin,W.-Q. Pang, Ammonium exchange in aqueous solution using Chinese
natural clinoptilolite and modified zeolite, J. Hazard. Mater. 142 (2007)160~164.
[8]
A. Farkas, M. Rozic, Z. Barbaric-Mikocevic, Ammonium exchange in leakage waters of
waste dumps using natural zeolite from the Krapina region, Croatia, J. Hazard. Mater. 117
(2005) 25~33.
[9]
Wang Dacui, Xu XinHua, Song Shuang. The treatment manual of pollutants in industrial
wastewater. Chemical Industry Press.
[10] Wang Yaping, Liu Yun, Dong Yuanhua, Ma Yijie. Adsorption of Ammonia Nitrogen from
Waste Water by Natural Clinoptilolite. NON-METALLIC MINES. 2007, 30(6): 60~62.
Manufacturing Science and Technology, ICMST2011
10.4028/www.scientific.net/AMR.383-390
A Study on Ammonia Nitrogen, Phosphorus and Organic Pollutants Removal of Zeolites by Salt
Modification
10.4028/www.scientific.net/AMR.383-390.947
DOI References
[7] Y. -F. Wang, F. Lin,W. -Q. Pang, Ammonium exchange in aqueous solution using Chinese natural
clinoptilolite and modified zeolite, J. Hazard. Mater. 142 (2007)160~164.
10.1016/j.jhazmat.2006.07.074
[8] A. Farkas, M. Rozic, Z. Barbaric-Mikocevic, Ammonium exchange in leakage waters of waste dumps
using natural zeolite from the Krapina region, Croatia, J. Hazard. Mater. 117 (2005) 25~33.
10.1016/j.jhazmat.2004.05.035