Computational Water, Energy, and Environmental Engineering, 2013, 2, 12-15
doi:10.4236/cweee.2013.23B003 Published Online July 2013 (http://www.scirp.org/journal/cweee)
Oil Pollutants Degradation of Nano-MgO in
Micr o-Polluted Water
Meng-Fu Zhu, Cheng Deng, Hong-Bo Su, Xiu-Dong You, Lu Zhu, Ping Chen, Ying-Hai Yuan
Institute of Medical Equipment, Academy of Military Medical Sciences, Tianjin
ReceivedApril, 2013
ABSTRACT
The removal of oil pollutants from water and purifying process of oil-pollu ted water are studied through catalytic deg-
radation method with nano-MgO. The results indicated that catalytic degradation effect of nano-MgO on the oil pollut-
ants was associated with dosage of nano-MgO, pH and water temperature. When oil content was 1.8 mg/L, 0.17 g
nano-MgO was used and the removal rate of oil was 93.92%. Furthermore, nano-Mgo was a non-photosensitiv e catalyst.
GC/MS analysis showed that the amount of petroleum-based pollutants in water was reduced 73.77% from the previous
61 kinds to 16 kinds, and the total peak area was reduced 96.05% after catalytic degradation of nano-MgO. Therefore,
nano-MgO has an excellent effect on the catalytic degradation of oil pollutants and can be applied in the treatment of oil
wastewaters.
Keywords: Nano-MgO; Oil Pollutants; Catalytic Degradation; Micro-Polluted Water; Water Treatment
1. Introduction
Micro-polluted water refers to that water whose physi-
cal, chemical and microbial properties can’t meet the
demands of water quality as a source of drinking water.
Generally speaking, pollutants in the micro-polluted wa-
ter are often regarded as trace organics, including natural
organic matter (NOM) and synthetic organic compound
(SOC). Due to the accidents of oil spill and the over
emission of oily sewages from industry, agriculture,
transportation and daily life, the concentration of oil and
its related products in our drinking water increased con-
tinuously. Thus oil pollutants have become one of the
major problems toward the present water pollution. In
China, Drinking Water Sanitary Standard has strictly
regulated the ingredients of petroleum products [1]. O il is
comprised of hundreds of organics, mainly including
alkanes, aromatic hydrocarbons and cyclones, which
account for 50% - 90% of the total oil content, and the
rest are non-hydrocarbon oxygenates, sulfur or nitroge-
nous nitrogenous compounds [2]. The oil pollutants are
considered to have adverse effects on human body and
natural environment because of their high mutagenic
activity, whereas nanomaterials have excellent properties
of adsorption and catalytic degradation of the organic
pollutants in the water, due to the small particle size,
high specific surface area, high surface activity, a great
numbers of surface defects and surface ions, etc [3,4,5,6].
In this study, self-made nano-MgO was used as the cata-
lyst for the treatment of oil pollutants in micro-polluted
water to investigate the catalytic degradation and con-
tributing factors off nano-MgO.
2. Experiment
2.1. Reagent and Instrument
Carbon tetrachloride, analytically pure, ChangMao che-
mical regent factory (Beichen District, Tianjin); An- hy-
drous sodium sulfate, analytically pure, ChangMao
chemical regent factory (Beichen District, Tianjin); Po-
tassium permanganate, analytically pure, Tianjin No.1
chemical regent factory; Sodium oxalate, standard, Bei-
jing chemical plant; Petroleum, obtained from Jilin oil-
field; Nano-MgO, particle size 8.5 nm, specific surface
163.23 m2/g, thin needle-like crystal, self-mad e.
JDS-105U infrared spectrophotometry oil measuring
instrument, BeiGuang analytic instrumental factory;
5890-5971 GC/MS, Agilent Technology.
2.2. Experimental Method
Crude oil was used to prepare the micro-polluted water.
A certain amount of nano-MgO was added into the mi-
cro-polluted water, and then stirred uniformly. After a
period of catalytic degradation reaction, the oil content in
the water was measured by oil measuring instrument and
the original oil content was also measured as a control
before the reaction. Finally, we calculated the degrada-

M.-F. ZHU ET AL. 13
tion rate and analyzed the components through GC/MS.
3. Result and Discussion
3.1. The Influence of Dosage of MgO on Oil
Degradation
Different amount of nano-MgO was added into the mi-
cro-polluted water, whose original state was 1.8 mg/L in
oil content, 7 in pH and 20˚C in temperature. As the re-
action time went to 30 min, we began to study the in-
fluence of the amount of nano-MgO on the oil removal.
The results in Figure 1 showed that the degradation rate
of oil was raised with increase of the dosage of nano-
MgO. When dosage reached to 0.17 g, the degradation
rate was the most, and then it began to decrease with
increase of the dosage of nano-MgO. It might be due to
the fact that the increasing amount of nano-MgO caused
a larger numbers of hydroxyl radicals in solution, the
enhancement of oxidation ability and an increase in reac-
tive center, thereby improving the effect of oil removal.
When dosage was above 0.17 g, nano-MgO particles
were easily to aggregation, leading to less specific sur-
face area and the decrease of oil degradation rate.
3.2. The Influence of pH on the Oil Degradation
Figure 2 showed the plot of pH versus oil degradation
rate of nano-MgO. The reaction temperature was 20˚C
and reaction time was 30 min. The original content of oil
and dosage of MgO were 1.8 mg/L and 0.17 g respec-
tively. We can find that the degradation rate was closely
relevant to pH, and indeed the rate was raised with the
increase of pH. This results from the fact that the solution
pH can change the surface charge properties of nano-
MgO and the ionic composition of the organic matter in
water, determine the interaction of electrostatic attraction
and repulsion between catalyst surface and organics,
thereby influencing the results of organic catalytic de-
gradation.
0.00 0.05 0.10 0.15 0.20 0.25 0.30
0
20
40
60
80
100
Removal Rate (%)
Dosage (g)
Figure 1. The influence of dosage of MgO on oil degrada-
tion.
3.3. The Influence of Temperature on Oil
Degradation
Figure 3 showed the plot of temperature versus oil deg-
radation rate of nano-MgO. The reaction time was 30
min. The original content of oil and dosage of MgO were
1.8 mg/L and 0.17 g respectively. With the increase of
reaction temperature, the oil degradation was raised
gradually. It was because that increasing the temperature
can enhance the diffusion and transfer of reactant mole-
cules or intermediates on the surface of catalyst, resulting
in more chances of contact between reactant molecules
and intermediates. Beyond 20℃, however, temperature
changes made little influence on oil degradation. There-
fore, normal temperature was suitable for nano-MgO to
catalytic degradatio n of oil pollutant in water.
3.4. The Influence of Reaction Time on Oil
Degradation
Figure 4 showed the plot of reaction time versus oil deg-
radation rate of nano-MgO. The reaction temperature
was 20˚C. The original content of oil and dosage of MgO
were 1.8 mg/L and 0.17 g respectively. Because of the
limitation of experimental devices, removal rate could
only be detected after 10 min. The results showed that
0369
0
20
40
60
80
100
12
Removal Rate(%)
pH
Figure 2. The influence of pH on oil degradation.
0102030
0
20
40
60
80
100
40
Removal rate(%)
Temperature(℃)
Figure 3. The influence of temperature on oil degradation.

M.-F. ZHU ET AL. 14
0
the removal rates of oil were greater than 90% during 60
min reaction time and nearly can’t be influenced with the
reaction time goes on, which indicated that the reaction
of catalytic degradation was very fast and completed in a
relative short time.
3.5. The Influence of Light Irradiation on Oil
Degradation
On the condition of light irradiation, most nano-metal
oxides are able to absorb electron-hole pairs the photon
producing. Then electrons and holes are separated under
the force of electric field and migrate to different location
of nano-particles respectively, which are beneficial to
photocatalytic reaction between nano-particles and or-
ganics. In order to study the relation between catalytic
degradation property and light irradiation condition, we
compare the removal properties of nano-MgO under the
condition of indoor natural light and completely dark
(Table 1). The results demonstrated that there was no
significant different under the condition of light irradia-
tion and dark, indicating nano-MgO was a non-photosen-
sitive catalyst.
3.6. GC/MS Analysis
GC/MS is a useful method to learn the species and re-
lated information about organic compounds. Figure 5
showed the GC/MS graph of micro-polluted water of
which oil content was 4.0 mg/L. For this graph, the se-
quence of organic peaks indirectly represents the boiling
point of organics. In other words, the boiling point de-
termines the consequence of peaks. GC/MS analysis de-
tected 72 peaks totally and each peak corresponded to
relevant organic compound. Every peak was arranged on
the graph in the light of boiling point, and the total area
of peaks was 1.14 × 108. There were 61 kinds of organ-
ics in original micro-polluted water by GC/MS, mainly
including 24 alkanes, 10 esters, 6 alkenes, 5 acids, 3 al-
cohols, 3 ethers, 2 amines and 9 others. Most of their
molecular weight ranged from 100 to 300. Among those
organics, alkanes were the most, which accounted for
39.34% of the total numbers of organics, and peak area
of alkanes accounted for 64.76% of the total peak area,
indicating that oil was a kind of mixture of hydrocarbons.
Figure 6 showed the GC/MS graph of oil polluted
water after catalytic degradation of nano-MgO. The MgO
0 10203040506
0
20
40
60
80
100
Removal Rate(%)
Reaction time(min)
Figure 4. The influence of reaction time on oil degradation.
Table 1. The influence of light irradiation on oil degrada-
tion.
Oil content, mg/L
condition Before reactionAfter reaction Removal rate, %
Indoor light
irradiation 1.84 0.11 94.02
Dark 1.96 0.06 96.94
Note: MgO dosage 0.17 g, pH 7, temperature 20˚C, re action time 30 min.
time
Figure 5. GC/MS graph of oil micro-polluted water.

M.-F. ZHU ET AL. 15
time
Figure 6. GC/MS graph after catalytic degradation of nano-MgO.
dosage was 0.40 g and reaction time was 30 min. After
the treatment of nano-MgO, the numbers of organic spe-
cies in water reduced to 16 kinds. Comparing the organic
composition of original water, there were 59 kinds of
organics that existed in original water didn’t be detected
after treatment and only 2 species were remained. But
another new 14 kinds of organics were detected in water
after catalytic degrad ation of nano-MgO , including acid s,
amines and aldehydes. Generally speaking, the numbers
of organic species reduced from original water’s 61 to 16
species, by a reduction of 45 kinds. The numbers of
peaks also reduced from 72 to 15. The total area de-
creased from 1.14108 to 4.5106, by a reduction of
96.05%. It indicated that nano-MgO was able to catalytic
degrade most of organics referring petroleum, and most
of them were oxidized to CO2 and H2O, and parts of or-
ganics were oxidized to small molecule intermediates.
4. Conclusions
Catalytic degr adation effect of nano- MgO on the oil pol-
lutants was associated with dosage of nano-MgO, pH and
water temperature. When oil content was 1.8 mg/L, 0.17
g nano-MgO was used and the removal rate of oil was
93.92%. Furthermore, nano-Mgo was proved to be a
non-photosensitive catalyst. Most of organics were oxi-
dized to CO2 and H2O, and parts of them were oxidized
to small molecule intermediates. In conclusion, nano-
MgO has an excellent effect on the catalytic degradation
of oil pollutants and can be applied in the treatment of oil
wastewaters.
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