filtration, the concentration of oil in the permeate was
reduced from 200 to 8.7 mg/L at 1.1 bar which has passed
the Chinese standard for PW discharge.
With referring to previous MF membrane studies, there is
something common which is the use of inorganic or ceramic
membrane which attracted interest. Pre-treatment step by
flocculation prior to filtration process improved the efficiency of the membrane and avoids the fouling formation of
cake layer on the membrane surface (Alzahrani and
Mohammad 2014).
2.2 Ultrafiltration (UF)
One the hand, the membrane filtration where the pore size of
the membrane is between 0.01 and 0.1 lm is called ultrafiltration or UF. Initially, UF was accompanied along with
MF to enhance the MF. However, in PW or oil treatment, it
was found that UF membranes are prone to fouling due to its
high permeation flux. Hence, in UF studies, this matter is
being stress on how to reduce the fouling especially on
membrane’s surface also the effect of the fouling to the
performance of the system. One of effective ways to reduce
fouling is by reducing the roughness of the membrane surface and make it more hydrophilic.
Wandera et al. (2011) has reported that in his study of
using UF membrane for synthetic PW treatment with modified hydrophilic cellulose and unmodified to enhance the
surface roughness of the membrane. From the study, the
unmodified membrane showed higher water flux if to be
compared with modified due to grafted polymers which
covered the surface of modified membrane. However, the
unmodified membrane appeared to recover only 81% of
permeation flux compared to modified membrane where
almost 100% permeation flux recovery was recorded using
simple water rinse. Further study by the same group Wandera et al. (2012), where the study on the effect of grafting
density of polymer to prevent fouling indicated that there
was decreasing in permeation flux as the density of the
grafted polymer was increased. Further decline of permeation flux was showed as the operation was continued, and it
was remarkably significant compared to unmodified membrane showing that grafted polymer thus brought effect to the
pore size of the membrane and hence influences the permeation flux.
Another study by Yan et al. (2009) where the ability of
modified and unmodified UF membrane for PW treatment
was investigated using polyvinylidene fluoride (PVDF)
mixed with nano-sized alumina particles fabricated in a
tubular-shaped module. The results discovered that in term
of organic pollutants removal, modified UF showed better
performance compared to unmodified where the modified
UF membrane exhibited more advantages such as high
permeation flux more than 170 L/m
2 h bar, upgraded
anti-fouling performance as well as almost 100% permeation
flux was recovered after a few cleaning testing using some
chemicals. It was also suggested that back-wash using
OP-10 surfactant could be used for an enhanced cleaning
testing to maintain high performance of the UF membrane
whenever fouling was happened.
On the other hand, study by Kang et al. (2007) uses a
modified UF membrane from PAN on the effect of hydrophilic modification to counter membrane’s fouling in PW
treatment. 20 wt% of PAN-g-PEO was added, and three different sources of PW were used, and for comparison, a
commercial Serpo PAN400 was used as an unmodified
membrane. From the study, the membranes showed a successful removal of grease and oil in the PW using a dead-end
filtration system as shown in Fig. 6. The modified hydrophilic
PAN membrane was able to recover up to 25% initial flux
irreversibly compared to unmodified PAN membrane. In
addition, the hydrophilic modified UF membrane showed a
significant increase in rate of permeation flux compared to
unmodified membrane which clearly indicated the success of
hydrophilicity modification on the membrane’s surface
compared to commercial unmodified UF membrane where the
permeation flux was declined in the PW treatment operation.
Report on using a hybrid PVDF/MWCNT nanocomposite
UF membrane has been done by Moslehyani et al. (2015)
used in a photocatalytic reactor together with UF filtration
for petroleum refinery wastewater treatment. The membranes
were fabricated using multi-wall carbon nanotubes
(MWCNT) combined with 200 ppm of TiO 2 and UV light to
enhance the photocatalytic reaction of the PW treatment.
From the study, up to 90% of organic pollutant was
removed, and more than 90% of organic matters were
decomposed by the photocatalytic reaction after 6 h UV
radiation process by studying the content in the permeate.
Interestingly, it also discovered that the TiO 2 photocatalyst
also recovered to more than 99% efficiency compared to
normal catalytic reactor. Hence, the modified membrane
acted as double usage simultaneously to filter the PW water
and also for photocatalyst purpose.
In order to optimize an effective separation of oil in PW,
other factors such as physiochemical nature of the UF
membrane should be considered for a practical use in
membrane technology. Seyed Shahabadi and Reyhani
(2014) used commercial PAN350 UF membrane to investigate the effect of operating condition of membrane including
cross flow velocity (CFV), temperature (T), transmembrane
pressure (TMP), TOC rejection, permeation flux and resistance to fouling. The study reported that TMP showed significant influence on the fouling resistance and permeation
flux while TOC removal greatly influenced by the CFV. The
claim was supported by comparison in experimental and full
factorial design methodology for data optimization and from
Hydrocarbon Separation and Removal Using Membranes
79
reduced from 200 to 8.7 mg/L at 1.1 bar which has passed
the Chinese standard for PW discharge.
With referring to previous MF membrane studies, there is
something common which is the use of inorganic or ceramic
membrane which attracted interest. Pre-treatment step by
flocculation prior to filtration process improved the efficiency of the membrane and avoids the fouling formation of
cake layer on the membrane surface (Alzahrani and
Mohammad 2014).
2.2 Ultrafiltration (UF)
One the hand, the membrane filtration where the pore size of
the membrane is between 0.01 and 0.1 lm is called ultrafiltration or UF. Initially, UF was accompanied along with
MF to enhance the MF. However, in PW or oil treatment, it
was found that UF membranes are prone to fouling due to its
high permeation flux. Hence, in UF studies, this matter is
being stress on how to reduce the fouling especially on
membrane’s surface also the effect of the fouling to the
performance of the system. One of effective ways to reduce
fouling is by reducing the roughness of the membrane surface and make it more hydrophilic.
Wandera et al. (2011) has reported that in his study of
using UF membrane for synthetic PW treatment with modified hydrophilic cellulose and unmodified to enhance the
surface roughness of the membrane. From the study, the
unmodified membrane showed higher water flux if to be
compared with modified due to grafted polymers which
covered the surface of modified membrane. However, the
unmodified membrane appeared to recover only 81% of
permeation flux compared to modified membrane where
almost 100% permeation flux recovery was recorded using
simple water rinse. Further study by the same group Wandera et al. (2012), where the study on the effect of grafting
density of polymer to prevent fouling indicated that there
was decreasing in permeation flux as the density of the
grafted polymer was increased. Further decline of permeation flux was showed as the operation was continued, and it
was remarkably significant compared to unmodified membrane showing that grafted polymer thus brought effect to the
pore size of the membrane and hence influences the permeation flux.
Another study by Yan et al. (2009) where the ability of
modified and unmodified UF membrane for PW treatment
was investigated using polyvinylidene fluoride (PVDF)
mixed with nano-sized alumina particles fabricated in a
tubular-shaped module. The results discovered that in term
of organic pollutants removal, modified UF showed better
performance compared to unmodified where the modified
UF membrane exhibited more advantages such as high
permeation flux more than 170 L/m
2 h bar, upgraded
anti-fouling performance as well as almost 100% permeation
flux was recovered after a few cleaning testing using some
chemicals. It was also suggested that back-wash using
OP-10 surfactant could be used for an enhanced cleaning
testing to maintain high performance of the UF membrane
whenever fouling was happened.
On the other hand, study by Kang et al. (2007) uses a
modified UF membrane from PAN on the effect of hydrophilic modification to counter membrane’s fouling in PW
treatment. 20 wt% of PAN-g-PEO was added, and three different sources of PW were used, and for comparison, a
commercial Serpo PAN400 was used as an unmodified
membrane. From the study, the membranes showed a successful removal of grease and oil in the PW using a dead-end
filtration system as shown in Fig. 6. The modified hydrophilic
PAN membrane was able to recover up to 25% initial flux
irreversibly compared to unmodified PAN membrane. In
addition, the hydrophilic modified UF membrane showed a
significant increase in rate of permeation flux compared to
unmodified membrane which clearly indicated the success of
hydrophilicity modification on the membrane’s surface
compared to commercial unmodified UF membrane where the
permeation flux was declined in the PW treatment operation.
Report on using a hybrid PVDF/MWCNT nanocomposite
UF membrane has been done by Moslehyani et al. (2015)
used in a photocatalytic reactor together with UF filtration
for petroleum refinery wastewater treatment. The membranes
were fabricated using multi-wall carbon nanotubes
(MWCNT) combined with 200 ppm of TiO 2 and UV light to
enhance the photocatalytic reaction of the PW treatment.
From the study, up to 90% of organic pollutant was
removed, and more than 90% of organic matters were
decomposed by the photocatalytic reaction after 6 h UV
radiation process by studying the content in the permeate.
Interestingly, it also discovered that the TiO 2 photocatalyst
also recovered to more than 99% efficiency compared to
normal catalytic reactor. Hence, the modified membrane
acted as double usage simultaneously to filter the PW water
and also for photocatalyst purpose.
In order to optimize an effective separation of oil in PW,
other factors such as physiochemical nature of the UF
membrane should be considered for a practical use in
membrane technology. Seyed Shahabadi and Reyhani
(2014) used commercial PAN350 UF membrane to investigate the effect of operating condition of membrane including
cross flow velocity (CFV), temperature (T), transmembrane
pressure (TMP), TOC rejection, permeation flux and resistance to fouling. The study reported that TMP showed significant influence on the fouling resistance and permeation
flux while TOC removal greatly influenced by the CFV. The
claim was supported by comparison in experimental and full
factorial design methodology for data optimization and from
Hydrocarbon Separation and Removal Using Membranes
79