THE CAPABILITY OF COPOLY(EUGENOL-DIVINYLBENZENE), CO-EDVB AS A CARRIER OF PHENOL TRANSPORT WITH

POLYMER INCLUSION MEMBRANE (PIM)

Agung Abadi Kiswandono1,2,*, Dwi Siswanta2, Nurul Hidayat Aprilita2, Sri Juari Santosa2, Takashi Hayashita3

1Faculty of Public Health, Prima University, Medan, Indonesia2Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada,

Sekip Utara, Yogyakarta, Indonesia, 552813Department of Materials and Life SciencesFaculty of Science and Technology, Sophia University, Kioicho, Chiyoda-

ku, Tokyo102-8554, Japan

e-mail : nau_shila@yahoo.com

Abstract

The study was taken to observe phenol transport by employing Polymer Inclusion Membrane (PIM) method which contained copoly(eugenol-DVB), co-EDVB as the carrier. The parameters such as pH of source phase, concentration of NaOH, membrane thickness, concentration of carrier, variants of transpor time, and Membrane Liquid (ML) loss as well as lifetime had been published in the previous journal. On this writing, co-EDVB containing 12% of DVB (divinylbenzene) had been observed with both the effect of NaNO3 salt and the reuse of membrane as the parameters. As the ingredients, carbon atom, hydrogen, and oxygen had been examined through elemental analysis, co-EDVB’s characterized through TG-DTA, and after-transport membrane characterized through SEM. The result of study showed that the increase of NaNO3 salt concentration could both fade ML loss away and affect the transported phenol concentration. Such a decrease of ML loss was supported by a morphological appearance on the membrane resulted from SEM, it was pores closing. Another fact revealing during the study was that membrane could be used more than once with little ML loss.

Keywords: crosslinked, PIM, carrier, co-EDVB, ML loss

1. INTRODUCTION

Liquid Membrane (LM) is a method combining extraction with separation together in a phase, so that the transfer of unequal mass in separation is not limited by the balanced condition [1,2]. Then, polymer inclusion membrane (PIM) can be defined as a kind of liquid membrane method recently having proven to be an effective one used for the separation process of any anion and cation [3-6]. Both flexibility and utility or function of such a membrane method have proved good based on its various applications over the last years [8-10], and the fact that the leak of membrane can be maintained, thereby producing long membrane lifetime [11] are good reasons why such a method has to be pushed up maximally. However, the application of this facilitated membrane carrier can be quite expensive while the carrier compound being a core of such a method is costly, inaccessible, or hard to be synthesized.

The transport of a targeted compound employing liquid membrane method always entails carrier compounds. One of the compounds usable, whose basis is natural substance, are they coming from

eugenol polymerisation, and so generating polymer having both hidroxyl active sides and benzene rings. The carrier compounds’ active sides are the factor determining that these targeted compounds are easy to transport, and the membrane’s capacity is continually usable. In addition, the capacity to be used repeatedly is a strength of a membrane analyzed through such PIM method.

We had carried out a study showing that co-EDVB membrane examined by PIM method was repeatedly usable, by having only little loss of components composing the membrane. In fact, this was a part of the study previously published. Such phenol transport was conducted by making use of both co-EDVB’s active sides and difference between two phases’ pH, so that phenol as the targeted compound could be transported from the source phase to the receiving one.

2. EXPERIMENTAL SECTION

The condition of transport process was similar to that of Kiswandono et al. [7,11], including the instruments to transport (Chamber), the compound composition, the membrane generation, and the procedure of phenol transport. A set of phenol transport instruments (PIM cell) comprised two cylinder chambers separated by a membrane. Then, each chamber contained about 50 ml of solution which was stirred then, and the effective diameter to easily contact with the phenol solution was 2,5 cm, and it was the center of transport process.

The analytic measurements, pH meter (HANNA Instruments, M-18654), UV-spectrometer (772-Spectrophotometer), TG-TGA (Perkin Elmer) were taken at Analytic Laboratory of UGM. Meanwhile, Scanning Electron Microscope (Hitachi SU8000), infrared spectrophotometer Shimadzu model IR Prestige-21 with magnetik KBR pellet holder 0016-008 and Elemental Analisis Perkin Elmer Series CHNS/O Analyzer 2400 were taken at Materials and Life Sciences Laboratory, Faculty of Science and Technology, Sophia University, Chiyoda-ku Tokyo Japan.

Synthesis of co-EDVB Synthesis of co-EDVB in this study employed basic ingredients of eugenol and catalyst BF3O(C2H5)2 as conducted by Kiswandono et al. [7], with DVB’s variations as the crosslinking agent by 0% and 12% of the eugenol’s mass, and the synthesis result of these two materials were powder. In addition, the synthesis of co-EDVB was taken by DVB crosslinking agent, while boron trifluoride diethyl ether acid BF3O(C2H5)2 functioned as the catalyst. Then, the polymer on a synthesis employing only eugenol and boron trifluoride diethyl ether as the catalyst (DVB : 0%) was called as polyeugenol which then was stored in decicator to be at the end characterized.Preparation of membranePIM membrane was formed with PVC as the matrix polymer, co-EDVB as the carrier compound, and DBE as the plasticizer which were mixed then into a mould. Moreover, the organic solvent, tetrahydrophurane (THF) was used to homogenize the mixture on the mould. After the solution was homogeneous, the membrane was left for 3 days. Phenol transport Such a study was managed to meet the standard condition in line with that of Kiswandono et al. [11]. The transport process was taken by putting 50 ml of phenol 60 ppm into the source phase, and 50 ml of NaOH 0,25 M into the receiving phase. In addition, both phases were completed by stirrer. Then, they were carefully stirred in room temperature. The concentration of phenol in both source and receiving phase was analyzed through 4-aminoantiphyrine method [12,13], and then its absorbency was measured through UV-vis of 450 nm in wave length.

The loss of membrane components was determined by measurement method, stating that the total sum of membrane liquid loss was obtained by measuring the membrane after and before transport employing analytic scale once the membrane was still dry. Then, the phenol and water intake in

membrane liquid or membrane pores were likely to cause any fault in ML loss measurement, yet such a difference was much lower than the experimental one, and for that reason it was negligible. Once there were some water molecules inside the membrane pores, by using such a measurement method their present mass was still lower than the real ML loss [14,15]. The transport capability evaluated in this study was the repeated use of membrane, the effect of NaNO3 salt addition, and the effect of NaNO3 salt ‘s increasing concentration.CharacterizationThe polymer formed in both the elemental and thermal analysis then was characterized through SEM. The membrane used before and after the transport process was characterized through SEM and IR aiming to identify both the surface morphological change, and the capability cluster of membrane during the transport process.

3. RESULTS AND DISCUSSIONS

Synthesis and CharacterizationThere were eugenol co-polymerisation with DVB (called co-EDVB) and eugenol only (called polieugenol) taken in this study. Both eugenol and DVB had allyl cluster which played an important role in polymerisation reaction. Most of monomers having double bond C=C could have radical polymerisation, however they having cationic polymerisation were monomers having substitution cluster releasing electron only. The eugenol monomer had double bond C=C (vinyl substitution cluster) causing it radical polymerisation. Such a vinyl group of eugenol experienced additional reaction, so that this co-polymerisation was called as cationic additional co- polymerisation. Moreover, the reaction of eugenol co- polymerisation with crosslinking agent would cause the molecule heavier, thereby affecting the membrane’s capability of interacting with the targeted compound. Then, the polymer resulting from such a synthesis had bigger mass, so that it would have much more active side (cluster –OH and benzene ring). The increase of polymer’s active sides as the result of synthesis was expected to elevate the transport capability so that its process could be quicker and able to be used repeatedly. Then, each polymer synthesized then was tested by elemental analysis in order to identify the percentage of carbon atom, hydrogen, and oxygen as displayed in Table 1.

Table 1. Profile of co-EDVB powder

DVB (w/w)% of weight

DVB to Eugenol

Melting point (°C)

The number of crosslinking agents

Elemental analysis(%)

g (×10-3) Mol (×10-4) C H O

Co-EDVB 0% (polyeugenol) 80.3-82.7 0 0 71,36 7,06 21,58

Co-EDVB 12% 100.6-109.0 696 53 72,98 7,11 19,91

Based on Table 1, it was clearly identified that the level of carbon was relatively increasing, yet the hydrogen atom’s was gradually weakening due to the increase of DVB’s moleculs. It indicated that the polymer chain was getting longer. Such a fact was supported by the IR spectra data, comprising both the width of co-EDVB spectra peak, and the polymer’s melting point [7]. Definitely, the increasing melting point was in line with the addition of DVB’ amount. It was believed that such occurence was happening since the co-EDVB molecules’ mass was heavier owing to more DVB added up. Another reason was that the carbon chain was getting longer. The characterization of polyeugenol powder and its derivatives formed was then analyzed through SEM as displayed in Fig. 1. The morphology generated by SEM as displayed in Fig. 1 showed that polyeugenol crystal and its derivatives had the same and homogenous morphological pattern. It was believed that such a phenomenon happened because of the same shape and colour of polymer powder resulted: brownish

soft powder dissolving in chloroform [7]. In addition, the magnification of 250x on co-EDVB 12% (Fig. 1b) showed the same homogenous pattern similar with polyeugenol, so that it could be concluded that the polyeugenol crystal and its derivatives had the same homogenous morphological pattern.

Next, in order to provide another proof of crosslink reaction, the Thermographimetric Analysis (TGA) was then carried out. In general, what is called as thermographimetric is a technique usable to measure changes on mass of particular compounds as the function of temperature. The result of such an analysis is in form of continuous diagram record showing gradual schematic decomposition reaction. Decomposition of polimer is caused by the existence of

Figure 1. Morphology of SEM result from powder of (a) polyeugenol, and (b) co-EDVB 12%, 250x

thermochemical process. The explanation of such a process comes from the DTA result. DTA is a measurement technique of temperature difference between sample and reference materials. It is called as thermogram which can give some information about both physical and chemical characteristic changes. Some physical processes well-known are endothermic and exothermic. Then, thermographimetric was applied to polyeugenol and co-EDVB in temperature range of 30-900 °C and 10 °C/min in heating speed.

Decomposition of co-EDVB (Fig. 2) in curve of TGA showed that the changing mass taking place in ~33 °C till ~550 °C was in line with the DTA as the exothermic and endothermic processes happening in turn on such a temperature interval. The changing mass in ~33 °C to ~320 °C was related to the sample dehydration, while the change detected by the DTA was in ~320 °C to ~395 °C, having no similar trace in TGA, due to connecting with recrystallisation reaction in co-EDVB dehydrated. Such a second process was characterized endothermic (peak b), then followed by exothermic one in temperature interval of ~395 °C to ~545 °C ( peak c,d) showing that the structure adopted between ~395 °C to ~545 °C was metastable. Such an exothermic process of DTA indicated an enthalpy decrease of sample and change leading to more stable structure.

Furthermore, the same thing happened to polyeugenol compound having pattern of mass decrease similar to that of co-EDVB, yet it had different DTA’s curve pattern as displayed in Fig. 2. Both decomposition of polyeugenol in TGA’s curve, and changing mass in ~33 °C to ~550 °C were also shown in DTA as both exothermic and endothermic processes taking place in turn in such a temperature interval. The changing mass in ~33 °C to ~323 °C (peak a) was related to sample dehydration, followed by the change detected by the DTA was in ~323 °C to ~398 °C, having no visible trace in TGA. Such a second process was characterized endothermic (peak b), then followed by exothermic one (peak c,d) in temperature interval showing that the structure adopted between ~398 °C to ~529 °C was metastable and related to the recrystallisation reaction of polyeugenol. At last, such an exothermic process of DTA indicated an enthalpy decrease of sample and change leading to more stable structure.

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Figure 2. Curve of TG-DTA polyeugenol and co-EDVB

In general, all samples had experienced crystallisation after the elimination of H2O or water release. Such a crystallisation was shown by peak to the top (exothermic reaction). The elimination temperature of H2O for the sample of both polymers was about 33 °C to 350 °C with the losing mass on average of 15,5% (polyeugenol) 14,9% (1,03 mg) for co-EDVB and the reaction taking place in water release was endothermic one. The amount of enthalpy in endothermic reaction was similar to that of the losing water mass. The greater the losing water mass, the bigger the energy absorbed. The small endothermic peak, added by decomposition of sample mass in 323 °C, and 398 °C, was caused by the existence of methoxy released to be methyl (-CH3) in such a temperature. The losing mass in methoxy elimination was on average 13,7% (0,85 mg). In addition, the losing mass in methoxy elimination of polyeugenol was bigger than the amount of losing mass in co-EDVB (12,6%). After the H2O elimination had exothermic process continuously, it indicated that the polymer components obtained had amorphous phase. Heating caused crystallisation, and the longer the crystallisation process, the greater the mass decomposition, reaching 59,5% in polyeugenol and 62,7% in co-EDVB.

Phenol transport with reuse of PIM membraneThe repeated use of membrane aimed both to examine its endurance and to identify its stability. The result showed that once the membrane had been used two and three times, the phenol transport from source phase to the receiving phase one was weakening gradually. In addition, Fig. 3 displayed the comparison of phenol transport used for in turn one, two, and three times during 48 hours. It was believed that both the second and third weakening phenol transports were caused by the species of leaching membrane existing in the first, reducing the phenol concentration of the last two transports. In addition, the diminishing phenol concentration having transport to the receiving phase was predictably due to the leaching coming from molecule carrier of co-EDVB. Once both the second and third membranes were used, the amount of active cluster was decreasing. Such a decrease would cause interaction of π−π , and the hydrogen bond formed between phenol and co-EDVB to weaken, so that the phenol transport to the receiving phase was getting smaller. Obviously, the ML loss of the last two’s reuse got increasing by relatively stable score. Then, Fig. 3 provided with some information that the small gaps of ML loss in the first, second, and third use,which were 3,5% and 0,6%, indicated that the membrane components leaching and diminishing due to its pores gradually covered by sediments of some chemical components such as PVC or the other ones, was losing its ML loss step by step. In addition, Fig. 4 depicted that the membrane’s pores were slowly covered by sediments of some chemical components contained in the solution. Then, Fig. 4b looked greater than Fig. 4a, since such a membrane had been exploited three times. Next to the result of SEM, the loss of components constructing membrane was also recorded by the IR spectra. The increasing amount of components constructing membrane which was lost, was unexpectedly followed by the diminishing absorption in both OH and also DBE peak as described

in Fig. 5. Indeed, it indicated that the loss of components constructing membrane was coming from not only carrier compound, but also DBE or PVC.

Figure 3. The graphic of phenol transport and ML loss with repeated use of PIM membrane

Effect of NaNO3 concentration increaseThe stability of membran could be predicted by observing the effect of NaNO3 salt’s concentration

Figure 4. The SEM of co-EDVB 12% membrane, and Used (a) once time (b) three times, 1000x

Figure 5. The result of IR spectra on membrane co-EDVB 12% with the use for 1x48 hour and 3x48 hour

increase. Then, phenol transport was carried out through two variations; by adding various concentration of NaNO3 into source phase with stable condition of receiving phase, and putting various concentration of NaNO3 into receiving phase with stable condition of source phase.

a ba

The result showed that the greater the concentration of NaNO3, the smaller the percentage of phenol transported to the receiving phase (Fig. 6). Then, the molecule carrier employed in membrane was co-EDVB 12% whose active cluster was –OH, which then formed hydrogen bond with phenol transported to the receiving phase through membrane. The existence of NaNO3 in source phase would disturb the form of hydrogen bond between phenol and co-EDVB. Such a phenomenon was taking place due to the existence of Na+ ion in NaNO3 penetrating membrane, then binding –O– in co-EDVB. The greater the concentration of NaNO3, the smaller the active sides in co-EDVB, so that the phenol transport was weakening. The addition of NaNO3 concentration in receiving phase had lower phenol percentage than that of source phase. The increasing concentration of NaNO3 in receiving phase would surely prevent phenol in source phase from transporting to receiving phase.

Figure 6. The curve of effect of NaNO3 salt’s various concentrations on % phenol, %CP (FS : Source phase, FP : receiving phase)

Figur 7. The SEM result of co-EDVB 12% membrane, 2500x employing (a) NaNO3 0,1 M, and (b) NaNO3 0,001 M

The greater the concentration of NaNO3 added, the smaller the percentage of phenol transported to receiving phase. The addition of NaNO3 salt influenced the membrane loss in membrane itself.

Fig. 7 described the result of membrane’s SEM whose NaNO3 were 0,001 M and 0,1 M. Moreover, it was clearly shown that membrane whose NaNO3 concentration was 0,1 M had more pores covered by salt sediment than that of membrane whose NaNO3 concentration was 0,001 M. It indicated that the greater the NaNO3 added, the lower the ML loss of membrane whose NaNO3 was 1M, about 3,4% since the pores was covered by NaNO3 sediment. The greater the salt concentration in both source and receiving phase, the smaller the loss of organic phase in membrane, thereby elevating both the stability and age of membrane [11].

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Some researchers had conducted studies on membrane’s capability related to its age [11,16]. In detail, Kiswandono, et.al. [11] explained the effect of NaNO3 salt use; the utilization of NaNO3 0,1 M would increase the membrane’s age, about 62 days, meanwhile the membrane containing no NaNO3 was durable only about 7 days. Fig. 7 also gave some information that nearly the entire surface of membrane in the examination was covered by a lot of sediment particles, so that all membrane’s pores were blanketed by sediment. In addition, such a sedimentation was probably taking place due to salting-out effect, reducing the ML loss and slowing the membrane’s leak down, so that it increased the membrane’s age. In general, salting out is a purification method making use of the diminishing solubility of particular molecules in solution whose ion power is absolutely high [11].

Effect of NaNO3 1M salt addition to phenol transport time Phenol transport was taken in condition that there was no NaNO3 and NaNO3 1M salt addition to source phase. Moreover, such a phenol transport aimed to identify the stability of membrane determined through membrane loss on transport time. The addition of NaNO3 1 M to source phase could reduce membrane loss and elevate the stability of membrane (Fig. 8).

Figure 8. The curve of transport time with addition of NaNO3 1 M salt on % membrane loss

Such a phenomenon was occuring since NaNO3 salt could cover the membrane’s pores (Fig. 7). During the transport time, ML loss at the beginning would go up, yet the longer the transport process, the smaller the ML loss since there would be much greater NaNO3 salt covering the membrane’s pores, reducing the ML loss. In addition, the increasing ML loss in the initial process was influenced by the stirring process. Zheng et.al. [17] and Nosrati et.al. [18] state that in spite of its capability of homogenizing all the reagents in solution, stirring process could increase the physical disturbances on membrane, thereby multiplying the losing components which constructed the membrane. It was strengthened by a study on phenol transport taken by Kiswandono et al. [11]. Besides, during the transport process, the longer the transport time, the lower the surface tension and contact angle of the three phases. When the surface tension was decreasing in particular level, there would be emulsification suddenly formed, causing membrane loss in its sides close to source phase.

4. CONCLUSIONS

The membrane whose co-EDVB functioned as carrier compound could be used for phenol transport more than once by employing PIM method with percentage of components constructing membrane getting smaller. Based on SEM’s result, the use of NaNO3 salt in phenol transport process could blanket the membrane’s pores, thereby upgrading the stability of PIM membrane since it reduced the percentage of components constructing membrane which was lost.

Acknowledgement

We are indebted the Directorate General of Higher Education (DGHE), Republic of Indonesia who has facilitated the accomplishment of this study through the sandwich program 2012, then we are also grateful to Dr. T. Hashimoto (Materials and Life Sciences Laboratory, Faculty of Science and Technology, Sophia University, Tokyo Japan) who has sincerely provided us with a lot of time to have discussions.

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