- Email: [email protected]
Chemical destabilization of oil-in-water emulsion by novel polymerized diethanolamines
Journal of Colloid and Interface Science 284 (2005) 167–175 www.elsevier.com/locate/jcis
Chemical destabilization of oil-in-water emulsion by novel polymerized diethanolamines A.A. Hafiz a,∗ , H.M. El-Din b , A.M. Badawi a a Egyptian Petroleum Research Institute (EPRI), Applied Surfactant Laboratory, Nasir City, Egypt b Cairo Oil Refining Company, Cairo, Egypt
Received 31 May 2004; accepted 13 October 2004 Available online 24 December 2004
Abstract The main objective of this study was to synthesize novel demulsifiers for resolving oil-in-water emulsions. Diethanolamine polyethers are considered as a cationic polymer type. The study describes an improved synthesis of a series of diethanolamine polyethers via condensation of 3–7 or 9 mol of diethanolamine. The structure and the molecular weights of the major components in the reaction mixture were confirmed via IR and MS analyses. The demulsifiers were used for treatment of pollution in the refinery wastewater with or without FeCl3 . The flocculation efficiency of the synthesized demulsifiers was determined by turbidity measurement of the treated and untreated O/W emulsion in the Cairo Oil Refinery Company. The critical flocculation concentration (CFC) and charge density of the synthesized demulsifiers were determined. Biodegradation of diethanolamine polyethers was measured in river water within 7–8 days. 2004 Elsevier Inc. All rights reserved. Keywords: Diethanolamine polyether; Cationic emulsion breakers; Chemical destabilization; Condensation polymerization
1. Introduction The principal family of cationic emulsion breakers is polyamines Cationicity is derived from the quadrivalent nitrogen, either via protonation of primary, secondary, or tertiary amines or via generation of quaternary nitrogen groupings [1,2]. Polyalkylene polyamines are prepared by condensation of diethylenetriamine, triethylenetetramine, and tetraethylene pentamine [3]. Triethanolamine is condensed in the presence of different catalysts, and the structure and degree of polymerization were determined via mass spectroscopy as a molecular weight of the major component that results during the synthesis process [4]. The pollution in oil refinery comes from the petroleum emulsions that contain in practice oil, water, and an emulsifying agent. The emulsifying agent re* Corresponding author.
E-mail address: [email protected] (A.A. Hafiz). 0021-9797/$ – see front matter 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2004.10.010
duces the interfacial tension and prevents coalescence of oil droplets [5]. The resulting O/W emulsion is destabilized by chemical methods, via addition of organic emulsion breakers with or without an inorganic one [6]. Inorganic emulsion breakers might be aluminum sulfate, aluminum chloride [7], or ferric chloride [8]. The polyamine type strongly cationic emulsion breakers give the treated water improved quality in breaking O/W emulsions [9,10]. The present investigation is concerned with the synthesis and evaluation of novel emulsion breakers (D3 –D7 and D9 ).
2. Experimental 2.1. Synthesis of diethanolamine polyether Diethanolamine was polymerized in the presence of different catalysts to form diethanolamine polyether of controlled molecular weight [11]. One mole of diethanolamine was charged into a three-necked flask where the polymerization process is performed. The catalyst was added while
168
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
Table 1 The catalyst, molar ratio, and physical properties of diethanolamine polyether (D3 –D7 , D9 ) Compound
Catalyst
Ratio (M/L)
Color
pH
D3 D4 D5 D6 D7 D9
CaCl2 H3 PO4 /CH3 COOH H3 PO4 NaOH Al2 (SO4 )3 /CH3 COOH Al2 (SO4 )3
0.02 0.005/0.02 0.005 0.04 0.04/0.02 0.04
Light Brown Light Brown Yellow Yellow
8.53 7.75 7.65 8.01 6.83 7.83
Table 2 Water analyses for Cairo Refining Co. Test
Unit
pH Salinity Mg2+ Ca2+ HCO− 3 SO2− 4 Fe Oil Turbidity
5.3 2670 ppm 586 ppm 504 ppm 10 ppm 12.6 ppm 3.85 ppm 200 ppm 250 NTUa
a NTU refers to nephelometric turbidity unit.
(%) efficiency NTU untreated emulsion – NTU treated emulsion = NTU untreated emulsion × 100. 2.2.4. Critical flocculation concentration (CFC) CFC was determined from the relation between (%) efficiency and different concentrations of the emulsion breaker. 2.2.5. Specific charge-density measurements The specific charges of the emulsion breakers were determined using conductometric titration (conduct meter, CONSORT-C834) of 1 ppm of the emulsion breaker solution D3 –D7 , D9 against 0.1 mol/L CaCl2 . The chemicals used were AR grade and the distilled water used was double distilled and deionized. The contents of the titration vessel were stirred with a magnetic stirrer [14]. From the end point of the conductometric titration, the number of moles equivalent can be determined and hence the quantity of electricity according to Faraday’s laws. The charge density was then calculated for each sample in terms of coulombs (c/g) [15].
stirring, then the reaction mixture was heated at 140–160 ◦ C for 12 h [12]. The different catalysts used, their molar ratios, and physical properties are recorded in Table 1. The reaction mixture was worked out as follows: Methanol was added for separating the catalyst, and then evaporation of methanol was performed using a rotary evaporator. IR spectroscopic analysis was confirmed via Fourier transform infrared, ATM Mattson Genesis, FTIR spectrophotometer. Mass spectra were confirmed via mass spectrometer HP Model MS5488.
2.2.6. Biodegradation of the prepared emulsion breakers The prepared emulsion breakers (D3 –D7 and D9 ) were dissolved in 200 ml of river water at a concentration which represents the CFC for each compound. The concentration of undergraded amine was determined by titrating 30 ml of the previous solutions against 0.001 M HCl using phenolphthalein as indicator and was followed up daily for 8 days to indicate the rate of degradation [16].
2.2. Jar test measurements
3.1. Synthesis of diethanolamine polyether
2.2.1. Emulsion The emulsion used was the wastewater produced in the Cairo Oil Refining Co., Egypt, which has the specifications illustrated in Table 2. A jar test procedure was carried out to evaluate the compounds (D3 –D7 and D9 ) as emulsion breakers.
The condensation process takes place in the absence of solvent and the addition of an effective amount of dehydrating agent. A series of diethanolamine polyether are synthesized via condensation of 3–7 or 9 mol of diethanolamine
2.2.2. Jar test Jar tests were conducted according to the procedure of Herbert et al. [13], using the jar test apparatus flocculator, Floccumatic Code 3000834. The oil content of emulsion before and after treatment was determined by Turbid Meter Model 2100P, expressed as turbidity content (NTU). 2.2.3. Percentage efficiency of the prepared emulsion breakers Percentage efficiency of the emulsion breaker is calculated as follows:
3. Results and discussion
These products are mixtures of different components. The structure elucidation of these products can be considered as a kind of fingerprint and an identity card of the original material, without the need to identify all components of the mixture [17–19]. The structures of compounds (D3 –D7 and D9 ) were made accessible to infrared and mass spectrometric analysis, as follows:
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
169
Fig. 1. MS spectrum of D3 .
(i) Infrared spectra of polydiethanolamine (D3 –D7 and D9 ) show a νC–O–C band of ether linkage in range of 1190– 1205 cm−1 , which is characteristic for the condensation process, a broad absorption band in 3 µm region νOH , a νCH band at 2850–3000 cm−1 , and a νCN band at 1000– 1350 cm−1 .
(ii) Chemical ionization/mass spectra (CI/MS) can be used to determine the molecular weight represented by the molecular weight of the major component [20]. CI/MS chromatograms and spectra of compounds D3 –D7 and D9 are shown in Figs. 1–6, and the respective fragmentation patterns are shown in Schemes 1–6.
170
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
Fig. 2. MS spectrum of D4 .
Scheme 3. CI/MS fragmentation patterns of D5 . Scheme 1. CI/MS fragmentation patterns of D3 .
3.2. Destabilization of O/W emulsions Jar testing is a relatively quick method for selecting the demulsifier dosages and treatment conditions (mixing intensity, time, and settling time). The percentage residual turbidity in each dosage based on the initial stock of the wastewater turbidity gives the flocculation efficiency of the used dose [21].
Scheme 2. CI/MS fragmentation patterns of D4 .
3.2.1. Determination of critical flocculate ion concentration The critical flocculation concentration (CFC) is determined as the smallest amount of demulsifier achieving
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
171
Fig. 3. MS spectrum of D5 .
Scheme 4. CI/MS fragmentation patterns of D6 .
Scheme 6. CI/MS fragmentation patterns of D9 .
Scheme 5. CI/MS fragmentation patterns of D7 .
reasonable separation of the emulsion after 15 min. This concentration, in general, corresponded to a break in the plot of flocculation efficiency (%) vs demulsifier concentration (ppm). The flocculating efficiency of the synthesized demulsifiers is governed by multiple interactions such as
172
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
Fig. 4. MS spectrum of D6 .
the electrostatic interactions, hydrogen bonding, structure, charge density, and molecular weight of the cationic demulsifier [21]. Fig. 7 shows the values of CFC, efficiency for compound D4 compared with a commercial one (cationic polyelectrolyte) (KLAR AID4081, Grace Dearborn Co.). Table 3 shows CFC and corresponding efficiencies for compounds (D3 –D7 , D9 ), commercial. The flocculation efficiency curve can be classified to three ranges as follows: Range 1. The amount of demulsifier is insufficient, so that only part of the emulsion is destabilized. Range 2. The optimum concentration leads to high efficiency of CFC. The electrostatic barrier ensuring the stability of the emulsion is initially due to the presence of negative charges of anionic surface active has disappeared. The quadrivalent demulsifier has neutralized most of the negative charges. This refers to the optimization range of flocculation. Range 3. Efficiency again decreases noticeably. Positive charges are brought by the hydrated demulsifier, which
are destabilized when they perfectly neutralize opposing charges, where they create new positive ionic layers which are created when added in greater concentrations. An electrostatic barrier appears between positive charges and the emulsion stability is formed due to the overdosage of the demulsifier used which results in reemulsification of the already broken emulsion, and consequently complete breaking of emulsion is only possible in a relatively narrow dosage range of the demulsifier. Below this range, breaking is incomplete. This optimal dosage range necessary for CFC determination is achieved by constant trial-and-error testing of the type and quantity of the demulsifier. 3.2.2. Relation between molecular weight of diethanolamine polyethers and their CFC Fig. 8 shows the relation between the molecular weight of diethanolamine polyethers (D3 –D7 and D9 ) and their CFC, where CFC decreases as the molecular weight increases. The higher the molecular weight polymer, the lower the concentration needed for interparticle bridging required for neutralization [21].
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
173
Fig. 5. MS spectrum of D7 .
3.2.3. Relation between molecular weight of diethanolamine polyethers and their efficiency Fig. 9 shows the relation between molecular weight of the diethanolamine polyethers (D3 –D7 and D9 ) and their efficiency. As previously discussed, three ranges of flocculation efficiency appear. The highest efficiency is recorded by D4 and D7 . 3.2.4. Relation between charge density and flocculation efficiency As discussed before, the CFC is a criterion of the flocculation efficiency. CFC is influenced by the charge density existing on the emulsifying agent producing the emulsion. Here, the higher the charge density, the stronger the resulting repulsion between the particles of the emulsion and hence the more stable one. Therefore, charge density existing at the CFC of the demulsifier should be effective for charge neutralization of the emulsified oil. Table 4 shows the variation of the flocculation efficiency with the charge density of diethanolamine polyethers (D3 –D7 and D9 ). The results in Table 3 show that the flocculation efficiency increases as the charge density of the demulsifier increases till CFC of each
Table 3 CFC and corresponding efficiency for demulsifiers (D3 –D7 , D9 ) Demulsifier
CFC (ppm)
Efficiency without coflocculant (%)
Efficiency with coflocculant (%)
D3 D4 D5 D6 D7 D9 Commercial
5 30 10 40 30 30 30
34 45 28 28 41 32 43
63 65 28 44 66 28 –
demulsifier, above it, over charge decrease the efficiency. Thus it is possible that the overdose of the demulsifier results in reemulsification of the already broken emulsion. 3.3. Coflocculation efficiency enhancement In the present work, FeCl3 (5 ppm) as a coflocculant is mixed with the prepared organic demulsifier at its CFC dosage. The results for coflocculation efficiency are recorded in Table 3.
174
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
Fig. 6. MS spectrum of D9 .
Fig. 7. Efficiency % vs dose D4 compared with commercial one.
Fig. 8. Effect of molecular weight (D3 –D7 , D9 ) on the critical flocculation concentration (CFC).
Biodegradability of the synthesized diethanolamine polyethers (D3 –D7 and D9 ) is evaluated at 25 ◦ C for 8 days by monitoring the time-dependent charge in the demulsifier concentration followed by the titration of undergraded con-
centration. The degradation process takes place under the action of microorganisms in river freshwater [16]. Fig. 10 is an example of the rate of biodegradation for compound D4 . The rate of biodegradation of all demulsifiers increases gradually by time until a complete degradation at
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
175
7–8 days. This behavior is attributed to an increase in the molecular weight (leading to an increase in the number of hydroxyl groups) which results in an increase in the solubility of the demulsifiers. Finally, it can be concluded that the biodegradability of the synthesized demulsifiers makes them favorable ecologically.
References
Fig. 9. Effect of molecular weight (D3 –D7 , D9 ) on their efficiency. Table 4 Variation of flocculation efficiency (%) with charge density (c/g) for demulsifiers (D3 –D7 , D9 ) Dose (ppm)
D3
5 10 20 30 40 50 60 70 90 100
1.7 3.4 6.8 10.2 13.6 17.0 20.4 23.8 30.6 34.0
D4
D5
D6
D7
D9
(c/g) (%) (c/g) (%) (c/g) (%) (c/g) (%) (c/g) (%) (c/g) (%) 34a 15 – – – 2 13 – – 4
2.1 4.2 8.4 12.6 16.8 21.0 25.2 29.4 37.8 42.0
– 9 23 43a 33 25 20 12 9 –
2.4 4.8 9.6 14.4 19.2 24.0 28.8 33.6 43.2 48.0
2 18 8 5 12 16 21 28a 26 11
2.5 5.0 10.0 15.0 20.0 25.0 30.0 35.0 45.0 50.0
5 – – 12 15 20 28a 23 16 11
a Refers to the dose of CFC.
Fig. 10. Biodegradation of D4 .
2.8 5.6 11.2 16.8 22.4 28.3 33.6 39.2 50.4 56.0
– 34 32 41a 12 12 20 19 12 19
3.2 6.4 12.8 19.2 25.6 32.0 38.4 44.8 57.6 64.0
– 6 15 32a 25 26 19 29 13 –
[1] C. Claudia, M. Zappia, V. Bacharch, Adv. Polyamine Res. 3 (1981) 493. [2] B.C. Fee, U.S. patent 4,387,028 (1983). [3] G.A. Smith, patent applied WO 0047,524 (2000). [4] A.A. Hafiz, Ph.D. thesis, Ain Shams University, Faculty of Girls, 1997. [5] S. Hartland, S.A.K. Jeelani, Colloids Surf. A 88 (1994) 289. [6] A. Botha, G. Offringa, D. Whyte, Chemsa 15 (3) (1989) 3. [7] D. Petruzzelli, R. Passino, G. Tiravanti, Ind. Eng. Chem. Res. 34 (1995) 2612. [8] D. Deepak, S.G. Roy, K. Raghavan, S. Mukherjee, Roorkee, Indian J. Environ. Health 30 (1989) 43. [9] G. Nemtoi, A. Onu, N. Aelenei, S. Dragan, C. Beldie, Eur. Polym. J. 36 (2000) 2679. [10] L. Ghimici, I. Dranca, S. Dragan, T. Lupascu, A. Maftuleac, Eur. Polym. J. 37 (2001) 227. [11] Th.J. Bellos, U.S. patent 4,404,362 (1983). [12] R. Fikentscher, K. Oppenlaender, J. Dix, W. Sager, H. Vogel, K. Barthold, G. Elfers, U.S. patent 5,393,463 (1995). [13] E. Herbert, Hudson Jr., Water Clarification Processes, Practical Design and Evaluation, Van Nostrand–Reinhold, New York, 1981, chap. 3, p. 40. [14] A. Abdel Hakim, E. Tombacz, F. Szanto, Acta Phys. Chem. Szeged 34 (1988) 109. [15] A. Vogel, Vogel’s Textbook of Quantitative Inorganic Analysis, fourth ed., 1978, chap. 12, p. 515. [16] T. Ohura, Y. Aoyagi, K. Takagi, Y. Yoshida, K. Kasuya, Y. Doi, Polymer Degrad. Stability 63 (1999) 23. [17] A.J.H. Boerboom, in: S. Facchatti (Ed.), Mass Spectrometry of Large Molecules, Elsevier, New York, 1983, p. 265. [18] S. Foti, G. Montaudo, in: S. Facchatti (Ed.), Mass Spectrometry of Large Molecules, Elsevier, New York, 1983, p. 286. [19] R. Self, M.N. Short, A. Parente, in: S. Facchatti (Ed.), Mass Spectrometry of Large Molecules, Elsevier, New York, 1983, p. 151. [20] A.A. Hafiz, M.I. Abdu, J. Surfactants Detergents 6 (2003) 243. [21] X. Zhu, B.E. Reed, W. Lin, P.E. Carriere, G. Roark, Sep. Sci. Technol. 32 (1997) 2173.
Chemical destabilization of oil-in-water emulsion by novel polymerized diethanolamines A.A. Hafiz a,∗ , H.M. El-Din b , A.M. Badawi a a Egyptian Petroleum Research Institute (EPRI), Applied Surfactant Laboratory, Nasir City, Egypt b Cairo Oil Refining Company, Cairo, Egypt
Received 31 May 2004; accepted 13 October 2004 Available online 24 December 2004
Abstract The main objective of this study was to synthesize novel demulsifiers for resolving oil-in-water emulsions. Diethanolamine polyethers are considered as a cationic polymer type. The study describes an improved synthesis of a series of diethanolamine polyethers via condensation of 3–7 or 9 mol of diethanolamine. The structure and the molecular weights of the major components in the reaction mixture were confirmed via IR and MS analyses. The demulsifiers were used for treatment of pollution in the refinery wastewater with or without FeCl3 . The flocculation efficiency of the synthesized demulsifiers was determined by turbidity measurement of the treated and untreated O/W emulsion in the Cairo Oil Refinery Company. The critical flocculation concentration (CFC) and charge density of the synthesized demulsifiers were determined. Biodegradation of diethanolamine polyethers was measured in river water within 7–8 days. 2004 Elsevier Inc. All rights reserved. Keywords: Diethanolamine polyether; Cationic emulsion breakers; Chemical destabilization; Condensation polymerization
1. Introduction The principal family of cationic emulsion breakers is polyamines Cationicity is derived from the quadrivalent nitrogen, either via protonation of primary, secondary, or tertiary amines or via generation of quaternary nitrogen groupings [1,2]. Polyalkylene polyamines are prepared by condensation of diethylenetriamine, triethylenetetramine, and tetraethylene pentamine [3]. Triethanolamine is condensed in the presence of different catalysts, and the structure and degree of polymerization were determined via mass spectroscopy as a molecular weight of the major component that results during the synthesis process [4]. The pollution in oil refinery comes from the petroleum emulsions that contain in practice oil, water, and an emulsifying agent. The emulsifying agent re* Corresponding author.
E-mail address: [email protected] (A.A. Hafiz). 0021-9797/$ – see front matter 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2004.10.010
duces the interfacial tension and prevents coalescence of oil droplets [5]. The resulting O/W emulsion is destabilized by chemical methods, via addition of organic emulsion breakers with or without an inorganic one [6]. Inorganic emulsion breakers might be aluminum sulfate, aluminum chloride [7], or ferric chloride [8]. The polyamine type strongly cationic emulsion breakers give the treated water improved quality in breaking O/W emulsions [9,10]. The present investigation is concerned with the synthesis and evaluation of novel emulsion breakers (D3 –D7 and D9 ).
2. Experimental 2.1. Synthesis of diethanolamine polyether Diethanolamine was polymerized in the presence of different catalysts to form diethanolamine polyether of controlled molecular weight [11]. One mole of diethanolamine was charged into a three-necked flask where the polymerization process is performed. The catalyst was added while
168
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
Table 1 The catalyst, molar ratio, and physical properties of diethanolamine polyether (D3 –D7 , D9 ) Compound
Catalyst
Ratio (M/L)
Color
pH
D3 D4 D5 D6 D7 D9
CaCl2 H3 PO4 /CH3 COOH H3 PO4 NaOH Al2 (SO4 )3 /CH3 COOH Al2 (SO4 )3
0.02 0.005/0.02 0.005 0.04 0.04/0.02 0.04
Light Brown Light Brown Yellow Yellow
8.53 7.75 7.65 8.01 6.83 7.83
Table 2 Water analyses for Cairo Refining Co. Test
Unit
pH Salinity Mg2+ Ca2+ HCO− 3 SO2− 4 Fe Oil Turbidity
5.3 2670 ppm 586 ppm 504 ppm 10 ppm 12.6 ppm 3.85 ppm 200 ppm 250 NTUa
a NTU refers to nephelometric turbidity unit.
(%) efficiency NTU untreated emulsion – NTU treated emulsion = NTU untreated emulsion × 100. 2.2.4. Critical flocculation concentration (CFC) CFC was determined from the relation between (%) efficiency and different concentrations of the emulsion breaker. 2.2.5. Specific charge-density measurements The specific charges of the emulsion breakers were determined using conductometric titration (conduct meter, CONSORT-C834) of 1 ppm of the emulsion breaker solution D3 –D7 , D9 against 0.1 mol/L CaCl2 . The chemicals used were AR grade and the distilled water used was double distilled and deionized. The contents of the titration vessel were stirred with a magnetic stirrer [14]. From the end point of the conductometric titration, the number of moles equivalent can be determined and hence the quantity of electricity according to Faraday’s laws. The charge density was then calculated for each sample in terms of coulombs (c/g) [15].
stirring, then the reaction mixture was heated at 140–160 ◦ C for 12 h [12]. The different catalysts used, their molar ratios, and physical properties are recorded in Table 1. The reaction mixture was worked out as follows: Methanol was added for separating the catalyst, and then evaporation of methanol was performed using a rotary evaporator. IR spectroscopic analysis was confirmed via Fourier transform infrared, ATM Mattson Genesis, FTIR spectrophotometer. Mass spectra were confirmed via mass spectrometer HP Model MS5488.
2.2.6. Biodegradation of the prepared emulsion breakers The prepared emulsion breakers (D3 –D7 and D9 ) were dissolved in 200 ml of river water at a concentration which represents the CFC for each compound. The concentration of undergraded amine was determined by titrating 30 ml of the previous solutions against 0.001 M HCl using phenolphthalein as indicator and was followed up daily for 8 days to indicate the rate of degradation [16].
2.2. Jar test measurements
3.1. Synthesis of diethanolamine polyether
2.2.1. Emulsion The emulsion used was the wastewater produced in the Cairo Oil Refining Co., Egypt, which has the specifications illustrated in Table 2. A jar test procedure was carried out to evaluate the compounds (D3 –D7 and D9 ) as emulsion breakers.
The condensation process takes place in the absence of solvent and the addition of an effective amount of dehydrating agent. A series of diethanolamine polyether are synthesized via condensation of 3–7 or 9 mol of diethanolamine
2.2.2. Jar test Jar tests were conducted according to the procedure of Herbert et al. [13], using the jar test apparatus flocculator, Floccumatic Code 3000834. The oil content of emulsion before and after treatment was determined by Turbid Meter Model 2100P, expressed as turbidity content (NTU). 2.2.3. Percentage efficiency of the prepared emulsion breakers Percentage efficiency of the emulsion breaker is calculated as follows:
3. Results and discussion
These products are mixtures of different components. The structure elucidation of these products can be considered as a kind of fingerprint and an identity card of the original material, without the need to identify all components of the mixture [17–19]. The structures of compounds (D3 –D7 and D9 ) were made accessible to infrared and mass spectrometric analysis, as follows:
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
169
Fig. 1. MS spectrum of D3 .
(i) Infrared spectra of polydiethanolamine (D3 –D7 and D9 ) show a νC–O–C band of ether linkage in range of 1190– 1205 cm−1 , which is characteristic for the condensation process, a broad absorption band in 3 µm region νOH , a νCH band at 2850–3000 cm−1 , and a νCN band at 1000– 1350 cm−1 .
(ii) Chemical ionization/mass spectra (CI/MS) can be used to determine the molecular weight represented by the molecular weight of the major component [20]. CI/MS chromatograms and spectra of compounds D3 –D7 and D9 are shown in Figs. 1–6, and the respective fragmentation patterns are shown in Schemes 1–6.
170
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
Fig. 2. MS spectrum of D4 .
Scheme 3. CI/MS fragmentation patterns of D5 . Scheme 1. CI/MS fragmentation patterns of D3 .
3.2. Destabilization of O/W emulsions Jar testing is a relatively quick method for selecting the demulsifier dosages and treatment conditions (mixing intensity, time, and settling time). The percentage residual turbidity in each dosage based on the initial stock of the wastewater turbidity gives the flocculation efficiency of the used dose [21].
Scheme 2. CI/MS fragmentation patterns of D4 .
3.2.1. Determination of critical flocculate ion concentration The critical flocculation concentration (CFC) is determined as the smallest amount of demulsifier achieving
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
171
Fig. 3. MS spectrum of D5 .
Scheme 4. CI/MS fragmentation patterns of D6 .
Scheme 6. CI/MS fragmentation patterns of D9 .
Scheme 5. CI/MS fragmentation patterns of D7 .
reasonable separation of the emulsion after 15 min. This concentration, in general, corresponded to a break in the plot of flocculation efficiency (%) vs demulsifier concentration (ppm). The flocculating efficiency of the synthesized demulsifiers is governed by multiple interactions such as
172
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
Fig. 4. MS spectrum of D6 .
the electrostatic interactions, hydrogen bonding, structure, charge density, and molecular weight of the cationic demulsifier [21]. Fig. 7 shows the values of CFC, efficiency for compound D4 compared with a commercial one (cationic polyelectrolyte) (KLAR AID4081, Grace Dearborn Co.). Table 3 shows CFC and corresponding efficiencies for compounds (D3 –D7 , D9 ), commercial. The flocculation efficiency curve can be classified to three ranges as follows: Range 1. The amount of demulsifier is insufficient, so that only part of the emulsion is destabilized. Range 2. The optimum concentration leads to high efficiency of CFC. The electrostatic barrier ensuring the stability of the emulsion is initially due to the presence of negative charges of anionic surface active has disappeared. The quadrivalent demulsifier has neutralized most of the negative charges. This refers to the optimization range of flocculation. Range 3. Efficiency again decreases noticeably. Positive charges are brought by the hydrated demulsifier, which
are destabilized when they perfectly neutralize opposing charges, where they create new positive ionic layers which are created when added in greater concentrations. An electrostatic barrier appears between positive charges and the emulsion stability is formed due to the overdosage of the demulsifier used which results in reemulsification of the already broken emulsion, and consequently complete breaking of emulsion is only possible in a relatively narrow dosage range of the demulsifier. Below this range, breaking is incomplete. This optimal dosage range necessary for CFC determination is achieved by constant trial-and-error testing of the type and quantity of the demulsifier. 3.2.2. Relation between molecular weight of diethanolamine polyethers and their CFC Fig. 8 shows the relation between the molecular weight of diethanolamine polyethers (D3 –D7 and D9 ) and their CFC, where CFC decreases as the molecular weight increases. The higher the molecular weight polymer, the lower the concentration needed for interparticle bridging required for neutralization [21].
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
173
Fig. 5. MS spectrum of D7 .
3.2.3. Relation between molecular weight of diethanolamine polyethers and their efficiency Fig. 9 shows the relation between molecular weight of the diethanolamine polyethers (D3 –D7 and D9 ) and their efficiency. As previously discussed, three ranges of flocculation efficiency appear. The highest efficiency is recorded by D4 and D7 . 3.2.4. Relation between charge density and flocculation efficiency As discussed before, the CFC is a criterion of the flocculation efficiency. CFC is influenced by the charge density existing on the emulsifying agent producing the emulsion. Here, the higher the charge density, the stronger the resulting repulsion between the particles of the emulsion and hence the more stable one. Therefore, charge density existing at the CFC of the demulsifier should be effective for charge neutralization of the emulsified oil. Table 4 shows the variation of the flocculation efficiency with the charge density of diethanolamine polyethers (D3 –D7 and D9 ). The results in Table 3 show that the flocculation efficiency increases as the charge density of the demulsifier increases till CFC of each
Table 3 CFC and corresponding efficiency for demulsifiers (D3 –D7 , D9 ) Demulsifier
CFC (ppm)
Efficiency without coflocculant (%)
Efficiency with coflocculant (%)
D3 D4 D5 D6 D7 D9 Commercial
5 30 10 40 30 30 30
34 45 28 28 41 32 43
63 65 28 44 66 28 –
demulsifier, above it, over charge decrease the efficiency. Thus it is possible that the overdose of the demulsifier results in reemulsification of the already broken emulsion. 3.3. Coflocculation efficiency enhancement In the present work, FeCl3 (5 ppm) as a coflocculant is mixed with the prepared organic demulsifier at its CFC dosage. The results for coflocculation efficiency are recorded in Table 3.
174
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
Fig. 6. MS spectrum of D9 .
Fig. 7. Efficiency % vs dose D4 compared with commercial one.
Fig. 8. Effect of molecular weight (D3 –D7 , D9 ) on the critical flocculation concentration (CFC).
Biodegradability of the synthesized diethanolamine polyethers (D3 –D7 and D9 ) is evaluated at 25 ◦ C for 8 days by monitoring the time-dependent charge in the demulsifier concentration followed by the titration of undergraded con-
centration. The degradation process takes place under the action of microorganisms in river freshwater [16]. Fig. 10 is an example of the rate of biodegradation for compound D4 . The rate of biodegradation of all demulsifiers increases gradually by time until a complete degradation at
A.A. Hafiz et al. / Journal of Colloid and Interface Science 284 (2005) 167–175
175
7–8 days. This behavior is attributed to an increase in the molecular weight (leading to an increase in the number of hydroxyl groups) which results in an increase in the solubility of the demulsifiers. Finally, it can be concluded that the biodegradability of the synthesized demulsifiers makes them favorable ecologically.
References
Fig. 9. Effect of molecular weight (D3 –D7 , D9 ) on their efficiency. Table 4 Variation of flocculation efficiency (%) with charge density (c/g) for demulsifiers (D3 –D7 , D9 ) Dose (ppm)
D3
5 10 20 30 40 50 60 70 90 100
1.7 3.4 6.8 10.2 13.6 17.0 20.4 23.8 30.6 34.0
D4
D5
D6
D7
D9
(c/g) (%) (c/g) (%) (c/g) (%) (c/g) (%) (c/g) (%) (c/g) (%) 34a 15 – – – 2 13 – – 4
2.1 4.2 8.4 12.6 16.8 21.0 25.2 29.4 37.8 42.0
– 9 23 43a 33 25 20 12 9 –
2.4 4.8 9.6 14.4 19.2 24.0 28.8 33.6 43.2 48.0
2 18 8 5 12 16 21 28a 26 11
2.5 5.0 10.0 15.0 20.0 25.0 30.0 35.0 45.0 50.0
5 – – 12 15 20 28a 23 16 11
a Refers to the dose of CFC.
Fig. 10. Biodegradation of D4 .
2.8 5.6 11.2 16.8 22.4 28.3 33.6 39.2 50.4 56.0
– 34 32 41a 12 12 20 19 12 19
3.2 6.4 12.8 19.2 25.6 32.0 38.4 44.8 57.6 64.0
– 6 15 32a 25 26 19 29 13 –
[1] C. Claudia, M. Zappia, V. Bacharch, Adv. Polyamine Res. 3 (1981) 493. [2] B.C. Fee, U.S. patent 4,387,028 (1983). [3] G.A. Smith, patent applied WO 0047,524 (2000). [4] A.A. Hafiz, Ph.D. thesis, Ain Shams University, Faculty of Girls, 1997. [5] S. Hartland, S.A.K. Jeelani, Colloids Surf. A 88 (1994) 289. [6] A. Botha, G. Offringa, D. Whyte, Chemsa 15 (3) (1989) 3. [7] D. Petruzzelli, R. Passino, G. Tiravanti, Ind. Eng. Chem. Res. 34 (1995) 2612. [8] D. Deepak, S.G. Roy, K. Raghavan, S. Mukherjee, Roorkee, Indian J. Environ. Health 30 (1989) 43. [9] G. Nemtoi, A. Onu, N. Aelenei, S. Dragan, C. Beldie, Eur. Polym. J. 36 (2000) 2679. [10] L. Ghimici, I. Dranca, S. Dragan, T. Lupascu, A. Maftuleac, Eur. Polym. J. 37 (2001) 227. [11] Th.J. Bellos, U.S. patent 4,404,362 (1983). [12] R. Fikentscher, K. Oppenlaender, J. Dix, W. Sager, H. Vogel, K. Barthold, G. Elfers, U.S. patent 5,393,463 (1995). [13] E. Herbert, Hudson Jr., Water Clarification Processes, Practical Design and Evaluation, Van Nostrand–Reinhold, New York, 1981, chap. 3, p. 40. [14] A. Abdel Hakim, E. Tombacz, F. Szanto, Acta Phys. Chem. Szeged 34 (1988) 109. [15] A. Vogel, Vogel’s Textbook of Quantitative Inorganic Analysis, fourth ed., 1978, chap. 12, p. 515. [16] T. Ohura, Y. Aoyagi, K. Takagi, Y. Yoshida, K. Kasuya, Y. Doi, Polymer Degrad. Stability 63 (1999) 23. [17] A.J.H. Boerboom, in: S. Facchatti (Ed.), Mass Spectrometry of Large Molecules, Elsevier, New York, 1983, p. 265. [18] S. Foti, G. Montaudo, in: S. Facchatti (Ed.), Mass Spectrometry of Large Molecules, Elsevier, New York, 1983, p. 286. [19] R. Self, M.N. Short, A. Parente, in: S. Facchatti (Ed.), Mass Spectrometry of Large Molecules, Elsevier, New York, 1983, p. 151. [20] A.A. Hafiz, M.I. Abdu, J. Surfactants Detergents 6 (2003) 243. [21] X. Zhu, B.E. Reed, W. Lin, P.E. Carriere, G. Roark, Sep. Sci. Technol. 32 (1997) 2173.