Synthesis of a Cleavable Vanillin-Based Polyoxyethylene Surfactant

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Synthesis of a Cleavable Vanillin-Based Polyoxyethylene Surfactant and its Pilot Application in Cotton Fabric Pretreatment Fengmei Ding, Xiang Zhou, Zhenfeng Wu, and Zhiqi Xing ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b06668 • Publication Date (Web): 06 Feb 2019 Downloaded from http://pubs.acs.org on February 12, 2019

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ACS Sustainable Chemistry & Engineering

Synthesis of a Cleavable Vanillin-Based Polyoxyethylene Surfactant and its Pilot Application in Cotton Fabric Pretreatment

Fengmei DING†,‡，Xiang ZHOU *†,‡, Zhenfeng WU †,‡, Zhiqi XING ‡

†Key

Laboratory of Science and Technology of Eco-Textiles, Ministry of Education, and ‡College

of Chemistry, Chemical Engineering and Biotechnology, Donghua University, 2999 North Renmin Road, Shanghai 201620, China

*Corresponding author: Email: [email protected]

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ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Abstract A novel series of non-ionic surfactants (vanillin-1,2-octanediol acetal ethoxylates, VAEO) was synthesized. VAEO was based on natural edible flavor vanillin. These new eco-friendly surfactants contain cleavable acetal bonds which decompose easily under acidic conditions. VAEO was synthesized via a two-step reaction and its structure was characterized by 1H-NMR, 13C-NMR and LC-MS. VAEOn with a series number of EO units (n = 4-12) showed good surface activities, wettability, emulsibility and low-foaming properties, which were comparable with NPEO10. VAEOn were applied to cotton fabric pretreatment and satisfactory fabric performances were obtained. A pilot application of VAEO6 in cotton fabric pretreatment was successfully conducted. The capillary effect and whiteness of the treated cotton fabrics met the quality criteria well. Furthermore, the toxicity experiments showed that VAEO is a low to moderately toxic chemical. The rapid biodegradability test showed its biodegradation rate in 28 days is 92%. And the endocrine disrupting effects trial proved that VAEO has no endocrine disrupting effects. Therefore, VAEO meets DfE criteria for safer surfactants. Keywords: Cleavable surfactants, Vanillin, Vanillin-1,2-octanediol acetal ethoxylates, Cotton fabric pretreatment, NPEO

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Introduction Over the last several decades, there has been a growing attention to the environmental fate of hazardous chemicals. This has positively influenced the attitudes of individuals and societies toward the rapid and healthy development of chemical industry and chemical applications. Researchers in these fields have made enormous efforts to conserve the environment by means of exploring new technologies to reduce chemical consumption. More importantly, there are many researchers working on substituting hazardous chemicals with alternative compounds that are environmental friendly and biodegradable.1 Textile, dyeing and printing industry consume large amounts of chemicals. These chemicals include dyestuff, surfactants and functional finishing agents.2 For example, in order to endow permeability and high whiteness to cotton fabrics, surfactants are usually used as penetrants and emulsifiers to work together with alkali and decolorizers in the pretreatment of cotton fabrics. 3There are several types of excellent surfactants yet with serious environmental problems, for example, alkylphenol polyethoxylates (APEO) with estrogenic activity and bioaccumulation,4-6 linear alkylbenzene sulfonates (LAS) with their toxicity to aquatic life.7-8 Thus, development of environmental friendly surfactants to replace those surfactants with environmental problems is necessary. Alkylphenol ethoxylates are believed to be endocrine disruptors and can cause feminisation of male fish. Moreover, it is believed that APEO can produce metabolites that are even stronger endocrine disruptors than the parent compounds.9 The main substitutes for APEO in the market are the fatty alcohol ethoxylates and carbohydratebased surfactants such as the alkyl glycoside (APG),10 but none of these excels at performance when compared to APEO. Among the environmentally benign surfactants which resounded the industrial and research interest,11-14 there is a kind of cleavable surfactant featured with acetal or ketal structure which is quite stable in alkaline, neutral and oxidizing conditions but decompose in acidic conditions by the cleavage of the acetal bond. Some natural compounds with aldehyde group are the perfect raw material candidates of such green surfactants. Vanillin (C8H8O3), obtained from the seeds of vanilla or microbial synthesis, 3



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could be used to produce cleavable surfactants based on its reaction with monohydric

or dihydric alcohol, yielding acetals. Besides, with a benzene ring in its hydrophobic group, vanillin based surfactants may have advantages over aliphatic chain based ones. Vanillin has been used in the synthesis of some cationic surfactants which completely degraded in 30 days and polyoxyethylene surfactants whose biodegradability was 70~89% after 28 days, 16-17 though none of them was cleavable. In this study, vanillin reacted with 1,2-octanediol to form vanillin-octanediol acetal, then ethylene oxide was added to the product to produce a series of cleavable vanillinbased non-ionic surfactants (VAEOn). The physicochemical properties and application performances of VAEOn were examined and compared with NPEO10, which was once a surfactant with the largest dosage in pretreatment of cotton fabrics. Additionally, the ecological safety of VAEO was investigated on the basis of OECD guidelines. EXPERIMENTAL

Materials. For lab-scale and pilot-scale cotton fabric pretreatment experiments, a greige cotton poplin (100s/2×100s/2, 150×80) manufactured by Luthai Textile Co., Ltd. was used. For bioexperiments, Pseudokirchneriella subcapitata was purchased from Institute of Hydrobiology, Chinese Academy of Sciences and the Zebra fish (Batch: BM20150109001) were from Shanghai Lanling Fishery. The daphnids are laboratory bred, free from overt disease. ER, AR, TR recombinant gene double hybrid yeast cells were provided by SKLEAC, Research Center for Eco-Environmental Science, Chinese Academy of Sciences. Vanillin, 1,2-octanediol, phosphoric acid (85%), hexane, sodium bicarbonate, sodium hydrogen sulfite, potassium hydroxide, ethyl acetate, n-heptane, hydrogen peroxide (30%), sodium meta silicate and other reagents were purchased from Sinopharm Chemical Reagent Co., Ltd. Ethylene oxide was purchased from Sinopec Zhenhai Refining & Chemical Company. Nonylphenol ethoxylate NPEO10 was acquired from Zhejiang Kaide Chemical Co., Ltd. Ethylene oxide and NPEO10 were industrial grade and the others were chemically pure. All the chemicals were used as received. 4


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Synthesis of vanillin 1,2-octanediol acetal. Vanillin (60.8 g, 0.4 mol) and 1,2octanediol (87.6 g, 0.6 mol) were dissolved in hexane (160 mL) in a four-necked 500mL round-bottom flask equipped with a Dean Stark apparatus and a serpentine reflux condenser and the catalyst phosphoric acid (2 g) was added. Then, the mixture was stirred and refluxed under nitrogen till no water produced in the Dean Stark receiver arm. When cooled to room temperature, saturated potassium hydrogen carbonate solution was added to neutralize the catalyst in the mixture. By separating funnel, the organic layer containing the synthesized product was obtained and then the residue water was extracted with anhydrous sodium sulfate. After filtration, the solution was concentrated by rotary evaporator, yielding the crude product. Then saturated sodium hydrogen sulfite solution was slowly added into the crude product to remove the unreacted vanillin to yield the acetal product (128.4 g, yellowish oil) which would be used to react with ethylene oxide. For characterization of vanillin acetal, the resulting acetal product was further purified by column chromatography (silica gel column, eluant: ethyl acetate/heptane = 1/10 (v/v)) to get rid of the residual 1,2-octanediol. Finally, colourless oil of 96.2 g (yield 85.9%) was obtained with the purity of vanillin 1,2-octanediol acetal to be 97.9% detected by HPLC. Synthesis of Vanillin 1,2-octanediolacetal polyoxyethylene ethers. The yellowish Vanillin 1,2-octanediolacetal (250 g) and potassium hydroxide (0.3 g) were mixed in a high pressure reaction kettle which was connected to a vacuum pump and nitrogen cylinder. The air in the kettle was evacuated and replaced with nitrogen. Then the mixture was stirred and heated to 110°C and kept for 1~2 h with trace of nitrogen being introduced into the kettle to remove water. In this procedure, the pressure was less than or equal to -0.098 MPa. The cylinder of ethylene oxide was placed on a weighing scale and connected to the reaction kettle. Ethylene oxide was passed into the kettle and the process should be completed in 3~4 h, where the temperature was slowly raised to 150~160°C. At the same time, the pressure must be under 0.4 MPa. After ethylene oxide was added, the temperature was maintained within 150~160°C until the pressure no longer decrease. Then the temperature was decreased to 110~115°C and during which the unreacted ethylene oxide was removed at the pressure of ≤ -0.098 MPa. The 5



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mixture was subsequently cooled to 60~65°C and glacial acetic acid was added to neutralize potassium hydroxide and the final polyethoxylated vanillin 1,2octanediolacetal was obtained. By controlling the amount of ethylene oxide, the number of ethylene oxide attached to the vanillin acetal was approximately 4, 6, 8, 10 and 12, respectively. The ethoxylated products obtained were designated as VAEO4, VAEO6, VAEO8, VAEO10 and VAEO12 accordingly. Figure 1 displays the synthetic route of VAEO.

Figure 1. Synthetic route of VAEO.

Characterization. The structure of the vanillin acetal was confirmed by means of 1HNMR,

13

C-NMR, LC-MS at room temperature. NMR spectra was recorded using a

Bruker Avance 400 spectrometer and with CD3OCD3 as the solvent. The final surfactant products were characterized via MALDI-TOFMS using a Shimadzu AXIMA Performance

MALDI

TOF/TOF

Mass

Spectrometer

and

with

α-cyano-4-

hydroxycinnamic acid dissolved in acetonitrile/tetrahydrofuran as the matrix. The structure of vanillin 1,2-octanediol acetal was characterized via LC-MS, 1HNMR and 13C-NMR. LC-MS: m/z=281.4 (M++H). 1H-NMR (D6-Acetone): 0.90~0.94 (3H, CH3, 1), 1.33~1.37 (6H, CH2, 3), 1.49~1.54 (2H, CH2, 2), 1.64~1.69 (2H, CH2, 4), 2.05~2.06 (Solvent), 3.54~3.67 (1H, CH, 5), 3.85 (3H, OCH3, 7), 4.03~4.24 (2H, CH2, 6), 5.69, 5.81 (1H, CH，8), 6.85~7.08 (3H, Ar-H), 7.66 (1H,OH,2).

13

C-NMR (D6-

Acetone): 13.62 (CH3, 1), 22.46 (CH2, 2), 25.67 (CH2, 5), 29.08 (Solvent, CH3), 31.72 (CH2, 4), 33.32 (CH2, 6), 33.58 (CH2, 3), 55.39 (OCH3, 16), 70.43 (CH2, 8), 76.19, 76.87 (CH, 7), 102.97, 103.91 (CH, 9), 110.1~147.16 (Ar-H, 10~15), 205.6 (Solvent, CO). The number-average molar mass (Mn) of VAEOn (n=4, 6, 8, 10 and 12) was 496, 549, 663, 732 and 767, respectively, by the MALDI-TOFMS and the distributions 6


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conformed to the Poission’s distribution. NPEO10 was also tested by the MALDITOFMS to obtain its Mn of 738. Laboratory-scale pretreatment experiments. The laboratory pretreatment process for cotton fabric was as follows: the greige fabric was soaked in hot water (90°C) for 5 min, followed by desizing-scouring and bleaching processes. Table 1 presents the chemical formulae of the desizing-scouring and bleaching bathes. The fabric was immersed in the desizing-scouring bath and passed through the padder with two dips and two nips to get an approximate pickup of 100% before it was steamed for 1 h at 100°C. Then the fabric was washed with hot water three times and rinsed with tape water, immersed in the bleaching bath and passed through the padder with two dips and two nips to get an approximate pickup of 100%, and then steamed for 45 minutes at 100℃. Finally the fabric was washed with hot water and cold water and dried at 80℃. Table 1. Cotton Fabric Pretreatment Formulae Process

Cpd.

Concentration (g/L)

Desizingscouring

NaOH

20

Surfactant

x

Bleaching

Hydrogen peroxide (30％) Sodium metasilicate Surfactant

8 8 1

Pilot-scale pretreatment. Shandong Fukang Pharmaceutical Co., Ltd. for producing the hydrophobic part vanillin 1,2-octanediolacetal and Zhejiang Kaide Chemical, Co., Ltd. for producing the final product VAEO6 (1000 kg) by the reaction of vanillin 1,2-octanediolacetal and ethylene oxide. Pilot-scale cotton fabric pretreatment was conducted at Luthai Textile Co., Ltd. The pretreatment process was carried out on a desizing-scouring-bleaching combining machine (ModelⅡ, Brugman). The greige fabric was singed and padded through hot water (90°C) before it was immersed in the the desizing-scouring bath and passed through the padder with one dip and one nip to get an approximate pickup of 110%. Then it went into the 100°C steaming box with a feed speed of 70 m/min to attain a steaming time of 45 min. After 7



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going out of the steamer, the fabric was washed through five rinsing tanks and immersed in the bleaching bath and passed through the padder with one dip and one nip to get a pickup of 110%. Then it entered the steaming box for bleaching to be steamed for 45 min. After that there are six rinsing tanks and three groups of drying cylinder to make the fabric fully washed and dried. The desizing-scouring formula contained 20 g/L of sodium hydroxide and 1.6 g/L of the surfactant to be evaluated. The bleaching formula contained 25 g/L of H2O2 (27.5%), 1g/L of the surfactant, 2 g/L of a stabilizer, and about 10 g/L of sodium hydroxide to adjust pH = 10 - 11. Properties and Performance Tests. Surface tension of dilute solutions of the surfactants was determined using a surface tension meter (JK99C, Shanghai Zhong Chen digital technology Co., Ltd.) by the automatic model of the du Nöuy Ring technique at 25±0.1°C. Cloud point was determined by method A of GB/T 5559-2010. The wetting power was determined according to GB/T 11983-2008 at 25±0.1°C. The emulsibility of the surfactants was determined by measuring the time of phase separation of 10 mL water from the mixture of 40 mL water containing the surfactant and 40 mL paraffin after being shocked vigorously at 25 ± 0.1°C. The foaming properties were determined by a modified Ross-Miles method using Ross-Miles foam analyzer (GRM-52A, Shanghai Longtuo Instrument and Equipment Co., Ltd.) at 50± 0.1°C according to GB/T 7462-94. The capillary effect of fabrics which is a measure of permeability was tested according to FZ/T 01071-2008 using a YG (B) 871 capillary effect tester (Wenzhou Darong textile instruments Co. Ltd.). CIE whiteness index (WI) was determined on a Datacolor-650 spectrophotometer according to AATCC Test Method 110-2005. Breaking strength (BS) was tested on a H10K-S Tinius Olsen benchtop tester according to ASTM D 5035-06. The breaking strength along the weft direction was tested and breaking strength retention (RBS) was calculated by formula (1). 𝐵𝑆

RBS (%) = 𝐵𝑆 × 100% 0

(1)

where BS is the breaking strength of the fabric after treatment, BS0 is the breaking 8


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strength of the fabric before treatment (control). Eco-toxicity Tests. The eco-toxicity tests were conducted at Shanghai Research Institute of Chemical Industry. Rapid biodegradability was tested according to OECD Guidelines for the Testing of Chemicals 301 F “Manometric Respirometry Test” (1992). The acute toxicity of VAEO to Zebra fish was tested in compliance with OECD Guidelines for the Testing of Chemicals No. 203 “Fish, Acute Toxicity Test”(1992). The immobilization of VAEO to the Daphnia sp. (Daphnia magna Straus) was tested on the basis of OECD guidelines for the Testing of Chemicals No. 202 "Daphnia sp., Acute Immobilization Test "(2004). The effects of the VAEO on the growth of algae (Pseudokirchneriella subcapitata) was tested on the basis of OECD guidelines for the Testing of Chemicals No. 201 "Freshwater Alga and Cyano bacteria, Growth Inhibition Test" (2011). The endocrine effects of VAEO and NPEO were detected by the yeasttwo-hybrid technique using ER, AR, TR recombinant gene double hybrid yeast cells. RESULTS AND DISSCUTION Physicochemical properties of VAEOn. Due to the amphipathic structure, the surfactants own unique interfacial properties, such as critical micelle concentration (CMC), surface tension at CMC (γcmc), hydrophilic-lipophilic balance value (HLB) and cloud point. HLB values of VAEOn and NPEO10 were calculated from formula (2).18 HLB = 20 × 𝑀

𝑀𝐻

(2)

𝐻+𝑀𝐿

where 𝑀𝐻 is the formula weight of the hydrophilic portion of the molecule and 𝑀𝐿 is the formular weight of the hydrophobic portion of the molecule. Table 2 summarizes the CMC, γcmc, HLB values and cloud points of VAEOn and NPEO10. It can be seen that the CMC of VAEOn were 2.61-8.06×10-4 mol/L while that of NPEO10 was 6.8×10-5 mol/L. With increasing number of EO units, the CMC of VAEOn decreased while γcmc increased. Though the CMC of NPEO10 was much lower than those of VAEOn, the γcmc, cloud points and HLB values of VAEO6 and VAEO8 were close to those of NPEO10, suggesting that they may have some similar surface activities and application performances. The main difference of VAEO and NPEO in molecular structure is the acetal structure. As shown in Fig.1, VAEO contains a five9



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member ring with two oxygen atoms, this structure can influence their aggregation behavior in aqueous solution. Table 2. Physicochemical Properties of VAEOn and NPEO10 CMC×104

γcmc

(mol/L) VAEO4

Cloud point

(mN/m)

HLB value

8.06

30.5

13.3

29

VAEO6

6.38

31.5

13.9

51

VAEO8

4.52

32.9

15.0

60

VAEO10

3.64

35.1

15.4

69

VAEO12

2.61

37.1

15.6

70

NPEO10

0.68

32.5

14.5

60

Surfactants

(℃)

The application performances of VAEOn. The main application performances of surfactants include wettability, emulsibility, foaming properties and hydrotropy.19 These properties are closely related to their efficacy in cotton fabric pretreatment. Figure 2 presents the wettability, emulsibility and foaming properties of VAEOn. As the EO units grew, the wettability decreased due to the increasing γcmc of VAEOn and molecular volume. VAEO6 displayed the best emulsibility. In fact, the wettability and emulsibility of VAEO6 was the most similar to that of NPEO10. Foamability is a parameter usually to evaluate the level of surfactants to produce foam. It is defined by the volume of foam initially produced in the Ross-Miles test. Foam stability is defined by the volume of foam after 5 minutes. The larger the volume of the foam initially produced or left after 5 minutes, the higher the ability of the surfactant to produce foam or maintain the foam. It can be seen from Figure 2 that the foamability and foam stability of VAEOn were much lower than NPEO10; the increasing EO units also weakened the foamability and foam stability. In textile wet processing, except for foam dyeing and finishing, low foam is expected in most of the processes for easy to control the amount of processing bath and to rinse fabrics with less water consumption. 10


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Figure 2. The application performances of VAEOn and NPEO10, where the concentration of the surfactants was 3 mmol/L.

Laboratory-scale cotton fabric pretreatment. VAEO was further examined in cotton fabric pretreatment. Three most important criteria in assessing the fabrics quality achieved from pretreatment process, capillary effect, whiteness index (WI) and breaking strength retention (RBS), were investigated in this study. Figure 3 shows the performances of cotton fabrics treated with the formulae containing VAEOn or NPEO10. It was found that the capillary effect, WI and RBS of the cotton fabrics treated by VAEOn met the quality criteria. Among them, VAEO6 behaved slightly better than the others, which endowed cotton fabric with the highest capillary effect and whiteness, as well as the RBS. Therefore, VAEO6 was chosen to be produced in pilot scale by two chemical plants for pilot examination in pretreatment of cotton fabrics.

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Figure 3. The effects of cotton fabric pretreatment with VAEOn and NPEO10 (The concentration of surfactants in desizing-scouring was 2 g/L).

In the pretreatment process, the treating solution penetrates into cotton fabrics and removes the wax on cotton fibers by the wetting and emulsifying effect of surfactants. The performance of the treated cotton fabrics is closely related to the wettability and emulsibility of surfactants. Surfactants with excellent wettability and emulsibility can endow fabrics with better performances. As shown in Figure 2, the wettability of VAEOn decreased and the emulsibility increased initially and then decreased as the EO units grew. VAEO6 displayed good wettability and the best emulsibility, so VAEO6 brought about the best performance. In fact, all performances of surfactants are related to their molecular structure. For example, the hydrophobic and hydrophilic chain length, the position of the hydrophilic group in a surfactant molecular structure will affect its wettability. The arrangement of surfactant molecules at the oil-water interface will affect its emulsibility. The relationship between the performance and molecular structure of VAEOn will be conducted in further study. At present, the substitutes of APEO in the market are mainly isomeric alcohol polyoxyethylene ethers, such as Lutensol® TO, Lutensol® XL, Lutensol® XP produced by BASF. And XL70 is used as a component of auxiliaries in pretreatment of 12


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cotton fabrics. Therefore, XL70 was compared with VAEO6 and NPEO10 in cotton fabrics pretreatment. The performances of the surfactants were also compared at different concentrations. The results were shown in Table 3. At the same concentration, XL70 and NPEO10 showed better wettability than VAEO6, while VAEO6 and NPEO10 showed better emulsibility, better capillary effects and WI of the treated cotton fabrics than XL70. When the concentration of surfactants is 1 g/L, the capillary effects and WI of cotton fabrics is a little worse, while they could meet the pretreatment requirements at the concentration of 1.6 g/L. Though cotton fabrics could obtain better performances at the concentration of 2 g/L, the concentration of 1.6 g/L was chosen in the subsequent applications based on the consideration of reducing the amount of chemicals. Table 3. The performances of XL70, VAEO6 and NPEO10 Concentration Surfactants

in desizingscouring (g/L)

Surface tensiona

Cotton fabric Wettabilitya

Emulsibilitya

(s)

(mL)

(mN/m)

effect(cm)

1 XL70

VAEO6

NPEO10

Capillary

WI

65

55

10.1

79.4

23

83

11.2

80.5

2

13

112

12.3

81.3

1

110

137

10.8

81.2

51

254

11.6

82.3

2

42

279

13.8

85.4

1

45

144

10.6

81.8

20

261

11.5

84.3

17

282

13.0

84.9

1.6

1.6

1.6

26.9

31.4

32.3

2

a For these performances tests the solution contained the surfactant only.

In order to obtain more excellent performances, surfactants are usually compounded in application. XL70 was compounded with VAEO6 (produced in pilot scale) in the pretreatment formulae. The optimal mass ratio of VAEO6 and XL70 was 1:1 which is labelled as VAEO6-XL70. The performances of the solutions containing 1.6 g/L of VAEO6, VAEO6-XL70 and NPEO10, respectively, were studied and the results were listed in Figure 4. The surface tension of VAEO6 and VAEO6-XL70 was lower than that 13



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of NPEO10. The emulsibility of VAEO6 and VAEO6-XL70 is close to that of NPEO10 while the former two featured lower foamability. VAEO6-XL70 has the best wettability among the three. The above results show that VAEO6-XL70 possessed an advantage in overall performances. VAEO₆

VAEO₆-XL70

NPEO₁₀ 760 470 254

310

261 155

31.4 28.1 32.3

51 17 20

Surface tension

Wettability

Emulsibility

Foamability

(mN/m)

(s)

(mL)

(mL)

Figure 4. The performances of VAEO6, VAEO6-XL70 and NPEO10, where the concentration of surfactants was 1.6 g/L.

The performances of cotton fabrics pre-treated with the formulae containing VAEO6, VAEO6-XL70 and NPEO10 were shown in Figure 5. It could be seen that all of them met the expected effect of pretreatment.

Figure 5. Performances of cotton fabrics pre-treated with the formulae containing VAEO6, 14


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VAEO6-XL70 and NPEO10, where the concentration of surfactants in desizing-scouring was 1.6 g/L.

Pilot-scale cotton fabric pretreatment. Pilot-scale pretreatment of cotton fabrics using VAEO6 and VAEO6-XL70 was carried out to demonstrate the potential of VAEO to replace NPEO in the actual industrial production. NPEO10 has been forbidden in the production line of Luthai to avoid pollution, so only VAEO6 and VAEO6-XL70 were explored. For each surfactant, 500 m greige cotton poplin was prepared. After the fabrics coming down from the end of the combining machine, three samples ready for tests were taken from different locations of the fabrics. The test results are shown in Figure 6. The capillary effect and WI of the cotton fabrics treated with VAEO6 and VAEO6-XL70 met the quality requirements and there was no damage in the breaking strength. So it is concluded that VAEO6 and VAEO6-XL70 can be potentially used in industrial pretreatment of cotton fabrics.

Figure 6. Results of pilot-scale pretreatment experiments using VAEO6 and VAEO6-XL70.

The Ecological Security of VAEO. Since VAEO is developed as a green chemical to replace NPEO, it is crucial to validate its superiority to NPEO in terms of environmental friendliness. Since VAEOn are homologs of varying ethoxylates, they have similar ecological properties. Hence, VAEO6 was chosen as a representative for 15



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the ecological safety tests, which included the acute toxicity to Zebra fish, the effects on the growth of algae, the immobilization to the Daphnia sp, the endocrine disrupting effects and the readily biodegradability. The test results are shown in Table 4 and Figure 7, where the values of NPEO for the acute toxicity to fish, the effects on the growth of algae and the ready biodegradability were obtained from literature.20 Table 5 gives an overview of the toxicity level to interpret the data in Table 4. Table 6 lists the Criteria for Safer Surfactants developed by EPA’s Design for the Environment (DfE) Program. For fishes, the 96 h-LC50 value of VAEO8 was 40.5 mg/L, classified as the moderate toxicity according to Table 5. The NOEC value at 96 h was 28 mg/L, more than 10 mg/L, which is in accordance with the low toxicity class. The 96 h-LC50 value and the NOEC value at 96 h for fish of NPEO were 1-11.2 mg/L and 0.002 mg/L, respectively, which are classified to the high and very high toxicity classes. Therefore, VAEO8 is low or moderately toxic chemical, while NPEO is high or very high toxic. There were no estrogenic effect, androgen effect and thyroid hormone effect for VAEO6, while the endocrine disrupting effect of NPEO was detected. The estrogenic effect, androgen effect and thyroid hormone effect IC20 of NPEO were 7.01 ± 2.04, 0.81 ± 0.29, and 12.57 ± 6.03 mg/L, respectively. Table 4. The Ecological Security of VAEO6 and NPEO Test items The acute toxicity to fish (mg/L)

The inhibition to the growth of algae (mg/L)

The immobilization to the Daphnia sp (mg/L)

Effect type

VAEO6

NPEOn (n≤15)

96 h-LC50

40.5

1-11.2

NOEC

28

0.002

EC100

80

/

48 h-ErC50

40.0

/

72 h-ErC50

43.9

0.009-0.0122

96 h-ErC50

/

0.09-12

24 h-EC50

48.5

/

48 h-EC50

32.4

/

EC0

10

/

96 h-LC50

80

/

16


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Endocrine disrupting effects IC20 (mg/L)

ER Two-hybrid yeast

ND*

7.01±2.04

AR Two-hybrid yeast

ND*

0.81±0.29

TR Two-hybrid yeast

ND*

12.57±6.03

* ND means not detected

Figure 7 presents the ready biodegradability of VAEO6 and the control substance (sodium benzoate) which showed 95.21% degradability within 28 days for sodium benzoate, the half-life of VAEO6 was less than 4 days, the biodegradation rate in 10 days and 28 days of VAEO6 were 74.35% and 92.32%, respectively. VAEO6 passes the ready biodegradability test with the 10-day window (Table 5), classified as the low toxicity class. Varineau and Williams (1997) reported that NPEO9 showed 53-58% ultimate degradability (measured as CO2% generated in 28 days) in the OECD 301B ready biodegradability test. In all OECD tests of biodegradability of nonylphenol, it showed significant biodegradability but failed to meet the criteria for ready biodegradability (10 day window). It is thus obvious that the ready biodegradability of VAEO is much better than NPEO’s.

Figure 7. The ready biodegradability of VAEO6 and sodium benzoate.

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Page 18 of 21

Table 5. Used Classification Systems for Aquatic Toxicity Hazard

Acute Aquatic Toxicity

Chronic Aquatic Toxicity

Level

(mg/L)

(mg/L)

Persistence Half-life in water, soil, or

Very High

LC/EC50 < 1

NOEC/LOEC < 0.1

sediment

>

180

days

or

recalcitrant. High

1 ≤ LC/EC50 ≤ 10

Moderate

10 < LC/EC50 ≤ 100

0.1 ≤ NOEC/LOEC ≤ 1

Half-life in water, soil, or sediment 60-180 days. Half-life in water, soil, or

1 < NOEC/LOEC ≤ 10

sediment < 60 but ≥ 16 days. Half-life in water, soil, or

Low

LC/EC50 > 100

sediment < 16 days or passes the

NOEC/LOEC > 10

ready biodegradability test not including the 10-day window. Passes

Very Low

/

/

the

ready

biodegradability test with the 10day window.

Table 6. DfE Criteria for Safer Surfactants[22] Acute Aquatic Toxicity(L/E/IC50 Value)

Rate of Biodegradation May be acceptable if biodegradation occurs

≤ 1 ppm

within a 10-day window without degradates of concern Biodegradation occurs within a 10-day

> 1 ppm and ≤ 10 ppm

window without degradates of concern Biodegradation occurs within 28 days without

> 10 ppm

degradates of concern

Finally, based on Table 6 and the above analyses, it is concluded that VAEO6 meets DfE criteria for safer surfactants and therefore, so do the homologous series of VAEO. CONCLUSIONS A series of cleavable vanillin-based polyoxyethylene nonionic surfactants VAEOn (n = 4 - 12) were synthesized in this study. The surface activities, wettability, emulsibility, foaming properties were studied and compared with NPEO10. It was found that when n = 4 - 8, lowγcmc comparable to NPEO10 could be obtained and the whole 18


Page 19 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


series showed low-foaming properties. When applied in the pretreatment of cotton fabrics, VAEOn achieved similar performance as NPEO10 while VAEO6 showed the best capillary effect and WI. VAEO6 produced on pilot scale and VAEO6-XL70 (1:1) were successfully employed in the pilot scale cotton fabric pretreatment. More importantly, VAEO was tested to be a low to moderately toxic chemical with no endocrine disrupting effect which suggested that VAEO meets DfE criteria for safer surfactants. Therefore, VAEO can be used as a green surfactant to be promoted in large-scale application. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]. Tel.: +86(21)67792595. Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS We would like to acknowledge the Chinese National High Technology Research and Development Program 863 Project (2013AA06A307) for financial supports. The authors would also like to thank Luo Qing in Zhejiang Kaide Chemical Co., Ltd. for providing the epoxy ethane reaction equipment and the help during the synthesis process. Thanks Ma Mei in Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences for the help of testing the data of endocrine disrupting effects of VAEO and NPEO. REFERENCES (1) Fisk, P. Chemical risk assessment: a manual for REACH; John Wiley & Sons, Ltd: New Jersey, 2013. (2) Shishoo.R. The global textile and clothing industry; Woodhead Publishing Limited: London, 2012. (3) Fischer, K.; Marquardt, K.; Schlüter, K.; Gebert, K.; Borschel, E. M.; Heimann, S.; Kromm, E.; Giesen, V.; Schneider, R.; Jr, R. L. W. Textile Auxiliaries; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, 2000. (4) Staples, C.; Klecka, G.; Naylor, C.; Losey, B. C8-and C9-alkylphenols and ethoxylates: I. Identity, physical characterization, and biodegradation pathways analysis. Human and Ecological Risk Assessment 2008, 14 (5), 1007-1024. (5) R, W.; S, J.; SA, H.; JP, S.; MG, P. Environmentally persistent alkylphenolic compounds are estrogenic. Endocrinology 1994, 135 (1), 175-182. 19



(6) Routledge, E. J.; Sumpter, J. P. Estrogenic activity of surfactants and some of their degradation products assessed using a recombinant yeast screen. Environmental Toxicology & Chemistry 2010, 15 (3), 241-248. (7) Moreno-Garrido, I.; Hampel, M.; Lubián, L.; Blasco, J. Marine microalgae toxicity test for linear alkylbenzene sulfonate (LAS) and alkylphenol ethoxylate (APEO). Fresenius Journal of Analytical Chemistry 2001, 371 (4), 474-478. (8) Hampel, M.; Moreno-Garrido, I.; Sobrino, C.; Lubian, L.; Blasco, J. Acute toxicity of LAS homologues in marine microalgae: esterase activity and inhibition growth as endpoints of toxicity. Ecotoxicology & Environmental Safety 2001, 48 (3), 287-292. (9) Ahel, M.; Molnar, E.; Ibric, S.; Giger, W. Estrogenic metabolites of alkylphenol polyethoxylates in secondary sewage effluents and rivers. Water Science and Technology 2000, 42 (7), 15-22. (10) Chen, R. Q. Prohibition and substitution of APEO. Dyeing & Finishing 2006, 12, 45-49. (11) Tehrani-Bagha, A.; Holmberg, K. Cleavable surfactants. Current Opinion in Colloid & Interface Science 2007, 5 (1), 27-30. (12) Chu, Z.; Feng, Y. Vegetable-derived long-chain surfactants synthesized via a “Green” route. ACS Sustainable Chemistry & Engineering 2013, 1 (1), 75-79. (13) Malferrari, D.; Armenise, N.; Decesari, S.; Galletti, P.; Tagliavini, E. Surfactants from Itaconic Acid: Physico-chemical Properties and Assessment of the Synthetic Strategies. ACS Sustainable Chemistry & Engineering 2015, 3 (7), 1579-1588. (14) Rio J G D.; Hayes D. G.; Urban V. S. Partitioning behavior of an acid-cleavable, 1,3-dioxolane alkyl ethoxylate, surfactant in single and binary surfactant mixtures for 2- and 3-phase microemulsion systems according to ethoxylate head group size. Journal of Colloid and Interface Science, 2010, 352(2):424-435. (15) Yang, W. W. Biosynthesis of natural vanillin-the queen of food ingredients. Microbiology China 2013, 40 (6), 1087-1095. (16) Negm, N. A.; Kandile, N. G.; Mohamad, M. A. Synthesis, characterization and surface activity of new eco-friendly schiff bases vanillin derived cationic surfactants. Journal of Surfactants & Detergents 2011, 14 (3), 325-331. (17) Sayed, G. H.; Ghuiba, F. M.; Abdou, M. I.; Badr, E. A. A.; Tawfik, S. M.; Negm, N. A. M. Synthesis, Surface, Thermodynamic Properties of Some Biodegradable Vanillin-Modified Polyoxyethylene Surfactants. Journal of Surfactants & Detergents 2012, 15 (6), 735-743. (18) Rosen, M. J.; Kunjappu, J. T. Surfactants and interfacial phenomena. John Wiley & Sons, Ltd: New Jersey, 2012. (19) Liu, X. F. Applications of surfactants in textile industry. China Surfactant Detergent & Cosmetics 2006, 36 (2), 99-102. (20) Groshart, C.; Okkerman, P.; Wassenberg, W.; Pijnenburg, A. Chemical study on alkylphenols. Report, 2001.

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Table of the Content

Synopsis: A new surfactant was developed to substitute the endocrine disrupter NPEO in dyeing and finishing industry, endowing cotton fabrics with good pretreatment effects.

21


Synthesis of a Cleavable Vanillin-Based Polyoxyethylene Surfactant

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