nano-TiO2 composite fatliquoring agent via a Pickering emulsion method

Accepted Manuscript Preparation and application of castor oil/nano-TiO2 composite fatliquoring agent via a Pickering emulsion method Bin Lyu, Hong-Di Wang, Jian-zhong Ma, Dang-ge Gao, Pan Jin PII:

S0959-6526(16)30011-7

DOI:

10.1016/j.jclepro.2016.02.099

Reference:

JCLP 6800

To appear in:

Journal of Cleaner Production

Received Date: 15 October 2015 Revised Date:

20 February 2016

Accepted Date: 25 February 2016

Please cite this article as: Lyu B, Wang H-D, Ma J-z, Gao D-g, Jin P, Preparation and application of castor oil/nano-TiO2 composite fatliquoring agent via a Pickering emulsion method, Journal of Cleaner Production (2016), doi: 10.1016/j.jclepro.2016.02.099. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT

Preparation and application of castor oil/nano-TiO2 composite fatliquoring agent via a Pickering emulsion method

a

RI PT

Bin Lyua,b*, Hong-Di Wanga, Jian-zhong Ma a,b,c, Dang-ge Gaoa and Pan Jina College of Resources and Environment, Shaanxi University of Science and

b

SC

Technology, Xi’an 710021, P.R. China

Key Laboratory of Auxiliary Chemistry and Technology for Chemical Industry,

M AN U

Ministry of Education, Shaanxi University of Science & Technology, Xi’an 710021, P.R. China c

Shaanxi Research Institute of Agricultural Products Processing Technology, Xi’an

AC C

EP

TE D

710021, P.R. China

*

Corresponding author. Tel:+086-029-8613-2559; fax: +086-029-86132559. E-mail: xianyanglvbin @163. com 1

ACCEPTED MANUSCRIPT

Abstract Castor oil in water emulsions known as fatliquors is used for the lubrication of tanned leather fibres to get softness and also to improve the strength properties.

RI PT

Fatliquoring agents are usually obtained by chemical modification. In this research, fatliquoring agent based on castor oil was prepared using nano-TiO2 as emulsifying agent by mechanical mixing. So castor oil/nano-TiO2 composite fatliquoring agent

SC

(CTF) was obtained via Pickering emulsion method. The presence of nano-TiO2

M AN U

resulted in a stable emulsion. The results of transmission electron microscope showed that the castor oil was surrounded by nano-TiO2. Finally, CTF was applied in the leather fatliquoring process of goatskin garment. Physical and mechanical properties of leather fatliquored by CTF were improved compared with those of leather

TE D

fatliquored by sulfated castor oil. CTF was easily biodegradable as compared to modified castor oil fatliquoring agent. Composite fatliquoring agent leads to reduction of many chemicals utilized to get the lightfastness of leather for adding nano-TiO2.

AC C

EP

Key words: castor oil, nano-TiO2, Pickering method, power ultrasound, leather

2

ACCEPTED MANUSCRIPT

1. Introduction Fatliquoring is an important process in leather making which is mainly to add oil into crust leather (Zar1ok et al., 2014). It can prevent the fibers from being putrefied,

RI PT

make the fibres stick together, soften the leather and improve their mechanical properties and physical features (Lyu et al., 2015). The most commonly used fatliquoring agents are natural animal or vegetable fats after chemical modification in

SC

the form of water emulsions. Chemical modification method is an important means to

M AN U

give fatliquoring agent good stability (Sivakumar et al., 2012; Sivakumar et al., 2009). In the conventional process, emulsifying agent is also added to increase the stability of emulsions. However, the emulsifying agents generally used are chemicals (Sivakumar et al., 2008).

TE D

Environmental responsibility is the contemporary consciousness in industrial production and its effect is the main reason for the development of technology. Major investment is being made for environmental protection (Sivakumar et al., 2012).

EP

Pickering emulsion is a new kind of emulsion stabilized by solid particles instead of

AC C

traditional organic surfactants and chemical modification (Kpogbemabou et al., 2014). In comparison with conventional emulsion, Pickering emulsion has the merit of strong interfacial stability, reduced bubbles, regeneration, low cost, and possesses wide applicable prospects in the fields of cosmetics, food, medicine, petroleum, and the waste water disposal (Tsabet et al., 2015). Moreover, the Pickering emulsion is generally stable even if there are changes in some physicochemical parameters such as pH of the continuous phase (water), temperature and composition of the oil phase 3

ACCEPTED MANUSCRIPT (Zhang et al., 2015). Nano-TiO2 is commonly used to prepare Pickering emulsion (Kawazoe et al., 2011). Nano-TiO2, a kind of critical inorganic nanoparticle for the development of

RI PT

superior composite materials, has self-cleaning property, high surface activity, low cost and excellent photocatalytic properties (Anpo., 2000). It can mainly be found in three different crystalline forms: anatase, rutile and brookite. Brookite TiO2 is not

SC

stable enough to be used for industrial applications. Anatase TiO2 is commonly known

M AN U

as the most active phase and is therefore extensively used in a variety of photocatalytic applications. Its high activity is directly connected with the prolonged lifetime of charge carriers (conduction band electrons and valence band electron vacancies) and spatial charge separation. Rutile TiO2 is known to be the stable form

TE D

and has better ultraviolet absorption and reflection (Kaplan et al., 2016). It is a kind of good inorganic light material and has been applied in many fields (Lewis et al., 2012). Usually, leather inevitably exposes itself to the sunshine. Lightfastness of leather

EP

is triggered by oxidization of unsaturated bond of leather chemicals and collagen

AC C

under light and heat conditions (Zhang et al., 2009). Adding light resistant agent is an efficient way to improve lightfastness of leather (Ren et al., 2010). Castor oil as a kind of renewable material has been applied in leather fatliquoring process. In this research, fatliquoring agent based on castor oil was prepared using nano-TiO2 as emulsifying agent by mechanical mixing instead of chemical modification, and castor oil/nano-TiO2 composite fatliquoring agent (CTF) was obtained. Composite fatliquoring agent leads to reduction of many chemicals utilized to get the 4

ACCEPTED MANUSCRIPT lightfastness of leather for adding nano-TiO2.

2. Experimental 2.1 Materials and instrument

RI PT

Castor Oil (industrial grade) was made by Xi'an Fuji Oil Co. Ltd. China. The rutile nano-TiO2 (analytically pure) was purchased from Shandong Depu Chemical Industry Science and Technology, Co. Ltd. China. Experiments were carried out using

SC

Ultrasonic cell crusher SCIENTZ-IID from Ningbo Xingzhi Biotechnology Co., Ltd.

M AN U

China.

Basic parameters of castor oil are shown in table 1.

2.2 Preparation of acrylic copolymer retanning agent

The acrylic copolymer retanning agent (ACR) was prepared from acrylic acid,

TE D

ethyl acrylate and acrylamide according to former studies by our research group. The molecule structure of ACR is shown in figure 1. The weight-average molecular weight of tanning agent (ACR) is about 104. It may penetrate into the leather fibers.

EP

Hydroxyls in ACR are helpful in the intercalation with collagen. The –NH2, -COOH

AC C

of acrylic copolymer retanning agent molecule and collagen molecule can be held together by hydrogen bonding, electrostatic attraction and chemical bonding. The physical and mechanical properties of leather would be improved. ACR used as co-emulsifier in CTF promoted the penetration and absorption of castor oil into leather. 2.3 Preparation of CTF

5

ACCEPTED MANUSCRIPT Castor oil, ACR and nano-TiO2 were added to the distilled water and the system was stirred with 400 r·min–1 for 60 min at 85°C. Then the system was exposed to ultrasonic waves for 35 min. Schematic diagram is shown in figure 2. The details of

Total amount of castor oil and water = 100 g; Content of castor oil = 40 g;

SC

Content of water = 50 g;

M AN U

Content of ACR = 7.5 g; Content of nano-TiO2 = 2.5 g;

RI PT

the experiment are as follows:

Ultrasound output power = 360 W. 2.4 Application of CTF

TE D

2.4.1 Leather fatliquoring process

Fatliquoring process has been carried out in order to investigate the applicability of CTF on leather. And sulfated castor oil was used as control sample. The wet blue

EP

goatskins were taken for the fatliquoring experiment. The leather was cut into two

AC C

halves through backbone as left and right hand sides for the comparison of the fatliquoring process with CTF and sulfated castor oil. The thickness of leather samples was about 1mm. The main steps of fatliquoring process are as follows: Goatskin leather was made in the drum as usual and the weight was based on the

wet blue goatskin. (i) Wetting-back: The wet-blue goatskin was wetted back in 150 wt% H2O and 1.5 wt% rewetting agent for 120 min at room temperature, and then washed with 150 6

ACCEPTED MANUSCRIPT wt% H2O three times. (ii) Fatliquoring: After washing, the skin was fatliquored with 14 wt% fatliquoring agent (CTF or sulfated castor oil) and 150 wt% H2O for 90 min at 55

.

RI PT

(iii) Fixing: 2 wt% formic acid was added to drum to up pH to 3.8-4.0 for 90 min, and then the skin was washed for 15 min. 2.4.2 Properties of fatliqoured leather

and relative humidity of 50 ± 5%.

M AN U

parts of the leather and placed for 24 h at 23 ± 2

SC

Three leather samples with a diameter of 20 cm were obtained from different

Then the samples were tested (GT-303, Dongguan Gotech Testing Machines Co., Ltd.).

The samples were obtained from different parts of the leather and placed for 24 h and relative humidity of 50 ± 5%.Then the physical and mechanical

TE D

under 23 ± 2

properties of the leather samples were tested according to the industry standard (GT-U55, Dongguan Gotech Testing Machines Co., Ltd).

and relative humidity of 50 ± 5%. Then the lightfastness of the

AC C

under 23 ± 2

EP

The samples were obtained from different parts of the leather and placed for 48 h

leather samples was tested according to the industry standard (GT-7035-NUAB). The fullness of the fatliquored leather was evaluated by the thickening rate. The

higher the thickening rate is, the better the fullness of the leather is. The thickening rate (R) was defined as follows: R = [(S2 - S1) / S1] × 100 % The thickness of leather sample was measured with a vernier caliper. S1 is 7

ACCEPTED MANUSCRIPT average thickness of leather samples before fatliquoring; S2 is average thickness of leather samples after fatliquoring. 2.4.3 Analysis of fat content in leather and fatliquoring bath

RI PT

Fat content in the leather (dried leather weight basis) was determined by the following Soxhlet extraction method using petroleum ether as solvent according to the official method of GB/T 22933-2008.

SC

The fat content in the fatliquoring bath was determined by the following Soxhlet

M AN U

extraction method using petroleum ether as solvent as per the official method of GB/T 5512-2008.

2.4.4 Environmental impact assessments

The wastewater of fatliquoring process containing a large number of pollutants

TE D

has an impact on the environment and humans. The wastewater analysis includes biochemical oxygen demand and chemical oxygen demand. The wastewater from the experimental processing was collected and analysed for COD and BOD5 by using a

EP

standard procedure (APHA, 1995).

AC C

2.5 Characterization

CTF was investigated using Transmission electron microscope (TEM) instrument

(FEI Tecnai G2 F20 S-TWIN, America). The Zeta potential of emulsions was determined on a Zeta PALS dynamic light scattering (DLS) detector (Nano-ZS, Malvern Instruments Ltd., UK). Energy dispersive X-ray (EDX) measurements were conducted on an EDAX 32 system micro analyzer equipped in the scanning electron microscope (S-4800, Hitachi Limited, Japan). The cross section of the resulting 8

ACCEPTED MANUSCRIPT leather samples of about 3 mm thickness was freezing fractured, and the cross section was coated with a thin layer of gold using a vacuum sputter at an acceleration voltage of 5 kV and then were observed by using EDX techniques.

3.1 Emulsion stability of CTF In order to have good penetration and absorption

RI PT

3. Results and discussion

fatliquoring agent in leather

SC

industry should have certain stability. As shown in figure 3, castor oil with ACR is

M AN U

unstable with phase separation for 5 min. The CTF is stable without any phase separation as oil and water for more than 90 days. It indicated that castor oil was stabilized by nano-TiO2 instead of traditional organic surfactants and chemical modification. It is expected that the fatliquor will have very good shelf life.

TE D

3.2 Zeta potential of CTF

As the Zeta potential of particles ranges from –30 mV to 30 mV, the particles are easy to coagulate. Besides, the greater absolute value of Zeta potential indicates the

EP

high stability of emulsion (Xu et al., 2007). The absolute value of CTF was 38.1 mV,

AC C

which demonstrated good stability of CTF. This result was consistent with stability of CTF.

3.3 TEM images of CTF CTF was tested by TEM to further explore its structure. As shown in figure 4(a),

nano-TiO2 shows rod-like structure and the morphology of nano-TiO2 is not neat. Nano-TiO2 formed a circle around castor oil in figure 4(b). It indicated that CTF is a kind of oil-in-water emulsion emulsified by nano-TiO2. 9

ACCEPTED MANUSCRIPT 3.4 Lightfastness of fatliquored leather samples As shown in figure 5, leather samples fatliquored by CTF have good lightfastness compared with the leather fatliquored by sulfated castor oil. The rutile

RI PT

nano-TiO2 had certain absorption on medium wave area and long wave ultraviolet light and further reduced the effect of ultraviolet light on fibers (Chen et al., 2003). CTF permeated the collagen fiber and formed a continuous layer of organic -

SC

inorganic compound oil film on the surface of collagen fibers. It prevented the direct

3.5 Softness of fatliquored leather

M AN U

effect of ultraviolet light to fibers.

The softness of leather samples fatliquored by CTF was about 6.21 mm which was comparable to that of the sulfated castor oil (6.32 mm). When CTF was applied

TE D

in the leather process, the castor oil was wrapped around the surface of collagen fibers. Thus, molecule chain of collagen fibers has good flexibility (Hou, 2015). 3.6 Mechanical analysis of fatliquored leather

EP

The mechanical properties of leathers fatliquored with CTF and sulfated castor

AC C

oil prepared by the same fatliquoring process were compared. Mechanical properties like tensile strength, tear strength, elongation at break, softness were studied. As shown in figure 6, the tensile strength of the leather fatliquored by CTF was

about 23.6 N·mm–2, which was comparable to that of sulfated castor oil. The leather fatliquored by CTF had better tear strength compared with that of the leather fatliquored by sulfated castor oil. The elongations at break of the leather fatliquored by CTF and sulfated castor oil were both more than 30%. The results of mechanical 10

ACCEPTED MANUSCRIPT properties of leathers fatliquored with CTF are in accordance with the requirements of garment in China (according to QB/T 2710-2005). Thickening rate is an index to characterize the fullness of leather treated with CTF. The results of thickening rate of

RI PT

fatliquored leather are shown in figure 6. The thickening rate of leather treated with CTF was much higher than that of leather treated with sulfated castor oil. Hydroxyls in ACR are helpful in the intercalation with collagen. The ACR as filler could

SC

penetrate into and fill between collagen fibers. The fatliquoring agent with added

M AN U

ACR can improve the filling property of leather, but has no effect on the softness of leather. CTF has improved the physical and mechanical properties of leather. 3.7 Fat content in leather and fatliquored bath

The fat content in leather and fatliquored bath is an important index to

TE D

investigate the fatliquoring effect of fatliquoring agent. The higher the fat content in leather is, the better combining performance of fatliquoring agent is. The fat uptake in leather and fatliquored bath using 14% CTF has been shown in table 2. The fat

EP

contents in leather and fatliquored bath fatliquored with CTF are comparable with

AC C

leather fatliquored with sulfated castor oil. The results indicate that CTF may add oil into crust leather and soften the leather. 3.8 Analysis of the EDX spectra about fatliquored leather samples The area of fatliquored leather was examined by EDX to elucidate nano-TiO2 in

collagen fibers. Figure 7 gives the EDX analysis of element composition and content in the leather sample. Collagen fiber is a group of naturally occurring proteins. The main element components of collagen fiber are C, N and O. Cr, S and Cl were used to 11

ACCEPTED MANUSCRIPT prepare the wet blue goatskin before fatliquoring process (Ma et al., 2014). Therefore, Cr, S and Cl can be examined among fibers as shown in figure 7(a). Ti element was also among in fibers. The average Ti content is 0.57 wt% in the elements of C, O, S,

RI PT

Cl, Ti and Cr. It proved that nano-TiO2 can enter the interior of leather, and attach itself to the collagen fibers.

The longitudinal-section of the leather sample was characterized by line

SC

spectrum scanning in order to investigate the distribution of nano-TiO2. The SEM

M AN U

photograph of longitudinal-section of the fatliquored leather sample is shown as figure 7(c). The distribution of Ti along the mark line is shown as figure 7(b). It can be seen that the distribution of Ti was uneven from the grain layer to the flesh layer. Most of titanium element scattered near the grain layer and flesh layer. Only small

TE D

amount of titanium element scattered in the intermediate layer. It indicated that nano-TiO2 scattered unevenly on the cross section of wet blue. It is conducive to the absorption on medium wave area and long wave ultraviolet light. And it reduces the

EP

effect of ultraviolet light on fibers.

AC C

3.9 Environmental impact assessments BOD5 parameter is an indication of the ability of the specified microorganisms to

oxidize available organic matter. COD provides a means of measurement of the environmental health of the system in terms of the oxygen demand placed upon organic matter needed for degradation. The COD and BOD5 results of the wastewater after fatliquoring are shown in table 3. It indicated that COD and BOD5 of the wastewater after fatliquoring by CTF were lower than those of sulfated castor oil. 12

ACCEPTED MANUSCRIPT When the BOD5·COD–1 value is greater than 0.3, the biodegradability of wastewater is good (Cossu et al., 2012). During the test, the BOD5·COD–1 of the wastewater was more than 0.3, which demonstrated that the effluent of CTF was

RI PT

easily biodegradable and better than sulfated castor oil.

4. Conclusions

Increasing population concomitantly and raising environmental awareness mean

SC

that tanneries are faced with some obligation like more effectively using fewer

M AN U

chemicals. In this research, CTF was obtained by using mechanically mixed castor oils and ACR with nano-TiO2. CTF was obtained without being chemical modified to get the performance properties in leather. CTF can effectively improve the lightfastness of fatliquored leather, while improving the mechanical properties of

TE D

leather. CTF is an environmentally friendly nanocomposite fatliquoring agent made from bioresources without being chemically modified and is easily biodegradable.

Acknowledgements

EP

This work was financially supported by National Science Foundation of China

AC C

(21406135), Natural Science Basic Research Plan in Shaanxi Province of China (2015JM2061), Key Scientific Research Group of Shaanxi province (2013KCT-08) and Doctoral Fund of Shaanxi University of Science and Technology (BJ13-16).

References

Anpo M., 2000. Applications of titanium oxide photocatalysts and unique second-generation TiO2 photocatalysts enable to operate under visible light irradiation for the reduction of environmental toxins on a global scale. Stud surf sci 13

ACCEPTED MANUSCRIPT catal , 130, 157- 166. Chen, J. J., Wang, Z. Y., Qian, G. D., Qian, G. D., Fan X. P., 2003. Preparation and UV shielding of homogeneous dispersion nanometer TiO2, J. Mater Protec. 36, 7-

RI PT

9. Cossu, R., Lai, T., Sandon, A., 2012. Standardization of BOD5/COD ratio as a biological stability index for MSW, Waste Manage. 32, 1503- 1508.

SC

Hou, X.Y, 2015. Preparation and performance of enzyme-containing additives for

M AN U

leather manufacturing, Shaanxi: Shaanxi University of Science & Technology. Kaplan R., Erjavec B., Drazic G., Grdadolnik J., Pintar A., 2016. Simple synthesis of anatase/rutile/brookite TiO2 nanocomposite with superior mineralization potential for photocatalytic degradation of water pollutants. Appl Catal B.181, 465- 474.

TE D

Kawazoe, A., Kawaguchi, M., 2011. Characterization of silicone oil emulsions stabilized by TiO2 suspensions pre-adsorbed SDS, Colloid Surf. A-Physicochem. Eng. Aspect. 392, 283- 287.

EP

Kpogbemabou, D., Lecomte-Nana, G., Aimable, A., Bienia, M., Niknam, V., Carrion

AC C

C., 2014. Oil-in-water Pickering emulsions stabilized by phyllosilicates at high solid content. Colloid Surf. A-Physicochem. Eng. Aspect. 463, 85- 92.

Lewis, O. D., Critchlow, G. W., Wilcox, G. D., deZeeuw, A., Sander, J., 2012. A study of the corrosion resistance of a waterborne acrylic coating modified with nano-sized titanium dioxide. Prog Org Coat. 73, 88- 94. Lyu, B., Duan, X. B., Gao, D. G., Ma, J. Z., Hou, X. Y., Zhang, J., 2015. Modified rapeseed oil/silane coupling agent-montmorillonite nanocomposites prepared by 14

ACCEPTED MANUSCRIPT in-situ method: Synthesis and Properties. Ind Crop Prod, 70, 292- 300. Ma, J. Z., Lv, X. J., Gao, D. G., Li, Y., Lv, B., Zhang, J., 2014. Nanocomposite-based green tanning process of suede leather to enhance chromium uptake. J. Clean. Prod.

RI PT

72, 120- 126. Ren, M., Yin, H. B., Lu, Z. Z., Yu, L. B., Jiang, T. S., 2010. Evolution of rutile TiO2

properties. Powder Technology. 204, 249- 254.

SC

coating layers on lamellar sericite surface induced by Sn4+ and the pigmentary

M AN U

Sivakumar, V., Prakash, R. P., Rao, P. G., Ramabrahmam, B. V., Swaminathan, G., 2008. Power ultrasound in fatliquor preparation based on vegetable oil for leather application. J. Clean. Prod. 16, 549- 553.

Sivakumar, V., Chandrasekaran, F., Swaminathan, G., Rao, P.G., 2009. Towards

TE D

cleaner degreasing method in industries: ultrasound-assisted aqueous degreasing process in leather making. J Clean Prod. 17,101- 104. Sivakumar, V., Gayathri, K., Pranavi, P. S., Chandrasekaran, F., 2012. Ultrasound

EP

assisted cleaner alternate emulsification method for oils and fats: tallow emulsion -

AC C

fatliquor preparation for leather application. J. Clean. Prod. 37, 1-7. Tsabet, È., Fradette, L., 2015. Effect of the properties of oil, particles, and water on the production of Pickering emulsions, Chem Eng Res Des. 97, 9-17.

Xu, M. J., Yuan, L. M., Bo, P., 2007. Effects of strength of interfacial film and Zeta potential on oil-in-water emulsion stability, Chi. J. Appl. Chem. 14, 623- 627. Zar1ok, J., Smiechowski, K., Mucha, K., Tecza, A., 2014. Research on application of flax and soya oil for leather fatliquoring. J. Clean. Prod. 65, 583- 589. 15

ACCEPTED MANUSCRIPT Zhai, W. Z., Wu, Z. M., Wang, X. W., Song, P. F., He, Y. F., Wang, R. M., 2015. Preparation of epoxy-acrylate copolymer@nano-TiO2 Pickering emulsion and its antibacterial activity, Prog Org Coat. 87, 1223- 1228.

RI PT

Zhang, S. M., Zhou, Y. H., Yang, C., 2015. Pickering emulsions stabilized by the complex of polystyrene particles and chitosan, Colloid Surf. A-Physicochem. Eng. Aspect. 482, 338–344.

SC

Zhang, Y., Wang, L., 2009. Recent research progress on leather fatliquoring agents,

AC C

EP

TE D

M AN U

Polym-Plast Technol. 48, 285-291.

16

ACCEPTED MANUSCRIPT

Figure caption Figure 1 The molecule structure of ACR Figure 2 Representative CTF processing Figure 3 Emulsion stability photos of CTF

Figure 5 Lightfastness of fatliquored leather samples

RI PT

Figure 4 TEM images of CTF

Figure 6 Mechanical properties of leather samples fatliquored by CTF

Figure 7 Scan electron microscope photograph and energy dispersive spectrometer of

SC

leather fatliquored by CTF

M AN U

Table caption Table 1 Basic parameters of castor oil

Table 2 Fat content in leather and fatliquored bath

Table 3 Biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) in

AC C

EP

TE D

the wastewater treated with CTF

ACCEPTED MANUSCRIPT Table 1 Basic parameters Iodine value

Value 82.3 g iodine· 100 g oil 160.6 mg KOH·g-1

Acid value

3.2 mg KOH·g-1

Saponification value

181.1 mg KOH·g-1

Water content

0.4%

Palmitic acid

M AN U

Fatty acids composition

AC C

EP

TE D

Stearic acid

90.85%

SC

Ricinoleic acid

RI PT

Hydroxyl value

-1

0.72% 0.64%

ACCEPTED MANUSCRIPT

Table 2 Sulfated castor oil

CTF

Fat content in leather

180.1±2.1 mg·g-1

176.3±1.7 mg·g-1

Fat content in fatliquored bath

6770±32 mg·L-1

6020±27 mg·L-1

AC C

EP

TE D

M AN U

SC

RI PT

Fat content

ACCEPTED MANUSCRIPT

Table 3 COD (mg·L-1)

BOD5 (mg·L-1)

BOD5·COD-1

CTF

1120

538

0.48

Sulfated castor oil

1876

602

AC C

EP

TE D

M AN U

SC

RI PT

Wastewater after fatliquoring

0.32

ACCEPTED MANUSCRIPT Figure 1 xCH2 = C

+ yCH2 = C

COOH

+

z CH2 = C CONH2

COOC4H8

CH2

CH

CH

CH2

COOC4H8 y

CH

CONH2

AC C

EP

TE D

M AN U

SC

COOH x

CH2

RI PT

Initiator

z

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

Figure 2

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

Figure 3

ACCEPTED MANUSCRIPT

SC

RI PT

Figure 4

a) Nano-TiO2

AC C

EP

TE D

M AN U

b) CTF

ACCEPTED MANUSCRIPT

M AN U

SC

RI PT

Figure 5

AC C

EP

TE D

a) Leather sample fatliquored by CTF light for 0 h. b) Leather sample fatliquored by CTF light for 48 h. c) Leather sample fatliquored by sulfated castor oil light for 0 h. d) Leather sample fatliquored by sulfated castor oil light for 48 h.

ACCEPTED MANUSCRIPT Figure 6 120

RI PT

80

SC

40

M AN U

Physical and mechanical properties

-2

Tensile strength (N·mm ) -1 Tear strength (N· mm ) Elongation at break (%)

0

AC C

EP

TE D

Sulfated castor oil CTF Type of fatliquoring agent

ACCEPTED MANUSCRIPT Figure 7

6000

C

Element

Wt%

At%

C

61.52

72.33

O

27.50

24.28

S

01.59

00.70

Cl

01.01

00.40

Ti

00.57

00.17

Cr

07.81

02.12

O

Cr

2000

S Cl Ti 0 0

2

4

6

8

10

SC

Energy (keV)

RI PT

Counts

4000

M AN U

a) EDX of fatliquored leather samples 400

Ti

200

100

0 0

100

200

300

400

TE D

Content of Ti (a.u)

300

500

600

700

800

900

1000 1100

Distance (µm)

AC C

EP

b）Ti spectroscopy (longitudinal-section)

c) SEM photograph of longitudinal-section

ACCEPTED MANUSCRIPT Highlights: Environmental friendly fatliquoring agent was obtained without being modified. Fatliquoring agent was prepared via a Pickering emulsion method with nano-TiO2.

AC C

EP

TE D

M AN U

SC

RI PT

The lightfastness of leather was improved by the addition of nano-TiO2.