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Reducing environmental pollution of the textile industry using keratin as alternative sizing agent to poly(vinyl alcohol)
Journal of Cleaner Production 65 (2014) 561e567
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Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro
Reducing environmental pollution of the textile industry using keratin as alternative sizing agent to poly(vinyl alcohol) Narendra Reddy a, Lihong Chen b, Yue Zhang a, Yiqi Yang a, b, c, d, * a Department of Textiles, Merchandising & Fashion Design, 234, HECO Building, East Campus, University of Nebraska e Lincoln, Lincoln, NE 68583-0802, USA b Key Laboratory of Science and Technology of Eco-Textiles, Ministry of Education, Donghua University, Shanghai 200051, China c Department of Biological Systems Engineering, 234, HECO Building, East Campus, University of Nebraska e Lincoln, Lincoln, NE 68583-0802, USA d Nebraska Center for Materials and Nanoscience, 234, HECO Building, East Campus, University of Nebraska e Lincoln, Lincoln, NE 68583-0802, USA
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 March 2013 Received in revised form 27 September 2013 Accepted 28 September 2013 Available online 8 October 2013
Keratin from chicken feathers used as warp sizing agents on polyester/cotton blends and polyester provide similar sizing performance compared to poly(vinyl alcohol) and are also easily degradable in activated sludge. Poly(vinyl alcohol) (PVA), the most common sizing agent is not degradable in textile effluent treatment plants. Efforts to find substitutes to PVA that can provide similar sizing performance, be biodegradable and cost-effective have not been successful. In this research, keratin was studied as potential sizing agents for polyester and polyester/cotton materials and the sizing performance was evaluated in comparison to PVA. Keratin provided similar cohesion and strength improvements but had low abrasion resistance on polyester/cotton fabrics. Keratin in activated sludge showed a substantial decrease in Chemical Oxygen Demand (COD) whereas there was a negligible decrease in COD for PVA. Overall, the low cost and biodegradable keratin exhibited potential to replace PVA. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Biodegradation Polyvinyl alcohol Sizing Keratin Chicken feathers
1. Introduction Textile processes such as sizing and desizing consume considerable amounts of water, energy and chemicals and are mostly responsible for the toxic effluents released into the environment from textile plants (Moore and Ausley, 2004; Du et al., 2007). Textile industry is one of the largest consumers of water in the world. For instance, processing a ton of textiles is estimated to consume about 80e100 m3 of water that is subsequently released into the environment (Fu et al., 2011; Hamilton and Chiweshe, 1998; Hebeish et al., 2008). Several reports have highlighted the problems and concerns on processing textiles and their effects on the environment (Fu et al., 2011). Most countries, especially in the European Union have enacted several regulations to limit the environmental impacts of textile processing. Among the various textile processes, sizing and desizing account for 40e60% of the effluent load in a textile mill (Hebeish et al., 2006). Traditionally, starch and starch derivatives for cotton and poly(vinyl alcohol) * Corresponding author. Department of Textiles, Merchandising & Fashion Design, 234, HECO Building, East Campus, University of Nebraska e Lincoln, Lincoln, NE 68583-0802, USA. Tel.: þ1 402 472 5197; fax: þ1 402 472 0640. E-mail address: [email protected] (Y. Yang). 0959-6526/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jclepro.2013.09.046
(PVA) for synthetic fibers and blends have been the preferred sizing agents. Relatively low price, good performance properties and easy biodegradability are the advantages of starch whereas PVA is preferred for the excellent sizing performance and easy desizeability although PVA is more expensive than starch. However, PVA accounts for 45% of the total BOD load but does not degrade in textile effluent treatment plants and is reported to persist in water released from treatment plants (Ren, 2000; Savin and Butnaru, 2008). Attempts to recover and reuse PVA and other sizing agents and limit their release into the environment have been technically challenging and/or economically unviable (Sun et al., 2012; Sarkar et al., 2012). Substituting PVA with sizes developed from biopolymers has been attempted to reduce the environmental impacts of PVA. Starch has been modified by grafting with acrylates to make starch more suitable for sizing synthetic fibers and their blends (Zhu and Cheng, 2008; Zhu et al., 2008). In another report, starch was grafted with methacrylates and sized on cotton, polyester and polyester/ cotton (P/C) yarns and found that a proper grafting ratio was necessary to achieve good tensile properties (Zhu and Cao, 2004). Other biopolymers such as cyclodextrans and chitosan have also been studied as potential sizing agents (Hebeish et al., 2006, 2008; Stegmaier et al., 2008).
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Ability to form films, adhere to fibers, provide flexibility and easy removal from the fibers after weaving are some of the most desirable features of a sizing agent. Starch and PVA are preferred for sizing due to their good sizing performance and relatively easy desizeability although enzymes are used to remove starch based size. Plant proteins such as wheat gluten and soy proteins have been made into films for food and medical applications, used as adhesives for various applications and also made into regenerated protein fibers for textile and medical applications (Reddy and Yang, 2011a). Proteins have also been used as adhesives for composites and wheat gluten has been studied as a binder for textile printing paste (Reddy and Yang, 2011b; Hamilton and Chiweshe, 1998). These properties make plant proteins suitable for sizing applications. We have recently demonstrated that plant proteins such as soy proteins and wheat gluten and chicken feathers used as sizing agents on cotton, polyester and polyester/cotton provide similar performance properties to PVA and were also easily degradable in activated sludge (Chen et al., 2013a,b; Reddy et al., 2013; Yang and Reddy, 2013). Similar to plant proteins, poultry feathers have also been studied for various non-food applications. Feathers or keratin from feathers have been made into fibers, composites, films, sponges, hydrogels for various end-uses (Reddy and Yang, 2010; Hill et al., 2010). Unlike plant proteins, feathers do not have food applications and their non-food applications are also limited. About 1.8e2 million tons of chicken feathers are available in the United States and most of the feathers are disposed in landfills. However, unlike plant proteins, it is difficult to dissolve feathers and develop products. Most of the previous applications have used feathers in their original form (reinforcement for composites) or extracted keratin from feathers to be processed into films, hydrogels and fibers (Huda and Yang, 2008; Wang et al., 2012). The large availability and virtually no cost makes feathers attractive raw material for sizing textile yarns. However, appropriate methods of dissolving feathers and the ability of feather to provide the desired improvement in strength and abrasion resistance need to be investigated. In this research, keratin from chicken feathers was used to size polyester and polyester/cotton yarns. Effects of size preparation conditions and amount of size (add-on, %) on the tensile properties and abrasion resistance of rovings and yarns were studied. Biodegradability of keratin solutions in activated sludge and the ability of keratin to be desized were also investigated. Commercially available PVA based sizing agents were used to evaluate the performance of keratin as sizing agent.
Feathers were pre-treated in alkaline solution to dissolve the feathers and obtain keratin. Pre-treatment was done by heating the feathers in alkaline solution (0.25e1%) at 90 C for 30 min. After heating, the solution was filtered, pH of the solution adjusted between 8 and 10 and the solution was reheated to 90 C. The rovings and yarns wound onto frames were placed in shallow plates and sized at 90 C for 5 min. After sizing, the materials were allowed to dry at 21 C and 65% relative humidity. Fabrics were also sized similarly, except that after sizing, the fabrics were passed through a laboratory padder to ensure constant pick-up and penetration of size into the fabrics. PVA based sized were applied onto the rovings, yarns and fabrics based on the manufacturers recommended conditions (heating 1e2% PVA in water and sizing at 90 C). A two-step pre-treatment was used to prepare the sizing solution for polyester rovings. Since extraction of keratin from the feathers required higher concentrations of alkali (up to 100% by weight of feathers), considerable amounts of acid (hydrochloric acid) was added to reduce the pH of the solution to 7e9 after the initial pre-treatment. Addition of the strong acid into the strong alkali solution resulted in formation of salts in the solution. After sizing, salt on the polyester rovings caused high moisture sorption during conditioning and decreased the mechanical properties considerably. To decrease the amount of salts in the sizing solution, a two-step pre-treatment was used. Initially, feathers (10%) were soaked in 1% NaOH for 12 h at room temperature. Feathers were later washed thoroughly in warm water to remove the alkali until the pH of the feather was 7. Later, the keratin obtained were dried and used for sizing by treating with 0.25% alkali for 1 h at 95 C. Sizing of the roving was done as described earlier. Samples were dried in an oven at 105 C for 3 h and their dry weight was determined before and after sizing. Amount of size (add-on, %) on the materials was calculated based on the difference in weight of the samples before and after sizing using Equation (1).
2. Materials and methods
Add on; % ¼ ½ðWa WbÞ=Wb 100
2.1. Materials
where, Wa is the dry weight of the samples after sizing and Wb is the dry weight of the samples before sizing. Viscosity of the sizing solution was determined on a Brookfield (R/S plus) rheometer using a CC-25 spindle and cup. Measurements in terms of mPas were taken with solution concentration between 0.25 and 2% for 1 h, maintaining the temperature of the solution at 90 C using a water bath.
Whole chicken feather consisting of quills, barbs and barbules were supplied by Feather Fiber Corporation (Nixa, MO). Feathers were ground into powder using a Wiley mill and used for alkaline hydrolysis. Sizing was done on rovings to measure the cohesion between fibers, on yarns and fabrics to determine the changes in strength and abrasion resistance due to sizing. Polyester/cotton (65/35) rovings (70s Hank) and yarns (15s Ne) were supplied by Mount Vernon Mills, Mauldin, S.C. Cotton used in the P/C blend was strict low middling with average length of 27 mm. Polyester fibers in the blend were of 1.4 denier, 38 mm cut length, breaking tenacity of 6.5 g/den and 27.8% elongation. Polyester (100%) rovings and yarns used in the study were supplied by Shuford Yarns LLC, Hickory, NC. Fabrics (P/C type 7435) and 100% polyester (Dacron type 54) were purchased from Test Fabrics Inc., West Pittston, PA. Two types of commercially available PVA based sizes (named PVA 1 and PVA 2) were obtained from major sizing chemical
manufacturers in the United States to compare the properties of the feather sized materials. PVA 1 was a fully hydrolyzed copolymer with a molecular weight (Mw) of approximately 65 kDa. Viscosity of PVA 1 at 20 C was 11.6e15.4 mPas at 4% solid content. PVA 2 containing 80e85% PVA had a hydrolysis value between 88 and 96% and a viscosity of 14e25 mPas for 4% solid content at 20 C. Sodium hydroxide and other chemicals required for the study were obtained from VWR international, Bristol, CT. 2.2. Preparation of the keratin sizing solution
(1)
2.3. Property evaluation 2.3.1. Cohesion test Ability of the size to adhere to the fibers was evaluated in terms of cohesive strength of the rovings. Since rovings are a loose assembly of fibers that have almost no strength, increase in roving strength would be a good indicator of the adhesion/cohesion between fibers (Stegmaier et al., 2008) Tensile properties of rovings were tested on an MTS tensile tester (MTS Corporation, Eden Prairie, MN, Model: Q Test 10) using a load cell of 500 N and
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Fig. 1. Influence of concentration of alkali used during pre-treatment on the tensile properties of the polyester and P/C rovings. Feathers were pre-treated at 90 C for 30 min, pH of the solution during sizing was 8 and the add-on (%) on the roving was 10%. Data points having statistically significant difference have been represented with different alphabets.
traverse speed of 50 mm min1 and gauge length of 10 cm. Yarn strength was measured on an Instron tensile tester (Model 4444) using a gauge length of 10 cm and crosshead speed of 18 mm min1. At least 25 samples from each condition were tested and each experimental condition was repeated three times. Average and one standard deviation between the three experiments were calculated and reported here.
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Fig. 3. Comparison of the performance of the P/C and polyester rovings at different humidities. Sizing was done at 90 C for 30 min and the add-on (%) was 10%.
65% relative humidity for about 48 h before being peeled off from the plates. Films were tested for tensile strength and elongation on an MTS tensile tester according to ASTM standard D 882. At least 10 sample each from three separately cast films were tested and the average and one standard deviation were reported.
2.3.3. Film properties Keratin films were prepared by heating 6% feather in 0.25% alkali solution at 95 C for 1 h. After heating, the pH of the solution was adjusted to 8 and the solution (200 g) was cast onto Teflon coated plates. Glycerol (10% on weight of feathers) was added to reduce the brittleness of the keratin films. The solution was dried at 21 C and
2.3.4. Biodegradation 2.3.4.1. COD and BOD5. Biodegradability of the keratin solutions in activated sludge was evaluated by measuring the changes in Chemical oxygen Demand (COD), 5-day Biochemical Oxygen Demand (BOD5) and total and ammonia nitrogen. COD and BOD5 were measured according to the American Public Health Association Standards. Activated sludge was collected from the local waste water treatment plant and acclimatized in the laboratory for 48 h. Keratin and PVA solutions (300 ppm) were prepared and about 35 ml of activated sludge collected from the waste water treatment plant was added along with nutrient buffers. COD of the diluted activated sludge added into the keratin and PVA solutions was low (about 20 mg L1) to ensure that the sludge did not interfere with the biodegradation measurements. Treatment of the keratin and PVA solution was continued for up to twelve days and oxygen was pumped into the containers to maintain the aerobic conditions. Samples were taken about every 24 h from the containers and the
Fig. 2. Influence of pH of the sizing solution on the tensile properties of the polyester and P/C rovings. Feathers were pre-treated at 90 C for 30 min using 0.5% NaOH and the add-on (%) on the roving was 10%. Data points having statistically significant difference have been represented with different alphabets.
Fig. 4. Comparison of the abrasion resistance of the polyester and P/C fabrics treated with keratin and PVA at different add-on (%). Sizing was done at 90 C for 30 min and the pH of the keratin solution was 8. In each curve, data points with different alphabets denote statistically significant difference.
2.3.2. Abrasion resistance Abrasion resistance was measured on both fabrics and yarns. Sized fabrics were tested for abrasion resistance on a CSI Universal Wear Tester using “0” emery sand paper. Standard weight of 454 g for the polyester fabrics and 227 g for the P/C fabrics were used.
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COD, BOD5 and total and ammonia nitrogen were determined. COD was determined according to US EPA Standard 8000 reactor digestion method using the HACH test kit (TNT plus 822). BOD5 was determined by measuring the concentration of dissolved oxygen before and after incubation for 5 days in the dark at 20 C. Concentration of the PVA and keratin for the BOD5 tests was also 300 ppm and it was ensured that the dilution water used had an oxygen consumption of less than 0.2 mg L1. Nutrient buffers were added as prescribed in the standard procedures. 2.3.4.1.1. Total and ammonia nitrogen. Total and ammonia nitrogen released from the feather keratin during degradation in activated sludge was measured to determine if the keratin would impede the biodegradation. An alkaline persulfate oxidation digestion method was used to determine the ammonia content. In this method, salicylate and hypochlorite in an alkaline a sodium nitroferricyanide buffer turn the effluent water green and the intensity of the color is proportional to the amount of ammonia in the sample. To determine the amount of nitrogen released during degradation, about 50 g L1 of salicylic acid and potassium sodium tartrate each, 0.32 mol L1, 10 g L1 of sodium nitroferricyanide and sodium hypochlorite solution (3.5 g L1 active chlorine, 0.75 mol L1 free alkali) were added. After addition the sludge was allowed to stand for 1 h at room temperature and samples were drawn and measured for absorbance at 697 nm in a spectrophotometer (Beckman Coulter, CU 920). At least three samples were drawn for each time point and a calibration curve prepared with known concentrations of nitrogen were used to determine the nitrogen released due to the degradation of the feathers. To determine total nitrogen, samples drawn from the activated sludge containing keratin were added with 40 g L1 of potassium persulfate,15 g L1 of sodium hydroxide and the samples were digested at 120 C for 40 min. The digestion was terminated by adding 1 ml HCl and the absorbance of the solution at 220 and 275 nm were measured on a spectrophotometer. Concentration of the total nitrogen was calculated based on the absorbance values using a calibration curve.
3. Results and discussion 3.1. Film properties Keratin films obtained in this research had a low breaking load of 1 MPa, elongation of 1.3% and modulus of 334 MPa compared to PVA films that had much higher breaking stress (24.3 3.9 MPa) and elongation (278 34%). Inferior strength and elongation of the keratin films should mainly be due to the lower molecular weight and hydrophilicity of the keratin compared to PVA. Although keratin films were considerably weaker and brittle compared to PVA films, keratin had good adhesion to the fibers, especially cotton and therefore provided better sizing performance as discussed below. Table 1 Comparison of the desizing ability (size removal) of the feather keratin and PVA on polyester and P/C fabrics under various desizing conditions. Type of fabrics
Desizing conditions
Polyester 90
5
20 90
5 5
20
5
P/C
% Size removed
Temp Time, Water to fabric ratio C min Washing Rinsing 5:1 5:1 10:1 10:1 5:1 5:1 10:1 10:1
5:1 5:1 5:1 5:1 5:1 5:1 5:1 5:1
# Of rinses 1 2 1 1 1 2 1 1
Keratin
PVA
92.63.7 99.4 0.5 97.8 3.8 100 89.8 4.0 99.3 1.2 100 95.1 2.6
76.7 95.7 99.4 61.5 77.0 100 100 82.3
4.6 3.8 1.0 3.4 4.3
3.9
Fig. 5. Comparison of the biodegradation of chicken feather keratin and PVA (300 ppm) in activated sludge measured in terms of the changes in the COD and BOD5.
3.2. Viscosity of the sizing solution Pre-treating the chicken feathers in various concentrations of alkali at 90 C for 30 min dissolved the feathers and provided keratin solution with viscosity of 1.5 mPas compared to 2 mPas for PVA. The viscosity of the keratin solution was considerably lower than that of chitosan (20e140 mPas) suggesting that higher concentrations of keratin solution could be used for sizing (Stegmaier et al., 2008). 3.3. Effect of alkali concentration Keratin obtained using higher concentrations (1%) of alkali provided considerably lower strength to both the P/C and polyester rovings as seen from Fig. 1. Considerable hydrolysis of the feathers occurred when 1% NaOH was used and therefore the strength of the rovings was lower compared to the respective strength at 0.25 and 0.5% alkali. A similar trend was also observed for the elongation of the rovings. Although alkali concentrations lower than 0.25% may increase the strength of the rovings, feathers did not dissolve completely when the alkali concentration was lower than 0.25%. Compared to plant proteins such as soy proteins and wheat gluten that were studied as potential sizing agents, much higher concentration of alkali was required to dissolve the feathers since feathers are highly crosslinked with cysteine linkages (Chen et al., 2013a,b). 3.4. Effect of pH of sizing solution pH of the sizing solution affected the tensile strength and elongation of polyester rovings but the properties of the P/C rovings did not show any significant change with changes in pH as seen from Fig. 2. Both strength and elongation of the polyester roving were lower at pH 7 and increased with increasing pH up to 10. Considerable amounts of acid were added to obtain pH 7 sizing solution after pre-treatment with 0.5% NaOH. Addition of the acid into the alkaline solution resulted in the formation of salt which changes the attraction between the proteins and the fibers and also makes the proteins more hydrophilic. Therefore, there would be less binding (cohesion) between the polyester fibers and feathers at pH 7 and the higher amounts of moisture on keratin would also reduce the attraction towards the hydrophobic fibers leading to lower strength and elongation. At high pH (11), there is little salt and considerable repulsion between the fibers and the protein solution and therefore lower strength and elongation. A pH range of 8e10 was found to be most suitable for sizing polyester with feather keratin. P/C rovings were relatively unaffected by the pH of
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Fig. 6. Total and ammonia nitrogen released from the feather keratin during degradation in activated sludge.
the sizing solution because cotton had good attraction to the keratin solution at all the pHs studied. 3.5. Effect of humidity on tensile properties Relative humidity had a significant influence on the strength and elongation of both polyester and P/C rovings treated with keratin as seen from Fig. 3. While the strength of the P/C roving increased with increasing humidity, the strength of the polyester rovings decreased at high (75%) humidity. Similar trend was observed for the elongation of the rovings. At low humidity (55%), the keratin films on the fibers are brittle and therefore the rovings have lower strength and elongation. Increasing humidity increases moisture on the films and provides better flexibility to the rovings leading to higher strength and elongation. However, when the humidity if 75%, there is probably excessive moisture on keratin that increased the repulsion between the hydrophobic polyester and hydrophilic proteins. This could decrease the strength and elongation of the polyester rovings at 75% humidity. 3.6. Abrasion resistance Keratin size on polyester fabrics provided substantially higher abrasion resistance whereas abrasion resistance of P/C fabrics treated
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with keratin was lower compared to PVA as seen from Fig. 4. There was a continual increase in abrasion resistance with increase in addon (%) but the increase on polyester fabrics was considerably higher compared to the same fabrics treated with PVA. Even at a percentage add-on of 1.9%, the polyester fabrics treated with keratin had substantially higher resistance of 660 cycles. Further increase in add-on up to 6% did not show any appreciable increase until about 8% addon when the abrasion resistance increased to 1035 cycles. Contrary to the changes in abrasion resistance seen on polyester fabrics, the P/C fabrics treated with keratin had lower abrasion resistance than PVA treated fabrics at all the add-ons (%) studied. Highest abrasion resistance obtained on P/C fabrics treated with keratin was 99 cycles (addon 8.3%) compared to 250 cycles for PVA at an add-on of 7.6%. Abrasion resistance is related to the film forming properties of the sizing solution. Since there was low attraction between the hydrophilic keratin and hydrophobic polyester fibers, most of the sizing solution would have remained on the surface forming a thick film when the solution was dried. Cotton in the P/C fabrics would have absorbed the sizing solution and the solution had penetrated inside with relatively thinner film on the surface. Therefore, the polyester fabrics treated with keratin had higher and the P/C fabrics lower abrasion resistance compared to PVA. This result is contrary to the roving strength improvements where the polyester rovings had lower and the P/C rovings similar strength compared to PVA. Poor attraction and therefore poor adhesion between polyester and keratin causes the polyester rovings to have lower strength but the film formation on the surface provides good abrasion resistance. 3.7. Desizing Size applied onto fibers should be easily removed (desized) after weaving. Desizing of starch is done using enzymes whereas PVA can be desized using hot water (70e90 C), one of the benefits of using PVA as warp size (Du et al., 2007). Ideally, size removal must be >90% and should not require additional chemicals and high temperature. As seen from Table 1, keratin can be easily desized from both polyester and P/C fabrics with low amounts of water even at room temperature. A 100% removal of keratin was observed for polyester fabrics when desized at 20 C for 5 min with a fabric to water ratio of 1:10 compared to 62% removal for PVA under similar desizing conditions. Alternatively, complete removal of the size was also obtained when the desizing was done at 90 C for 5 min but using 1:5 ratio of water and two rinses. In the case of P/C fabrics, size removal varied from 90 to 100% depending on the temperature and washing and rinsing conditions used. A desizing efficiency of 95% was obtained when the fabrics were treated at 20 C for 5 min with a fabric to water ratio of 1:10 compared to 82% removal for PVA. Keratin was easily desized from both the polyester and polycotton fabrics without using high temperatures or large amounts of water suggesting that sizing with keratin would save energy, reduce costs and benefit the environment. 3.8. Biodegradability
Fig. 7. Comparison of the performance of the keratin size on P/C and polyester rovings at different add-on (%) with two different commercially available PVA based sizes.
Poor degradability of PVA in textile waste water treatment plants is the primary reason for the efforts to find biodegradable substitutes. As seen from Fig. 5, PVA had marginal decrease in COD from 399 mg L1 to 308 mg L1 after treating in activated sludge for 3 days whereas the keratin solution showed continued decrease in COD until 12 days. There was a 70% decrease in COD for the keratin solution and a 30% decrease for the PVA solution during the period studied. PVA size had an initial BOD5 of 17 mg1 and reduced to 2 mg L1 after three days of degradation suggesting that there was no further biodegradable material left in the PVA size. In the case of keratin, the BOD5 before treating in the sludge was 76 mg L1 and
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continued to decrease to 5 mg L1 after 12 days. Although the COD values for keratin were considerably lower than that of PVA, there was some non-biodegradable material present in the feathers since the COD values was more than 100 mg L1 after 12 days of degradation and when the BOD5 was lower than 100. Addition of fresh sludge into the keratin solution after 6 days did not result in further decrease in COD also suggesting that some portion of the keratin was non-biodegradable. However, the concentration of the sludge used for biodegradation in this study was considerably low compared to the levels existing in textile effluent plants and a much higher concentration of PVA and keratin (300 ppm) than found in textile waste water treatment plants was used in the study. Therefore, under practical sizing conditions, it is anticipated that keratin would be easily degradable in textile waste water treatment plants based on the changes in COD and BOD5 observed. Presence of high levels of proteins is reported to be undesirable in waste water treatment plants due to the inhibition of microorganisms by the ammonia released from proteins during degradation. Fig. 6 shows the amount of total and ammonia nitrogen released from the keratin during the 6 days of treatment in activated sludge. There is a sharp decline in the total nitrogen after treating in the sludge for up to 3 days and the total nitrogen later stabilized. A corresponding increase in ammonia nitrogen was seen until day 4 and then the ammonia nitrogen released from the keratin decreased sharply. It should be noted that the amount of total and ammonia nitrogen released is negligible and should not inhibit the biodegradation of the sludge. Based on the changes in COD, BOD5, total and ammonia nitrogen, it is clear that feather keratin had considerably better biodegradation in activated sludge compared to PVA demonstrating the potential to replace PVA for textile warp sizing and offers a potential solution to decrease the sizing related pollution from the textile industry. 3.9. Comparison of the performance of chicken feather keratin as size with PVA Fig. 7 provides a comparison of the tensile strength of the P/C and polyester sized rovings treated with feather keratin and two commercially available PVA based sizing agents. P/C rovings sized with feather keratin provided similar strength compared to PVA 1 and higher strength than PVA 2 but at a relatively higher add-on %. Highest strength provided by PVA 1 on P/C rovings was 225 N at an add-on of 13% and 176 N at an add-on of 10% for PVA 2. Keratin solution provided a highest strength of 217 N at an add-on of 18% but the strength was relatively low (111 N) at add-on of 10%. Higher amount of keratin solution was required to provide strength improvement comparable to PVA because of the lower strength and elongation of the keratin films compared to PVA films. Strength improvement provided by the keratin solution on polyester rovings was slightly inferior compared to both the PVAs studied. At similar add-on (10e11%), the rovings sized with keratin had strength of 169 N compared to 190 N for PVA 1 and 188 N for PVA 2. Lower strength provided by the keratin solution on the polyester rovings should be due to the poor attraction between polyester and keratin. Since the roving strength is a measure of cohesion between fibers, poor attraction means less binding and therefore lower strength. Although PVA size provided higher strength of the rovings, the difference between PVA and the keratin size under the optimize condition was about 20N which may not be significant in terms of performance on the weaving machines. In addition, the commercial sizing agents contain additives such as plasticizers, preservatives and stabilizing agents that help to improve the performance properties. Such additives could also be added into the keratin size to improve the performance properties on polyester and/or to obtain similar increase in strength but at
lower add-on. Since keratins can be derived from coproducts with limited use and at almost no cost and the size preparation only used alkali solution, the keratin size would still be highly competitive price-wise to PVA even if higher add-on (%) are required. 4. Conclusions Keratin obtained from chicken feathers after treating with alkali was found to be highly effective as sizing agents. At similar add-on (%), abrasion resistance of polyester fabrics treated with keratin was considerably higher but P/C fabrics were lower compared to PVA. Our results demonstrate that cohesion between fibers is more critical to obtain good improvement in strength and the ability of the sizing solution to form films on the surface influences the abrasion resistance. Keratin solutions were easily biodegradable in activated sludge and there was negligible release of total and ammonia nitrogen. Overall, chicken feather keratin as warp size would be inexpensive, biodegradable and provide good sizing performance and therefore be ideal substitute to PVA. Acknowledgments The authors thank Agricultural Research Division, Multi-State Project S1054 (NEB37-037), USDA Hatch Act at the University of Nebraska-Lincoln and Chinese National High Technology Research and Development Program 863 Project (2013AA06A307), the Doctoral Dissertation Innovation Program BC201040, Fundamental Research Funds for the Central Universities (No. 2011D10543) of Donghua University for providing the financial support to complete this work. Living expenses provided by the China Scholarship Council for Lihong Chen are also gratefully acknowledged. References Chen, L., Reddy, N., Yang, Y., 2013a. Remediation of environmental pollution by substituting poly(vinyl alcohol) with biodegradable warp size from wheat gluten. Environ. Sci. Tech. 47, 4505e4511. Chen, L., Reddy, N., Yang, Y., 2013b. Soy proteins as environmentally friendly sizing agents to replace poly(vinyl alcohol). J. Environ. Poll. Res. 20 (9), 6085e6095. Du, G., Liu, L., Song, Z., Hua, Z., Zhu, Y., Chen, J., 2007. Production of polyvinyl alcohol-degrading enzyme with Janthino-bacterium sp. and its application in cotton fabric desizing. Biotechnol. J. 2, 752e758. Fu, Z., Zhang, Y., Wang, X., 2011. Textiles wastewater treatment using anoxic filter bed and biological wriggle bed-ozone biological aerated filter. Bioresour. Technol. 102, 3748e3753. Hamilton, L.E., Chiweshe, A., 1998. Textile pigment printing binders prepared by modifying wheat gluten with methyl acrylate. Starch/Stärke 50, 213e218. Hebeish, A., Aly, A.A., El-Shafei, A.M., Zaghloul, S., 2008. Innovative starch derivatives as textile auxiliaries for application in sizing, finishing and flocculation. Starch 60, 97e109. Hebeish, A., Higazy, A., El-Shafei, A., 2006. New sizing agents and flocculants derived from chitosan. Starch 58, 401e410. Hill, P., Brantley, H., Dyke, M.V., 2010. Some properties of keratin biomaterials: kerateines. Biomaterials 31, 585e593. Huda, S., Yang, Y., 2008. Composites from ground chicken quill and polypropylene. Compos Sci. Technol. 68 (3e4), 790e798. Moore, S.B., Ausley, L.W., 2004. Systems thinking and green chemistry in the textile industry: concepts, technologies and benefits. J. Cleaner. Prod. 12, 585e601. Reddy, N., Yang, Y., 2010. Light-weight polypropylene composites reinforced with whole chicken feathers. J. Appl. Polym. Sci. 116, 3668e3675. Reddy, N., Yang, Y., 2011a. Potential of plant proteins for medical application. Trends Biotechnol. 29 (10), 490e498. Reddy, N., Yang, Y., 2011b. Completely biodegradable soyprotein-jute biocomposites developed using water without any chemicals as plasticizer. Ind. Crops Prod. 33, 35e41. Reddy, N., Zhang, Y., Yang, Y., 2013. Corn distillers dried grains as sustainable and environmentally friendly warp sizing agents. ACS Sustainable Chem. Eng.. http://dx.doi.org/10.1021/sc4002017. Ren, X., 2000. Development of environmental performance indicators for textile process and product. J. Cleaner Prod. 8, 473e481. Sarkar, A., Sarkar, D., Gupta, M., Bhattacharjee, C., 2012. Recovery of polyvinyl alcohol from desizing wastewater using a novel high-shear ultrafiltration module. CLEAN 40 (8), 830e837.
N. Reddy et al. / Journal of Cleaner Production 65 (2014) 561e567 Savin, I., Butnaru, R., 2008. Wastewater characteristics in textile finishing mills. Environ. Eng. Manag. J. 7 (6), 859e864. Stegmaier, T., Wunderlich, W., Hager, T., Siddique, A., Sarsour, J., Planck, H., 2008. Chitosan-a sizing agent in fabric production development and ecological evaluation. CLEAN 36 (3), 279e286. Sun, W., Tian, J., Chen, L., He, S., Wang, J., 2012. Improvement of biodegradability of PVA-containing waste water by ionizing radiation pretreatment. Environ. Sci. Pollut. Res. 19, 3178e3184. Wang, S., Taraballi, F., Tan, L.P., Ng, K., 2012. Human keratin hydrogels support fibroblast attachment and proliferation in vitro. Cell Tissue Res. 347, 795e802.
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Yang, Y., Reddy, N., 2013. Potential of using plant proteins and chicken feathers for cotton warp sizing. Cellulose 20 (4), 2163e2174. Zhu, Z., Cao, S., 2004. Modifications to improve the adhesion of crosslinked starch sizes to fiber substrates. Text. Res. J. 74 (3), 253e258. Zhu, Z., Cheng, Z., 2008. Effect of inorganic phosphates on the adhesion of monophosphorylated cornstarch to fibers. Starch 60, 315e320. Zhu, Z., Lin, X., Long, Z., Wang, Y., 2008. Adhesion, film and anti-flocculation behavior of amphoteric starch for warp sizing. AATCC Rev. 8 (4), 38e43.
Contents lists available at ScienceDirect
Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro
Reducing environmental pollution of the textile industry using keratin as alternative sizing agent to poly(vinyl alcohol) Narendra Reddy a, Lihong Chen b, Yue Zhang a, Yiqi Yang a, b, c, d, * a Department of Textiles, Merchandising & Fashion Design, 234, HECO Building, East Campus, University of Nebraska e Lincoln, Lincoln, NE 68583-0802, USA b Key Laboratory of Science and Technology of Eco-Textiles, Ministry of Education, Donghua University, Shanghai 200051, China c Department of Biological Systems Engineering, 234, HECO Building, East Campus, University of Nebraska e Lincoln, Lincoln, NE 68583-0802, USA d Nebraska Center for Materials and Nanoscience, 234, HECO Building, East Campus, University of Nebraska e Lincoln, Lincoln, NE 68583-0802, USA
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 March 2013 Received in revised form 27 September 2013 Accepted 28 September 2013 Available online 8 October 2013
Keratin from chicken feathers used as warp sizing agents on polyester/cotton blends and polyester provide similar sizing performance compared to poly(vinyl alcohol) and are also easily degradable in activated sludge. Poly(vinyl alcohol) (PVA), the most common sizing agent is not degradable in textile effluent treatment plants. Efforts to find substitutes to PVA that can provide similar sizing performance, be biodegradable and cost-effective have not been successful. In this research, keratin was studied as potential sizing agents for polyester and polyester/cotton materials and the sizing performance was evaluated in comparison to PVA. Keratin provided similar cohesion and strength improvements but had low abrasion resistance on polyester/cotton fabrics. Keratin in activated sludge showed a substantial decrease in Chemical Oxygen Demand (COD) whereas there was a negligible decrease in COD for PVA. Overall, the low cost and biodegradable keratin exhibited potential to replace PVA. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Biodegradation Polyvinyl alcohol Sizing Keratin Chicken feathers
1. Introduction Textile processes such as sizing and desizing consume considerable amounts of water, energy and chemicals and are mostly responsible for the toxic effluents released into the environment from textile plants (Moore and Ausley, 2004; Du et al., 2007). Textile industry is one of the largest consumers of water in the world. For instance, processing a ton of textiles is estimated to consume about 80e100 m3 of water that is subsequently released into the environment (Fu et al., 2011; Hamilton and Chiweshe, 1998; Hebeish et al., 2008). Several reports have highlighted the problems and concerns on processing textiles and their effects on the environment (Fu et al., 2011). Most countries, especially in the European Union have enacted several regulations to limit the environmental impacts of textile processing. Among the various textile processes, sizing and desizing account for 40e60% of the effluent load in a textile mill (Hebeish et al., 2006). Traditionally, starch and starch derivatives for cotton and poly(vinyl alcohol) * Corresponding author. Department of Textiles, Merchandising & Fashion Design, 234, HECO Building, East Campus, University of Nebraska e Lincoln, Lincoln, NE 68583-0802, USA. Tel.: þ1 402 472 5197; fax: þ1 402 472 0640. E-mail address: [email protected] (Y. Yang). 0959-6526/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jclepro.2013.09.046
(PVA) for synthetic fibers and blends have been the preferred sizing agents. Relatively low price, good performance properties and easy biodegradability are the advantages of starch whereas PVA is preferred for the excellent sizing performance and easy desizeability although PVA is more expensive than starch. However, PVA accounts for 45% of the total BOD load but does not degrade in textile effluent treatment plants and is reported to persist in water released from treatment plants (Ren, 2000; Savin and Butnaru, 2008). Attempts to recover and reuse PVA and other sizing agents and limit their release into the environment have been technically challenging and/or economically unviable (Sun et al., 2012; Sarkar et al., 2012). Substituting PVA with sizes developed from biopolymers has been attempted to reduce the environmental impacts of PVA. Starch has been modified by grafting with acrylates to make starch more suitable for sizing synthetic fibers and their blends (Zhu and Cheng, 2008; Zhu et al., 2008). In another report, starch was grafted with methacrylates and sized on cotton, polyester and polyester/ cotton (P/C) yarns and found that a proper grafting ratio was necessary to achieve good tensile properties (Zhu and Cao, 2004). Other biopolymers such as cyclodextrans and chitosan have also been studied as potential sizing agents (Hebeish et al., 2006, 2008; Stegmaier et al., 2008).
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Ability to form films, adhere to fibers, provide flexibility and easy removal from the fibers after weaving are some of the most desirable features of a sizing agent. Starch and PVA are preferred for sizing due to their good sizing performance and relatively easy desizeability although enzymes are used to remove starch based size. Plant proteins such as wheat gluten and soy proteins have been made into films for food and medical applications, used as adhesives for various applications and also made into regenerated protein fibers for textile and medical applications (Reddy and Yang, 2011a). Proteins have also been used as adhesives for composites and wheat gluten has been studied as a binder for textile printing paste (Reddy and Yang, 2011b; Hamilton and Chiweshe, 1998). These properties make plant proteins suitable for sizing applications. We have recently demonstrated that plant proteins such as soy proteins and wheat gluten and chicken feathers used as sizing agents on cotton, polyester and polyester/cotton provide similar performance properties to PVA and were also easily degradable in activated sludge (Chen et al., 2013a,b; Reddy et al., 2013; Yang and Reddy, 2013). Similar to plant proteins, poultry feathers have also been studied for various non-food applications. Feathers or keratin from feathers have been made into fibers, composites, films, sponges, hydrogels for various end-uses (Reddy and Yang, 2010; Hill et al., 2010). Unlike plant proteins, feathers do not have food applications and their non-food applications are also limited. About 1.8e2 million tons of chicken feathers are available in the United States and most of the feathers are disposed in landfills. However, unlike plant proteins, it is difficult to dissolve feathers and develop products. Most of the previous applications have used feathers in their original form (reinforcement for composites) or extracted keratin from feathers to be processed into films, hydrogels and fibers (Huda and Yang, 2008; Wang et al., 2012). The large availability and virtually no cost makes feathers attractive raw material for sizing textile yarns. However, appropriate methods of dissolving feathers and the ability of feather to provide the desired improvement in strength and abrasion resistance need to be investigated. In this research, keratin from chicken feathers was used to size polyester and polyester/cotton yarns. Effects of size preparation conditions and amount of size (add-on, %) on the tensile properties and abrasion resistance of rovings and yarns were studied. Biodegradability of keratin solutions in activated sludge and the ability of keratin to be desized were also investigated. Commercially available PVA based sizing agents were used to evaluate the performance of keratin as sizing agent.
Feathers were pre-treated in alkaline solution to dissolve the feathers and obtain keratin. Pre-treatment was done by heating the feathers in alkaline solution (0.25e1%) at 90 C for 30 min. After heating, the solution was filtered, pH of the solution adjusted between 8 and 10 and the solution was reheated to 90 C. The rovings and yarns wound onto frames were placed in shallow plates and sized at 90 C for 5 min. After sizing, the materials were allowed to dry at 21 C and 65% relative humidity. Fabrics were also sized similarly, except that after sizing, the fabrics were passed through a laboratory padder to ensure constant pick-up and penetration of size into the fabrics. PVA based sized were applied onto the rovings, yarns and fabrics based on the manufacturers recommended conditions (heating 1e2% PVA in water and sizing at 90 C). A two-step pre-treatment was used to prepare the sizing solution for polyester rovings. Since extraction of keratin from the feathers required higher concentrations of alkali (up to 100% by weight of feathers), considerable amounts of acid (hydrochloric acid) was added to reduce the pH of the solution to 7e9 after the initial pre-treatment. Addition of the strong acid into the strong alkali solution resulted in formation of salts in the solution. After sizing, salt on the polyester rovings caused high moisture sorption during conditioning and decreased the mechanical properties considerably. To decrease the amount of salts in the sizing solution, a two-step pre-treatment was used. Initially, feathers (10%) were soaked in 1% NaOH for 12 h at room temperature. Feathers were later washed thoroughly in warm water to remove the alkali until the pH of the feather was 7. Later, the keratin obtained were dried and used for sizing by treating with 0.25% alkali for 1 h at 95 C. Sizing of the roving was done as described earlier. Samples were dried in an oven at 105 C for 3 h and their dry weight was determined before and after sizing. Amount of size (add-on, %) on the materials was calculated based on the difference in weight of the samples before and after sizing using Equation (1).
2. Materials and methods
Add on; % ¼ ½ðWa WbÞ=Wb 100
2.1. Materials
where, Wa is the dry weight of the samples after sizing and Wb is the dry weight of the samples before sizing. Viscosity of the sizing solution was determined on a Brookfield (R/S plus) rheometer using a CC-25 spindle and cup. Measurements in terms of mPas were taken with solution concentration between 0.25 and 2% for 1 h, maintaining the temperature of the solution at 90 C using a water bath.
Whole chicken feather consisting of quills, barbs and barbules were supplied by Feather Fiber Corporation (Nixa, MO). Feathers were ground into powder using a Wiley mill and used for alkaline hydrolysis. Sizing was done on rovings to measure the cohesion between fibers, on yarns and fabrics to determine the changes in strength and abrasion resistance due to sizing. Polyester/cotton (65/35) rovings (70s Hank) and yarns (15s Ne) were supplied by Mount Vernon Mills, Mauldin, S.C. Cotton used in the P/C blend was strict low middling with average length of 27 mm. Polyester fibers in the blend were of 1.4 denier, 38 mm cut length, breaking tenacity of 6.5 g/den and 27.8% elongation. Polyester (100%) rovings and yarns used in the study were supplied by Shuford Yarns LLC, Hickory, NC. Fabrics (P/C type 7435) and 100% polyester (Dacron type 54) were purchased from Test Fabrics Inc., West Pittston, PA. Two types of commercially available PVA based sizes (named PVA 1 and PVA 2) were obtained from major sizing chemical
manufacturers in the United States to compare the properties of the feather sized materials. PVA 1 was a fully hydrolyzed copolymer with a molecular weight (Mw) of approximately 65 kDa. Viscosity of PVA 1 at 20 C was 11.6e15.4 mPas at 4% solid content. PVA 2 containing 80e85% PVA had a hydrolysis value between 88 and 96% and a viscosity of 14e25 mPas for 4% solid content at 20 C. Sodium hydroxide and other chemicals required for the study were obtained from VWR international, Bristol, CT. 2.2. Preparation of the keratin sizing solution
(1)
2.3. Property evaluation 2.3.1. Cohesion test Ability of the size to adhere to the fibers was evaluated in terms of cohesive strength of the rovings. Since rovings are a loose assembly of fibers that have almost no strength, increase in roving strength would be a good indicator of the adhesion/cohesion between fibers (Stegmaier et al., 2008) Tensile properties of rovings were tested on an MTS tensile tester (MTS Corporation, Eden Prairie, MN, Model: Q Test 10) using a load cell of 500 N and
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Fig. 1. Influence of concentration of alkali used during pre-treatment on the tensile properties of the polyester and P/C rovings. Feathers were pre-treated at 90 C for 30 min, pH of the solution during sizing was 8 and the add-on (%) on the roving was 10%. Data points having statistically significant difference have been represented with different alphabets.
traverse speed of 50 mm min1 and gauge length of 10 cm. Yarn strength was measured on an Instron tensile tester (Model 4444) using a gauge length of 10 cm and crosshead speed of 18 mm min1. At least 25 samples from each condition were tested and each experimental condition was repeated three times. Average and one standard deviation between the three experiments were calculated and reported here.
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Fig. 3. Comparison of the performance of the P/C and polyester rovings at different humidities. Sizing was done at 90 C for 30 min and the add-on (%) was 10%.
65% relative humidity for about 48 h before being peeled off from the plates. Films were tested for tensile strength and elongation on an MTS tensile tester according to ASTM standard D 882. At least 10 sample each from three separately cast films were tested and the average and one standard deviation were reported.
2.3.3. Film properties Keratin films were prepared by heating 6% feather in 0.25% alkali solution at 95 C for 1 h. After heating, the pH of the solution was adjusted to 8 and the solution (200 g) was cast onto Teflon coated plates. Glycerol (10% on weight of feathers) was added to reduce the brittleness of the keratin films. The solution was dried at 21 C and
2.3.4. Biodegradation 2.3.4.1. COD and BOD5. Biodegradability of the keratin solutions in activated sludge was evaluated by measuring the changes in Chemical oxygen Demand (COD), 5-day Biochemical Oxygen Demand (BOD5) and total and ammonia nitrogen. COD and BOD5 were measured according to the American Public Health Association Standards. Activated sludge was collected from the local waste water treatment plant and acclimatized in the laboratory for 48 h. Keratin and PVA solutions (300 ppm) were prepared and about 35 ml of activated sludge collected from the waste water treatment plant was added along with nutrient buffers. COD of the diluted activated sludge added into the keratin and PVA solutions was low (about 20 mg L1) to ensure that the sludge did not interfere with the biodegradation measurements. Treatment of the keratin and PVA solution was continued for up to twelve days and oxygen was pumped into the containers to maintain the aerobic conditions. Samples were taken about every 24 h from the containers and the
Fig. 2. Influence of pH of the sizing solution on the tensile properties of the polyester and P/C rovings. Feathers were pre-treated at 90 C for 30 min using 0.5% NaOH and the add-on (%) on the roving was 10%. Data points having statistically significant difference have been represented with different alphabets.
Fig. 4. Comparison of the abrasion resistance of the polyester and P/C fabrics treated with keratin and PVA at different add-on (%). Sizing was done at 90 C for 30 min and the pH of the keratin solution was 8. In each curve, data points with different alphabets denote statistically significant difference.
2.3.2. Abrasion resistance Abrasion resistance was measured on both fabrics and yarns. Sized fabrics were tested for abrasion resistance on a CSI Universal Wear Tester using “0” emery sand paper. Standard weight of 454 g for the polyester fabrics and 227 g for the P/C fabrics were used.
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COD, BOD5 and total and ammonia nitrogen were determined. COD was determined according to US EPA Standard 8000 reactor digestion method using the HACH test kit (TNT plus 822). BOD5 was determined by measuring the concentration of dissolved oxygen before and after incubation for 5 days in the dark at 20 C. Concentration of the PVA and keratin for the BOD5 tests was also 300 ppm and it was ensured that the dilution water used had an oxygen consumption of less than 0.2 mg L1. Nutrient buffers were added as prescribed in the standard procedures. 2.3.4.1.1. Total and ammonia nitrogen. Total and ammonia nitrogen released from the feather keratin during degradation in activated sludge was measured to determine if the keratin would impede the biodegradation. An alkaline persulfate oxidation digestion method was used to determine the ammonia content. In this method, salicylate and hypochlorite in an alkaline a sodium nitroferricyanide buffer turn the effluent water green and the intensity of the color is proportional to the amount of ammonia in the sample. To determine the amount of nitrogen released during degradation, about 50 g L1 of salicylic acid and potassium sodium tartrate each, 0.32 mol L1, 10 g L1 of sodium nitroferricyanide and sodium hypochlorite solution (3.5 g L1 active chlorine, 0.75 mol L1 free alkali) were added. After addition the sludge was allowed to stand for 1 h at room temperature and samples were drawn and measured for absorbance at 697 nm in a spectrophotometer (Beckman Coulter, CU 920). At least three samples were drawn for each time point and a calibration curve prepared with known concentrations of nitrogen were used to determine the nitrogen released due to the degradation of the feathers. To determine total nitrogen, samples drawn from the activated sludge containing keratin were added with 40 g L1 of potassium persulfate,15 g L1 of sodium hydroxide and the samples were digested at 120 C for 40 min. The digestion was terminated by adding 1 ml HCl and the absorbance of the solution at 220 and 275 nm were measured on a spectrophotometer. Concentration of the total nitrogen was calculated based on the absorbance values using a calibration curve.
3. Results and discussion 3.1. Film properties Keratin films obtained in this research had a low breaking load of 1 MPa, elongation of 1.3% and modulus of 334 MPa compared to PVA films that had much higher breaking stress (24.3 3.9 MPa) and elongation (278 34%). Inferior strength and elongation of the keratin films should mainly be due to the lower molecular weight and hydrophilicity of the keratin compared to PVA. Although keratin films were considerably weaker and brittle compared to PVA films, keratin had good adhesion to the fibers, especially cotton and therefore provided better sizing performance as discussed below. Table 1 Comparison of the desizing ability (size removal) of the feather keratin and PVA on polyester and P/C fabrics under various desizing conditions. Type of fabrics
Desizing conditions
Polyester 90
5
20 90
5 5
20
5
P/C
% Size removed
Temp Time, Water to fabric ratio C min Washing Rinsing 5:1 5:1 10:1 10:1 5:1 5:1 10:1 10:1
5:1 5:1 5:1 5:1 5:1 5:1 5:1 5:1
# Of rinses 1 2 1 1 1 2 1 1
Keratin
PVA
92.63.7 99.4 0.5 97.8 3.8 100 89.8 4.0 99.3 1.2 100 95.1 2.6
76.7 95.7 99.4 61.5 77.0 100 100 82.3
4.6 3.8 1.0 3.4 4.3
3.9
Fig. 5. Comparison of the biodegradation of chicken feather keratin and PVA (300 ppm) in activated sludge measured in terms of the changes in the COD and BOD5.
3.2. Viscosity of the sizing solution Pre-treating the chicken feathers in various concentrations of alkali at 90 C for 30 min dissolved the feathers and provided keratin solution with viscosity of 1.5 mPas compared to 2 mPas for PVA. The viscosity of the keratin solution was considerably lower than that of chitosan (20e140 mPas) suggesting that higher concentrations of keratin solution could be used for sizing (Stegmaier et al., 2008). 3.3. Effect of alkali concentration Keratin obtained using higher concentrations (1%) of alkali provided considerably lower strength to both the P/C and polyester rovings as seen from Fig. 1. Considerable hydrolysis of the feathers occurred when 1% NaOH was used and therefore the strength of the rovings was lower compared to the respective strength at 0.25 and 0.5% alkali. A similar trend was also observed for the elongation of the rovings. Although alkali concentrations lower than 0.25% may increase the strength of the rovings, feathers did not dissolve completely when the alkali concentration was lower than 0.25%. Compared to plant proteins such as soy proteins and wheat gluten that were studied as potential sizing agents, much higher concentration of alkali was required to dissolve the feathers since feathers are highly crosslinked with cysteine linkages (Chen et al., 2013a,b). 3.4. Effect of pH of sizing solution pH of the sizing solution affected the tensile strength and elongation of polyester rovings but the properties of the P/C rovings did not show any significant change with changes in pH as seen from Fig. 2. Both strength and elongation of the polyester roving were lower at pH 7 and increased with increasing pH up to 10. Considerable amounts of acid were added to obtain pH 7 sizing solution after pre-treatment with 0.5% NaOH. Addition of the acid into the alkaline solution resulted in the formation of salt which changes the attraction between the proteins and the fibers and also makes the proteins more hydrophilic. Therefore, there would be less binding (cohesion) between the polyester fibers and feathers at pH 7 and the higher amounts of moisture on keratin would also reduce the attraction towards the hydrophobic fibers leading to lower strength and elongation. At high pH (11), there is little salt and considerable repulsion between the fibers and the protein solution and therefore lower strength and elongation. A pH range of 8e10 was found to be most suitable for sizing polyester with feather keratin. P/C rovings were relatively unaffected by the pH of
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Fig. 6. Total and ammonia nitrogen released from the feather keratin during degradation in activated sludge.
the sizing solution because cotton had good attraction to the keratin solution at all the pHs studied. 3.5. Effect of humidity on tensile properties Relative humidity had a significant influence on the strength and elongation of both polyester and P/C rovings treated with keratin as seen from Fig. 3. While the strength of the P/C roving increased with increasing humidity, the strength of the polyester rovings decreased at high (75%) humidity. Similar trend was observed for the elongation of the rovings. At low humidity (55%), the keratin films on the fibers are brittle and therefore the rovings have lower strength and elongation. Increasing humidity increases moisture on the films and provides better flexibility to the rovings leading to higher strength and elongation. However, when the humidity if 75%, there is probably excessive moisture on keratin that increased the repulsion between the hydrophobic polyester and hydrophilic proteins. This could decrease the strength and elongation of the polyester rovings at 75% humidity. 3.6. Abrasion resistance Keratin size on polyester fabrics provided substantially higher abrasion resistance whereas abrasion resistance of P/C fabrics treated
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with keratin was lower compared to PVA as seen from Fig. 4. There was a continual increase in abrasion resistance with increase in addon (%) but the increase on polyester fabrics was considerably higher compared to the same fabrics treated with PVA. Even at a percentage add-on of 1.9%, the polyester fabrics treated with keratin had substantially higher resistance of 660 cycles. Further increase in add-on up to 6% did not show any appreciable increase until about 8% addon when the abrasion resistance increased to 1035 cycles. Contrary to the changes in abrasion resistance seen on polyester fabrics, the P/C fabrics treated with keratin had lower abrasion resistance than PVA treated fabrics at all the add-ons (%) studied. Highest abrasion resistance obtained on P/C fabrics treated with keratin was 99 cycles (addon 8.3%) compared to 250 cycles for PVA at an add-on of 7.6%. Abrasion resistance is related to the film forming properties of the sizing solution. Since there was low attraction between the hydrophilic keratin and hydrophobic polyester fibers, most of the sizing solution would have remained on the surface forming a thick film when the solution was dried. Cotton in the P/C fabrics would have absorbed the sizing solution and the solution had penetrated inside with relatively thinner film on the surface. Therefore, the polyester fabrics treated with keratin had higher and the P/C fabrics lower abrasion resistance compared to PVA. This result is contrary to the roving strength improvements where the polyester rovings had lower and the P/C rovings similar strength compared to PVA. Poor attraction and therefore poor adhesion between polyester and keratin causes the polyester rovings to have lower strength but the film formation on the surface provides good abrasion resistance. 3.7. Desizing Size applied onto fibers should be easily removed (desized) after weaving. Desizing of starch is done using enzymes whereas PVA can be desized using hot water (70e90 C), one of the benefits of using PVA as warp size (Du et al., 2007). Ideally, size removal must be >90% and should not require additional chemicals and high temperature. As seen from Table 1, keratin can be easily desized from both polyester and P/C fabrics with low amounts of water even at room temperature. A 100% removal of keratin was observed for polyester fabrics when desized at 20 C for 5 min with a fabric to water ratio of 1:10 compared to 62% removal for PVA under similar desizing conditions. Alternatively, complete removal of the size was also obtained when the desizing was done at 90 C for 5 min but using 1:5 ratio of water and two rinses. In the case of P/C fabrics, size removal varied from 90 to 100% depending on the temperature and washing and rinsing conditions used. A desizing efficiency of 95% was obtained when the fabrics were treated at 20 C for 5 min with a fabric to water ratio of 1:10 compared to 82% removal for PVA. Keratin was easily desized from both the polyester and polycotton fabrics without using high temperatures or large amounts of water suggesting that sizing with keratin would save energy, reduce costs and benefit the environment. 3.8. Biodegradability
Fig. 7. Comparison of the performance of the keratin size on P/C and polyester rovings at different add-on (%) with two different commercially available PVA based sizes.
Poor degradability of PVA in textile waste water treatment plants is the primary reason for the efforts to find biodegradable substitutes. As seen from Fig. 5, PVA had marginal decrease in COD from 399 mg L1 to 308 mg L1 after treating in activated sludge for 3 days whereas the keratin solution showed continued decrease in COD until 12 days. There was a 70% decrease in COD for the keratin solution and a 30% decrease for the PVA solution during the period studied. PVA size had an initial BOD5 of 17 mg1 and reduced to 2 mg L1 after three days of degradation suggesting that there was no further biodegradable material left in the PVA size. In the case of keratin, the BOD5 before treating in the sludge was 76 mg L1 and
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continued to decrease to 5 mg L1 after 12 days. Although the COD values for keratin were considerably lower than that of PVA, there was some non-biodegradable material present in the feathers since the COD values was more than 100 mg L1 after 12 days of degradation and when the BOD5 was lower than 100. Addition of fresh sludge into the keratin solution after 6 days did not result in further decrease in COD also suggesting that some portion of the keratin was non-biodegradable. However, the concentration of the sludge used for biodegradation in this study was considerably low compared to the levels existing in textile effluent plants and a much higher concentration of PVA and keratin (300 ppm) than found in textile waste water treatment plants was used in the study. Therefore, under practical sizing conditions, it is anticipated that keratin would be easily degradable in textile waste water treatment plants based on the changes in COD and BOD5 observed. Presence of high levels of proteins is reported to be undesirable in waste water treatment plants due to the inhibition of microorganisms by the ammonia released from proteins during degradation. Fig. 6 shows the amount of total and ammonia nitrogen released from the keratin during the 6 days of treatment in activated sludge. There is a sharp decline in the total nitrogen after treating in the sludge for up to 3 days and the total nitrogen later stabilized. A corresponding increase in ammonia nitrogen was seen until day 4 and then the ammonia nitrogen released from the keratin decreased sharply. It should be noted that the amount of total and ammonia nitrogen released is negligible and should not inhibit the biodegradation of the sludge. Based on the changes in COD, BOD5, total and ammonia nitrogen, it is clear that feather keratin had considerably better biodegradation in activated sludge compared to PVA demonstrating the potential to replace PVA for textile warp sizing and offers a potential solution to decrease the sizing related pollution from the textile industry. 3.9. Comparison of the performance of chicken feather keratin as size with PVA Fig. 7 provides a comparison of the tensile strength of the P/C and polyester sized rovings treated with feather keratin and two commercially available PVA based sizing agents. P/C rovings sized with feather keratin provided similar strength compared to PVA 1 and higher strength than PVA 2 but at a relatively higher add-on %. Highest strength provided by PVA 1 on P/C rovings was 225 N at an add-on of 13% and 176 N at an add-on of 10% for PVA 2. Keratin solution provided a highest strength of 217 N at an add-on of 18% but the strength was relatively low (111 N) at add-on of 10%. Higher amount of keratin solution was required to provide strength improvement comparable to PVA because of the lower strength and elongation of the keratin films compared to PVA films. Strength improvement provided by the keratin solution on polyester rovings was slightly inferior compared to both the PVAs studied. At similar add-on (10e11%), the rovings sized with keratin had strength of 169 N compared to 190 N for PVA 1 and 188 N for PVA 2. Lower strength provided by the keratin solution on the polyester rovings should be due to the poor attraction between polyester and keratin. Since the roving strength is a measure of cohesion between fibers, poor attraction means less binding and therefore lower strength. Although PVA size provided higher strength of the rovings, the difference between PVA and the keratin size under the optimize condition was about 20N which may not be significant in terms of performance on the weaving machines. In addition, the commercial sizing agents contain additives such as plasticizers, preservatives and stabilizing agents that help to improve the performance properties. Such additives could also be added into the keratin size to improve the performance properties on polyester and/or to obtain similar increase in strength but at
lower add-on. Since keratins can be derived from coproducts with limited use and at almost no cost and the size preparation only used alkali solution, the keratin size would still be highly competitive price-wise to PVA even if higher add-on (%) are required. 4. Conclusions Keratin obtained from chicken feathers after treating with alkali was found to be highly effective as sizing agents. At similar add-on (%), abrasion resistance of polyester fabrics treated with keratin was considerably higher but P/C fabrics were lower compared to PVA. Our results demonstrate that cohesion between fibers is more critical to obtain good improvement in strength and the ability of the sizing solution to form films on the surface influences the abrasion resistance. Keratin solutions were easily biodegradable in activated sludge and there was negligible release of total and ammonia nitrogen. Overall, chicken feather keratin as warp size would be inexpensive, biodegradable and provide good sizing performance and therefore be ideal substitute to PVA. Acknowledgments The authors thank Agricultural Research Division, Multi-State Project S1054 (NEB37-037), USDA Hatch Act at the University of Nebraska-Lincoln and Chinese National High Technology Research and Development Program 863 Project (2013AA06A307), the Doctoral Dissertation Innovation Program BC201040, Fundamental Research Funds for the Central Universities (No. 2011D10543) of Donghua University for providing the financial support to complete this work. Living expenses provided by the China Scholarship Council for Lihong Chen are also gratefully acknowledged. References Chen, L., Reddy, N., Yang, Y., 2013a. Remediation of environmental pollution by substituting poly(vinyl alcohol) with biodegradable warp size from wheat gluten. Environ. Sci. Tech. 47, 4505e4511. Chen, L., Reddy, N., Yang, Y., 2013b. Soy proteins as environmentally friendly sizing agents to replace poly(vinyl alcohol). J. Environ. Poll. Res. 20 (9), 6085e6095. Du, G., Liu, L., Song, Z., Hua, Z., Zhu, Y., Chen, J., 2007. Production of polyvinyl alcohol-degrading enzyme with Janthino-bacterium sp. and its application in cotton fabric desizing. Biotechnol. J. 2, 752e758. Fu, Z., Zhang, Y., Wang, X., 2011. Textiles wastewater treatment using anoxic filter bed and biological wriggle bed-ozone biological aerated filter. Bioresour. Technol. 102, 3748e3753. Hamilton, L.E., Chiweshe, A., 1998. Textile pigment printing binders prepared by modifying wheat gluten with methyl acrylate. Starch/Stärke 50, 213e218. Hebeish, A., Aly, A.A., El-Shafei, A.M., Zaghloul, S., 2008. Innovative starch derivatives as textile auxiliaries for application in sizing, finishing and flocculation. Starch 60, 97e109. Hebeish, A., Higazy, A., El-Shafei, A., 2006. New sizing agents and flocculants derived from chitosan. Starch 58, 401e410. Hill, P., Brantley, H., Dyke, M.V., 2010. Some properties of keratin biomaterials: kerateines. Biomaterials 31, 585e593. Huda, S., Yang, Y., 2008. Composites from ground chicken quill and polypropylene. Compos Sci. Technol. 68 (3e4), 790e798. Moore, S.B., Ausley, L.W., 2004. Systems thinking and green chemistry in the textile industry: concepts, technologies and benefits. J. Cleaner. Prod. 12, 585e601. Reddy, N., Yang, Y., 2010. Light-weight polypropylene composites reinforced with whole chicken feathers. J. Appl. Polym. Sci. 116, 3668e3675. Reddy, N., Yang, Y., 2011a. Potential of plant proteins for medical application. Trends Biotechnol. 29 (10), 490e498. Reddy, N., Yang, Y., 2011b. Completely biodegradable soyprotein-jute biocomposites developed using water without any chemicals as plasticizer. Ind. Crops Prod. 33, 35e41. Reddy, N., Zhang, Y., Yang, Y., 2013. Corn distillers dried grains as sustainable and environmentally friendly warp sizing agents. ACS Sustainable Chem. Eng.. http://dx.doi.org/10.1021/sc4002017. Ren, X., 2000. Development of environmental performance indicators for textile process and product. J. Cleaner Prod. 8, 473e481. Sarkar, A., Sarkar, D., Gupta, M., Bhattacharjee, C., 2012. Recovery of polyvinyl alcohol from desizing wastewater using a novel high-shear ultrafiltration module. CLEAN 40 (8), 830e837.
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