Leather Technology

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Approach Towards High Performance Water Vapour Permeability Upper Leather from Goat Skin
(Addis Ababa University, 2014-09) Mekonnen, Bekele; Muralidharan, B (PhD); Das, B.N. (PhD); John, Sundar (Mr.)
The mechanism of increasing WVP Goat upper leather, the processes have been developed. These process developed during the project were, increased percentage of bating enzyme during bating process, increased the duration time of liming process, avoided the qubracho powder and acrylic syntan during retanning process, decreasing of synthetic fat liquor and instead used semi synthetic fat liquor, increased the percentage of degreaser during degreasing process, after wet blue for 2hrs treated the leather with 1% of urea and acetic acid. For each process, the physical properties such as WVP, tensile strength, percentage elongation at break, tear strength and grain crack were carried out. The result obtained from each process at crust and finished listed in chapter 4 in table form. The experiments carried out for both control and experiments for all experiments.
Approaches to Near Zero Utilization of Water in the Post tanning Operations of Leather Processing
(AAU, 2014-09) Solomon, Fessehaye; K J., Sreeram (PhD)
Any industrial activity would generate waste, whose form would be as solid, liquid and/or gas. While industrialization is important to a nation’s economy, the wellbeing of human kind is even more important. The conflict for water between mankind consumption and industrial activity is increasing day by day as the population is increasing. An industrial activity like leather processing is a water intensive process, with most of the industries consuming 35 L of water to process every kilogram of hide/skin. While it is easy to wish away an activity like leather processing, an analysis of the relevance of this industry to Nation building would reveal that this is the only industry that uses a byproduct of meat industry, viz., skin and converts it into a fashion commodity. In the transformation, a host of rural men and women are involved directly or indirectly. For the nation, it is a good source of export income. This research work is one of an out-of-the-box thinking of systematic reduction and utilize known concepts of recycle, reduce or recovery of used water from processing. For this, the methodology has relied upon the replacement of water with environmentally benign and clean/green solvent for transporting chemicals into the skin matrix instead. The work consists of identifying the appropriate solvent or solvent mixture that a) did not have any adverse effect on the fibre structure, b) where a significant number of leather auxiliaries could be dissolved or dispersed and c) could be easily recovered and reused. The combination of solvents was selected from amongst reported clean/green solvents and the solubility / stability of the auxiliary dispersions determined by the measurement of the zeta potential of the system. The initial interaction of the dispersed auxiliaries with skin matrix being one of adsorption, various models of adsorption can be fitted to understand the nature of binding. The physical and visual properties of developed leathers have also been compared.
Characterization and Enzymatic Transesterification of Pork Lard for the Synthesis of Leather Fatliquor and Biodiesel
(Addis Ababa University, 2014-09) Tsega, Teklu; Baskar, Geetha (PhD)
Pork lard (PL) is a class of lipids and oils organic compounds consisting of both saturated and unsaturated fatty acids that can be modified into biodiesel and leather fatliquor for industrial applications. The fat of the pork was collected from the back attached below the skin and around the belly and kidney of the Caracas. After the oils and fats were extracted and purified, characterization for its physicochemical properties, pattern of triglycerides and fatty acid compositions was done by analytical analysis and using Gas Chromatography (GC), Gas Chromatography Mass Spectroscopy (GC-MS) and Fourier transform infrared spectroscopy (FTIR) instrumental tools. The aim of present research work was the synthesis of biodiesel or Fatty Acid Methyl Ester (FAME) by enzyme catalysed transesterification process using Porcine Pancreatic Lipase (PPL) as a catalyst and the production of leather fatliquor by sulfitation and external emulsification processing methods. The effect of three parameters including Pork Lard to methanol molar ratio, temperature and reaction time on the transesterification reaction (TER) was investigated by keeping 5% enzyme concentration (based on oil weight) and 200 revolutions per minute (rpm) stirring rate constant. The maximum yield of biodiesel was 81 % at 1:4 molar ratio of oil to methanol and 40 oc temperatures after 36 hours reaction time. PL consists of 44% oleic acid and 11%linoleic acid which are suitable to add polar functional group by sulfitation reaction. In this study a promising fatliquor was synthesized from PL by sulfitation and external emulsification method after complete characterization of the fats and lipids. The synthesized sulphited fatliquor gives the leather better multifunctional properties such as softness, handle, colour uniformity, roundness, and better tensile and tear strength properties. This new fatliquor also has unique waxy characteristics which give an attractive burnishable effect in finishing especially for shoe upper leather that most of the conventional commercial fatliquors cannot give.
Characterization and Optimization of Chrome Free Tanning System Using Combination of Chestnut and Tetrakis Hydroxymethyl Phosphonium Sulfate
(Addis Ababa University, 2021-09) Haftom, Girmay; Berhanu, Assefa (PhD)
Currently, chrome tanning accounts for more than 90% of global leather manufacturing. This tanning system result in significant material loss and considerable environmental concerns. In the present work, chrome free combination tanning system using a combination tanning system based on Chestnut and THPS is presented. The processing method for Experimental tanning trials were carried out with different percentages of Chestnut as a tannage followed by varying percentages of THPS as a re-tannage for process optimization. The leathers obtained were characterized for their physical strength characteristics, comfort & organoleptic properties, scanning electron microscopic analysis, reflectance measurements and environmental characteristics. The Chestnut-THPS leathers tanned using 20% chestnut followed by 2% THPS resulted in shrinkage temperature of 95OC. The hydrothermal stability of the combination has been found better than the Chestnut alone and THPS alone tanned leathers, respectively. The strength properties and comfort properties of leathers obtained are on par with or better than the control chrome, Chestnut alone and THPS alone tanned leathers. The organoleptic properties of the experimental crust leathers exhibit good grain smoothness, fullness, grain tightness, general appearance compared to control chrome tanned crust leathers. Environmental impact assessment shows the combination tanning system results a significant reduction in TS, TDS, TSS and BOD in the waste water when compared to that of control tanning system. The study presented in this paper established the use of Chestnut and THPS combination tanning system as an effective alternative cleaner tanning methodology.
Combination Tanning Based on Tara and Sodium Metasilicate a New Chrome Free Tanning System
(Addis Ababa University, 2014-09) Getaneh, Andualem; Madhan, B. (PhD)
Chrome is the well-established tanning system adopted globally. Consumer awareness and short coming of chrome tanning system calls for a need for the development of chrome free tanning, Hence this research work is focused on, the development of silica and vegetable tanning agent (Tara) combination tanning system as an alternative to chrome tanning. This tanning system eliminates the use of chromium in tanning process thereby environmental impact of chromium can be avoided. Silica remains in solution at a narrow pH range and hence in order to keep the silica in sol at pH of about 3, silica tanning salt was prepared by masking with salts viz., sodium citrate and sodium tartrate. The combination tanning based on silica and tara were optimised for the amount of tara, order of addition and masking salt used for the preparation of silica tanning agent. The order of addition of silica and tara, amount of tara and also the type of masking agent had a significant influence on the shrinkage temperature, physical strength and organoleptic properties of the leathers produced. Tanning system with tara followed masked silica gives resulted in wet white leathers with shrinkage temperature of 80oc. Among the combination system evaluated, leathers obtained by vegetable (Tara) pretannage followed by retannage with masked sodium metasilicate were observed to be stronger, fuller and better general appearance with the durable characteristics. In contrast, pre-tanning with masked sodium metasilicate resulted in leathers with poor organoleptic properties and less hydrothermal stability. In general the characteristics of the leathers obtained by tara- silica combination system provides leathers with good organoleptic properties and comparable physical strength for upper leathers. Physical testing and organoleptic properties of the matched pair leathers of the tara-silica combination tanning system were comparable to that of chrome tanned control leathers. Skins stabilized with tara - silica combination tanning could be adapted to shaving readily; most important is that it would not produce wastes containing chromium means it is zero chrome discharge because chromium is not used in this tanning system. Therefore the tara-silica combination tanning is a good tanning system for the manufacture of upper leathers. The tara-silica combination tanning system also resulted in leathers with good buffeability and hence the leather made from this tanning system is also suitable for the manufacture of suede leathers especially for upper. The cost of the new system is higher but can be compensated with the environmental benefits by eliminating chrome in leather manufacture.
Dehairing Protease Production and Evaluation of The Efficacy of Protease Products of Relevant Downstream Processing
(Addis Ababa University, 2014-09) Abebe, Birhanu; Kuppuswami, Gowthaman M. (PhD)
Globally as well as in Ethiopia the tanning industries are under a high pressure from strict legislation articulated for the purpose of protecting and preserving the environment. In the current situation of Ethiopia this industry is viewed from two perspectives; being an important economic activity and the most environment polluting industry. In order to operate within environmentally compatible limits and sustain the realization of Agriculture Development Led Industrialization (ADLI), the current development strategy of Ethiopia, with respect to the tanning industry, some sort of solutions should come out that mitigate the adverse effect of the conventional leather processing methods particularly that of lime-sulphide unhairing operation. This study deals with dehairing enzyme production as green technology alternative for the conventional unhairing practice. The B.subtilis strain was obtained from Department of Biotechnology, CLRI, sub-cultured and characterized for its growth and dehairing protease production in terms of pH, temperature, incubation time and growth and production media composition. The combined effects of pH and temperature on protease production also investigated and they were found to have high interactive effect. Once the culture conditions for production were studied and known, the alkaline protease was produced in a pilot scale fermenter by submerged fermentation using soy bean flour media at optimal conditions of pH 6.5, temperature 310C and incubation period of 27 hours. The final protease product was recovered, partially purified and stabilized by primary downstream processing such as crude enzyme formulation, ammonium sulphate precipitation, ultrafiltration and spray drying. The use of the protease products of each technique on sheep skins and cow hide resulted in a highly promising hair removal efficiency that can really compete with lime-sulphide chemical unhairing process.
Enhancing Unit Value Realization of Hair Sheep Skin- an Assessment of Changes Between Butt and Belly Regions and its Value Addition Using Collagen Hydrolysate
(Addis Ababa University, 2014-09) Negasa, Dagnew; Rao, J. Raghava (PhD)
Skin will undergo changes in biochemical and biophysical properties during leather processing. Biochemical composition varies with respect to different regions of the skin like butt, belly, and neck. Supported with the nature of structure and chemical constituents of the skin, leather processing chemicals do have different propensity to different parts of the skin. Belly region’s looseness and substance non-uniformity are the main problem in leather making from sheep skin (SS) particularly for shoe upper. Having a back with the leather processing practice and statistical data, an exuberant substance non-uniformity for sheep shoe upper is still recurrent in our country’s context. To address same issue, this work focusses on the analysis of histology and biochemical properties of butt and belly portion of hair sheep skin besides the investigation of application collagen hydrolysate on the value addition of dyed crust leather and emission load during pre-tanning. Globular proteins are relatively higher in the butt region than the belly, whereas it is reverse in the case of fibrous proteins except collagen. Interestingly, the presence of proteoglycans content in butt regions is significantly high compared to belly and in case of fat it is reverse. Thus, the effect of liming and bating operations in removing unwanted skin constituents is stronger in butt and belly regions of SS, respectively, which reflects the requisite importance of the two unit operations in the pre-tanning operations. ASC contribution is higher in butt region than belly and the reverse is true in the case of PSC. The overall collagen content is considerably higher in butt than belly which may be the major cause of the higher strength characteristics of butt regions. Cr2O3 content is high in butt region than belly which corroborates with protein content and its interaction with tanning agents. Distribution of pore size influences the breathability property of leather which has been seen to vary in all the unit operations. Scanning electron microscope study complements same trend with respect to changes in the cross-section of the skin during leather processing. Therefore, the considerable variations observed among the two regions of SS would help the tanners and chemical manufactures to have more information on the parts of skins so as to improve the cutting value of the thin part of skin. Collagen hydrolysate being prepared under thermal alkaline condition enhances the hide substance of both belly and butt regions of sheep skin during pre-tanning when offered at pH 9.0. Despite the fact that Cr2O3 uptake found to be reduced in same way the CH uptake increased in both regions of SS, the Ts still found to be greater than 90oC thereby strengthening xv the application of CH in leather processing. In addition to the pore size distribution of the regions of SS, it has been observed that the fibre density of skin matrix also plays its own part for the uptake and retainment of treatment chemicals. The higher increase in the protein content of butt part of SS than belly augments same. The dyestuff exhaustion is by far better for CH treated leather than commercial protein fillers (CPF) used during the study. The increased in the dye exhaustion and overall physico-chemical properties of CH treated upper leathers would highly help the competitiveness of the tanner for the use of CH particularly coined as wealth from waste. The use of CH would be convenient for the value addition of lower end products. The emission load of tanning process liquor with CH is higher than conventional one and same is true for post-tanning process liquor with CPF.
Extraction and Characterization of Chlorogenic Acid from Coffee Husk and its investigation of Applicability as Preservative in Leather Processing
(Addis Ababa University, 2018-06) Daniel, Tesfaye; Shegaw, Ahmed (Assoc. Prof.)
Leather is a perishable material so it has to be preserved from attack of microorganisms. In leather processing steps, skins can be stored at pickle, wet blue, crust and finished stages. Wet blue preservation is prevents the leather from fungal attack and its commercial carried out using TCMTB based chemicals. This TCMTB based commercial chemicals has adverse effect on human health as well as on aquatic lives. Chlorogenic acid, the major active component of coffee husk, extracted by varying solvent, extraction time and solvent to sample ratio using Soxhlet extractor. Twenty Four extractions were randomly done and results were analysed using Design Expert software version 6.0.8. The extraction procedure using Methanol as solvent, extraction time of 4 hours and 10:1 ratio of sample to solvent resulted as the highest value, which is 681 ppm. The minimum yield (468ppm) was obtained at Ethanol solvent, extraction time of 6 hours and 5:1 ratio of sample to solvent. Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus cereus, Escherichia coli and Aspergillus niger were obtained and tested for the susceptibility and it was found to be Aspergillus niger, a fungi, is more susceptible or sensitive than both gram positive and gram negative bacteria to Chlorogenic acid extracted from coffee husk. The Minimum Inhibitory Concentration (MIC) for Aspergillus niger was found to be 62.5µg/mL. The wet blue preserved using the extracted Chlorogenic acid was tested for its resistance to fungal attack and resist any attack till 15 days. The wet blues were processed to crusting and tested for its strength properties and found to have no change of those properties upon the use of Chlorogenic acid for preservative. The waste water from the process were tested and showed significant minimization of COD and TSS.
Extraction and Characterization of Elastin from Raw Hide Trimmings using Autoclave Extraction Technology
(Addis Ababa University, 2018-06) Zerihun, Yoseph; Berhanu, Assefa (PhD)
During leather processing, raw skins/hides are trimmed and thrown as wastes and accounting for pollution load in leather industry. Elastin is a fibrous protein with multifaceted applications in biomedical field due to its intrinsic biological annotations viz elasticity and cell interactions, the extraction process is challenging task due to their cell interactive properties, the application is versatile and the price is in current international market is highly expensive. In this context, leather solid wastes specifically raw hide trimmings have been found out in the research as the potential source of raw material for elastin extraction. In this research, the raw Hide Trimming elastin content was estimated between in the range of 122 mAUmin and 97 mAUmin using the combination of FPLC, UV-Spectroscopy, SDS-PAGE protein scientific characterization techniques. The Elastin was extracted from leather waste through autoclaving technology, the method yield was found to be 90%. In addition, the biocompatibility study confirms that there is no toxic nature of extracted elastin for biological application. This implies that the selected extraction process was effective and efficient. The physical characterization using DSC result indicates that the melting peak of elastin was -0.5420 watt/g at 103.23 C, elastin showed very high denaturation temperature of 275.82 o C and TGA studies confirm that elastin have six mass loss degradation steps. The chemical characterization result using o C Solid state NMR and FTIR that elastin shows random coil, α-helix and β-strand secondary structure. Moreover, the FTIR confirm that amide A, I, II, III, IV, V, VI, and VII functional group existed in the elastin fiber. The biological characterization using amino acid analysis result show that the amino acid composition chain of the product have high amount of glycine, non-polar amino acid, low amount of acidic amino acids, low amount of hydroxyl amino acid and there is no hydroxylsine, tryptophan and Cysteine amino acids in the amino acid composition of the protein fiber. The little variations were the existence of high amount of basic amino acids in the protein amino acid composition due to the presence of collagen residues. Finally, the biocompatibility study shows that there is no toxicity nature of the extracted elastin fiber for human keratinocyte cells culture. There result is scientifically justified and confirmed that the raw hide trimmings extracted elastin makes feasible for biological and biomedical applications.
Extraction and Optimization of Natural Protein (Keratin) from Waste Chicken Feather for the Development of Anti-Ageing Cream
(Addis Ababa University, 2017-10) Tewodors, Abebe; Karthikeyan, R. (PhD)
Treatment and conversion of by-products into value added products would help not only to strengthen the economy of a country but also to protect the environment from pollution and to improve the socio-economic status of the people by creating employment. Keratin is abundantly available as a byproduct from poultry, slaughterhouse, tanning and fur processing industry. Chicken feathers, cattle and buffalo horns, tannery hair are the abundantly available sources of keratin which could be successfully converted into high value products on a large scale. In the present investigation has been made to extract valuable protein from chicken feathers and to study change in temperature, time and chemical concentration during thermo-chemical treatment thereby optimize the extraction conditions for the development of anti-ageing cream. Sodium hydroxide is used to digest the raw chicken feathers. Once the feathers are dissolved, hydrochloric acid solution is added to the solution for the precipitation of protein. The precipitated protein is washed with water several times and the protein was subjected to separation by centrifugation and freeze-drying. The effect of different parameters, such as extraction temperature, time, and NaOH concentration was studied in relation to extraction yield of keratin protein. The percentage keratin yield was found to be 23 to 82% in different extraction conditions. The extracted keratin protein was further analyzed by biuret test, FT-IR, XRD and TGA. Biuret test, FT-IR studies have been done to confirm the protein nature. XRD and TGA were used to know physical characteristics of the regenerated protein from chicken feather. A general factorial design was applied to both extraction processes using Design Expert software and linear regression model was obtained growing the individual effect of extraction temperature, time, and NaOH concentration and their interaction in the entire extraction process. The optimum condition for the extraction of keratin protein from chicken feathers was found to be 5g feather, 0.75 N NaOH and 45 minutes reaction time at 60oC temperature. The keratin extraction developed by the optimized thermo-chemical conditions was used to produce anti-aging cream by using ingredients which include emulsifier, emollient, preservatives and surfactant.
Extraction Of Glycosaminoglycan’s from Raw Hides Trimming Waste by Using Papain Enzyme
(Addis Ababa University, 2023-01) Woldeamanuel Wondaferash; Shegaw Ahmed (PhD)
Glycosaminoglycans are the most plentiful type of organic active polysaccharides mainly found in animals. Chondroitin sulfate (CS) are one of the classes of glayconsaminoglaycans that can commonly use in pharmaceutical, cosmetics and beverage industries as well as in treatment of arthritis and eye diseases. Therefore, taking out of Glayconsaminoglaycans from cow hide trimming waste by papain enzyme is necessary. In these process temperature, time, enzyme and PH are variables that can affect the result of Glayconsaminoglaycs. The best result of data was taken at pH of 6.7, enzymes concentration 0.6 %, temperature of 68OC and hydrolysis time 3 hours. The extracted Glayconsaminoglaycans were 0.5 % and its composition were 62.7% carbohydrates and16.4 % proteins, moisture content 13.1%, and ash content 7.8 %. The experiment analysis was analyzed by using UV spectroscopy and characterize by FTIR and NMR analysis.
High Performance Glove Leather from Goat Skin: Role of Physico-Chemical Properties
(Addis Ababa University, 2014-09) Tarekegn, Jida; ChandraBabu, N.K. (PhD); Aravindhan, R. (PhD)
The chemical and physical characteristics of the goat skins are essential to make glove leathers. The characteristic of skin can be analyzed by using Scanning Electron Microscope (SEM), light microscope and studying histological structure of the skin as well as through various chemical characteristics. The fiber opening operation as well as the post tanning auxiliaries like syntans and fatliquors are known to significantly influence the properties of glove leathers. The right choice of lyotropic agents, fatliquors and syntans are critical to obtain the leathers with good gloving property. Hence, in this thesis an attempt has been made to study the physico-chemical properties of the skin and to study systematically the influence of various lyotropic agents, fatliqours and syntans on the gloving properties of leather made from goat skins. Care was taken to ensure that the properties of gloving leathers viz.run, softness, strength properties and other subjective properties like smoothness and stretch based on the physico-chemical properties of the skin were obtained.
Improvement of Colour Uniformity During Dyeing Operation: The Case of Dress Gloving Leather
(Addis Ababa University, 2018-06-17) Wondwossen, Mamuye; Berhanu, Assefa (PhD); Aravindhan, R. (PhD); Jawahar, Malathy (Mrs.)
In leather industry, the tanner produces a production lot with large number of leather samples to match a colour provided by a client. However, even when the leathers are dyed with the same colorants under well monitored conditions may show some colour non-uniformity. This is highly challenging today for leather manufacturers, especially glove producers to sort colour of leathers consistently. The present study is focused on identifying the factors of colour variation during dyeing operation and reducing colour non-uniformity by managing the factors with welldesigned dyeing recipe. Dyeing properties of the dyestuffs was investigated, by choosing two commercially available dye stuffs. Factors of colour non-uniformity are identified by conducting dye trials on possible causes of colour non-uniformity with four different well-designed dyeing recipes. When concentration of dyestuff, substance of skin or length of dyeing float are varied individually keeping others factors the same, a perceivable total colour difference (∆E*≥0.5) is observed. Controlling and monitoring of colour non-uniformity is analyzed by conducting dye trials using four different well-designed dyeing recipes viz. reverse dyeing recipe, regular dyeing recipe, the multiple stage dyeing recipe and regular dyeing recipe with dye levelling agent. The total colour difference (∆E*) values obtained using multiple stage dyeing recipe was smallest as compared to the other three recipes by varying all possible factors of colour non-uniformity individually. From these observations, multiple stage dyeing recipe was the best alternative way to manage colour non-uniformity.
Improving Efficiency of Vegetable Tannin from Wattle Bark and Its Comparison with Different Conventional Extraction Methods
(Addis Ababa University, 2021-11) Fanuel, Tadesse; Shegaw, Ahmed (PhD)
Conventional extraction processes affect our environment and consume a huge amount of solvent and these problems have stimulated considerable interest in the development of environmentally friendly extraction methods, which are prepared by enzyme and microwave pre-treatment methods. The objective of this research is to improve the extraction efficiency of vegetable tannin and compare it to other extraction methods. Extraction pre-treated with Microwave pre-treated was found to be easier and time effective than other extraction. But the percent yield relative to enzyme pre-treated extraction methods is small. The extraction of wattle bark was also performed by enzyme pre-treatment at 48°C for 60 minutes using 2% of concentration. Enzyme pre-treatment extraction method is best method among all the extraction methods which been 64.585 % yield obtained which is (30.52%) much higher than the conventional extraction methods. The enzyme pre-treated wattle powder was characterized using dynamic light scattering (DLS) and a spectrophotometer. DLS determined the average particle size to be 167.0 nm, with a poly disparity index of 0.0369. Color the extract was measured using a Minolta CR400 Chroma meter. The spectrophotometer result shows that a higher breakdown of the desired product and increased extraction efficiency that the total phenolic contents in 2% of the enzyme were the highest (78.1669) mg GAE/g dry extract. The total phenolic content of the control was 55.6286, which was much lower than the enzymatic pre-treatment method. The tannins were applied to leather after characterizing the tannin extract. it is observed that the strength characteristics like tensile strength, % of elongation at break, tear load (double edge tear), ball burst (distention at a crack and burst, and load at burst) of the crust leather produced by wattle powder as re-tanning material is found to be good when compared to the conventional re-tanning process. Finally, study organoleptic properties in comparison to locally used commercial tannins were studied and a good result was achieved.
Integration of Ozonation and Activated Sludge Process for Sludge Reduction in Tannery Effluent Treatment
(Addis Ababa University, 2014-09) Getnet, Anteneh; Srinivasan, S.V. (PhD)
In tannery wastewater treatment plants, sludge comprising of primary and secondary sludge is generated. If the concentration of Cr (III) exceeds 5000 mg/kg, then it is considered as hazardous wastes and this sludge has to be disposed in hazardous waste landfill site as per existing statutory requirements in India. Further, for disposal of wastes into hazardous landfill, the amount of organics concentration in the sludge shall not exceed 20% and if so, then these wastes are not permitted to be disposed in hazardous wastes landfill. Currently, lime and fly ash are added to the wastes to reduce the concentration of organics. Hence, there is urgent need for treatment methods to reduce of organic content in sludge before disposal into hazardous landfill. In this study, attempt was made to reduce the volatile solids generated from secondary biological sludge using advanced oxidation process (AOP) i.e., ozonation. Lab scale aerobic process using sequential batch reactor (SBR) for treatment of tannery wastewater and ozonation of excess sludge generated from SBR were carried out with 24 hrs cycling time. SBR was operated with primary treated tannery wastewater and excess sludge generated was ozonated and returned back to SBR reactor. The performance of sequential batch reactor (SBR) operated with tannery wastewater alone as control and another SBR operated with tannery effluent along with ozonated excess bio-sludge were studied and compared. It was observed that 15 minutes is the optimum ozonation time for oxidation of excess sludge from SBR treating primary treated tannery waste water as influent and the optimum ozone dose respective to optimum ozonation time is found to be 0.168g-O3/g-MLSS. It was observed that COD in the final effluent was reduced to total and soluble COD concentrations in the range of 548.2mg/l and 379.2mg/l for control SBR and 537.581mg/l and 376.049 mg/l for SBR with ozonated sludge respectively at total cycling time of 24 h. In terms of overall sludge reduction, 35.1% reduction of the excess sludge could be achieved by ozone treatment at 0.168 g-O3/g-MLSS.
Manufacture of High-Performance Sheep Upper Leather From Low Quality Sheep Skins in Selection Through Process Upgradation and Optimization
(Addis Ababa University, 2018-06-27) Wondimu, Wolde; Abubeker, Yimam (PhD); Aravindhan, R. (PhD)
The quality of a raw material for any manufacturing industry or firm is one of the decisive factors controlling its productivity and profitability. Leather processing industries are no exceptions to this fact. The decline of quality raw material supply for the leather processing industries is a great challenge to be competent and survive in the industry these days. The quality of the raw material is largely affected by different factors. The problems leading to lower selection of raw skins or semi-processed skins in industry are categorized as ante-mortem and post-mortem defects. Especially the ante-mortem defect caused by ecto-parasite attack on the skins surface is one of the major problems for downgraded selection of sheep and goat skins. In this research work, an attempt has been made to upgrade poor and reject wet blue leathers due to mange disease damage or “Ekeke” on sheep skin. The problem of lower quality selection of skins could be improved and upgraded into better quality shoe upper leather by working on suitable leather processing techniques for covering the defects of mange damaged skins in wet-finishing and finishing by upgradation and optimization. In wet- finishing process, filler waxes and pigments combination were employed for upgradation. This has resulted in improved coverage of defects on dyed crust leathers. Physical strength tests and organoleptic property assessments performed on the treated leathers are found to be good. The optimized process of dyed crust leather is taken further for finishing, where five finishing methods were chosen for upgrading the uncovered defects in wetfinishing. Waxy, metallic, corrected grain and cationic finishing were employed against the conventional resin finishing. With cationic finishing, an improved and upgraded leather was obtained with better natural look or appearance of grain, good covering and comparable physical and organoleptic properties and better grade.
Manufacturing of synthetic tanning agent from kraft lignin
(Addis Ababa University, 2014-09) kassa, Tewodros; Rao, J. Raghava (PhD)
In chromium tanning adsorptive processes are minimal and leading to empty inter fibrillar spaces. Of these, the phenolic syntans are used which prepared from petroleum by products such as phenol, naphthalene and cresol. Being petroleum by products, the cost of these products is highly fluctuating. Therefor there is a need to evaluate alternatives for these products. In the current work, an effort has been made to develop phenolic synthetic tanning agent from waste of paper and pulp industry. Black liquor from pulp and paper waste was obtained and fully characterize. The treatment of this lignin with ferrous sulfate and hydrogen peroxide (5, 15 and 25 mmol of the reagent) and reaction temperature (25 oC, 45 oC and 65 oC) induces an extensive degradation in the native lignin. The effects of amount of H2O2 concentration, Fe2+concentration and reaction temperature on percentage of were determined by using Design Expert 7.0.0 software three factor Central Composite Design. As observed from optimized design at H2O2 concentration of 25 mmol, Fe2+ concentration of 15 mmol and 45oC the maximum percentage of lignin degradation was found 76.91%. Syntan preparation stage were investigate viz, sulphonation temperature, type of sulphonation agent, duration of reaction and amount of formaldehyde. The combined sulphonation product of sulphuric acid and sodium meta bisulfite (SS2) show better softens, roundness and grain smoothness and colour. Emission load of TS for commercial phenolic syntan is 43.61, whereas there is reduction in TS load by 41.7%-24.1% has been observed using lignin based syntan. Key word: Lignin degradation; Kraft black liquor; syntans; Hydrogen peroxide; Ferrous ion; free formaldehyde
Performance Analysis and Improvement of Ethiopian Leather Footwear Factories:
(Addis Ababa University, 2011-10) Cherkos, Tomas; Kitaw, Daniel (PhD))
Nowadays there is a need for business enterprises to measure, analyze and improve performance as they encounter increasing competition from an ever-changing business environment. Performance is the valued productive output of a system in the form of goods and services and performance measures are the lifeblood of organizations, since without them no decision can be made, as it is the first step to control and improvement. Though the Government of Ethiopia is promoting the leather footwear industry as a priority area and the sector has a huge potential for developing an economy, its performance is unsatisfactory due to external and internal problems that hinders its competitiveness. Thus, the aim of this study is to assess and evaluate performance management practice of Ethiopian Leather Footwear Factories, identify critical problems and propose a firm level total performance improvement method and suggest roles of stakeholders or improvement directions towards the external problems. To undertake this research, primary and secondary data are collected through a survey questionnaire, interviews (in the form of discussion) and physical observation in the case factory (Anbessa shoe share company), as well as referring previous research works and case company records. To analyze and present the data, pie charts, bar graphs, and cause and effect diagram are used. In addition, to see the performance gap of the case factory, benchmarking is done. From the research, it is concluded that the leather shoe factories have both internal and external problems resulting low performance and competitiveness. To alleviate the internal or firm level problems, a total performance improvement method called Total Performance Scorecard (TPS) is proposed. In addition improvement directions are forwarded towards the external or sector level problems. Regarding the proposed method, a performance measurement framework/scorecards and its implementation guideline is developed for Anbessa S.C. TPS is a combination and also an extension of the concept BSC, TQM and Competences Management which is being defined as a systematic process of continuous, gradual and routine improvement, development and learning. The process focused on the solid increase of both the personal and organizational performances. This method has an important aspect in maximizing the involvement and loyalty of all involved person, as well as encouraging individual and team learning and creativity via its Personal Balanced Scorecard (PBSC). Key words: Performance, Performance improvement models, ELFFs, footwear manufacturing, Total performance scorecard
Preparation of Collagen Hydrolysate Syntan from Delimed Pelt Trimmings for Post Tanning Application and for Stabilzing Collagen Fibers
(Addis Ababa University, 2014-09) Hussien, Mohammed; Balaraman, Madhan (PhD)
Delimed pelt trimmings are trimmings that are obtained from limed pelt trimmings by removing lime. Limed pelt trimmings are one of the solid wastes that are generated in leather processing which is common in Ethiopia unlike other countries. These wastes are important resources for producing collagen hydrolysate which can be applied in leather processing operations. The aim of this study is to prepare collagen hydrolysate from delimed pelt trimmings and to apply it in wet blue goat skin in post tanning operation to determine the optimum hydrolysis conditions and molecular weight of the collagen hydrolysate. And also to determine its stabilizing effect on collagen fibers by treating rat tail tendon with the collagen hydrolysates by carrying out enzymatic and thermal stability experiments. The optimum conditions of hydrolysis for post tanning operation was determined by preparing six different types of collagen hydrolysates and apply it post tanning operation as a retanning agent. Based on the absorption of chemicals and organoleptic properties, the best collagen hydrolysate is selected and characterized further using FPLC and MALDI. The results showed that collagen hydrolysates play a role in stabilizing collagen fibers. And also the best collagen hydrolysate for post tanning is obtained when the proportion of high molecular weight to low molecular weight proportion of the fractions is 80% to 20%. And the range of the molecular weight should be in between 2000 to 6000 daltons. This can be achieved when the hydrolysis condition is carried out by using 0.8% trypsin for duration of 3 hours. It is concluded that by preparing collagen hydrolysates syntans from delimed pelt trimmings satisfactory results can be achieved by applying it in post tanning operation during leather processing and also they can be used for stabilization of collagen fibers.
Preparation of leather Fat liquor cum filler from fleshing waste for Retanning process in leather manufacture
(Addis Ababa University, 2014-09) Kassahun, Wintana; Baskar, Geetha (PhD)
Skin/Hide fleshing wastes are the day to day activities to remove the flesh from the pelt, from tanneries are generated during leather processing when flesh of the soaked or limed hides skin/hides is removed with the fleshing machine. These skin/hide fleshing wastes from tanneries contain significant quantity of protein and fat content and are currently being wasted into dumping sites or in open areas, consequently creating the fleshing waste disposal major environmental problem of the tanning industries throughout the world. Approximately, 9-14 tonnes of fleshing waste are being generated from Ethiopian tanneries per day. The objective of this work is to elaborate a method/technique to develop fatliquor cum retanning agent for use in leather industry from the waste (fleshing) generated by the tanning industry. Skin/hide fleshing is source of fat/oil and protein matter. The extracted fleshing fat was first emulsified by adding emulsifier. Then the fleshing hydrolysate, containing the protein fractions was prepared by alkaline hydrolysis in the presence of sodium hydroxide at a pH of 5.6. The hydrolysate and the extracted oil were further characterized to find the suitability of production of fatliquor cum filler for retanning process. The fatliquor cum filling product was prepared and used in leather processing during retannage stage. Physical characterization of the leathers were carried out and compared with that of control leather processed with commercial fatliquors and retanning agents. Moisture, protein and fat content of the fleshing from cow hide were found to be 63.30, 12.82 and 4.84%, respectively. Similarly, the fleshing of sheep and goat skins have also been characterized and reported in the results and discussion section. The fat extracted from the fleshing was characterized for iodine, saponification and acid value. The fleshing hydrolysate was characterized for degree of hydrolysis, solid content, molecular weight, and particle size and zeta potential measurement. For making upper leathers, 8% of the fatliquor cum retanning agent per weight of skins/hides was employed, which gave better results. Similarly, for making nappa leathers, 16% of the prepared fatliquor cum retanning agent per weight of skins/hides was employed. Data from physical testing was quantified with statistical analysis and it was found significant. The leathers were not found greasy, indicating that the product penetrated into the leather matrix. The particle size of the prepared product was also determined and was found in the range of the commercially available retanning agents. xiv Organoleptic properties such as colour uniformity and intensity, roundness, softness and fullness properties of the two leather articles prepared using the developed product were evaluated by experts and found to be on par with that of the control leathers. This study represents that the waste protein and fat from skin/hide fleshing wastes can be utilized as a beneficial product after some chemical modifications. Waste skin/hide fleshing is a good alternative source for preparation of fatliquor cum retanning agent. This project also answered the disposal problem associated with the solid wasted (fleshing) generated form tanning industries. The proposed methodology could be easily adopted by all leather industries. Key words: Hydrolysis, Fleshing wastes, Fatliquor cum filler, Extraction, homogenization,

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