Innovative Approach to Sustainable Leather Tanning Process using a Lactic Acid Based Agent

by Malgorzata Kowalska, Anna Zbikowska and Magdalena Wozniak

The objective of the present study was to evaluate selected properties of leather samples treated with innovative lactic acid-based agents, applied during the soaking process. The quality of leathers soaked in the baths containing agents based on the organic lactic acid was compared to the products obtained by traditional tanning, in which surfactants were used during the leather soaking process. The obtained results showed that the hides soaked using the eco-compound met the same quality requirements as those soaked in traditional surfactants. The study has proven that the surfactants, which are universally applied during the traditional leather tanning technology, can be replaced with an environmentally friendly agent which effectively reduces effluent pollution as well as its quantity. The proposed method has been successfully tested by one of the largest tanneries in Poland and is in the process of implementation, thus becoming an ecotechnology.

JALCA December 2019

Enzymatic Reactions and Phylogenetic Analysis of Haloversatile Bacteria Isolated from Çamalti Saltern Salt Samples used in the Leather Industry

by P. Caglayan

Çamalti Saltern is one of the large seawater-based saltern located in Izmir, Turkey. The crude solar salt from Çamalti Saltern is used in leather industry. This type of salt may harbor viable microbial population which can spoil leather products during the curing process for hide/skins. Therefore, the objectives of this research were to isolate haloversatile bacteria from salt samples collected from Çamalti Saltern, to identify these isolates using both conventional and molecular methods, and to determine their hydrolytic enzymes such as protease, lecithinase, cellulase, lipase, deoxyribonuclease, pullulanase, amylase, urease, caseinase, xylanase and esterase. In addition, damage caused by lipase and protease producing haloversatile bacteria to the structure of salted sheep skins was examined. The effects of different salt concentrations, pH and temperature values on the growth of haloversatile isolates were also investigated. Sixty-nine isolates of aerobic Bacteria showing different colony morphology, pigmentation, colony shape, and size were selected for characterization of the isolates. Phylogenetic analysis showed isolates belonging to the genera Staphylococcus (9 species), Exiguobacterium (3 species), Bacillus (11 species), Microbacterium (3 species), Gordonia (1 species), Kocuria (3 species), Paracoccus (2 species), Micrococcus (2 species), Acinetobacter (1 species), Brevibacterium (1 species), Pseudomonas (1 species), Agrococcus (1 species), Sanguibacter (1 species) and Virgibacillus (1 species). The haloversatile isolates were able to produce different enzymes such as catalase (100%), oxidase (80%), protease (52%), lecithinase (51%), cellulase (33%), lipase (23%), deoxyribonuclease (17%), pullulanase (10%), amylase (7%), urease (4%) and caseinase (4%). Scanning electron micrographs of sheep skins showed that catabolic activities of haloversatile bacterial species found in crude salt were responsible for decomposition of skins. When the crude salt containing haloversatile bacteria is used as a preservative for skins, these haloversatile bacteria may damage skin structure.

JALCA December 2019

The Suitability of Leather as an Alternative Material for Sustaining Vessel Production in Ghana

by Baidu, K. A. O., Essuman, E. K., Asubonteng, K, Boahin, J. O. B.

Anecdotal evidence and a further report from leather experts show that there is close to no enlightenment of the production of leather vessels in Ghanaian leather industries. This study was, therefore, conducted as a result of the need to add leather as supplementary material to the traditional materials such as clay, metal, wood and half-gourd used for producing vessels in Ghana. The purpose of the study was to find out how Ghanaian indigenous leather could be used in the production of leather vessels. The qualitative study employed three key techniques, namely: ‘Cuir bouilli’ leather hardening methods, the sand pounding technique, and assemblage and construction technique. Based on the results, the baking and hot wax methods adversely affected the indigenous leather positively in the hardening of the leather. The results also show that using only one part of the leather (the back, belly or butt) affected the quality of the leather vessels, but incorporating the various parts of the hide helped improve the quality and durability of the leather vessels. The implications of the results and future research directions are also presented. This study has, therefore, expanded the usefulness of the Ghanaian indigenous vegetable tanned leather apart from the conventional usage for making shoes, bags and belts.

JALCA December 2019

Closed-Loop Processing: Management in Existing Tanneries and New-Builds Designed for Purpose

by Richard Daniels, Jiasheng Su, Falei Zhang, Zhuangdou Zhang

Closed-loop processing for unhairing/liming and tannage is established technology for the processing of raw hides to the wet blue state.

This approach produces a high value product and, as part of sustainable manufacture, is significant. Savings are gained in chemicals, water and energy and reductions in the wastewater load. In effluent treatment, both the sulfide oxidation stage and chrome recovery/regeneration systems are eliminated. Both sulfate and chloride are minimised, and a reduction in solid waste generation.

In November 2018 new-build tanneries with radically different layouts were at an advanced stage of construction and installation of new equipment. These were designed to management and technical requirements of this specific technology.

In addition, the technology had made the transition from bovine manufacture to nappa leathers production in a major sheepskin tannery. And within small scale operations – bovine hides, bovine bellies, sheep and goat skins – chrome tannage was taking place with processing adapted around the prevailing conditions and tanners requirements.

JALCA December 2019

Cleaner chrome tanning – technology of chrome-reduced tanning without salt, pickling and short procedure

by Luo Jian-Xun; Feng Yan-Juan

Tannery effluents with high salinity and containing chromium have a serious environmental impact. The traditional chrome tannage that involved the use of sodium chloride, acid and chromium is one of the main origins of salt and chromium pollution. In this study, a non-pickle, chrome-reduced tanning technology was developed. The novel chrome-free agent SL can be directly employed to tan bated bovine hide producing wet-white. The shaved wet-white was pre-treated by a poly-carboxylate auxiliary agent PAA and tanned by chrome powder. It was found that the shrinkage temperature of the wet-white tanned by SL reached over 80°C, the optimal consumption of poly-carboxylate auxiliary agent was 1.5- 2wt% based on the weight of the shaved wet-white, the better chrome-reduced tanning conditions were that the wet-white was tanned with 3-4wt% chromium powder for 150-180 minutes at room temperature when the initial pH value was 3.0-3.5. The next processes were same as those of a traditional chrome tannage. Meanwhile, the shrinkage temperature of the leather tanned by the chrome-reduced tannage reached more than 95°C, the absorption of chromium was 96%, the content of Cr2O3 in the effluent was under 200mg/L. For the chrome-reduced tanned leather,the absorption of dyestuff and fat-liquor reached 99.5% and 82.5% respectively. Compared with the traditional chrome tanning process, not only was the conventional pickling process eliminated, the process was shortened and reduced the pollution of sodium chloride. The process can reduce by 50% the consumption of chrome powder, improve the absorption of chromium and reduce the content of Cr2O3 in effluent.

From JSLTC Nov/Dec 2019

Advanced diagnostics and innovative solutions for leather defects: The problem of yellowing

by Florio, C.; Aveta, R.; Calvanese, G.; Naviglio, B.

Providing peculiar enhanced features to leather items is a factor of primary importance for the marketing of high-end articles; although tanning production is oriented to satisfy a wide market range, it is mainly in the ʻhigh endʼ and ʻpremium luxuryʼ categories that the quality properties of the material are more expressed, indeed. It is particularly on this market segment that the main current challenges have been focussed, according to the growing requirement of technological innovation, sustainability and product quality. Light-coloured leathers, with particular reference to white items, belong to the category of materials designed especially for the luxury market. For this type of articles, the uniformity of colour and the agreeable appeal of the overall surface appearance are crucial requirements for the most international fashion and luxury brands. One of the most common and undesirable defects of this type of article is the alteration of the colour,
with particular reference to the localised or diffused effects of yellowing of the surface of the material. There are several causes able to contribute to the production of this type of defects, due to the
complexity of the matrix and to the variability of traditional or innovative production processes used: from the intrinsic fragility, photosensitivity and thermo-sensitivity of the finishing polymers, to the chemical instability of some components of the finishing pigments, further the presence of photosensitive chemical additives, the migration of skin components or assembly components of the manufactured articles (fats, fillers, plasticisers, glues etc.), up to the indirect contribution of environmental and thermo-climatic factors able to affect negatively the performance of the material. SSIP, which has always been involved in research and consulting activities for the leather industry with regards to defect monitoring, through this work, would offer an overview of all the main tools for advanced diagnostics (with particular reference to Scanning Electronic Microscopy and to chromatographic and spectroscopic methods) aimed to the identification of the causes of yellowing, beside to explore innovative solutions for the development of strategies for the resolution and/or minimisation of the problem of yellowing. The technical solutions will include innovative tanning processes, innovative finishing methods, and leather surface treatments carried out in order to provide a sensible attenuation of surface absorption of IR and UV-visible radiation.

From JSLTC Nov/Dec 2019

The tanning performance of dialdehyde cellulose prepared by electrochemical oxidation system

by Hui Chen; Yao Hu; Shu-Qing Li; Li-Wei Chen; Jie Yi; Zhihua Shan; Rui Dai

The aim of this study was to develop a new dialdehyde cellulose tanning agent and discuss its tanning performance. Firstly, cellulose was dissolved with sodium hydroxide and urea. Secondly,
dialdehyde cellulose was prepared by an electrochemical oxidation system. The obtained dialdehyde cellulose contained 68.48% aldehyde groups. The reaction between dialdehyde cellulose and gelatin has been verified by the determination by Fourier transformed infrared testing. When pickled goatskin was tanned with dialdehyde cellulose, the optimal conditions were, dosage of dialdehyde cellulose 25%, initial pH4.5, tanning temperature 35°C. The tanned goat garment crust leather had a shrinkage temperature 82.2°C, tensile strength 28.23MPa, elongation at break 48.35%, all of which meet the standard for goat garment leather. After ageing for 20 days, all characteristics remained stable indicating that dialdehyde cellulose is a feasible and eco-friendly tanning agent.

From JSLTC Nov/Dec 2019

Retanning mechanism of polyacrylic acid from the point of fibre motion

by Zou Xianglong; Fang Qi; Chai Yuye; Li Zhongyu

The retanning mechanism of PAA was studied from the point of fibre motion. The stress state of collagen fibres retanned with PAA was analysed and the structure of retanned leather was
characterised by SEM and strain-stress analysis. The results show that PAA mainly interacts with collagen fibres by adhesive force (AF) between collagen fibres and capillary flow. As PAA dosage
increases, AF increases and the collagen fibreʼs array becomes more disordered.

From JSLTC Nov/Dec 2019

Physical properties of chrome-tanned Nile perch (Lates niloticus) fish leather

by Wairimu, Peter Maina; Ollengo, Moses A.; Nthiga, Esther W.

The aim of this study was to utilise the Nile perch fish skins which are usually a waste from fish filleting companies to make leather and then to determine its physical properties. The skins were
processed into leather using chromium(III) sulphate. The physical properties of leathers were determined using standard IUP methods which include: Tensile strength, Tear strength, Flexing endurance, Shrinkage temperature, Grain crack and Grain burst tests. The results demonstrated that the tensile, tear strength and elongation of the leather varied depending on the direction and location of the collagen fibres. The properties of the Nile perch leather were satisfying enough for the material to be used in the manufacture of high grade leather products. The study showed that the fish skins can supplement sources of raw materials in the leather industry and reduce the environmental pollution caused by disposing of the skins to the environment.

From JSLTC Nov/Dec 2019

Application of Mn-doped Mesoporous TiO2 in tannery wastewater treatment

by Xiu He; Xiaocong Wang; Baozhen Cheng; Shan Cheng; Shan Cao; Jianfei Zhou

Treatment of tannery wastewater is a challenging task because of its complex components, deep colour and high concentration of suspended solids. This study aims to develop a treatment system that can effectively reduce the pollutants in tannery wastewater to an environmentally acceptable level. Manganese (Mn)-doped mesoporous titanium dioxide (TiO2) was successfully synthesized via a solgel method using butyl titanate as a precursor and surfactant P123 as a template. When the dosage of Mn in the mesoporous TiO2 was 0.4%, the degradation rate of organic pollutants was nearly 90% after 8 hours of treatment with metal halide. The as-prepared products showed excellent photocatalytic activity even sunlight was used as an illuminant. The degradation rate of organic pollutants reached 87.5% when sunlight was used for excitation. Results of this study can be used as a reference in purifying various types of industrial wastewater.

From JSLTC Nov/Dec 2019

Efficient removal of total nitrogen from tannery wastewater by promoting denitrification with sodium acetate

by Ma Xiaojian; Zhou Jianfei; Zeng Yunhang; Shi Bi

Total nitrogen (TN) in tannery wastewater is difficult to remove completely, because the low C/N ratio of the wastewater leads to inadequate denitrification. Sodium acetate was used as an extra
carbon source to improve the denitrification efficiency and the TN removal. The appropriate COD/TN ratio for denitrification using sodium acetate was 5.1, at which the TN concentration of tannery wastewater decreased by 95%. A much faster removal of TN was obtained by adding sodium acetate in denitrification than by adding common glucose. These results showed that sodium acetate was a high-quality carbon source for a complete and rapid denitrification of tannery wastewater. The denitrification efficiency decreased with decreasing temperature and increasing chloride concentration. However, when the carbon source was made sufficient by adding sodium acetate, complete denitrification was still obtained even at 15°C or 10000mg/L of chloride concentration.

From JSLTC Nov/Dec 2019

On the application of automated machine vision for leather defect inspection and grading: A survey

by Aslam, Masood; Khan, Tariw M.; Naqvi, Syed S.; Holmes, Geoff ; Naffa, Rafea

Reliably and effectively detecting and classifying leather surface defects is of great importance to tanneries and industries that use leather as a major raw material such as leather footwear
and handbag manufacturers. This paper presents a detailed and methodical review of the leather surface defects, their effects on leather quality grading and automated visual inspection methods for leather defect inspection. A detailed review of inspection methods based on leather defect detection using image analysis methods is presented, which are usually classified as heuristic or basic machine learning based methods. Due to the recent success of deep learning methods in various related fields, various architectures of deep learning are discussed that are tailored to image classification, detection, and segmentation. In general, visual inspection applications, where recent CNN architectures are classified, compared, and a detailed review is
subsequently presented on the role of deep learning methods in leather defect detection. Finally, research guidelines are presented to fellow researchers regarding data augmentation, leather quality quantification, and simultaneous defect inspection methods, which need to be investigated in the future to make progress in this crucial area of research.

IEEE Access 2019