Papers by Virgilijus Valeika
Proceedings of the Estonian Academy of Sciences, 2024
The leather industry generates a significant amount of various wastes, and their utilisation is a... more The leather industry generates a significant amount of various wastes, and their utilisation is a serious task for researchers. Ways to reuse or decontaminate such waste are being developed intensively. Unfortunately, the reuse of finished leather, which eventually becomes waste, is almost unexplored. The present research is designed to evaluate the potential of finished leather hydrolysis to obtain protein hydrolysates suitable for reuse in leather processing and to establish factors that influence leather quality during such an application. Enzyme preparation Vilzim PRO Conc was characterised as a potential agent for such hydrolysis. The addition of 3-4% Vilzim PRO Conc is appropriate for the enzymatic stage of the hydrolysis process. It was established that after alkalineenzymatic hydrolysis of used leather powder the obtained hydrolysates are complicated systems containing proteins, chromium compounds, dyes, fatliquoring materials, etc. Hydrolysates could be used for the dyeing of chromed leather. The method of preparation for dyeing and dyeing of wetblue leather with the use of hydrolysate influences the depth of dye penetration and the quality of finished leather. It was established that the neutralisation process is not necessary before such dyeing. Also, an increased amount of formic acid is necessary to improve the bonding of fatliquors with dermal tissue after treatment with hydrolysate.
Journal of The Society of Leather Technologists and Chemists, 2017
Various methods of neutralisation of hide unhaired with sodium silicate and sodium sulphide have ... more Various methods of neutralisation of hide unhaired with sodium silicate and sodium sulphide have been investigated seeking to reduce or refuse ammonium sulphate conventionally applied for the neutralisation. Due to the high release of ammonia into the environment, alternative materials are being sought that do not impair the properties of the hide being processed and that a high-quality chromed semi-finished product of leather can be obtained. In the research, different methods of hide neutralisation and their influence on subsequent hide treatment processes qualitative indexes of the obtained leather were analysed and described. It has been found that after unhairing with sodium silicate and sodium sulphide hide, it is appropriate to neutralise and bate the hide by adding 1 % ammonium sulphate, 0.8 % lactic acid and 0.15 % proteolytic enzyme preparation OROPON ON2. To obtain the best quality of chromed semi-finished product of leather, it is advisable to pickle the hide using not more than 1 % sulfuric acid. In this way, neutralised-bated, pickled and chromed leather's quality meets the quality requirements for chromed semi-finished product of leather.
Journal of The American Leather Chemists Association, Nov 1, 2016
PLOS ONE, 2014
<p>Chemical and physical properties of leather produced under industrial conditions from pr... more <p>Chemical and physical properties of leather produced under industrial conditions from preserved by vacuum hides.</p
PLOS ONE, 2014
<p>Images of vacuumed hide (magnification 40 times) stored 1 day (A) and 22 days (B).</p
Journal of The Society of Leather Technologists and Chemists, 2015
It was investigated a behaviour of hide, which was stored 19 days under vacuum at low temperature... more It was investigated a behaviour of hide, which was stored 19 days under vacuum at low temperature, during processing into wet blue. Results of determination of collagen proteins removal when liming, deliming-bating and pickling are presented. The qualitative indexes of wet blue processed under laboratory conditions and of leather produced during industrial trials are presented as well. Such indexes as chromium compounds exhaustion, content of chromium in leather, content of matter soluble in dichloromethane, strength properties, and shrinkage temperature were determined. Obtained results allow supposition that hide under vacuum at low temperature can be stored during 19 days, and this does not cause lowering of leather quality
PLOS ONE, 2014
<p>Parameters of hide processing in laboratory conditions.</p
revistadechimie.ro
... Maybe, this problem could be solved using mixture of natural and synthetic preservatives. Ack... more ... Maybe, this problem could be solved using mixture of natural and synthetic preservatives. Acknowledgements: Authors are grateful to Prof. Dr. Audrius Maruka and Dr. Vilma Kakonienë for the help with GCMS, and Assoc. Prof. ...
IOP Conference Series: Materials Science and Engineering, 2019
This study investigated the use of carboxymethylated corn starch with sodium alginate for films p... more This study investigated the use of carboxymethylated corn starch with sodium alginate for films preparation. The rheological properties as well as water absorption and mechanical properties of aqueous solutions and films of corn starch, carboxymethylated starch, sodium alginate and mixtures of starch and sodium alginate were studied. It was found that application of modified starch allows obtaining of water resistant films characterized by better physicalmechanical properties comparatively to the corn starch based films. It was found that mechanical strength of the formed films is due to the fact that alginate and carboxymethylated corn starch are hydrocolloids with an unbranched structure. This composition is characterized by stronger structure gels and higher viscosity of the solutions.
Materials
Due to their variety, specific activity, and mild reaction conditions, enzymes have a wide applic... more Due to their variety, specific activity, and mild reaction conditions, enzymes have a wide application in beam house processes such as soaking, dehairing, bating, and de-greasing. Recently, due to improvements in biotechnology, re-bating after chroming has received increased attention. The aim of this work was to investigate the application of enzyme preparation in the re-bating process and its effect on the semifinished and finished product, as well as its influence on post-tanning operations. The enzymatic treatment of chromed semifinished leather (wet blue) led to a higher shrinkage temperature (1–6 °C), greater water vapour absorption (0.3–5.5%), better chromium compounds exhaustion during re-chroming (4–21%), and better dye penetration. Moreover, collagen was affected during the enzymatic process; the results showed a greater concentration influence in the operation compared to the process time. On the other hand, no effect on the physical and mechanical properties and fat-liqu...
Journal of The Society of Leather Technologists and Chemists, 2013
Proceedings of the Estonian Academy of Sciences, 2012
The aim of this study was to investigate the possibility of using essential oils of Thymus vulgar... more The aim of this study was to investigate the possibility of using essential oils of Thymus vulgaris as an alternative preservative for chromed leather. The differences between the chemical composition of commercial and pure essential oils of thyme were determined. It was observed that these differences have an influence on the antibacterial activity of essential oils. Gram-positive bacteria were found to be more sensitive to the essential oils of thyme than Gram-negative bacteria. The bacteria Pseudomonas aeruginosa had a low sensitivity to the action of the selected essential oils of thyme, but the leather samples treated with the essential oils of thyme remained resistant to the action of these bacteria. As the main result of this study, it was concluded that the essential oil of thyme could be used as a preservation agent in the leather tanning industry. The leather preserved with 2-(thiocyanomethylthio)benzothiazole had weaker protection after four weeks compared to the samples treated with the essential oil of thyme when the amount of the used essential oil was not less than 3% of the wet-blue mass. The essential oil of thyme was the more active component in the mixture of essential oil and synthetic biocide used for the preservation of leather.
Proceedings of the 9th International Conference on Advanced Materials and Systems, Nov 15, 2022
The use of enzymes in leather processes has increased in recent years. Enzymes have gained more r... more The use of enzymes in leather processes has increased in recent years. Enzymes have gained more recognition because of their properties, such as specific activity, simple application, mild enzymatic reaction conditions, and non-polluting effluent generations. However, not all enzymatic operations are well investigated, and there is still a lack of knowledge on ferment usage in posttanning processes. The aim of this study was to investigate the enzyme implementation in wet blue bating and its effect on semi-finished product. The various enzyme preparations were used for bating at different concentrations and process times. The amount of removed collagen proteins, the shrinkage temperature after bating and rechroming were assessed; on top of that, the amount of chrome compounds in semi-finished product and in the effluent was determined. The results showed that enzymatic bating had an effect on wet blue leather. The greatest difference was obtained using Zime SB enzyme preparation. The results obtained during the study are promising, even so, further research on mechanical properties, dying, and fatliquoring effects needs to be investigated to see enzymatic effect on the finished product.
Leather manufacture is one of the most polluting branches of industry in the world because of man... more Leather manufacture is one of the most polluting branches of industry in the world because of many chemical processes and hazardous materials, used in them. In order to replace harmful chemical products proteases, which can reduce pollution by changing some of its chemical materials, are used in the tanning processes. Collagen wastes hydrolysis by proteases allows production of hydrolysates, which can be used as a secondary raw material for fertilizers, cosmetic products and for other useful products to be made. Aim of the research was to check the suitability of new enzymatic preparation for hydrolysis of hide proteins and determine optimal conditions for the process. Pieces from butt part of salted cowhide after soaking and washing omitting fleshing was cut into pieces 3x3 mm and experimental series were prepared from these pieces. The analysis of the pieces was done and it was obtained that absolutely dry hide samples contained 92.9% proteins. New enzymatic preparation (EP) Vilzim PRO Conc produced by JSC "Baltijos Enzimai" (Lithuania) was used for the investigation. Firstly, proteolytic activity of the EP Vilzim PRO Conc was determined according to Anson method using sodium caseinate as substrate (Fig.). Figure. Dependence of EP Vilzim PRO Conc activity on temperature. 1-pH 7; 2-pH 9.5.
The change of tanning parameters reflects on leather chemical and physical properties. The standa... more The change of tanning parameters reflects on leather chemical and physical properties. The standardized determination methods of more important for customers leather indexes do not allow absolutely clear to conclude about suitability of developed tanning method for leather processing. Due to this DSC analysis and IR spectroscopy were employed as additionally analyses methods for the clarification of tanning process influence on leather qualitative properties. During research established structural characteristics of variously tanned leather show how differently tanning materials join to derma collagen and prove that content of linked tanning materials is not most important factor, which ordains the thermo stability of collagen, in the case of chrome-free tanning. The results of DSC and IR-spectroscopy clarify the data obtained by other investigation methods and allow more exactly estimation of the tanning method suitability for leather processing. It was established that variation o...
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Papers by Virgilijus Valeika