Leather Residues Research Articles

A portable colorimetric immunosensor for highly sensitive point-of-care testing of leather artifacts.

Apoint-of-care testing (POCT) platform, i.e., a portable colorimetric immunosensor based on iron oxide magnetic beads and AuNPs, has been developed for detecting leather residues. The immunosensor demonstrates a linear detection range from 1ng/mL to 10µg/mL, with a limit of detection (LOD) of 0.985ng/mL. The sensor exhibits high specificity and repeatability and performs effectively in detecting leather artifacts excavated from Inner Mongolia. Thus, the proposed colorimetric immunosensor not only enables the micro-detection of leather artifacts but also shows significant potential for on-site leather detection at archaeological sites.

The Influence of the Content of Recycled Natural Leather Residue Particles on the Properties of High-Density Fiberboards.

During the production of furniture, large amounts of waste materials are generated, which are most often stored in warehouses without a specific purpose for their subsequent use. In highly developed countries, as many as 25 million tons of textile waste are produced annually, of which approximately 40% is non-clothing waste such as carpets, furniture and car upholstery. The aim of this research was to produce and evaluate dry-formed high-density fiberboards (HDF) bonded with urea-formaldehyde resin, 12% resination, with various shares of recycled particles of natural leather used in upholstery furniture production at different contents (1, 5 and 10% by weight). The panels were hot-pressed (200 °C, 2.5 MPa, pressing factor 20 s mm-1). Mechanical properties (modulus of rupture, modulus of elasticity and screw withdrawal resistance) and physical properties (density profile, thickness swelling after water immersion, water absorption and surface absorption) were tested. The density profile and contact angle of natural leather have been also characterized. The results show that increasing the content of leather particles in HDF mostly has a positive effect on mechanical properties, especially screw withdrawal resistance and water absorption. It can be concluded that, depending on the further use of HDF, it is possible to use recovered upholstery leather particles as a reasonable addition to wood fibers in HDF technology.

Comparative study of three vulcanization kinetic models for natural rubber/leather wastes composites

In this article, the effect of leather residues from chrome tanning on the vulcanization kinetics and rheometric properties of a natural rubber composite was evaluated using three kinetic models proposed in the literature. Leather wastes were classified according to their size as fine (smaller than 0.6 mm) or coarse (between 0.84 and 2 mm). Subsequently, they were chemically treated with a sodium bicarbonate solution to neutralize their acidic nature derived from the tanning processes. The composites studied in this paper were obtained using a torque rheometer. Fine and coarse leather wastes were added to a natural rubber matrix in proportions of 20, 40, 60, 80, and 100 phr. The rheometric properties of all the composites were monitored during the curing process using a moving die rheometer. The addition of leather wastes increased the vulcanization time and stiffness of the composites; however, materials with fine leather wastes achieved lower vulcanization times than materials with coarse residues. The curves obtained during vulcanization rheometry were fitted to the three kinetic models, which made it possible to determine the kinetic parameters k and n. The fits for the three models were satisfactory based on the R-squared results. The values and trends of the kinetic parameters of each model were analyzed and related to the vulcanization phenomenon of each composite.

Determination of Cr(VI) in leather residues using graphite/paraffin composite electrodes modified with reduced graphene oxide nanosheets

In this study, we determined the Cr(VI) in samples of tanned leather residues by differential pulse voltammetry (DPV) using graphite/paraffin composite electrodes modified with reduced graphene oxide nanosheets (referred to as GPEs/nsRGO). After the modification, the composite electrodes were characterized by two electrochemical techniques (i.e., cyclic voltammetry, CV, and electrochemical impedance spectroscopy, EIS), scanning electron microscopy, and Raman spectroscopy. The electroanalytical method was applied using the GPEs/nsRGO. An analytical curve was obtained in a Clark-Lubs buffer solution (pH = 1), with a linear concentration range from 25.0 to 392.0 μmol L−1 and a limit of detection (LOD) of 1.01 μmol L−1. The GPEs/nsRGO showed good reproducibility in their manufacturing process and good response repeatability with an RSD of 4.59% over twelve measurements. These composite electrodes showed excellent selectivity, which was demonstrated by analyses in the presence of metal ions (Ca2+, Zn2+, Mg2+, Fe3+, Co2+, Na+, and Cu2+) that did not interfere in the analysis of Cr(VI). The GPEs/nsRGO were applied to the determination of Cr(VI) in real samples of wet-blue leather and leather ash using DPV. This approach was validated using the sample recovery method, where it presented values from 95.6 to 108.2%. The proposed method showed satisfactory results compared to the literature and can be considered a good alternative for the determination of Cr(VI) in aqueous samples.

Ciprofloxacin and carbamazepine adsorption on activated carbons produced from leather residues

Ciprofloxacin and carbamazepine adsorption on activated carbons produced from leather residues

Observation of autophagy during scrap Leather–Induced neuroinflammation via lysosome-targeting polarity-specific two-photon probe

Autophagy is a protective mechanism that exists in cells and plays an important role in maintaining the normal physiological morphology of cells and in the disease regulation of living organisms. Recent studies have shown that changes in lysosomal polarity can be an important indicator for assessing cellular autophagy. Thus, we developed a probe (Lyso-Pola) that is sensitive to lysosomal polarity to monitor these changes in order to assess the extent of cellular autophagy during scrap leather–induced neuroinflammation. The relationship between cellular autophagy, neuroinflammation, and scrap leather residues was also explored. The experimental results showed that the fluorescence signal of Lyso-Pola was significantly lower during cellular autophagy in two-photon confocal imaging. In addition, models of scrap leather–induced neuroinflammation in BV2 cells and mice showed that neuroinflammation can lead to the release of reactive oxygen species, which then induces cellular autophagy.

Effect of particle size of leather wastes on the processing, vulcanization, and physico-mechanical properties of natural rubber/leather wastes composites

In this work, the effect of particle size and the content of leather wastes on the processability, vulcanization, and mechanical properties of a natural rubber/leather wastes composites was studied. From a reduction process, leather waste was later sieved to classify particles smaller than 0.6 mm and particles between 0.84 and 2 mm, hereafter called fine and coarse residues, respectively. The morphology of the wastes was analyzed from scanning electron microscopy micrographs. Natural rubber/leather wastes composites with 20, 40, 60, 80, and 100 phr (parts per 100 parts of rubber) of treated leather wastes were obtained in a torque rheometer. Mixtures with coarse wastes exhibited a slightly higher torque than mixtures with the fine wastes; additionally, increasing the wastes content yields in an increased torque during the final stage of the process. The addition of leather wastes increased the vulcanization time and stiffness of the composites; additionally, materials with fine wastes showed lower vulcanization times compared to materials with coarse wastes. Composites with fine leather wastes exhibited higher density and tensile modulus than materials with coarse wastes; however, only the composites with 80 and 100 phr of wastes showed a statistically significant difference in hardness values. The specific energy consumption (SEC) was calculated from the results obtained with the torque rheometer; it was found that for all the formulations the SEC decreased as the phr of leather residues increased. It was found that it is possible to use leather wastes in natural rubber composites, to obtain adequate materials feasible for some applications.

Aging and emulsification analyses of hydrothermal liquefaction bio-oil derived from sewage sludge and swine leather residue

Hydrothermal liquefaction bio-oil is a renewable and potential alternative to fossil fuels. To date, however, the study of the aging and emulsification phenomena of bio-oils derived from sewage sludge and swine leather residue is still absent, which is important for the further applications of the bio-oils. In this study, bio-oils from the hydrothermal liquefaction of sewage sludge and swine leather residue were produced from two bio-oil separation methods, namely, extraction and distillation. It was found that the distilled bio-oil had less nitrogen-containing compounds and more low-boiling-point compounds than the extracted bio-oil, and thus possessed lower calorific value. The complicated composition and high oxygen content in the bio-oils triggered the aging reactions during storage, which was analyzed by measuring their water contents, total acid numbers, viscosities, and higher heating values. The aging behavior depended on the feedstocks and separation methods. The total acid number and water content of the bio-oil from swine leather residue had more vigorous change than those from sewage sludge. However, the variation in the higher heating values of the three bio-oils with storage time was not obvious owing to the trade-off among a variety of reactions. These phenomena could be explained by dehydration, acetyl, polymerization, condensation reactions in the bio-oils. Furthermore, the emulsification of 10 wt% bio-oil and 90 wt% diesel was evaluated by detecting the functional group spectra at different retention times. It suggested that the case of bio-oil/emulsifier = 1 could yield a stable and effective emulsion within 30 days storage, showing the promising emulsification applications of hydrothermal liquefaction bio-oil.

Assessing chromium pollution and natural stabilization processes in agricultural soils by bulk and micro X-ray analyses.

A combined approach based on multiple X-ray analytical techniques and conventional methods was adopted to investigate the distribution and speciation of Cr in a polluted agricultural soil, from the bulk-scale down to the (sub)micro-level. Soil samples were collected from two different points, together with a control sample taken from a nearby unpolluted site. The bulk characterization revealed that the polluted soils contained much higher concentrations of organic matter (OM) and potentially toxic elements (PTE) than the control. Chromium was the most abundant PTE (up to 5160gkg-1), and was present only as Cr(III), as its oxidation to Cr(VI) was hindered by the high OM content. According to sequential extractions, Cr was mainly associated to the soil oxidisable fraction (74%) and to the residual fraction (25%). The amount of Cr potentially bioavailable for plant uptake (DTPA-extractable) was negligible. Characterization of soil thin sections by micro X-ray fluorescence (μXRF) and field emission scanning electron microscopy coupled with microanalysis (FEGSEM-EDX) showed that Cr was mainly distributed in aggregates ranging from tens micrometres to few millimetres in size. These aggregates were coated with an aluminosilicate layer and contained, in the inner part, Cr, Ca, Zn, P, S and Fe. Hyperspectral elaboration of μXRF data revealed that polluted soils were characterised by an exogenous organic-rich fraction containing Cr (not present in the control), and an endogenous aluminosilicate fraction (present also in the control), coating the Cr-containing aggregates. Analyses by high-resolution micro X-ray computed tomography (μCT) revealed a different morphology of the soil aggregates in polluted soils compared with the control. The finding of microscopic leather residues, combined with the results of bulk- and micro-characterizations, suggested that Cr pollution was likely ascribable to soil amendment with tannery waste-derived matrices. However, over the years, a natural process of Cr stabilization occurred in the soil thus reducing the environmental risks.

Dechroming: An Alternative Treatment for Leather Shavings, to Obtain a Biocompatible Collagen without Environmental Impacts

One of the biggest problems facing the leather industry is the production of solid waste with chromium. Dechroming process remove chrome from leather waste and it is designed to recover the value of collagen in the waste. Thus, the aim of this study was try to improve a methodology of dechroming process already described in the scientific literature, seeking to increase the percentage of dechroming ratio, as well as to evaluate the cytotoxic and genotoxic effects of the dechromed samples obtained from the leather residue for possible applications that require non-toxic materials based on collagens. As results, the dechroming process has been shown to be effective, with 99.29% of chromium removed from the shavings. In addition, it is possible to infer that the process of dechroming performed in this study was efficient in the neutralization step of hexavalent chromium and that the collagen from the leather residue did not shows cytotoxic and genotoxic effects for the evaluatedin vitrotest system. Therefore, this treatment allows to obtain a valuable product extracted from what was previously a hazardous waste.

In vitro cytotoxicity and genotoxicity of composite mixtures of natural rubber and leather residues used for textile applications.

A novel composite material has been developed from natural rubber and leather waste, and a corresponding patent has been filed. This new material may be incorporated into textile and footwear products. However, as leather waste contains chromium, the biocompatibility of this new material and its safety for use in humans must be investigated. The aim of the present study was to investigate the presence of chromium in this new material, determine the amount of each form of chromium present (trivalent or hexavalent), and evaluate the potential cytotoxic and genotoxic effects of the novel composite in two cell lines. The cellular viability was quantified using the MTT3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction method and neutral red uptake assay, and genotoxic damage was analyzed using the comet assay. Our findings indicated that the extracts obtained from the composite were severely cytotoxic to both cell lines tested, and additionally highly genotoxic to MRC-5 cells. These biological responses do not appear to be attributable to the presence of chromium, as the trivalent form was predominantly found to be present in the extracts, indicating that hexavalent chromium is not formed during the production of the novel composite. The incorporation of this new material in applications that do not involve direct contact with the human skin is thus indicated, and it is suggested that the chain of production of this material be studied in order to improve its biocompatibility so that it may safely be used in the textile and footwear industries.

Pyrolysis of chromium rich tanning industrial wastes and utilization of carbonized wastes in metallurgical process

Pyrolysis is the thermal degradation of organic material in oxygen-free or very lean oxygen atmosphere. This study evaluates the use of pyrolysis for conversion of leather wastes from chromium tanning processes into Carbonized Leather Residues (CLR), and the utilization of CLR in metallurgical processes through the production of iron ore pellets. CLR was used to replace mineral coal in proportions of 10% and 25% on fixed carbon basis content in the mixtures for pellets preparation. Experimental conversions were performed on a pilot scale pyrolysis plant and a pelletizing reactor of the “pot grate” type. The results demonstrated the technical feasibility of using the charcoal product from animal origin as an energy source, with recovery of up to 76.47% of chromium contained in CLR in the final produced of iron ore pellets. Pellets with 25% replacement of fixed carbon in the coal showed an enhanced compressive strength, with an average value of 344kgfpellet−1, compared to 300kgfpellet−1 for standard produced pellets.

Use of Leather Residue in the Manufacturing of Soil-Cement Bricks

This work is an analysis of incorporation of leather powder residue to soil in order to apply it in soil-cement bricks. The leather powder is a byproduct of the finishing step of leather manufacturing that contains chromium in its composition. This element, when in its hexavalent form, is carcinogenic. Experiments were performed regarding brick pressing, water absorption, simple pressing, leaching and solubilization so that the mixtures have the minimum requisites for using the brick. The doses were 0%, 10%, 15%, 20%, and 30% in volume of leather powder in soil. Only the 10% dose met the requisites of ABNT: NBR 8491:1984 that prescribes a minimum resistance of 2 MPa and absorption content lower than 20%. For this dosage, according to the limits stated in ABNT regulation NBR 10004:2004 , the leaching extract was classified as a Class II non-inert, which makes it possible to use it for civil construction purposes.

CO₂ Separation and Capture Properties of Porous Carbonaceous Materials from Leather Residues.

Carbonaceous porous materials derived from leather skin residues have been found to have excellent CO2 adsorption properties, with interestingly high gas selectivities for CO2 (α > 200 at a gas composition of 15% CO2/85% N2, 273K, 1 bar) and capacities (>2 mmol·g−1 at 273 K). Both CO2 isotherms and the high heat of adsorption pointed to the presence of strong binding sites for CO2 which may be correlated with both: N content in the leather residues and ultrasmall pore sizes.

From Waste to Healing Biopolymers: Biomedical Applications of Bio-Collagenic Materials Extracted from Industrial Leather Residues in Wound Healing.

The biomedical properties of a porous bio-collagenic polymer extracted from leather industrial waste residues have been investigated in wound healing and tissue regeneration in induced wounds in rats. Application of the pure undiluted bio-collagen to induced wounds in rats dramatically improved its healing after 7 days in terms of collagen production and wound filling as well as in the migration and differentiation of keratinocytes. The formulation tested was found to be three times more effective than the commercial reference product Catrix® (Heal Progress (HP): 8 ± 1.55 vs. 2.33 ± 0.52, p < 0.001; Formation of Collagen (FC): 7.5 ± 1.05 vs. 2.17 ± 0.75, p < 0.001; Regeneration of Epidermis (RE): 13.33 ± 5.11 vs. 5 ± 5.48, p < 0.05).

Incorporation of chromium-tanned leather residue in mortars

To protect the environment there is worldwide pressure to establish sustainable conditions for all kinds of industrial processes. In the leather industry, tanning is the main process used to protect the hide from environmental effects such as heat and microbial degradation. In Brazil, 60% of the leather that is processed comes from an area in the state of Rio Grande do Sul called Vale dos Sinos, which has approximately 90 tanneries and accounts for 30% of Brazilian leather exports. Studies show that 30% of the leather processed in tanneries is rejected, especially after the shaving process, in which many chemical products are used. Chromium-tanned leather has been used for many decades in the manufacturing of a large variety of leather products for personal use. This process generates liquid and solid waste containing chromium salts that are discharged as effluents into the environment, mainly in water and into the ground. Some solutions can be used to minimise the amount of chromium residue, such as the increase of material fixation due to the control of pH, the recycling of chrome tanning liquors to reduce the discharge into wastewater, the pyrolysis of material for the production of activated carbon and use in Portland cement clinker production. In order to contribute with another alternative for the disposal of this residue, the present study evaluated the incorporation of the residue into mortars. Three mortar mixture proportions were studied, each one with five levels of sand replacement by residue. Tests were conducted in order to verify the mortar properties, in the fresh and hardened state and the evaluation of total and chrome VI. The results showed that there is potential for using chromium-tanned leather residue in civil engineering and that technical, economic and environmental benefits can be obtained.

Chromium poisoning in rats feeding on tannery residues

The Brazilian tannery industry produces annually an enormous amount of scraps and leather shavings impregnated with chromium due to the tanning process. Technologies have been developed to remove chromium from this material. The resultant residue from the chromium removal process is high in protein with a high digestibility, suggesting that this residue may be used to feed monogastric animals. However, due to the nature of this residue, there is a risk of chromium poisoning and the introduction of botulism. The aim of this work was to establish the risks of adding tannery residues to animal feeds, using rats as an experimental model. Forty-eight Wistar rats were placed under eight treatments in a 2 by 4 factorial arrangement. The rats were fed over 60 days with a standard AIN-93 diet and the treatments consisted of replacing part of the diet with 0, 25, 37.5 or 50% of the chromium-tanned leather residue, in natura, known as ‘wet blue’, or the same percentages of this residue after chromium extraction. Industrial processing was able to remove 70–80% of the chromium from the residue. This high chromium level had a negative effect on the weight gain of the animals and caused lesions in the kidneys especially due to the chromium extraction material, suggesting that the removal process increases the biological activity of chromium, making it nefrotoxic. The gravity of this effect was directly proportional to the inclusion level. The results of this study indicate that until industrial processing is refined so that more of the chromium residue is removed, the use of the tannery residues in animal feeds is not safe.

POTENCIALIDADES NUTRICIONAIS DE RESÍDUOS DE COURO WET BLUE PARA A ALIMENTAÇÃO DE RUMINANTES

The process of leather tanning produces enormous amount of residues contaminated with chromium, which constitute a serious environmental problem. Although technologies have been developed to remove chromium from these rejects, it is necessary to have an adequate destination for the resultant material with low chromium contents. Brazilian legislation still allow the feeding of ruminants with colagen derived from the leather and skin. Therefore, this study investigates an alternative strategy to minimize environmental contamination by leather residues. The ones found in nature (WB) and those that had the chromium extracted (CE) were compared. Both materials presented 99,7% of DM, but CE CP levels (90,4%) were higher than WB (74,3%). In situ ruminal degradability was 63% for CE DM and 65% for CE CP, and WB did not suffer ruminal degradation. Abomasal digestibility of CE DM was 98%, which may indicate that CE is potentially useful in the feeding of non-ruminants. Animal feeding could be a viable alternative for the destination of leather residues generated by tanneries and treated by extraction method, aiming to minimize environmental contamination.

Incorporation of chromium-tanned leather residue to asphalt micro-surface layer

A study on the incorporation of chromium-tanned leather residue to the cold asphalt micro-surface layer was performed using the dry mix process. Laboratory designs for asphalt micro-surface were performed according to the methods specified by NBR (National Brazilian Standards), with additions of 0.3%, 0.5% and 0.7% residue without adding fiber to the asphalt mass. According to the technical work specification DNER-ES 389/1999, the MRA was experimentally applied to a 320-m stretch of Hélio M. Salles Highway (215 km) in the town of São Sebastião da Grama – in the state of São Paulo, Brazil. The results showed that the incorporation of 0.3% of leather sawdust increased the engineering properties of asphalt mixtures and minimized the cracking of pavement surface layer due to the fiber incorporation in the asphalt micro-surface.

Utilização de resíduos da indústria de couro como fonte nitrogenada para o capim-elefante

Uma grande variedade de produtos tóxicos é emitida durante o processo de tratamento do couro nos curtumes que usam o cromo III para obter o couro wet blue. O resíduo sólido (raspas e aparas) contém cerca de 3 % de Cr III, que representa um sério problema ambiental e não tem, atualmente, destino adequado. O resíduo de couro após extração de Cr (colágeno) foi utilizado como fonte nitrogenada para o capim-elefante (Pennisetum purpureum Schum cv. Napier), em um Latossolo Vermelho-Amarelo, aplicando-se quatro doses do colágeno (4, 8, 16 e 32 t ha-1) e três tratamentos adicionais (testemunha; adubação com N mineral e resíduo de couro wet blue- sem a extração do Cr). O colágeno é uma boa fonte nitrogenada alternativa para crescimento do capim-elefante até a dose de 16 t ha-1. O resíduo de couro wet blue não disponibilizou N durante o cultivo de capim-elefante. Isso mostra que a extração do Cr utilizando-se o ácido fosfórico é fundamental para uso do rejeito de couro como fonte nitrogenada na agricultura. A aplicação do colágeno supriu a necessidade de N para plantas de capim-elefante, semelhantemente à adubação com N mineral.