Chrome-tanned Leather Shavings Research Articles

Co-pyrolysis of chrome-tanned leather shavings with wheat straw: Thermal behavior, kinetics and pyrolysis products

The thermal behavior and kinetics of chrome-tanned leather shavings (CLS)/wheat straw (WS) blends at different mass ratios during co-pyrolysis were investigated, and the pyrolysis products were characterized. Model-free isoconversional and master-plots methods were applied to determine kinetic triplet of the pyrolysis/co-pyrolysis of CLS, WS and their blends based on thermogravimetric (TG) analysis. Results showed that the activation energy for CLS pyrolysis was reduced by the addition of WS, and a synergistic promoting effect predominated across the majority of temperature ranges and feedstock compositions during the co-pyrolysis process. TG-Fourier transform infrared spectrometry-Mass spectrometry analysis showed the changes in evolution profiles of H2O, CO, CO2, HNCO and pyrrole during pyrolysis. The pyrolysis solid residues were characterized and results indicated that the addition of WS to CLS can increase solid residue yield and potentially inhibit the formation of hexavalent chromium during pyrolysis. This study helps to foster a promising solution for the valorization and safe disposal of chromium-containing solid wastes from leather industry.

An innovative ionic liquid-aqueous biphasic system for simultaneously highly efficient dechroming and collagen recovery from chrome-tanned leather shavings at room temperature

Chrome-tanned leather shavings (CTLS) with abundant collagen of 70–90 wt% but high Cr content of 2–4 wt% are considered as hazardous wastes. Due to the stable covalent bond between Cr and collagen, current processes for collagen recovery from CTLS face challenges including low dechroming efficiency, collagen disruption, high energy and chemical consumption and secondary pollution. In this paper, an innovative IL-targeted homogeneous isolation (IL-THI) process based on the reusable ionic liquid-aqueous biphasic system (IL-ABS) was established for the simultaneous resource recovery and complete dechroming of CTLS at room temperature, with the recovery rate of collagen reached 72.4 % while Cr content in collagen is reduced from 35.65 × 103 mg/kg to 1.78 mg/kg. This IL-ABS enriched TBAH in the upper phase and potassium tartrate in the lower phase. Moreover, TBAH demonstrated excellent reproducibility across five cycles, achieving consistently low Cr content of 2.65 mg/kg in collagen, far below the 50 mg/kg limit in national standards. The triple helix conformation and the molecular weight of the collagen product were confirmed via Fourier-transform infrared spectroscopy, X-ray diffraction analyses, circular dichroism spectra analysis and SDS-PAGE. Moreover, economic calculations demonstrated the suitability of this novel process for sustainable CTLS recovery. The superior dechroming ability of IL-ABS is attributed to the formation of Cr(III)-Tartrate complexes, which preferentially migrate to the lower phase due to the solvophobic effect, while dissolved collagen is recovered from the upper phase, as disclosed by UV–Vis spectra, ICP-OES, and all-atom molecular dynamics simulations. Additionally, IL-THI process demonstrates considerable potential for the isolation of Cr(III) and collagen in solid waste, with low energy consumption, improved separation efficiency, and increased design flexibility.

Experimental Study on Chrome Tanned Leather Shavings Modification—Properties and Prospective for Future Application

Chrome tanned leather shavings (CTLS) are considered one of the more difficult wastes to manage in the tanning industry. At the same time, this waste is an important source of good quality collagen. The few methods described in the literature for the valorization of these wastes usually require pre-treatment or activation. In this study, an attempt was made to see if raw chrome tanned leather shavings (CTLS) could be modified to obtain secondary raw materials with new physical properties. Glutaraldehyde, glycerol, EDCs, pectin, and tannins were selected for modification of the CTLS. The effectiveness of the processes carried out was confirmed by FTIR analysis of the materials obtained. Changes in the intensity of the characteristic collagen peak (amide I, amide II, and amide III) and changes in the position of the bands in the 1200–1000 cm−1 region were observed in the recorded spectra. The modifications introduced confirmed changes in the physical properties of samples M1–M5, including an increase in bulk density from 0.15 to 0.59 g cm−3, and improved tensile strength is some cases. The elemental content results of the samples tested showed the resulting modified CTLS were free of Cd, Hg, Pb, and Cr(VI). It was also confirmed tanning waste contained significant amounts of various valuable elements. The research also included preliminary tests to assess the environmental impact of the modified materials. In a phytotoxicity test conducted on modified CTLS, M1 with pectins showed the highest root stimulation (105%), while samples with glutaraldehyde and unmodified CTLS showed significant root inhibition (75%, 74%). Other samples showed moderate plant toxicity and seed germination was not significantly affected.

Extracellular activity of proteases from Yarrowia lipolytica IPS21 as a function of the carbon and nitrogen source

Abstract The yeast strain Yarrowia lipolytica IPS 21 was tested for its ability to produce the protease enzyme on analytically pure carbon sources as well as on waste carbon sources. It was confirmed that the yeast Y. lipolytica IPS21 can have a higher proteolytic activity in the presence of waste carbon sources in chrome-tanned leather shavings (CTLS) than on yeast extract alone. This is confirmed by the high concentration of amino acids in samples with CTLS, suggesting increased degradation of CTLS by Y. lipolytica or secretion of proteases into the medium. It was also confirmed that metals accumulate mainly in the biomass and not in the supernatant. The biomass was also found to contain high levels of Ca, K and P, which are essential for plant growth. These results show that Y. lipolytica strain IPS21 can be used for the production of extracellular alkaline proteases and for the degradation of protein waste.

Biotransformation of protein-rich waste by Yarrowia lipolytica IPS21 to high-value products-amino acid supernatants.

The yeast strain Yarrowia lipolytica IPS 21 was tested for its ability to degrade potentially toxic chrome-tanned leather shavings (CTLS) in a liquid environment. Biological and chemical parameters were monitored during a 48-h period of biotransformation of the protein-rich waste. CTLS was added at a concentration of 0.1-4% (wt/wt) to a modified YPG medium (15 g L-1 yeast extract and 5 g L-1 NaCl). Biodegradation and bioconversion were performed in a one-step process. It was found that the higher degradation rate depended on the activity of the proteases and the pH of the medium, but not on the initial inoculum ratio and the activity of the dehydrogenase. The highest efficiency of the process was obtained for 4% (wt/wt) CTLS on day 2 (degradation rate 58-67%, biomass production 2.11-2.20 g L-1, protease activity 312 U mg-1 protein, and pH 9.20). Our results showed that total chromium was probably not transported across the cytoplasmic membrane of Y. lipolytica IPS21 and that chromium (III) was not oxidized to chromium (VI). The phytotoxicity of selected amino acid supernatants [2.5% (vol/vol)] was tested after the bioconversion process. It was found that the supernatants had a stimulating effect on the plants tested. The root elongation was 29-28% higher than that of the reference samples. This result makes Y. lipolytica IPS21 a potential candidate for safely converting potentially toxic protein-rich wastes into valuable products without enzyme isolation, e.g., amino acid fertilizers. IMPORTANCE Enzyme technologies have the greatest practical relevance to environmental trends. Overcoming the barrier of the high cost of carbon substrates used for biotransformation is the main challenge of these methods. The huge potential of the use of extracellular proteases of Yarrowia species or amino acids in various industries indicates the need for the extension of basic research on waste as a carbon source for this yeast. The experiments demonstrated that it is possible to use Y. lipolytica IPS21 for bioconversion of chrome-tanned leather shavings (CTLS) in a single-step process and to produce high-value amino acid supernatant without having an isolated enzyme. In our study, we show the effect of 2.5% (vol/vol) CTLS supernatant obtained from Y. lipolytica IPS21 on the elongation of the root system of selected plants and provide information on the effect of environmental factors on the efficiency of the bioconversion and the migration of chromium.

Leather-based fertilizers from Personal Protective Equipment (PPE) reverse logistics: Technical efficiency and environmental safety

Agriculture and industry are seeking healthy food and enough goods to meet the global demand without causing environmental impacts, which motivates the search for sustainable and eco-efficient technologies. This study focuses on reverse logistics in the Personal Protective Equipment (PPE) industry. Chrome-tanned leather shavings from the manufacture of PPE and post-use leather PPE were used to produce leather-based fertilizers (LBFs), which were evaluated for their agronomic efficiency and food safety. N-rich liquid LBFs were successfully produced through hydrolysis, either with or without previous chromium extraction. At the dose of maximum technical efficiency, LBFs are safe, with acceptable levels of Cr in the plant biomass and the soil compartments. However, LBF overdoses promote Cr accumulation in plants and soils, which demonstrates the need for a rigorous control over the fertilization management to ensure successful PPE reverse logistics.

Recovery of Cr (Ⅵ) from tannery sludge and chrome-tanned leather shavings by Na2CO3 segmented calcination

Tannery sludge (Ts) and chrome-tanned leather shavings (CTLs) are regarded as hazardous wastes, which are produced considerably in industrial activities. It is urgent to develop an efficient and cost-effective method to treat these hazardous wastes and simultaneously recover their useful components. In this study, thermodynamic calculation and thermogravimetric characterization were used for analyzing the theoretical feasibility of calcinating Ts and CTLs and the factors affecting recovery of Cr in calcination process were investigated. The results showed that calcination environment, including Na2CO3 content, temperature, calcination time and organic compounds in materials, could greatly affect the recovery of Cr (Ⅵ) from Ts and CTLs. Meanwhile, the glassy chromate phase which formed in the calcination process could interfere with Cr (Ⅵ) release, resulting in decrease of recovery Cr. Thus, to overcome the existing negative effect in calcination process, a segmented calcination with Na2CO3 as a “catalyst” was developed and identified as a low-cost and simple process to effectively recover Cr (Ⅵ) from Ts and CTLs. The recovery of Cr (Ⅵ) from the Ts and CTLs increased by 12% and 38%, respectively, and the recovery of Cr (Ⅵ) from the mixed material reached 60%.

Regeneration of native collagen from hazardous waste: chrome-tanned leather shavings by acid method.

The collagens (COL2, COL4, and COL5) were extracted from chrome-tanned leather shavings via three distinctive routes of acid method. The dechroming degree of COL2 extracted with the easiest operation was the highest (95.6% ± 1.2%) and the yield exceeded 90%; however, the total amount of acid was the most and the cost was the highest. In the second route, although the three-step dechroming process brought cumbersome operation, the dechroming degree and yield of COL4 were 90.5% ± 0.8% and 92.2% ± 0.6%, respectively, and the acid amount was less than that in the first route. For COL5, the dechroming degree and yield was the lowest; nevertheless, this route had the advantages of lowest cost and simpler operation. Electrophoretic patterns showed that all the collagens contained α1, α2, and β chains without low molecular weight components and were close to those of type I collagen. Compared with native collagen extracted from fresh calf skin, the regenerated collagens also maintained unique triple helix conformation determined via ultraviolet, infrared spectra and X-ray diffraction, confirmed by the similar values of AIII/A1455 and Δν. Additionally, the collagens existed in the form of fibrils with D-period pattern of ~ 67nm. Furthermore, the denaturation temperatures of COL2, COL4, and COL5 were 71.2, 79.1, and 85.4°C, respectively, which were relevant to the tighter arrangement of fibrils with the increased chromium content.

Hybrid Carbon Nanochromium Composites Prepared from Chrome-Tanned Leather Shavings for Dye Adsorption

Every year, the leather tanning industry produces substantial quantities of residues such as chrome-tanned leather shavings (CTLS), which contain considerable amounts of Cr(III) salts. The residues have no particular value and under natural conditions can transform into toxic Cr(VI) wastes. The objective of the present work is to evaluate the transformation of these residues into carbon adsorbents at low temperatures (< 600 °C), using ZnCl2 as an activating agent. The pyrolysis temperature and residence times were studied. The materials were characterized and qualified by Acid Black 210 (AB) adsorption. The results indicated that low amounts of chromium oxides (less than 2% of Cr), in the form of 50–200 nm particles, remained after the synthesis procedure. The deposited chromium oxides were present in (II), (III), and (IV) oxidation states. The low preparation temperatures employed prevented further chromium oxidation to Cr(VI). Maximum surface areas of 439 m2/g were obtained. The materials efficiently removed AB (maximum experimental adsorption capacity of 44.4 mg/g) by means of electrostatic interaction caused by the positively charged distribution of the carbons. The adsorption capacity was not affected by temperature, but pH had a mixed effect due to the combination of a shift in surface charge distribution and dye speciation. The results demonstrated that it is possible to obtain a value-added product, i.e., carbons modified with chromium nanoparticles for dye removal, from a hazardous residue of the tanning industry.

Pyrolysis characteristics and Cr speciation of chrome-tanned leather shavings: influence of pyrolysis temperature

ABSTRACTChrome-tanned leather shavings (CTLS) are a type of solid waste generated from the leather industry. In this study, the pyrolysis experiment of CTLS was conducted in a high-temperature tubular furnace reactor at different temperatures. The results showed that the pyrolysis temperature highly affected the product yields. The tar generated from the CTLS pyrolysis presented a wide distribution of pyrolytic compounds, and nitrogenated derivatives were the major group. The scanning electronic microscopy (SEM) investigation showed that a continuous structure of irregular but rather uniformly distributed interconnected pores of the chars. Cr was found to exist in the char as its reduced state (Cr3+). This study provided basic data for the determination of pyrolysis temperatures of CTLS targeting different products.

Nitrogen-containing gaseous products of chrome-tanned leather shavings during pyrolysis and combustion

Chrome-tanned leather shavings (CTLS) are a type of solid waste generated from the leather industry. In this study, the pyrolysis and combustion of CTLS in nitrogen and air, respectively, were investigated using a thermogravimetric analyser coupled with Fourier transform infrared spectroscopy (TG-FTIR). A heating rate of 20 °C min−1 was applied, with a final temperature of 1000 °C. The pyrolysis process can be subdivided into three stages (drying the sample, fast thermal decomposition and a further cracking process), whereas the combustion process can be subdivided into four temperature stages. The TG/DTG curves for pyrolysis and combustion were similar at lower temperatures. Multiple peaks were observed for combustion in the temperature range of 250 °C to 580 °C. The emissions of CO2, NH3, HCN, HNCO, CO, acid and hydrocarbon were identified in CTLS pyrolysis. Similar gaseous products of combustion were found at lower temperatures, whereas CO2 is the dominant product of combustion at higher temperatures. Combustion was found to be better for disposal of CTLS than pyrolysis.

Soybean plant growth study conducted using purified protein hydrolysate-based fertilizer made from chrome-tanned leather waste.

Leather processing discharges enormous amount of chrome containing leather solid waste which creates a major disposal problem. Chrome-tanned leather solid waste is a complex of collagen and chromium. The presence of chromium limits protein application in fertilizer industry. The purified protein hydrolysate with zero chromium could be used as a nitrogen source for fertilizer formulation. In this study, an attempt has been made to employ purified protein hydrolysate derived from chrome-tanned leather shavings (CTLS) in formulation of fertilizer. The formulated fertilizer (1–3 t ha(-1)) is employed as nitrogen source in production of soybean. Plant growth study demonstrates that formulated fertilizer dosage 3 t ha(-1) produced similar effects of commercial fertilizer-treated plants. Application of formulated fertilizer yielded higher seed in plant than commercial fertilizer.

The effect of modified biopolymers and poly(vinyl alcohol) on carboxylated acrylonitrile-butadiene rubber properties

The aim of the research was to determine the impact of modified biopolymers such as: enzyme hydrolyzate of collagen, enzyme hydrolyzate of keratin and poly(vinyl alcohol) PVAL (or PVA) on the properties of carboxylated acrylonitrile-butadiene rubber (XNBR) vulcanizates. Biopolymers were obtained from industrial waste leather in the form of collagen from chrome tanned leather shavings and keratin from cattle hair. The rheometric, mechanical properties, cross-linking density, Fourier Transform Infrared spectra (FT-IR) and Ultraviolet-Visible spectra (UV-Vis) were examined. Thermo-oxidative aging and biodecomposition processes were also performed. The introduction of natural bioadditives and PVAL influenced the improvement of cross-linking density of the obtained XNBR composites — probably by creating a common spatial network with the elastomeric matrix. Increased hardness, resistance to thermal aging and susceptibility to the action of microorganisms in soil were observed.

A review on management of chrome-tanned leather shavings: a holistic paradigm to combat the environmental issues.

Raw hide/skins come to the tanners as a by-product of meat industry which is converted into value-added leather as product for fashion market. Leather manufacturing is a chemical process of natural biological matrix. It employs a huge quantity of water and inorganic and organic chemicals for processing and thereby discharges solid and liquid wastes into the environment. One of the potential solid wastes generated from leather industry is chrome-tanned leather shavings (CTLSs), and its disposal is increasingly becoming a huge challenge on disposal to tanners due to presence of heavy metal chromium. Hence, finding a sustainable solution to the CTLS disposal problem is a prime challenge for global tanners and researchers. This paper aims to the deeper review of various disposal methods on CTLS such as protein, chromium, and energy recovery processes and its utilization methodologies. Sustainable technologies have been developed to overcome CTLS solid wastes emanating from leather processing operations. Further, this review paper brings a broader classification of developed methodologies for treatment of CTLSs.

Chrome-tanned leather shavings as a filler of butadiene–acrylonitrile rubber

The noxious wastes from the tanning industry such as chrome-tanned leather shavings were used as the only filler of rubber mixes containing carboxylated butadiene–acrylonitrile rubber (XNBR) or butadiene–acrylonitrile rubber (NBR), and a dispersing agent Limanol PEV (Schill & Seilacher). The best form addition of leather powder to the rubber mixes is mixed the waste protein with zinc oxide. The leather powder added to the rubber mixes improves the mechanical properties: tensile strength ( T s), elongation at break ( ɛ b) and increase the cross-linking density of carboxylated XNBR and NBR rubber mixes. Satisfactory results of these studies are presented in this work.

Rendimentos de culturas e alterações químicas do solo tratado com resíduos de curtume e crômio hexavalente

O presente trabalho foi elaborado com o objetivo de avaliar o rendimento das culturas do trigo, alface e rabanete e as alterações químicas de um Latossolo resultantes da adição de resíduos de curtume e de crômio hexavalente. Microparcelas, constituídas por recipientes com 60 L de solo e mantidas em casa de vegetação, receberam os seguintes tratamentos: testemunha; calcário + NPK; lodo do decantador primário + PK; resíduo de rebaixadeira de couro + calcário + NPK; aparas de couro + calcário + NPK; Cr6+ + calcário + NPK ; Cr6+ + calcário + esterco bovino; calcário + esterco bovino. O lodo continha 8,5 g kg-1 de Cr e foi aplicado em dose correspondente a 8,8 t ha-1. O resíduo de rebaixadeira possuía 17,1 g kg-1 Cr e as aparas de couro, 19,4 g kg-1 Cr. Esses resíduos foram aplicados nas doses correspondentes a 4,4 e 3,8 t ha-1. As doses de Cr6+ (K2Cr2O7) e esterco bovino foram de 100 mg kg-1 e 20 t ha-1, respectivamente. A aplicação de lodo elevou o pH do solo de 5,1 para 5,8; os teores de N, de 1,26 para 1,51 g kg-1, e os teores de Ca, de 4,1 para 5,9 cmol c dm-3, proporcionando rendimentos das três culturas equivalentes aos obtidos com a aplicação de calcário + NPK. Os teores de crômio no solo e nas partes vegetativas das culturas nos tratamentos com aplicação dos resíduos de curtume variaram, respectivamente, de 40,7 a 71,2 e de 0,08 a 2,71 mg kg-1, sendo considerados normais. A adição de resíduo de rebaixadeira de couro ou das aparas de couro não reduziu os rendimentos das culturas e não alterou os teores de Cr do solo e das plantas. A adição de Cr6+ provocou um efeito tóxico nas plantas, sendo responsável pela diminuição do rendimento da cultura do trigo em 91 % e da cultura da alface em 86 %, quando comparadas ao tratamento Calcário + NPK. Este efeito foi diminuído com a adição de agentes redutores como o esterco bovino.