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7 figures, 4 tables.-- Supplementary information available.-- © 2022. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/, Developing chrome-free and sustainable tanning agents is extremely important to the sustainability of the leather industry. Herein, we have synthesized an Al-Zr-oligosaccharides tanning agent via a simultaneous degradation and oxidation of cellulose in waste paper. The influence of the temperature and the concentrations of AlCl3 and H2O2 during the synthesis were thoroughly investigated on the properties of the tanning agent and the leather produced. The synthesis temperature and the concentration of AlCl3 were the factors primarily affecting the effective depolymerization of cellulose. They controlled the conversion of waste paper into oligosaccharides with an appropriate molecular weight to efficiently penetrate the leather matrix. In parallel, the H2O2 concentration substantially influenced the tanning performance of the Al-Zr-oligosaccharides, diminishing the chromaticity of the tanning liquid via oxidation and promoting the conversion of C2/C3/C6-OH moieties into -CHO/-COOH. These functional groups increased the surface charge of the oligosaccharides allowing more effective coordination with Al/Zr, which facilitated the penetration of Al/Zr species into the leather matrix. Once inside the leather matrix, Al and Zr were released and reacted with the collagen fibers in leather, which resulted in effective leather tanning. The process optimization revealed that up to 57% of waste paper could be converted into a low-chromaticity (4350 AU) liquid hydrolysate with the synthesis conducted at 177 °C in a system comprising 47 mM AlCl3 and 5 vol% H2O2. The application of this liquid for tanning provided leather with a shrinkage temperature (86.5 °C) sufficiently high for commercial applications. These excellent results, combined with the intrinsic green nature of our approach, exemplify a step forward to simultaneously reduce pollution and hazards in leather industries giving a second life to waste paper., This work is financially supported by the National Natural Science Foundation of China (22078211). Javier Remón acknowledges the Spanish Ministry of Science, Innovation and Universities for the Juan de la Cierva (JdC) fellowship (Grant Number: IJC2018-037110-I) awarded.

Leather waste is one type of waste generated from the leather tanning industry. This study aims to obtain gelatin products from leather waste for pharmaceutical use. Gelatin is well-known for food industries but actually it is also used in non-food industries. The purification method used is to modify the filtering process using a filtration membrane. Observations were made on the parameters that became indicators of gelatin quality. The use of a 0.2 micrometer filtration membrane is suitable for small gelatin molecules having a molecular weight below 200kDa especially to remove lipopolysaccharide content from gelatin. Leather waste is a non- economic waste that has the potential as an alternative raw material for making gelatin with pharmaceutical quality standards. This research is expected to utilize chrome-free leather as non-economic waste into gelatin so it can have an impact on spurring the growth of the gelatin processing industry in Indonesia then reduce gelatin imports activities.

In this work, a new method is proposed to remove Cr (III) in tanning wastewater with low cost bare magnetic Fe3O4 nanoparticles. It has achieved ultra-high chromium capture capacity under high selectivity. The maximum capture capacity of magnetic Fe3O4 nanoparticles for Cr (III) in chromium containing tanning wastewater is 456.20 mg/g at optimal pH 8. In a pilot scale apparatus running continuously at 18 L/h for 8 h, the chromium removal efficiency could be stabilized above 98.5% with chromium concentration reduced from 1065 mg/L to about 15 mg/L at the primary treatment. After secondary treatment, the outlet chromium concentration drops to 0.2 mg/L (lower than 0.5 mg/L, the maximum allowable concentration of Cr total in tanning wastewater determined by China), and the chromium removal efficiency is steadily above 97.8%. The results revealed that the method could be used economically as an efficient technique for removal of Cr (III) in chromium containing leather tanning wastewater and has great potential in heavy metal wastewater treatment.

Rapid urbanization and technological advancement have led to worrisome challenges associated with increasing waste production, and its management is overly burdensome. Indonesia annually produces 100,000 tons of leather tanning waste (LTW) and 2600 tons of waste capiz-shell (WCS). This study proposed a zero-waste approach by utilizing WCS as the catalyst for biodiesel production from LTW. Based on the characterization results, the WCS-based catalyst is proven to possess high porosity and comparable catalytic activity to the other heterogeneous catalysts. The maximum yield of FAEE was 93.4 wt%, obtained at 60 °C, 4 h reaction time, 3 wt% catalyst loading, and ethanol to LTW molar ratio of 6:1. High FAEE yield (> 90 wt%) can be obtained by reusing the WCS-based catalyst until the third reaction cycle. To examine the feasibility of this zero-waste act, a simple viability study was also performed by comparing this process to the conventional basic transesterification process.

Trivalent chromium compounds are used for leather tanning, and chromium may be released during use of leather goods. In certain instances, small amounts of hexavalent chromium can be formed and released. Both trivalent and hexavalent chromium can elicit allergic skin reaction in chromium sensitised subjects, the latter being significantly more potent. Induction of sensitisation only occurs after exposure to hexavalent chromium. A minority of subjects are sensitised to chromium, and in a fraction of these subjects allergic skin reaction have been described after wearing leather shoes or, less frequently, other leather goods. The evidence that in all these cases the reaction is related to hexavalent chromium is not always strong. The content of hexavalent chromium in leather is regulated in European Union, but rate of release rather than content is relevant for allergic skin reaction. The role of trivalent chromium appear much less relevant if at all. Modern tanning procedure do not pose significant risk due to either hexavalent or trivalent chromium. Dismissing bad quality and worn-off leather goods is relevant in reducing or eliminating the skin reaction. It should also be pointed out that shoe components or substances other than chromium in leather may cause allergic/irritative skin reactions.

The optimum conditions for the removal of leather tanning agent syntan from aqueous solution by Fenton oxidation at 22 °C for an initial syntan concentration of 500 mg/L were pH 3, and concentrations of H 2 O 2 and FeSO 4 of 300 mg/L and 500 mg/L, respectively. Fenton oxidation followed by granular activated carbon (GAC) adsorption in fixed-bed column resulted in more than 95% removal of dissolved organic carbon, compared to 55–70% removal by Fenton oxidation alone and GAC adsorption alone. The removal of individual organic fractions was also higher for the combined treatment compared to the Fenton oxidation alone.

A greener and eco-friendly method to leather tanning process has been developed in the present investigation, which is based on d-Lysine aldehyde complex. This can be considered as a substitute for chrome-free tanning process. The physico-chemical and morphological characteristics, resistance to collagenolytic activity and organoleptic properties of the d-Lysine glutaraldehyde tanned leather were evaluated in terms of environmental impact assessment. The shrinkage temperature, denaturation temperature and mechanical strength of tanned leather were analysed by using shrinkage, differential scanning calorimetric and thermomechanical analysis techniques. It has been shown that the above properties of the tanned leather are better than that of glutaraldehyde alone or equal to chrome tanned leather. The density of the fibre structure throughout the cross section indicates the even structure and fibre bundles seem to be less dispersed compared to glutaraldehyde alone; were analysed by using scanning electron microscopic and atomic force microscopic techniques. This tanning tanned leather demonstrated a higher resistance to collagenolytic activity than conventional tanned leather. The tanned leather exhibited good fullness, softness, smoothness, colour and general appearance compared to glutaraldehyde alone. The significant reduction in total solids content such as dissolved solids and suspended solids present in the effluent compared to conventional tanning method is evident from environmental impact assessment studies. This tanning process has the cost advantages due to the possible decrease in chemicals consumptions and net saving from the reduced effluent treatment costs. The improved tanning process reduces generation of toxic waste compared to chrome tanning process and can be regarded as eco-friendly, which reducing the environmental impacts and contributes to the development of greener or cleaner process.

In the present study, green and sustainable method or eco-friendly approaches to tanning process based on unnatural D-amino acids (D-AA)-aldehyde (Ald) as a substitute for chrome-free tanning has been attempted. The distribution of optically active D-AA in tanned leather, the hydrothermal stability, the mechanical properties and resistance to collagenolytic activity of tanned leather, the evaluation of eco-friendly characteristics were investigated. Scanning electron microscopic (SEM) and Atomic force microscopic (AFM) analyses indicate the surface morphology and roughness, respectively, of the tanned leather collagen matrix. Shrinkage and Differential scanning calorimetric (DSC) analyses shows that the shrinkage temperature (T(s)) and denaturation temperature (T(d)) of tanned leather are related to the content of D-AA+Ald present in the leather matrix. It has been found that the T(s) of D-AA tanned leather is more than that of Ald tanned leather and also more or less equal to chrome tanned leather. Environmental impact assessment (EIA) shows that the developed process results in significant reduction in total solids content (TSC) and improves better biodegradability of organic compound present in the effluent compared to chrome tanning.

Cr (VI) is highly toxic and responsible for mutation, cancer and cell damage. Cr is one of the 129 priority pollutants. It has positive potential for bioaccumulation and food chain contamination, extremely toxic if ingested or inhaled. It is a definite human carcinogen when inhaled. Cr(III) is used widely in leather tanning process. In this article it was described how Cr(III) converts toxic Cr(VI).

The environmental impact of the tanning industry is generally significant with outputs of wastes, i.e. high concentrations of organics, salts and heavy metals (chromium compounds), both in solid and liquid form, as a result. In order to bring the tanning industry more in line with present environmental thinking, various methods have been devised to reduce impacts. The underlying study proposes a modification of the method for unhairing–liming of hides where the unhairing–liming liquids are reused several times after being recharged by reduced quantities of chemicals. The study, therefore, aims at reducing both the economic and environmental costs of the unhairing–liming process. Experiments were carried out at lab scale with a simulation apparatus designed for the purpose. Life cycle assessment was used to evaluate the net environmental benefits of the modified method. The present value approach was used to evaluate the economic feasibility of the modified method. The quality of the produced leather was assessed by experts from the tanning sector (tanners). On the environmental level, the modified method reduced the environmental impact of the process by 24%, COD was reduced by 50% as well as sulfide which was reduced by 73% when the process water was recycled four times. The modified method requires some investment in new equipment and is a little more labor intensive as compared with the conventional method but does permit for savings in water up to 58% and chemicals up to 28% as well as wastewater treatment cost which was reduced by 58%. The modified method allowed for four times reuse of the unhairing–liming liquor without visibly affecting the quality of the final product of leather. It was concluded that both the economic and the environmental costs of the unhairing–liming process were reduced relative to the same of the conventional method.

Chromium (Cr) is widely used in different industries, such as steel production, wood preservation, and leather tanning. It poses a severe threat to the ecological system due to its toxic effect on most life forms. In this paper, the response of Saccharomyces cerevisiae to different chromium concentrations was investigated. The results demonstrated that the growth of S. cerevisiae in the presence of chromium showed a lag phase much longer than in the absence of chromium. Inhibition was dependent upon the chromium concentrations. Chromium, at concentration of 15 μM, inhibited microbial growth by approximately 30% with regard to control, whereas chromium, at a concentration of 5 μM, did not have a significant effect on microbial growth. The existence of chromium did not perturb cell–protein synthesis and there was a good correlation between dry cell weights and total protein content (R=0.98). The RNA/DNA ratio in the microbial cells varied with the chromium concentration and there was a significant positive correlation between chromium concentration and the RNA/DNA ratio. Assimilation of ammonium ion was inhibited by chromium in the medium.

This article discusses the need to integrate scientific research with the concept of Industrial Ecology, acting as support for the development of Eco-technologies. In order to proceed with the discussion, an initial section presents the concepts. A new and more accurate position concerning the extension of Eco-technologies in the context of Industrial Ecology is proposed. Emphasis on the role of academic scientific research as a way to propose and support specific solutions for local problems. Thus, alternative solutions based on the application of non-conventional technologies, which explore the unique regional characteristics of a Brazilian region, are examined. The sharing of waste streams generated by two polluting industries, mining and leather tanning, can lead to lower environmental impact if compared with separate management of their wastes. A comprehensive bibliographic review of non-conventional technologies related to heavy metal attenuation is included.

Cr(VI) is highly toxic and responsible for mutation, cancer and cell damage. Cr is one of the 129 priority pollutants. It has positive potential for bioaccumulation and food chain contamination, extremely toxic if ingested or inhaled. It is a definite human carcinogen when inhaled. Cr(III) is used widely in leather tanning process. In this article it was described how Cr(III) converts toxic Cr(VI).

Wastes generated during leather tanning are commonly added to some commercially available organic fertilizers. Since such tannery wastes are typically high in chromium, the possibility of absorption of the metal by crops was of interest. Swiss chard was grown on a soil amended with 5, 10 or 15 percent of a tannery waste fertilizer. Significantly higher concentrations of chromium were found in swiss chard grown on the 10% and 15% treatments versus that in the control chard. Plant growth inhibition was noted at the 10% and 15% rates of tannery waste soil incorporation.

The purpose of this study was to evaluate the technical performance and cost effectiveness of a low temperature pyrolysis process which uses dry leather tanning wastes to provide energy and chrome tanning liquor for reuse in tanneries. Presently, leather waste is disposed of in landfills, resulting not only in a considerable loss of potential energy (estimated to be 633 TJ annually), but an even more significant loss of chromium (estimated to be 8.2 Gg annually). The pyrolysis process is shown to be technically feasible, economically viable, and can alleviate a leather waste management problem that is becoming increasingly more difficult to handle because of more stringent environmental chrome waste disposal requirements. Tanneries can save an estimated $7 million to $8 million annually by employing this pyrolysis process to conserve energy and chrome in dry tanning wastes.

The Bureau of Mines has been influential in increasing the recycling of mineral values from various waste materials. Industrial utilization of Bureau research includes cobalt and tungsten carbide recovery from machining tool scrap, regenerating chromic acid from spent electroplating solutions, and resource recovery from municipal solid waste. Current scrap and waste utilization studies are being directed in part toward developing environmentally acceptable and energy-efficient methods of recycling secondary lead, recovering chromium and other critical metals from scrap materials, and developing new uses for nonmetallic scrap. Work is conducted at Bureau research centers located throughout the country as well as at the facilities of private research organizations that have been awarded Bureau contracts. Work in cooperation with the Tanners' Council of America, Inc., has been directed toward developing effective methods for treating leather tanning wastes to prevent environmental degradation while recovering the chromium values for effective recycling. The status of current scrap and waste utilization research is shown in relation to the goals and objectives of the Bureau's mineral resources technology program.