Tanning Process Research Articles

Potential Human Health Risks of Tannery Waste-contaminated Poultry Feed.

For over a decade, solid tannery waste has been converted into protein concentrate and used as a feed ingredient because of its cheap availability. However, as chromium sulfate is commonly used in the tanning process, the chromium (Cr) content of tanned skin-cut wastes (SCW) may enter the edible parts of poultry through feed. Therefore, there is a chance that Cr and other heavy metals may be present in the edible portion of poultry and consequently transfer to humans upon poultry consumption. In this study, skin-cut wastes (SCW)-based poultry feed and the edible parts of chicken fed with this feed were analyzed to understand the potential health risks of their use as poultry feed. In the present study, the presence of heavy metal content in SCW, poultry feed, and edible portions of different kinds of chicken was determined using atomic absorption spectrophotometer methods and the associated health risk estimation was calculated by comparing the target hazard quotient (THQ) value and reference daily intake value. The results revealed the presence of Cr content ranging from 0.12-3.11 mg/kg and lead (Pb) content ranging from 8.06-22.0 mg/kg in SCW. In addition, Cr and Pb were present in the range of 0.27-0.98 mg/kg and 10.27-10.36 mg/kg, respectively, in poultry feed. However, no cadmium (Cd) was found in SCW, but the presence of Cd ranged from 0.03-0.05 mg/kg in feed. When contaminated poultry feed was fed to live poultry, the presence of Cr, Pb and Cd was observed in the edible portions (i. e. skin, liver, gizzard, and meat). Irrespective of the edible parts and chicken type, Cr values ranged from 0.1-2.440 mg/kg; Pb values ranged from 0.257-1.750 mg/kg; and Cd values ranged from below detection limit (BDL) to 0.037 mg/kg. The estimated daily intake value, THQ, along with the aggregate hazard index value, indicated a potential risk to consumers through consumption of contaminated chicken. Therefore, the study results clearly demonstrate heavy metals accumulation in chicken due to feeding SCW-based feed. The contaminated chicken further transfers these heavy metals to humans through ingestion. Hence, there is a potential human health risk through consumption of contaminated chicken meat.

Generation of fleshings at beamhouse in tannery and its environmental impact assessment: Bangladesh perspective

Leather processing involves the conversion of putrescible hide/skin into imputrescible leather and consequently huge amount of solid waste generated in tanning process. In tannery at beamhouse, fleshing is one of the most indispensable mechanical operations in leather processing where significant amount of solid waste (termed as fleshings) is produced. A work was carried out to estimate the generated fleshing and to assess its environmental impact. In Bangladesh yearly 20.1×103 MT fleshings was generated only from cow hide and goat skin where 10.3×103 MT for cow hide and 9.8×103 MT for goat skin. The generated fleshings are usually kept indiscriminately inside or outside the industrial area as green. In rainy season, all fleshings including other solid wastes are washed away and finally fall in to the river, Buriganga. Fleshings contained alkaline pH (12.3±0.2), fat, proteins, lime and sulphide. Improper management of fleshings has negative effect on human health, air, water, land and plant.Bangladesh J. Sci. Ind. Res. 50(3), 227-232, 2015

Green environment suffers by discharging of high-chromium-containing wastewater from the tanneries at Hazaribagh, Bangladesh

Application of chromium and discharging of high-chromium-containing wastewater is a major concern in leather processing. In tanning process, animal hide/skin collagen is stabilized against biodegradability mostly with basic chromium sulfate. Subsequently in chrome tanning, a fraction of chromium remains in the tan liquor, which is discharged in the waste steam. The study focused on the characterization of discharged chromium-containing wastewater from the tanneries. Results indicate that high concentration of chromium ranging from 2656 to 5420 mg/L was discharged as wastewater after wet-blue production. The physical parameter of spent chrome liquor: total solids (TS) were extremely high. The chemical parameter such as pH (2.4–3.0) was highly acidic. A fraction of discharged spent chrome liquor is directly mixed with the water of the River Buriganga, which causes serious environmental pollution; another fraction of chromium is settled out in the lagoon or adsorbed by sediment/soil. It is suspected that the adsorbed chromium could be eluted to groundwater in the tannery area, which could be a great threat in the near future. Practicing chromium recovery and reuse systems might be a good approach to make leather production environmental friendly, and consequently Bangladesh could save huge amounts of chemical costs.

Comparison of polyflavonoids in bayberry tanning effluent and commercial bayberry tannin: prerequisite information for vegetable tanning effluent recycling

Recycling system is capable to minimize the serious environmental issues in leather making. It also has the advantage of reducing chemical consumption and providing an efficient way to decrease the cost of leather manufacture. High chemical oxygen demand, bio-chemical oxygen demand and microbial toxicity are all considered as the characters of vegetable tanning effluent, however, only a few recycling technologies were developed. In this study, bayberry tanning effluent was obtained with a commercial bayberry tannin through a common vegetable tanning process, then the polyflavonoids in the bayberry tanning effluent and commercial bayberry tannin were characterized with Fourier translation infrared spectrum, matrix-assisted laser desorption/ionization time of flight mass spectrometry, nuclear magnetic resonance, gel permeation chromatography and an elemental analysis. The results showed that the flavanol subunit in the polyflavonoids of the bayberry tanning effluent was the same with the commercial bayberry tannin, however the differences of the polyflavonoids between the bayberry tanning effluent and commercial bayberry tannin were presented in the aspect of stereochemistry, molecular weight as well as the quantity of sulfonic acid group. Polyflavonoid in the bayberry tanning effluent was composed of cis isomers, while both cis and trans stereoisomers were found in the commercial bayberry tannin. Average molecular weight of the bayberry tanning effluent was 1130 Da, in contrast to an obviously higher value in the commercial bayberry tannin (2292 Da). Meanwhile, higher sulfonic acid group content was presented in the bayberry tanning effluent. These structural differences were deduced in accordance with the diversity of collagen binding activities of the polyflavonoids. For the first time, the polyflavonoids in vegetable tanning effluent were characterized, meanwhile, the structural differences between the polyflavonoids in tanning effluent and commercial tannin were found. The results can be applied on the development of the vegetable tanning effluent related recycling technology.

A salt-free and chromium discharge minimizing tanning technology: the novel cleaner integrated chrome tanning process

Chrome tanning is the most important and widely used tanning method in leather manufacture up to now. However, simultaneously control of the severe contamination of large amount of chromium and chloride discharge, both of which are serious environmental concerns, is highly challenging with the conventional chrome tanning process. Consequently, the development of leather manufacture is being unsustainable. In order to minimize the emissions of chromium and chloride integrately, a salt-free and high exhaustion chromium tanning method was designed and optimized in both laboratory and pilot scale. The results indicated that, being superior to the conventional process, the chrome tanning process was conducted in a salt-free condition smoothly and the chromium absorbility was increased to 98% from 73% in the novel process. Then the Cr dosage was minimized from 1.16% to 0.61% and the residual Cr concentration in the spent liquor dropped below to 50 mg/L from above 1100 mg/L. The pilot-scale experiments verified that the novel method was acceptable in the aspects of organoleptic and mechanical properties of resultant leather, product style and cost. It is anticipated that the spent liquor containing a very small amount of chrome and chloride can be more easily disposed and the generation of chromium-containing sludge will be stoichiometrical much less. The established novel chrome tanning process satisfactorily solves the longstanding problems commercially and matches the integral requirements of the modern sustainable leather industry.

Water-Soluble Graft Copolymer Synthesized from Collagenous Waste and Polyethylene Glycol (PEG) with Functional Carboxylic Chains: A Highly Efficient Adsorbent for Chromium(III) with Continuous Recycling and Molecular Docking Studies

A pragmatic pathway to zero emission is achieved by utilizing solid and liquid wastes completely by recycling and generating value-added auxiliaries from chrome shaving waste through process-intensified unit operations. Graft copolymer was synthesized from chrome shaving waste and polyethylene glycol (PEG), which is used as an adsorbent in the fresh chrome tanning process. The copolymer was characterized via thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, and particle size analyses. FT-IR results have been characterized, confirming that the presence of free functional carboxylic acid is involved in chromium adsorption. The application of 6% copolymer in chrome tanning showed 95.95% optimal adsorption of chromium in the first cycle and 98.90% optimal adsorption of chromium in the second cycle. 1H NMR investigation revealed a peak at 8.384 ppm (6% copolymer) in the experimental sample, confirming that the participation of free functional carboxylic acid groups plays a primary role in adsorbing chromium. Molecular modeling showed an increased adsorption of chromium and greater participation of ligand–copolymer with collagen, resulting in a docking energy of 3.9 kcal/mol through hydrogen bonding, establishing the spatial arrangement of the active functional groups. A mathematical model for the prediction of concentration of chromium adsorbed by the copolymer has been proposed. Scanning electron microscopy (SEM) and scanning electron microscopy coupled with energy-dispersive X-ray (SEM-EDX) studies confirmed an increase in the adsorption of Cr especially: 6.33 wt % of Cr (2.03 at. %) in samples containing 6% copolymer. Atomic force microscopy (AFM) studies from topography and deflection showed clear pictures of increased adsorption of chromium by the copolymer, indicated by the absence of chromium spots on the surface for the experimental samples.

Pilot-Scale Study on Masking Agents for Titanium Tanning

The many advantages offered by chrome tanning justify its widespread use for production of almost all types of leather. However, the traditional chromium (III) tanning process is constantly under threat from the pressure of legislation, and ever-tightening restrictions require to minimize chromium-containing effluents discharge and chromium-containing wastes production. Recently, the manufacture and use of chromium (III) free tanning agents compounds have been studied intensively. Among these, Titanium (IV)-based salts is one of the most promising substitutes.In this study, the use of titanyl sulfate as tanning agent for the production of high-quality bovine upper leather was investigated. In order to optimize the titanium tanning performances, a comparative evaluation, on pilot-scale, of citrate and lactate ions as masking agents was performed.The developed process has been validated through various analyses of the obtained crust leathers such as shrinkage temperature, scanning electron microscopy, and physical testing. The final leather obtained with the innovative method shows similar properties to those of the conventional tanned leather in terms of technical and mechanical properties.

Cleaner production of basic chromium sulfate – with a review of sustainable green production options

Ferrochromium and chromium based compounds are produced worldwide from chromite ore. Chrome chemicals are from chromium based compounds. Basic-chromium-sulfate (BCS) is a chrome chemical mostly required as main tanning agent in chrome tanning process in leather industry and also to synthesize other chromic compounds. During the preparation of basic-chromium- sulfate, sodium dichromate containing chromium (VI) is reduced to chromium (III) by sulfur-di-oxide in a packed tower at a chemical process industry (B&M Chemicals, India) where the BCS is produced at suboptimal efficiency due to inefficient (suboptimal) absorption of sulfur-di-oxide (as the gas enters the tower at a higher temperature) followed by reaction. Improper reduction leads to the presence of unconverted chromium (VI) that imparts toxicity, not only through product basic-chromium- sulfate but also through leather and articles produced using this chemical. Design and operating conditions of the packed bed absorber were found and effects of pH, temperature and concentration of SO2 on the performance of absorption were studied. The reaction is favored at pH 4. The overall efficiency of conversion in the tower is increased from 70% to 80% by operating the column at optimal operating conditions obtained using response surface method. Dispersion is achieved by random packing that provides complex countercurrent flow path resulting in greater probability of entraining gas inside the tower. Profiles of basic chromium sulfate are obtained along the height of the tower by solving mathematical models of the reactive absorption process. Chromium (VI) is 99% reduced to chromium (III) in the product. Leached residues and liquid wastes are treated with either ferrous sulfate or sodium sulfide to convert chromium (VI) to chromium (III) to provide sustainable technology. Treated solid waste is stored before safe disposal in hazardous landfill facility. As chromium (VI) is highly toxic, several sustainable methods are suggested to eliminate it from effluent to provide cleaner and sustainable production environment in the industry.

EFFICIENCY OF WASTEWATER TREATMENT PLANT IN THE PUNJAB TANNERY SECTOR: A CASE STUDY OF DADA TANNERY

Tanning industry of Pakistan contributes significantly towards foreign exchange earnings of the country. Growing concern of international buyers on environmental compliance, during tanning process, has forced this sector to install wastewater treatment plants to address the issue. This study aims to evaluate the performance of wastewater treatment plant (WWTP) of a local tanning industry. Raw wastewater showed high concentration of organic matter and Chromium. Phosphorous concentration was found deficient for satisfactory biological treatment. WWTP showed overall removal efficiency of 88.81, 84.54 and 62.31% for total suspended solids (TSS), five day biochemical oxygen demand (BOD) and chemical oxygen demand (COD), respectively. Whereas, the mean effluent concentrations of TSS, BOD and COD were 216 mg/L, 199 mg/L and 1023 mg/L, respectively. The effluent from WWTP exceeded the National Environmental Quality Standards (NEQS) for TSS, BOD and COD. It was due to the low concentration of Mixed Liquor Suspended Solids (MLSS) in aeration tank and low Phosphorous concentration in wastewater. NEQS limits for BOD and COD could be met by adding Phosphorous and increasing the MLSS in aeration tank

Multicriteria cost–benefit assessment of tannery production: The need for breakthrough process alternatives beyond conventional technology optimization

The worldwide use of chromium-based processes in tanneries generates increased concerns about their related environmental burdens. Cleaner production alternatives for leather production are being proposed, based on the optimization of specific aspects or criteria, for instance, reducing demand for specific materials and energy, or reducing local toxicological emissions. While improvement on individual characteristics of the process is certainly to be favored, a more comprehensive evaluation of alternatives is also needed to prevent the risk of shifting the burden to increase global load while addressing one specific critical factor of production. This work aims to discuss the importance of a multicriteria, multiscale approach to address cleaner production strategy costs and benefits. For this, materials balance, an economic approach, and emergy (with an “m”) accounting methods are applied to selected unhairing/liming, pickling/tanning and wastewater treatment steps in a tannery process, which was chosen as a case study. Results show that the assessed recycling cleaner production strategies assessed allow the manufacturer to reduce by one half the amount of water used and the demand for chemicals up to 4% with respect to the business-as-usual process, at the expense of increasing electricity demand by 10%. Economic cost-to-benefit ratio was 25$ benefits per 1$ invested, as well as an emergy-based cost-to-benefit of 33Em$ per 1Em$ invested, of course these improvements were limited to the three investigated process steps. The improvement in cost/benefit ratios indicates that converting scenario #0 into #1 is favorable under economic and emergy views. However, when the two scenarios are investigated from the point of view of the imbalance in local and renewable resource use versus imported and nonrenewable use, the emergy method shows a small overall increase in renewability (from 3.51% to 3.85%), a low, but expected, emergy yield ratio equal to 1, and a high environmental loading ratio (24.95 and 27.47). While the environmental cost–benefit ratio shows that recycling is a favorable option, the emergy performance indicators highlight that the efficiency of recycling is still insufficient and improvements in the tanning processes are needed to ensure renewability and sustainability. A number of process chemicals were involved in the investigated tannery operations, which required emergy evaluations. As a side result of this study, the Unit Emergy Values (UEVs) of SO2, H2SO4 Na2SO4, HCL, Na2S, NaOH, CaO, Ca(OH)2, Cr2O3, MnSO4, and Al(OH)3, were also calculated thus adding to the emergy database about chemicals.

Effets de la modernisation de tannerie sur l’impact de ses activités sur la qualité des eaux : cas de la tannerie de Maradi au Niger

The modernization of the tannery of Maradi had intervened in 2009 with the introduction of the process of tanning in the chromium. We estimated the influence of this change of operating process through an evaluation of the impact characteristics evolution of the solid and liquid discharges of this tannery on water. It stands out that the modernization of the tannery activities had more or less significant effects on these environment elements. We noted a relative improvement of the quality of underground waters illustrated by the regression of the content in chloride and nitrates rates stabilization. While the content in chromium evolved in a significant way as well as the pH. However, all the four above parameters remain below WHO standards. By cons, this modernization has almost not influenced the impact on the quality of surface waters. The values of BOD and COD have continued to rise despite the installation of a treatment system. Thus this surface water, including the pond, proved to be a major public health risk for domestic and agricultural use and is also a source of air pollution.

A novel function of bursicon in stimulation of vitellogenin expression in black tiger shrimp, Penaeus monodon

Abstract Bursicon is a cystine knot glycoprotein hormone that is composed of two subunits; alpha and beta. Bursicon plays several physiological roles in insects and crustaceans such as cuticle tanning, wing expansion and molting process. Because of its structural similarity with vertebrate gonadotropins, this study therefore aimed to investigate a novel function of bursicon in vitellogenin (Vg) stimulation in reproductive female shrimp, Penaeus monodon. Full-length cDNAs encoding the alpha and beta subunits of bursicon in P. monodon (Pmbursα and Pmbursβ) were obtained by rapid-amplification of cDNA ends. Both Pmbursα and Pmbursβ mRNA levels were dominantly expressed in subesophageal ganglia and thoracic ganglia. The expression of Pmbursα and Pmbursβ in subesophageal ganglia was significantly increased in early-vitellogenic stage of ovarian development suggesting a possible role of bursicon in vitellogenesis. To study the function of bursicon in shrimp reproduction, recombinant Pmbursα (rbursα), Pmbursβ (rbursβ) and Pmbursαβ (rbursαβ) were successfully expressed in the methylotrophic yeast, Pichia pastoris. A treatment of shrimp ovarian cells with recombinant Pmburs showed that only rbursαβ could induce the expression of Vg mRNA. In addition, injection of rbursαβ into female P. monodon broodstock caused an increase of Vg mRNA expression in the ovary as well as stimulated ovarian development. This study provides the first evidence for a reproductive role, most likely as an invertebrate neuropeptide gonad-stimulating hormone, of the heterodimeric bursicon in P. monodon. Statement of relevance Useful information for improvement of shrimp reproduction.

Processing of Leather Using Deep Eutectic Solvents

Processing of leather has an historical reputation as a chemically and energetically intensive process that produces large volumes of aqueous waste. Saline pollution combined with heavy-metal, dyes and acid and base streams make leather production an ecologically sensitive industry. The current study shows that a variety of deep eutectic solvents (DESs) may be used for the tanning, fatliquoring and dyeing of animal hides, being particularly useful for mineral (chromium) and vegetable tanning processes. The tanning agents are able to penetrate rapidly into the hide, driven by lyotropic swelling due to their high ionic strength. The samples are shown to have similar tanning agent content to the currently used aqueous chromium(III) sulfate solution; however, the waste metal content is shown to be significantly reduced. Incorporation of the DES Ethaline into the leather significantly alters the swelling properties of the leather increasing the flexibility and ductility of the material, therefore acting in the...

Integration of ion-exchange and nanofiltration processes for recovering Cr(III) salts from synthetic tannery wastewater

This study aims to investigate the possibility of integrating both ion-exchange (IX) and nanofiltration (NF) processes for the recovery of Cr(III) salts from a synthetic solution prepared with concentrations of Cr(III), and Cl− in the range of industrial effluents of tanneries. Ion exchange should be used as a pre-treatment for uptaking Cl− ions from the effluent, and thereafter the treated solution is fed to an NF unit to recover chromium sulphate salt for reuse in the tanning bath. The strong anionic resin Diaion PA316 was selected for evaluating chloride–sulphate ion-exchange equilibrium, with respect to mass of resin, NaCl concentration, temperature and ratio . It was observed that the separation factor, , depends on the total electrolyte concentration and the ratio plays a role as well. Moreover, it was determined that the resin prefers sulphate over chloride since is less than 1. The performance of the NF process is dependent on and the rejection of Cr(III) may decrease from 90% to 70% as the ratio increases from 0.5 to 2. Regarding the integration of both IX and NF, the feed solution after treatement with the resin was fed to NF where the ratio of led to the best operating conditions for this process (90% of Cr(III) rejection and up to 77% for ions). This strategy may be considered as a sustainable approach since it permits to obtain a solution enriched in Cr(III) salt for reuse in the tanning process, thus contributing to environmental protection.

Evaluation of a new sustainable continuous system for processing bovine leather

The aim of the present work is to evaluate a new sustainable continuous system for processing bovine leather. By means of a prototype described in the international patent WO, 2010/070571 (A2) of the technological centre AIICA, a dehydration process for bovine hides is carried out. What is obtained through this new process is a dehydrated leather with the optimal physical and chemical characteristics that will allow its subsequent tanning by immersion processes in aqueous solutions of chemical products. When compared to existing traditional processes, there are economic and environmental advantages resulting from the use of this new system. More specifically, the new process results in reductions of 30.6% in water use, 50.2% in chemical use and 16.4% in process time. In addition, a reduction of 27.3% in wastewater and a reduction of 47.5% of thermal energy consumption are obtained. However, this new system presents an increase in electricity consumption of 63.03% and an increase in gaseous emissions of 75% due to the use of acetone in the dehydration process and the 0.5% losses of acetone during the process.In order to better assess the environmental impact of this new tanning system, life cycle analysis methodology has been chosen to perform calculations on the Global Warming Potential (CO2 equivalent emissions) and the energy consumption comparing both traditional and new tanning processes.

Selective recovery of chromium ions from waste tannery solution for preparation of chromium oxide nanoparticles

This investigation seeks to reduce the envi- ronmental impact of the tanning process by recovering Ca and Cr from tannery waste solution. The treatment process reduces both the amount of Cr discharged to the environ- ment and the amount of raw Cr extracted from natural resources. The procedure was based on the selective separation of Ca ions from the waste solution as Ca ox- alate, prior to the recovery of Cr as the hydroxide pre- cipitate at pH 6.5. The dried Cr hydroxide cake was then subjected to heating (heating rate 0.5 C min -1 ) at differ- ent temperatures up to 500 C to produce Cr oxide nanoparticles. The physicochemical characteristics of the nanoparticles were investigated using X-ray diffraction, Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, surface area measure- ment and thermal analysis. Results revealed that heating of the treated Cr hydroxide at 300 C yielded amorphous Cr oxide, while with heating at 400 C, the Cr oxide started to crystallize to hexavalent, trivalent and divalent Cr species. At 500 C, a pure phase consisting of trivalent Cr oxide nanoparticles was formed that contained traces of hex- avalent Cr. A mechanism for the formation of the different forms of Cr oxide was proposed and confirmed by XRD.

Tanning facility wastewater treatment: Analysis of physical–chemical and reverse osmosis methods

The process of leather tanning produces harmful chemical and organic pollutants. This study explored physical and chemical treatment methods to efficiently treat the wastewater. Multiple wastewater streams representative of various stages in the tanning and wastewater treatment processes were initially characterized and subsequently treated through means of chemical coagulation and flocculation, adsorption, filtration and reverse osmosis. Through a series of jar test experiments, use of multiple industry-grade polymers as chemical coagulants greatly reduced chromium concentrations and turbidity levels. All samples had chromium levels below 5mg/L (below USEPA standards). A combination of the polyamine resins was the most effective at reducing chromium concentrations within a short settling period of less than 20min. Adsorption experiments utilizing titanium dioxide nanoparticles and activated carbon were conducted on the wastewater streams to determine chromium and nitrogen removal efficiency over a 24h period. Poor adsorption of chromium occurred for both the nanoparticles and activated carbon, the activated carbon was successful in reducing nitrogen levels to about 40%. Additionally, reverse osmosis was used to determine the effectiveness of removing pollutants of concern and to determine its ability to recycle and reuse the wastewater in the tannery processes. Results showed that RO treatment could be used to treat the wastewater to conditions similar to the potable water used. Having tested four different methods for wastewater treatment, the use of polymers as coagulants was the most successful at removal of chromium and improvement in clarity as a conventional method. However, as an alternative method, the reverse osmosis system proved the most successful due to the pristine quality of water produced, especially as a potential for reuse within the tanning facility and potentially a cost effective, sustainable option.

Removal of chromium from tanning wastewater and its reuse

The chromium (Cr) used in the manufacture of leather from hides has well-known adverse effects when inappropriately disposed in the environment. The tanneries use large quantities of water for processing hides. The recovery of Cr from the wastewater produced in the tanning step is an environmentally friendly and economically viable alternative avoiding the disposal of large amount of Cr-containing sludge in industrial hazardous waste landfills. This work aims at studying the removal of the Cr from the tanning wastewater through chemical precipitation (CP) and electrocoagulation (EC) techniques and its reuse in tanning process. In the CP experiments, efficient Cr removal from wastewater samples was achieved, with up to 99.74% removal efficiencies. In the EC experiments, three different electrode materials, Al, Cu, and Fe were tested. The highest removal efficiency of 97.76% was obtained with Al electrodes by conducting electrolysis at 3.0V for 110min. This was followed by Fe electrodes and Cu electrodes, which showed removal efficiencies of 90.27% (at 2.5V) and 69.91% (at 2.0V), respectively, for an electrolysis of 100min. The recovered Cr was reused as a tanning agent in leather processing, where good crossing of Cr was reached in leathers tanned with the liquors prepared from the sludge, and the pH and ash content values were measured. While the hides tanned with the Cr-containing liquor recovered by CP and by EC with Cu electrodes showed good hydrothermal stability and Cr content above 2.5% Cr2O3, the hides tanned with Cr-containing liquors recovered by chemical precipitation and by EC conducted with Fe and Cu electrodes showed contents of Cr according to technical specifications. However, the Cr samples obtained with the iron electrode showed a dark coloration due to oxidation of the iron. It can be concluded that the tanning process with Cr recovered by CP and by EC with Cu electrodes showed the best results.

Identification of impacts of stages and materials on life cycle of footwear

The environmental impacts caused by human activity, affects all productive and commercial activities that support the day to day. The products of massive consume such as footwear drive large impacts according to the materials and processes used for their manufacture. This paper present a literature review with the main aim to identify which are the phases and materials that cause greater environmental impacts to the environment, focusing on leather shoes. The results demonstrate that different authors reach similar results in terms of phases and high impact materials. The results permit change the current way of action and to focus the main efforts of research on tanning process.

Molecular and biochemical characterization of Paragonimus westermani tyrosinase.

Trematode tyrosinases (TYRs) play a major role in the tanning process during eggshell formation. We investigated the molecular and biochemical features of Paragonimus westermani TYR (PwTYR). The PwTYR cDNA was composed of 1568-bp encompassing a 1422-bp-long open reading frame (474-amino acid polypeptide). A strong phylogenetic relationship with Platyhelminthes and Deuterostomian orthologues was evident. The recombinant PwTYR expressed in prokaryotic cells promptly oxidized diphenol substrates, with a preferential affinity toward ortho-positioned hydroxyl groups. It demonstrated fairly weak activity for monophenol compounds. Diphenol oxidase activity was augmented with an increase of pH from 5.0 to 8.0, while monophenol oxidase activity was highest at an acidic pH and gradually decreased as pH increased. Transcription profile of PwTYR was temporally upregulated along with worm development. PwTYR was specifically localized in vitellocytes and eggs. The results suggested that conversion of tyrosine to L-dihydroxyphenylalanine by PwTYR monophenol oxidase activity might be rate-limiting step during the sclerotization process of P. westermani eggs. The pH-dependent pattern of monophenol and diphenol oxidase activity further proposes that the initial hydroxylation might slowly but steadily progress in acidic secreted vesicles of vitellocytes and the second oxidation process might be rapidly accelerated by neural or weak alkaline pH environments within the ootype.