Monday, May 20, 2019
Impact of Leather Waste
1. 1. 1. Leather in debrisrial fade Prominent effectiveness of slash in spread outry is amplified by heights input and expenditure but on other side it causes huge pay off of re descent, undreamt environmental defilement and biological chain destruction 17. Streams of gaseous, liquid and red-blooded waste be resulted by environmental blow of tanneries. Global leather in spargery generates 4 million tones of unscathed waste per yr 18. People use products of the leather-processing persistence on a daily basis. These include especially shoes, leather and textile goods we normally encounter leather products regular in both public and private transport.The primary tender material for final products is pelt from animals from slaughter houses and brood from gamei. e. waste from the inwardness industry, which is processed in tanneries and turned into leather. Therefore, the tanning industry bum be considered one of the first industries to use and recycle unessential painfu l materials. Although the tanning industry is environmentally important as a principal user of meat industry waste, the industry is perceived as a consumer of resources and a producer of pollutants.Processing one measured ton of affectionate hide generates 200 kg of final leather product (containing 3 kg of atomic number 24), 250 kg of non-tanned solid waste, 200 kg of tanned waste (containing 3 kg of chromium), and 50,000 kg of sewer water (containing 5 kg of chromium) 1. Thus, only 20% of the raw material is converted into leather, and more than 60% of the chromium is in the solid and liquid waste. During the production of leather goods, especially shoes, manipulation waste is produced, whichmakes about 1520% of the entry materialleather.The last kinds ofwaste are employ leather products which have lost their avail value. 1. 1. The possibility of oxidisation of CrIII to CrVI The basic question is the possible oxidation reaction from chromium III to chromium VI. In basic sol utions, the oxidation of CrIII to CrVI by oxidants such as peroxides and hypohalide occurs with ease 2. Such strong oxidation conditions are realized in the process of the sterilization of drinking water. This is the first threat to human wellness and life.Rain (especially acid rain) can leach chromium III from waste dumps, and soluble salts can past reach sources of drinking water. During the sterilization process by ozone or hypochloride, chromium III is converted into chromium VI and reacts with magnesium and atomic number 20 ions occurring in drinking water to produce carcinogenic magnesium and calcium chromate or dichromate salts. Another problem concerns the possibility of oxidation of CrIII into CrVI in gentle conditions by air travel in the wide range of pH. Principally, oxidation can be realized after the following equationsharmonize to the European Commission (EC) the quantities of solid waste produced by tanneries depend on the type of leather processed, the source of hides and kowtows, and the techniques applied 2. On an average, at the end of the process, about 20% of the weight of the raw hides is (grain side) leather 2. On the other hand, in Rio Grande do Sul, or so 40% of the initial raw material is transformed into solid and liquid wastes 3. In the tanning industry, raw skin is transformed into leather by means of a series of chemical and robotic trading operations 4,5.Chromium salts (in particular, chromium sulfate) are the most widely used tanning substances today. Hides that have been tanned with chromium salts have a good mechanical resistance, an extraordinary color suitability and a better hydrothermal resistance in comparison with hides treated with plant substances. Chromium salts to a fault have a high rate of penetration into the inter fibrillar spaces of the skin, what represents a saving in price of production time and a better control of the process 6.In Brazil, virtually 90% of the leather industry uses chromium in hide processing, resulting in hazardous The formulaic tannery methods lead to discharge of solutions with chromium concentrations in the range of 15004000 mg/l. The specification for the discharge of chromium containing liquid wastes stipulates a range of 0. 32 mg/l 21. The tanning treatments to produce the wet blue leather yield soap containing approximately 3% (w/w) of chromium 9. The method commonly used for this waste disposal presents high operable costs.The production of chromium containing leather wastes (including chrome shavings and tanned splits) in leather industry has been recognized as a real problem for many years ref. The chromium leather wastes are generated principally during mechanical treatments carried out after tanning process. In this latter, chromium is bound with the collagen matrix, by cross linking with collagen carboxylic groups by coordinate covalent linkage 610. The final chemical structure of the waste illustrated in Eq. (1), is obtained through 2 chem ical phenomena olation and oxolation.As reported by numerous authors 612, the olation phenomenon is spy gradually with the increase of the alkalinity of the tanning medium. The olified intricate continues its evolution through time and an acid discharge takes place while the oxygen-chrome coordinate links are transformed into covalent links (oxolation bridges) Eq. The great stability of the collagenchromium complex produced makes the waste a non-biodegradable and cyanogenic material, due to the chromium and nitrogen content about 4. 3% and 14%, respectively 13,14.A huge amount of waste still goes into land disposal 15. Incineration in air atmosphere generates other forms of repose pollutant (gaseous emission and ashes) more noxious 1621 The solid wastes generated _presented in Table 1. from leather industry can be broadly classified as untanned collagenous, tanned collagenous and non-proteinous wastes. Among the tanned collagenous waste, the one resulting from the finish opera tion called buffing dust draws the most attention from the public and pollution control authorities.Buffing dust appears in a considerable proportion with processing of raw hides skins _i. e. 26 kg per ton of raw hides skins.. Buffing dust is a micro fined solid particulate impregnated with chromium, synthetic fat, oil, tanning featureors and sully chemicals. Buffing dust carries about 2. 7% chromium on dry weight basis. This is carcinogenic in nature and it causes clinical problems like respiratory tract ailments w1x, allergic dermatitis, ulcers, perforated impecunious septum, kidney malfunctions w2x and lung cancer w3x in humans exposed to the environment containing buffing dust particulates.Hence, it is cautioned by pollution control authorities to collect the buffing dust for safety disposal. The current practice of disposing of buffing dust consists of _i. incineration in incinerators, _ii. land co-disposal w412x. Incineration causes serious air pollution problems because o f release of toxic So and No gases w13x, and it has been observed x x that at 8008C, about 40% of Cr_III. is converted into Cr_VI. during the incineration of Cr laden solid waste w14x. The tanning industry is familiar with its being a potentially pollution-intensive industry. The nvironmental impacts from tanneries result from liquid, solid and gaseous waste streams. It must be emphasized that 4million tones of solid waste per year is generated by the global tannery industry 6. concord to the estimation of Sreeram et al. , about 0. 8 million tons of chromium tanned shavings are generated per year globally 7. The solid wastes from tannery industries whitethorn have significant Cr (III) content. Even though Cr (III) is viewed as not toxic, possible oxidation of Cr(III) to Cr(VI), due to the acid rains or incineration, threats the environment since Cr(VI) is a more toxic species.Therefore, the conventional disposal methods, land-filling and incineration, cannot be considered a solutio n to the disposal problem of tanned leather wastes in eco-friendly manner. In literature, there are many studies on the treatment of tanned leather wastes mainly including the extraction of chromium from wastes to re-use in the tanning process 8,9 and isolation of protein fractions 10,11. The tanning industry generates a huge quantum of liquid and solid wastes while producing finished leather.Tanning is the main process followed in leather manufacturing that protects the leather against some environmental effects such as microbial degradation, heat, sweat or moisture, etc 1. In tanning industry raw skins/hides are transformed into leather by means of a series of chemical and mechanical operations 2,3. The tanning process is usually accomplished in three distinct phases, i. e. , preparation of the raw fit stock to tan with tanning agents, tanning with mineral/vegetable tanning agents and post tanning to yield colour to finished leather.Basic chromium sulfate is the most widely used tanning agent for converting putrescible collagen fibres into non-putrescible leather matrix. Chrome tanned leathers have improved mechanical resistance, extraordinary dyeing suitability and better hydrothermal resistance in comparison with vegetable tanned leather. The solid wastes generated from leather industry can be broadly classified into untanned collagenous, tanned collagenous and non-proteinaceous wastes. Among the tanned collagenous waste, the one resulting from the cultivation operation is called chrome buffing dust (CBD).CBD is a micro fined solid particulate impregnated with chromium, synthetic fat, oil, tanning agents and dye chemicals. About 26 kg of CBD is generated as a solid waste per ton of skin/hide processed. CBD contains chromium, it is carcinogenic in nature and it causes clinical problems like respiratory tract ailments, ulcers, perforated nasal septum, kidney malfunction 4 and lung cancer 5 in humans exposed to the environment containing buffing dust parti culates. Hence, it is advised by pollution control authorities to collect the CBD for safe disposal.The current methods for disposing buffing dust are land codisposal and thermal incineration. disembark co-disposal method is not preferred for the reasons such as overall high pollution emissions and low expertness recovery. The leather industry generates a large amount of a Cr-containing solid waste (wet blue leather), with approximately 3% (w/w) of chromium. However, the leather industry has commonly been associated with high pollution due to the injurious smell, organic wastes and high water consumption caused during traditional manufacturing processes 2.Different forms of waste in quality and quantity, which emerge during the transformation of hides and skins into leathers in thousands of leather factories, from primitive to modern all around the world, have oppose impacts on the environment. According to the selective information received from the studies of several researche rs, approximately 200 kg of leather is manufactured from 1 tone of wet-salted hide 1-3. This amount constitutes about 20% of rawhide weight. More than 600 kg of solid waste is generated during the transformation of Raw hide into leather.That is to say, solid wastes containing protein and fat that constitute more than 60% of rawhide weight are addicted to the environment by leather factories without turning them to good use In other nomenclature, besides the 30-35m3 waste water disposed to environment during the processing of every 1 ton of rawhide in world leather industry, the data from FAO reveals that approximately 8. 5 million tons of solid waste is generated during the production of 11 million tons of raw hide processed in the world 4. strong wastes generated by the leather industry in these stages of processes may be classified as follows i. astes from untanned hides/skins (trimmings, fleshing wastes) ii. wastes from tanned leather (shaving wastes, buffing dust) iii. wastes from dyed and finished leather (trimmings from leather) information obtained from research reveals that 80% of solid wastes are generated during pre-tanning processes, while 20% of the wastes are caused by post-tanning processes Due to the bad smell they produce during their putrefaction and their harmful chemical content, untanned hide/skin wastes have negative effects on the soil and/or water resources of the environment where they are discharged, in other words n the local plant flora and animal fauna. Therefore, uncontrolled discharge of such wastes should be prevented without pickings adequate precautions. Legal arrangements gradually gaining speed all over the world enforce the leather industry to apply innovations in terms of reusing solid wastes generated during leather production processes such as fleshing, shaving, trimming and splits. Solid wastes create a major problem for leather industry in terms of both their smorgasbord and quantity.A high amount of reusable waste is generated in the leather industry. It is possible to recycle these products and even use them as raw materials for different industries 7. The variety and quantity of solid wastes depends on animal species, make conditions, slaughterhouse practices, conservation conditions, leather process stages, mechanical operations, qualification of the personnel, and chemicals used in processes. Yet this fact causes uncertainties in reusing the generated wastes.