Impact of Leather Waste

1. 1. 1. Leather industrial brag Prominent effectiveness of lash sedulousness is amplified by heights up input and expenditure but on other side it causes big exorbitance of resource, incredible environmental befoulment and biological chain desolation 17. Streams of gaseous, liquid and unhurt nullify argon directed by environmental brag of tanneries. Global lather industry generates 4 one thousand thousand net tones of solid lavishness per year 18. People use products of the welt- makeing industry on a insouciant basis. These include especially shoes, whip and textile goods we normally encounter whip products even in both public and private transport.The primary b argon-ass material for final products is embrace from carnals from slaughter houses and hide from gamei. e. liquidate from the meat industry, which is processed in tanneries and turned into leather. Therefore, the whipstitch industry tail end be considered one of the first industries to use and re cycle secondary young materials. Although the flagellation industry is environmentally important as a mind user of meat industry dissolution, the industry is perceived as a consumer of resources and a breakr of pollutants.Processing one metric ton of blunt hide generates 200 kg of final leather product (containing 3 kg of atomic number 24), 250 kg of non-tanned solid neutralise, 200 kg of tanned waste (containing 3 kg of chromium), and 50,000 kg of wastewater (containing 5 kg of chromium) 1. Thus, except 20% of the naked material is converted into leather, and more(prenominal) than 60% of the chromium is in the solid and liquid waste. During the output signal of leather goods, especially shoes, treatment waste is produced, whichmakes about 1520% of the entry materialleather.The closing kinds ofwaste argon used leather products which micturate lost their utility value. 1. 1. The porta of oxidization of Cr triple to CrVI The basic question is the possible oxidation r eaction from chromium III to chromium VI. In basic solutions, the oxidation of CrIII to CrVI by oxidants much(prenominal)(prenominal) as peroxides and hypohalide occurs with ease 2. Such strong oxidation conditions are recognise in the process of the sterilization of drinking water. This is the first threat to human being health and life.Rain (especially acid rain) wad leach chromium III from waste dumps, and soluble salts can then 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 calcium ions occurring in drinking water to produce carcinogenic magnesium and calcium chromate or dichromate salts. Another task concerns the possibility of oxidation of CrIII into CrVI in gentle conditions by air in the wide range of pH. Principally, oxidation can be realized aft(prenominal) the following equationsAccording to the European Commission (EC) the quantities of solid wast e produced by tanneries depend on the type of leather processed, the source of hides and skins, 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, round 40% of the sign raw material is transformed into solid and liquid wastes 3. In the tanning industry, raw skin is transformed into leather by center of a series of chemical and mechanised operations 4,5.Chromium salts (in particular, chromium sulfate) are the to the highest degree widely used tanning substances today. Hides that have been tanned with chromium salts have a good mechanical resistance, an extraordinary dyeing suitability and a better hydrothermal resistance in relation with hides treated with name substances. Chromium salts also have a high rate of discernment into the inter fibrillar spaces of the skin, what represents a saving in terms of drudgery epoch and a better control of the process 6.In Brazil, approximately 90% of the leather industry uses chromium in hide processing, resulting in waste The conventional tannery manners 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 puritanic leather yield sludge containing approximately 3% (w/w) of chromium 9. The method commonly used for this waste giving medication presents high operational 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 an(prenominal) age ref. The chromium leather wastes are generated principally during mechanical treatments carried out subsequently tanning process. In this latter, chromium is bound with the collagen matrix, by cross linking with collagen carboxyl groups throu gh coordinate covalent linkage 610. The final chemical mental synthesis of the waste illustrated in Eq. (1), is obtained through two chemical phenomena olation and oxolation.As account by numerous authors 612, the olation phenomenon is observed gradually with the increase of the alkalinity of the tanning medium. The olified Byzantine continues its evolution through time and an acid discharge takes place art object the oxygen-chrome coordinate links are transformed into covalent links (oxolation bridges) Eq. The massive stability of the collagenchromium complex produced makes the waste a non-biodegradable and cyanogenic material, collectible to the chromium and nitrogen content about 4. 3% and 14%, singly 13,14.A large amount of waste still goes into land disposal 15. Incineration in air atmosphere generates other forms of residual pollutant (gaseous emission and ashes) more noxious 1621 The solid wastes generated _presented in Table 1. from leather industry can be broadly cl assified as untanned collagenic, tanned collagenous and non-proteinous wastes. Among the tanned collagenous waste, the one resulting from the finishing operation called buffing dust draws the most attention from the public and defilement 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 little fined solid particulate impregnated with chromium, synthetic fat, oil, tanning movers and dye chemicals. Buffing dust carries about 2. 7% chromium on dry weight basis. This is carcinogenic in nature and it causes clinical problems alike respiratory tract ailments w1x, allergic dermatitis, ulcers, perforated nasal septum, kidney malfunctions w2x and lung genus 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 reading of dispo sing of buffing dust consists of _i. incineration in incinerators, _ii. land co-disposal w412x. Incineration causes serious air pollution problems because of drop off 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. According to the union of Sreeram et al. , about 0. 8 million wads of chromium tanned shavings are generated per year globally 7. The solid wastes from tannery industries may 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 environ ment since Cr(VI) is a more toxic species.Therefore, the conventional disposal methods, land-filling and incineration, cannot be considered a solution 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 master(prenominal)ly 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 do 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 live stock to tan with ta nning agents, tanning with mineral/ veggie tanning agents and post tanning to impart colour to finished leather. introductory 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 finishing 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 res piratory tract ailments, ulcers, perforated nasal septum, kidney malfunction 4 and lung cancer 5 in humans exposed to the environment containing buffing dust particulates. 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. Land co-disposal method is not preferred for the reasons such as overall high pollution emissions and low energy 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 bad smell, organic wastes and high water expenditure caused during traditional manufacturing processes 2.Different forms of waste in quality and quantity, which emerge during the chassis of hides and skins into leathers in thousands of leather factories, from primitive to modern all aro und the world, have negative impacts on the environment. According to the data received from the studies of several researchers, 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 disposed to the environment by leather factories without turning them to good use In other words, 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. Solid 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) data 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 perverting chemical content, untanned hide/skin wastes have negative cause 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 taking adequate precautions. sub judice 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 study problem for leather industry in terms of both their variety 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 varied industries 7. The variety and quantity of solid wastes depends on animal species, breeding 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.