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Ammonia Free Deliming Process in Leather Industry Based on Eco-Benign Products

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Ammonia Free Deliming Process in Leather Industry Based on Eco-Benign Products Journal of Scientific & Industrial Research Vol 74, September 2015, pp. 518-521 Ammonia free deliming process in leather industry based on eco-benign products V Sivakumar1*, C Ponnusawmy2, K Sudalaimani2, T Rangasamy3, C Muralidharan3 and A B Mandal2 *1Chemical Engineering Division, Council of Scientific and Industrial Research (CSIR), Adyar, Chennai – 600 020, India 2CSIRCentral Leather Research Institute (CLRI), Council of Scientific and Industrial Research (CSIR), Adyar, Chennai – 600 020, India 3Tannery Division, Council of Scientific and Industrial Research (CSIR), Adyar, Chennai – 600 020, India Received 28 August 2014; revised 7 June 2015; accepted 16 August 2015 Deliming is one of the most important unit operations in leather processing. Conventional deliming process employs ammonium salts which generates considerable amount of ammonia during the process, making tannery environment unhealthy. Therefore ammonia free deliming process is necessary in view of environmental concern. Even though ammonia free alternate deliming processes have been studied earlier, they have not yet provided commercial viability so for. Hence in this paper, ammonia free deliming process based on eco-benign natural products as developed by CSIR-CLRI has been presented. Studies involve analyzing their efficiency, process parameters, quality of leather produced and to develop a viable ammonia free deliming system. The results indicate that complete deliming could be achieved using this product. Physical testing results indicate that strength properties are on par with control process and pass minimum test requirements for shoe upper leather. Organoleptic properties and overall assessments indicate that leathers delimed with CSIR-CLRI AFD are on par with that of conventional leathers. Thus, CSIR-CLRI based AFD could provide alternative system as ammonia free deliming process, which is of great environmental and safety concern. Keywords: Deliming, Leather processing, Ammonia free, Natural products, Eco-benign processing. Introduction ammonia and also contribute significantly to total Deliming is one of the important unit processes in Kjeldahl nitrogen (TKN) as reported by UNIDO4. leather making, carried out in order to remove the There is a significant reduction in both ammonia lime from the pelt. It is a process of neutralizing concentration and TKN in deliming sectional stream lime1. The objectives of deliming are of wastewater due to ammonia free systems, suitable for biological wastewater treatment methods as Removing the bound lime reported earlier: Ammonia liberated as (Kg/t raw hide) Lowering the pH, in preparation for bating for Ammonia free systems (AFS) is 0.070 as compared De-swelling the pelt, partially reversing the swelling to 2.69 for the conventional ammonium salts (AS) based If the pelts are not delimed and the limed pelts are systems. Similarly ammonia in waste water is 58 ppm directly introduced to vegetable tanning liquor, lime for AFS as compared to 2243 for AS. Whereas, TKN present in the pelt will react with vegetable tanning (Kg/t raw hide) another important parameter is 0.61.5 and produce calcium tannate. This is the precipitate for AFS as against 2.63.9 for AS process. which will deposit at the surface of the pelt to produce grain cracking. In case of chrome tanning, basicity of Liberation of ammonia in Ammonium salts based chrome liquor will go high and will be precipitated in deliming the bath itself. Conventional deliming is based on Use of ammonium chloride as deliming agent ammonium salts in which significant amount of While ammonium chloride is used as deliming ammonia is liberated which is of great environmental agent, it neutralizes the lime to produce calcium as well as health concern. Typical characteristics of chloride; the process involved is represented below wastewater generated from leather processing units Ca (OH)2 + NH4Cl are given elsewhere2-4. Ammonium salts based CaCl2 + NH3 + H2O … (1) deliming systems generate significant quantities of In the above reaction calcium chloride formed is ________________ Author for correspondence completely soluble in water. E-mail: [email protected] When ammonium chloride used as deliming agent SIVAKUMAR et al.: AMMONIA FREE DELIMING PROCESS IN LEATHER INDUSTRY 519 empty type of leather is produced. case of skins. Initial pH of the bath was found to be around 3.0 after the addition of the product with 100% Use of ammonium sulphate as deliming agent float. Amount of wastewater generated in conventional When it is used for deliming purpose it reacts with leather processing for converting raw hides in to calcium hydroxide produces calcium sulphate. The finished leather is ~40 L/kg as reported earlier4; this reaction involved is given below, value may not alter in the new process as our main (NH4)2SO4 + Ca (OH) 2 focus here is ammonia free deliming system. Similarly CaSO4 + 2NH3 + 2H2O … (2) this new process may have very little role in solid waste generated/Kg of hides, which is not unexpected. This ammonia liberated during the process lead to worker’s exposure to high concentration of ammonia Materials and Methods gas while opening the drum during or after deliming Five pieces of wet salted Goat skins (of weight process. This would also lead to prevalence of range 1.5- 2 Kg) were taken for the experimental ammonia in and around the tannery premises. trials and marked as (I, II, III) for different Environmental and health hazards associated with experiments with various additives for AFD ammonia (I: Sodium sulfite, II: poly ethylene glycol, III: sodium Based on the reports of National Institute for meta bisulfite) and IV control respectively as shown in Occupational Safety and Health5 (NIOSH) with regard Table 1. Commercial grade chemicals were used for to ammonia in work places, OSHA's former exposure the processing of leathers from raw to full chrome limit for ammonia was 50 ppm as an 8-hour Time upper leathers. Phenolphthalein indicator solution (AR) weighted average (TWA). OSHA proposed to revise this was procured from SD fine chemicals pvt. Ltd., India for checking the completion of deliming process. limit to 25 ppm TWA and to add a 35-ppm 15-minute Short-term exposure limit (STEL), based on the limits Deliming efficacy established by the American Conference of Deliming efficacy of different systems (I-IV) were Governmental Industrial Hygienists (ACGIH). Exposure ascertained by total absence of pink colour in the limit values and Health factor associated with Ammonia cross section of the pelt upon addition of gas are given by OSHA, US Department of Labor5. phenolphthalein indicator solution, which indicates Toxicity of ammonia has also been studied earlier6. completion of deliming process. Earlier reports on Ammonia free deliming (AFD) Strength property analysis AFD agents such as use of organic acids7, epsom Physical testing of leathers were carried out by salts8, carbon-di-oxide9 gas, Sulfonated Phthalic adopting SLTC official method of analysis13. Strength Magnesium Salt10, Infusion from Leaf of Hibiscus characteristics of the dyed leathers such as tensile Sabdariffa11 were attempted earlier. However, they strength13 (SLP6; IUP/6) and tongue tear strength could not able to provide successful ammonia free (Satra; TM-30)14 were tested using an Instron tensile deliming system, due to their certain limitations either tester and grain crack and distension (Satra; TM-24)14 in the process, operational difficulties, availability or were tested using lastometer. Leather samples for the environmental problems associated with the same. physical testing were taken parallel to backbone from Therefore, there is a need for the developments of the leather samples following the IUP/1 procedure for viable ammonia free deliming system in leather sampling and testing15. Colour fastness to circular processing based on replenish-able eco-benign rubbing both dry as well as wet method was also materials. CSIR-CLRI has developed such an AFD carried out (Satra; TM-8). Then the strength product for application in leather industry12. properties were compared with those values for full chrome upper leather as per the Indian standards IS: CSIR-CLRI Ammonia free deliming product 578, year-1985. AFD used in the present study is a CSIR-CLRI 12 Patented product derived from natural replenish-able Organoleptic properties material which is non toxic. The key ingredient of the Organoleptic properties of the final leathers were product is Gallic acid (3,4,5-Trihydroxybenzoic acid). assessed for different parameters such as Softness, Around 1% (% w/w based on fleshed wt.) of the Fullness, Grain tightness, Dyeing characteristics and product was sufficient to achieve complete deliming in overall assessment was made through a Senior 520 J SCI IND RES VOL 74 SEPTEMBER 2015 Table 1- Process recipe for ammonia free deliming process involving various steps for making shoe upper leather Process step Chemicals (%) Process Time and Details Soaking Water – 300% 6 hours in pits Soaking was done with three changes of water, finally washing was done. Liming Water - 300% + Lime – 8% Next day, unhairing + Sodium sulphide – 3% Left for 4 days in pits Then fleshing and scudding; then pelt weight was taken. Washed in drum Deliming* (Ammonia free and Control) Water – 100% + AFD product (I-III) (OR) Drumming for 45 minutes Ammonium chloride (IV)– 1% Completion of deliming was verified using phenolphthalein indicator. Then Draining out, washing. Chrome tanning Pickle water – 50% (% based on pelt wt.) + BCS – 4% 45 min. + BCS – 4% 30 min. + Sodium Formate – 0.5% 2 * 10 min. + Sodium bicarbonate – 1% 3 *10 min + 45 min. Then the chrome tanned leathers were piled over night, next day, semi dried, shaved to 1 mm thickness and shaved weight was recorded. Shaved leathers were washed in plain water and taken for Neutralization. Neutralization (% based on shaved wt.) Water – 100% + Sodium formate – 1% 30 min. + Sodium bicarbonate –0.5% 3 * 10 min. pH at cross section – 5.5 Washing was done. Retanning, Dyeing, Fatliquoring (% Water – 100% based on shaved wt.) + Relugan RE – 4% 30 min. + Basyntan DI – 4% 45 min.
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