Finished leather waste chromium acid extraction and anaerobic biodegradation of the products |
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| Authors: | Maria J Ferreira Manuel F Almeida Sílvia C Pinho Isabel C Santos |
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| Institution: | 1. Centro Tecnológico do Calçado de Portugal (Portuguese Footwear Technological Centre), CTCP Rua de Fundões, Devesa Velha, 3700-121 São João da Madeira, Portugal;2. LEPAE, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal;1. Departamento de Ciências e Engenharia do Ambiente, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal;2. MARE – Marine and Environmental Sciences Centre, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal;1. Laboratory for Leather and Environmental Studies – LACOURO, Chemical Engineering Department, Federal University of Rio Grande do Sul, Brazil;2. Bacteriology Laboratory, Microbiology Department, Institute of Basic Health Sciences – ICBS, Federal University of Rio Grande do Sul, Brazil;1. Laboratory for Leather and Environmental Studies – LACOURO, Chemical Engineering Department, Federal University of Rio Grande do Sul, Porto Alegre, Brazil;2. Research Institute of Leather and Plastic Sheeting – FILK, Freiberg, Germany;3. Bacteriology Laboratory, Microbiology Department, Institute of Basic Health Sciences – ICBS, Federal University of Rio Grande do Sul, Porto Alegre, Brazil;1. The National Research & Development Institute for Textiles and Leather – Division Leather and Footwear Research Institute, 93 Ion Minulescu Str., Bucharest, Romania;2. University Politehnica Bucharest, Splaiul Independentei Nr. 313, Sector 6, RO-060042 Bucharest, Romania |
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| Abstract: | Due to the amounts of chromium in the leachate resulting from leather leaching tests, chromium sulfate tanned leather wastes are very often considered hazardous wastes. To overcome this problem, one option could be recovering the chromium and, consequently, lowering its content in the leather scrap. With this objective, chromium leather scrap was leached with sulfuric acid solutions at low temperature also aiming at maximizing chromium removal with minimum attack of the leather matrix. The effects of leather scrap dimension, sulfuric acid and sodium sulfate concentration in the solutions, as well as extraction time and temperature on chromium recovery were studied, and, additionally, organic matrix degradation was evaluated. The best conditions found for chromium recovery were leather scrap conditioning using 25 mL of concentrated H2SO4/L solution at 293 or 313 K during 3 or 6 days. Under such conditions, 30–60 ± 5% of chromium was recovered and as low as 3–6 ± 1% of the leather total organic carbon (TOC) was dissolved. Using such treatment, the leather scrap area and volume are reduced and the residue is a more brittle material showing enhanced anaerobic biodegradability. Although good recovery results were achieved, due to the fact that the amount of chromium in eluate exceeded the threshold value this waste was still hazardous. Thus, it needs to be methodically washed in order to remove all the chromium de-linked from collagen. |
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