Silver Recovery from Synthetic, Photographic and Medical X-Ray Process E?uents using Activated Carbon
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Minerals Engineering xxx (2005) xxx–xxx This article is also available online at: www.elsevier.com/locate/mineng
Silver recovery from synthetic photographic and medical X-ray process effluents using activated carbon
K.G. Adani, R.W. Barley *, R.D. Pascoe
Camborne School of Mines, School of Geography, Archaeology and Earth Resources, University of Exeter, Tremough Campus, Treliever Road, Penryn, Cornwall TR10 9EZ, United Kingdom Received 29 April 2005; accepted 24 May 2005
Abstract Adsorption of silver from synthetic photographic and spent fix solutions on granulated activated carbon in a batch process has been investigated. The synthetic solutions prepared had similar properties to medical X-ray and photographic process effluents. Sodium and ammonium thiosulfates are the major lixiviants used in the dissolution of silver halides present in photographic and medical X-ray films. The resultant solutions contain substantial amounts of recoverable silver complexes in the form of thiosulfates. The as received carbons were alkaline in nature when contacted with deionised water. These carbons showed very low silver recoveries. However, when these carbons were pre-treated with 0.5 mol/dm3 sulphuric and nitric acids at 25 °C, it had resulted in significant silver recoveries of 98.5% and 95% from sodium and ammonium thiosulfate solutions, respectively. These results were achieved in a narrow range of pH between 3 and 4. Batch atmospheric stripping of adsorbed silver by 2.0 mol/dm3 HNO3 at 85 °C was also investigated. Ó 2005 Elsevier Ltd. All rights reserved.
Keywords: Hydrometallurgy; Waste processing; Activated carbon; Silver
1. Introduction Reade discovered dissolution of silver halides in photographic fixing process using ammonium thiosulfate (ATS) and sodium thiosulfate solutions (STS) as fixing baths in 1837 (Eaton, 1965). Conventional fixing of AgX in photographic and medical X-ray films has been extensively used in the photo-industry for more than
Minerals Engineering xxx (2005) xxx–xxx This article is also available online at: www.elsevier.com/locate/mineng
Silver recovery from synthetic photographic and medical X-ray process effluents using activated carbon
K.G. Adani, R.W. Barley *, R.D. Pascoe
Camborne School of Mines, School of Geography, Archaeology and Earth Resources, University of Exeter, Tremough Campus, Treliever Road, Penryn, Cornwall TR10 9EZ, United Kingdom Received 29 April 2005; accepted 24 May 2005
Abstract Adsorption of silver from synthetic photographic and spent fix solutions on granulated activated carbon in a batch process has been investigated. The synthetic solutions prepared had similar properties to medical X-ray and photographic process effluents. Sodium and ammonium thiosulfates are the major lixiviants used in the dissolution of silver halides present in photographic and medical X-ray films. The resultant solutions contain substantial amounts of recoverable silver complexes in the form of thiosulfates. The as received carbons were alkaline in nature when contacted with deionised water. These carbons showed very low silver recoveries. However, when these carbons were pre-treated with 0.5 mol/dm3 sulphuric and nitric acids at 25 °C, it had resulted in significant silver recoveries of 98.5% and 95% from sodium and ammonium thiosulfate solutions, respectively. These results were achieved in a narrow range of pH between 3 and 4. Batch atmospheric stripping of adsorbed silver by 2.0 mol/dm3 HNO3 at 85 °C was also investigated. Ó 2005 Elsevier Ltd. All rights reserved.
Keywords: Hydrometallurgy; Waste processing; Activated carbon; Silver
1. Introduction Reade discovered dissolution of silver halides in photographic fixing process using ammonium thiosulfate (ATS) and sodium thiosulfate solutions (STS) as fixing baths in 1837 (Eaton, 1965). Conventional fixing of AgX in photographic and medical X-ray films has been extensively used in the photo-industry for more than
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