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Energy - efficient noble metal recovery by the use of acid - stable nanomagnets / Michael Rossier in Industrial & engineering chemistry research, Vol. 49 N° 19 (Octobre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 19 (Octobre 2010) . - pp. 9355–9362 Titre : Energy - efficient noble metal recovery by the use of acid - stable nanomagnets Type de document : texte imprimé Auteurs : Michael Rossier, Auteur ; Fabian M. Koehler, Auteur ; Evagelos K. Athanassiou, Auteur Année de publication : 2010 Article en page(s) : pp. 9355–9362 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Metal  Nanomagnets Résumé : The present work investigates the potential use of metal-based carbon-coated magnetic nanoparticles for the efficient extraction of gold and platinum at high dilution (milligram to gram per ton ≡ ppb to ppm) at a mini-pilot level (0.1 m3). Acid-stable nanomagnets were first prepared by reducing flame synthesis and consisted of graphene-like carbon-coated cobalt metal nanoparticles (20−40 nm diameter) with an onion-like core/shell structure. The use of a metal core affords high saturation magnetization, while carbon shells are highly resistant to most chemical conditions. The nanomagnet surface was further coated with a standard noble metal extraction resin-like polymer (thiourea groups on a poly(ethylene imine)). Extraction runs were tested both at laboratory scale (0.1−10 L; Au and Pt removal > 95%; down to the milligram per ton level) and in a tank model (vertical tank section, 4 m height, 0.1 m3 volume, Pt removal > 80% at 50 mg/ton of acid water). Delivery of freshly dispersed nanomagnet dispersions onto the top layer of the tank model’s water zone (top 0.1 m) resulted in agglomeration and subsequent sedimentation through the tank model’s water column while simultaneously adsorbing platinum with an efficiency of 90%. At the bottom of the tank model, the nanomagnets could be efficiently collected through sweeping the tank model’s bottom surface with an array of permanent magnets. This process circumvents moving a tank’s liquid volume (energy costs for pumping) through conventionally used and time-consuming fixed-bed assemblies. In contrast, the presented process only moves a very small mass (<1 mass %) of the noble metal-containing volume and may therefore become an energy-efficient alternative to adsorption onto fixed beds or usually applied chromatography-type processes. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101117c [article] Energy - efficient noble metal recovery by the use of acid - stable nanomagnets [texte imprimé] / Michael Rossier, Auteur ; Fabian M. Koehler, Auteur ; Evagelos K. Athanassiou, Auteur . - 2010 . - pp. 9355–9362. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 19 (Octobre 2010) . - pp. 9355–9362 Mots-clés : Metal  Nanomagnets Résumé : The present work investigates the potential use of metal-based carbon-coated magnetic nanoparticles for the efficient extraction of gold and platinum at high dilution (milligram to gram per ton ≡ ppb to ppm) at a mini-pilot level (0.1 m3). Acid-stable nanomagnets were first prepared by reducing flame synthesis and consisted of graphene-like carbon-coated cobalt metal nanoparticles (20−40 nm diameter) with an onion-like core/shell structure. The use of a metal core affords high saturation magnetization, while carbon shells are highly resistant to most chemical conditions. The nanomagnet surface was further coated with a standard noble metal extraction resin-like polymer (thiourea groups on a poly(ethylene imine)). Extraction runs were tested both at laboratory scale (0.1−10 L; Au and Pt removal > 95%; down to the milligram per ton level) and in a tank model (vertical tank section, 4 m height, 0.1 m3 volume, Pt removal > 80% at 50 mg/ton of acid water). Delivery of freshly dispersed nanomagnet dispersions onto the top layer of the tank model’s water zone (top 0.1 m) resulted in agglomeration and subsequent sedimentation through the tank model’s water column while simultaneously adsorbing platinum with an efficiency of 90%. At the bottom of the tank model, the nanomagnets could be efficiently collected through sweeping the tank model’s bottom surface with an array of permanent magnets. This process circumvents moving a tank’s liquid volume (energy costs for pumping) through conventionally used and time-consuming fixed-bed assemblies. In contrast, the presented process only moves a very small mass (<1 mass %) of the noble metal-containing volume and may therefore become an energy-efficient alternative to adsorption onto fixed beds or usually applied chromatography-type processes. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie101117c

Scaling the long-term shear stability of aqueous pigment dispersions / Evagelos K. Athanassiou in Industrial & engineering chemistry research, Vol. 48 N° 19 (Octobre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 19 (Octobre 2009) . - pp. 8944–8949 Titre : Scaling the long-term shear stability of aqueous pigment dispersions Type de document : texte imprimé Auteurs : Evagelos K. Athanassiou, Auteur ; Hanspeter Gradischnig, Auteur ; Peter Siemsen, Auteur Année de publication : 2009 Article en page(s) : pp. 8944–8949 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : ShearPigment  dispersions Résumé : The industrial application of paints today involves the handling of millions of tons of pigment dispersions. Shear and mechanical stress during pumping, storage, or processing significantly affect color and shelf life. Currently, mainly empirical test series and pilot-scale process models are used to assess the stability of such dispersions and provide marginal guidance when developing or testing large-scale paint applications. Scaling the stability against shear stress is particularly important for water-based metal pigment dispersions where damage to the pigment flakes causes their deterioration. The present work investigates the scaling of shear stress from the production line (>1000 tons/yr) to laboratory scale (100-g scale). We analytically show why the integrated shear stress on a specific dispersion can be deconvoluted into a series of individual shear stress contributions. These individual contributions can be accurately reproduced in the laboratory using a Couette-type shearing setup similar to a classical rheometer. As a representative example, a stable and a shear-sensitive paint from an automotive production line was sampled over 4 months of production. The evolving deterioration, color changes, and dispersion instability could be accurately reproduced using the scaling method outlined here. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8017324 [article] Scaling the long-term shear stability of aqueous pigment dispersions [texte imprimé] / Evagelos K. Athanassiou, Auteur ; Hanspeter Gradischnig, Auteur ; Peter Siemsen, Auteur . - 2009 . - pp. 8944–8949. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 19 (Octobre 2009) . - pp. 8944–8949 Mots-clés : ShearPigment  dispersions Résumé : The industrial application of paints today involves the handling of millions of tons of pigment dispersions. Shear and mechanical stress during pumping, storage, or processing significantly affect color and shelf life. Currently, mainly empirical test series and pilot-scale process models are used to assess the stability of such dispersions and provide marginal guidance when developing or testing large-scale paint applications. Scaling the stability against shear stress is particularly important for water-based metal pigment dispersions where damage to the pigment flakes causes their deterioration. The present work investigates the scaling of shear stress from the production line (>1000 tons/yr) to laboratory scale (100-g scale). We analytically show why the integrated shear stress on a specific dispersion can be deconvoluted into a series of individual shear stress contributions. These individual contributions can be accurately reproduced in the laboratory using a Couette-type shearing setup similar to a classical rheometer. As a representative example, a stable and a shear-sensitive paint from an automotive production line was sampled over 4 months of production. The evolving deterioration, color changes, and dispersion instability could be accurately reproduced using the scaling method outlined here. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8017324