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Integrated Recovery Processes for Precious Metals from Urban Mine Sources and Case Studies
Published in Sadia Ilyas, Hyunjung Kim, Rajiv Ranjan Srivastava, Sustainable Urban Mining of Precious Metals, 2021
Sadia Ilyas, Hyunjung Kim, Rajiv Ranjan Srivastava
Ruthenium tetraoxides are then stripped to the gas phase and scrubbed with HCl in the distillation process. Ruthenium is precipitated from scrubbed solution as (NH4)2RuNOCl5 (ruthenium nitrosyl salt) and ignited to obtain pure ruthenium metal. The remaining metal-containing raffinate consists of Pt, Ir, and Rh. An increase in pH till 6 after ruthenium and/or osmium distillation will precipitate Rh and Ir as hydroxides. This slurry is filtered, boiled to eliminate excess acid, re-dissolved in demineralized H2O, oxidized and neutralized with alkali. Platinum is usually precipitated using NH4Cl to form ammonium hexachloroplatinate (NH4)2PtCl6. This salt is then ignited to form pure platinum metal (Crundwell et al., 2011; Sole et al., 2018; Fleming, 2002; Mpinga et al., 2015; Milbourne et al., 2003). The process is comprehensively illustrated in Figure 9.3.
Ultrasound assisted impregnation of platinum on carbon for ORR activity in PEM fuel cell
Published in International Journal of Ambient Energy, 2022
Rajesh Kumar Polagani, Mallappa Annarao Devani, Gara Uday Bhaskar Babu, Mahendra Chinthala, Kotaiah Naik Dhanavath, Shirish H. Sonawane
Recently, several researchers have developed different synthesis procedures to enhance the Pt utilisation as electrocatalyst in PEM fuel cells. Vaarmets et al. (2017) developed a versatile microwave-assisted synthesis method to prepare the Pt-nanoparticle and studied the effect of size, weight % of Pt, and pH of the deposition solution on the ORR activity of different carbon materials. Yang et al. (2016) established a novel one-pot hydrothermal synthesis method to produce the Pt nanocatalysts supported on carbon nanospheres with (Pt/CN-1) or without (Pt/CN-2) reducing agent (P123) utilising sucrose as carbon source. It was reported that Pt/CN-1 showed better ORR activity than the Pt/CN-2. Lee et al. (2012) dispersed Pt on carbon support using the modified polyol reduction method for PEM fuel cells as electrocatalyst. The obtained Pt/C catalyst with 40 wt. % Pt exhibited smaller particle size, higher active surface area, and superior performance than the commercial 40 wt. % Pt/C catalyst. Laurent-Brocq et al. (2014) synthesised 40% Pt (3 nm) nanoparticles uniformly distributed on carbon black using a novel low-temperature plasma method and studied the consequences of stirring effect, plasma power and duration, and Pt loading. Sharma et al. (2019) used microwave-assisted polyol synthesis to produce Pt/C (20 wt. %) catalysts from ammonium hexachloroplatinate and Chloroplatinic acid as precursors and compared the durability and ORR activities with commercial Pt/C. Nguyen et al. (2019) synthesised platinum nanoparticles with small size and narrow size distribution using the gamma-ray irradiation as a reducing agent and chitosan solution as a stabiliser. Show and Ueno (2017) obtained 4.1 nm Pt/C electrocatalyst with the in-liquid plasma method, which produced 216 mW/cm2 of peak power density in the fuel cell operation.