No abstract

This work examines the leaching of printed circuit boards (PCBs) from cell phones in aqueous solutions containing HF + H 2 O 2 or HF + NaClO under mild experimental conditions. The PCBs were not ground but were previously treated with 6 mol L -1 NaOH at 50 o C for 1 h to remove their soldering mask. , respectively. The processing of the solid residue is also described in detail. It was leached with water at ~90 o C followed by HNO 3aq. at 25 o C. Lead, palladium and silver were recovered in this order, leaving gold as final solid. After 1 h at [35][36][37][38][39][40] o C, 5 mol L -1 HF + 0.3 mol L -1 NaClO mixtures leached the base metals, copper, gold and palladium. Gold was recovered by liquid-liquid extraction with methyl isobutyl ketone. Silver precipitated as chloride. This salt was isolated by leaching with NH 3aq . Loss of fluoride ions (as HF) was below 0.5 wt.% after leaching and handling the solid residue.

this work describes a route for recovering nickel, cobalt, iron, zinc and lanthanides from spent nickel-metal hydride batteries. Formic acid was used as leachant. Experiments were run at 25-50°C for 1-4 h. Under the best conditions leaching yields surpassed 99 wt.%, except for iron. The insoluble matter contains almost solely iron as iron(III) basic formate. The leachate went through six separation procedures, combining solvent extraction with D2EHPA as extractant, and precipitation reactions. Fe2+ and Zn2+ were extracted together (> 99 wt.%) from the original leachate (pH ~1.5). Yttrium and lanthanides were precipitated as oxalates directly from the raffinate (> 99.9 wt.%) upon addition of sodium oxalate. In the next steps, Mn2+ and Co2+ were extracted with D2EHPA at buffered pH (3 and ~4.8, respectively), after adding NaOHaq. About 10 wt.% of leached Ni2+ was coextracted with Co2+. The remaining Ni2+ was precipitated from the raffinate after addition of aqueous sodium oxalate at pH 6. After precipitation of Al3+ upon addition of NaOHaq. until pH ~8, sodium formate was recovered after slow evaporation of the final aqueous solution at 60oC. It contains ~90 wt.% of the formate present in the leachant.