Leaching of Au, Ag, and Pd from waste printed circuit boards of mobile phone by iodide lixiviant after supercritical water pre-treatment

Abstract

a b s t r a c tPrecious metals are the most attractive resources in waste printed circuit boards (PCBs) of mobile phones. In this work, an alternative process for recovering Au, Ag, and Pd from waste PCBs of mobile phones by supercritical water oxidation (SCWO) pre-treatment combined with iodine-iodide leaching process was developed. In the process, the waste PCBs of mobile phones were pre-treated in supercritical water, then a diluted hydrochloric acid leaching (HL) process was used to recovery the Cu, whose leaching efficiency was approximately 100%, finally the resulting residue was subjected to the iodine-iodide leaching process for recovering the Au, Ag, and Pd. Experimental results indicated that SCWO pre-treatment temperature, time, and pressure had significant influence on the Au, Ag, and Pd leaching from (SCWO + HL)-treated waste PCBs. The optimal SCWO pre-treatment conditions were 420°C and 60 min for Au and Pd, and 410°C and 30 min for Ag. The optimum dissolution parameters for Au, Pd, and Ag in (SCWO + HL)-treated PCBs with iodine-iodide system were leaching time of 120 min (90 min for Ag), iodine/iodide mole ratio of 1:5 (1:6 for Ag), solid-to-liquid ratio (S/L) of 1:10 g/mL (1:8 g/mL for Ag), and pH of 9, respectively. It is believed that the process developed in this study is environment friendly for the recovery of Au, Ag, and Pd from waste PCBs of mobile phones by SCWO pre-treatment combined with iodine-iodide leaching process.

A novel reutilization method for waste printed circuit boards as flame retardant and smoke suppressant for poly (vinyl chloride)

“…The metals contents in the aqueous phase after SCWO treatment of waste PCBs were also determined and the results indicated that the major metals such as Cu, Pb, Sn, Ni, Fe, and Zn were not leached during SCWO process. According to previous studies [27][28][29], the resin material contained in waste PCBs could be effectively decomposed and removed by SCWO treatment, so the dominant ingredients in solid phase product after SCWO process were metals and glass fiber (e.g., SiO 2 ).…”

“…However, a large amount of toxic air pollutants were generated during the combustion process. Recent researches indicated that supercritical water oxidation (SCWO) treatment could solve this problem for the reason that the toxic organic matters in waste PCBs could be degraded safely in SCWO process and the formation of toxic air pollutants could be eliminated at the same time [27][28][29]. It's worth noting that the metals contained in waste PCBs can also be oxidized during SCWO process due to the reaction of oxidation atmosphere.…”

Direct extraction of palladium and silver from waste printed circuit boards powder by supercritical fluids oxidation-extraction process

“…When the supercritical fluid phase contacted with PMC, Pd and Ag in PMC could undergo oxidization and complexation on the interface with the I 2 -KI in the supercritical fluid, forming soluble halogen complexes (K[PdI 3 ] and K[AgI 2 ]) [39]. Through anion exchange, the complex anions of halogen complexes can react with protonated acetone ions (Eqs.…”

From E‐Waste to Nb‐Pb Co‐Doped and Pd‐Loaded TiO2/BaTiO3 Heterostructure: Highly Efficient Photocatalytic Performance

“…[4,5] Therefore, the recycling of e-waste has attracted much attentiona round the world. Some technologiess uch as mechanical-physical separation, [6,7] hydrometallurgy, [8] pyrometallurgy, [9] vacuum metallurgy separation, [10,11] bioleaching, [12] and supercritical water [13,14] have been appliedt ot he recycling of e-waste. More significantly,s ome researchers recently proposed an ew idea for preparing high-value-added functional materials from e-waste.…”