Cleaner Pre-concentration of Metals from Printed Circuit Board Waste Using Novel Dense Liquid Medium Based on Sodium Silicate

A toolbox for improved recycling of critical metals and materials in low-carbon technologies

“…There is room for the application of this process with less hazardous liquids like sodium polytungstate, which is however expensive. Other liquids like sodium silicate 68 or some brines 69 can reach high densities and can potentially be used as a heavy media for density separation purposes, without the environmental burdens of halogenated solvents. There may be potential to use deep eutectic solvents (DESs) for this application, particularly with metal bromide salts.…”

Gravity Concentration in Urban Mining Applications—A Review

“…However, before conducting gravity separation, PCBs must undergo size reduction through shredding and/or grinding to ensure adequate material liberation. Previous studies have revealed that the liberation of most plastics occurs in the 2-5 mm size range [137][138][139], making it suitable for separation in dense media, jigs, or CCF separators. Conversely, achieving complete liberation of metals is challenging, even at micrometric sizes.…”

“…Subsequently, the latter was subjected to magnetic separation to yield a ferromagnetic concentrate and a copper-rich product with enrichment ratios (concentrate grade/feed grade) greater than six. On the other hand, due to the impracticality of using organic liquids in large-scale operations because of their high toxicity and costs, Rodrigues et al [138] explored the use of sodium silicate solutions (with a media density of up to 2.4 g/cm 3 ) for separating the metallic and non-metallic fractions of PCBs below 0.62 mm, obtaining results comparable to using chloroform as the separating medium.…”