Municipal Solid Waste as Secondary Resource: Selectively Separating Cu(II) from Highly Saline Fly Ash Extracts by Polymer-Assisted Ultrafiltration

Abstract

Urban mining from fly ash resulting from municipal solid waste incineration (MSWI) is becoming more and more important due to the increasing scarcity of supply-critical metals. Metal extraction from acid fly ash leaching has already been established. In this context selective Cu recovery is still a challenge. Therefore, our purpose was the separation of Cu(II) from MSWI fly ash extracts by polymer-assisted ultrafiltration (PAUF). We investigated three polyethyleneimines (PEIs) with regard to metal retention, Cu(II) selectivity, Cu(II) loading capacity, and the viscosity of the PEI containing solutions. A demanding challenge was the highly complex matrix of the fly ash extracts, which contain up to 16 interfering metal ions in high concentrations and a chloride content of 60 g L−1. Overcoming that, Cu(II) was selectively enriched and separated from real fly ash extract at pH 3.0. At pH 1.0, a PEI-free Cu(II) concentrate was obtained and PEIs could be regenerated for reuse in further separation cycles. The PAUF conditions developed at laboratory scale were successfully transferred to pilot scale, and hyperbranched PEI (HB-PEI) was found to be the most suitable reagent for PAUF in a technical scale. Moreover, HB-PEI enables photometric control of the Cu(II) enrichment.

Development and characterization of porous membranes based on PPSU/PES using polyethylene glycol as porogen: Application for cobalt removal by polyelectrolyte‐enhanced ultrafiltration

“…This result can be explained by a competitive adsorption between Na + and Co 2+ on polymer and the conformational change of the polymer chains. It is well known that polyelectrolytes interact with positively charged divalent metal ions more strongly than with monovalent ions 56 . With increasing salt concentration, the distribution of complexes is displaced to the formation of chloro complexes (PEI–Cl); therefore the formation of (PEI–Co) complex decreases.…”

“…It is well known that polyelectrolytes interact with positively charged divalent metal ions more strongly than with monovalent ions. 56 With increasing salt concentration, the distribution of complexes is displaced to the formation of chloro complexes (PEI-Cl); therefore the formation of (PEI-Co) complex decreases. As a result, the cobalt ions pass through the membrane leading to a lower retention of these ions (48%).…”

Special Issue on “Advanced Technology of Waste Treatment”

“…Based on an inventory of MSW incineration fly ash in Switzerland by Zucha et al [16], Weibel et al [17] studied metal recovery from these materials by acid leaching, whereas Wolffers et al [18] investigated co-leaching of MSW incineration fly ash and waste wood fly ash. These leaching processes yield aqueous solutions which are used by Hettenkofer et al [19] for copper recovery using polymer-assisted ultrafiltration.…”