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.
Highlights
Prosperity has increased worldwide, which is reflected in a strong rise in resource consumption
The polymer-assisted ultrafiltration (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
The feed solutions consisted of fly ash extract from KEBAG Zuchwil and HB-PEI at a final concentration of 4.6 g L−1, Partially (80%) ethoxylated polyethyleneimine (PE-PEI) at 4.7 g L−1, and modified polyethyleneimine (MOD-PEI) at 3.7 g L−1
Summary
Prosperity has increased worldwide, which is reflected in a strong rise in resource consumption. In order to extend the spectrum of available techniques, the application of polymer-assisted ultrafiltration (PAUF) for selective separation of Cu from fly ash extract was studied. This ultrafiltration technique is called polymer-enhanced ultrafiltration (PEUF), polymersupported ultrafiltration (PSU), liquid-phase polymer-based retention (LPR), and polymer filtration (PF) [14]. The selective enrichment and separation of Cu(II) from MSWI fly ash extracts by PAUF was investigated. PEIs were examined in laboratory-scale experiments with fly ash extracts from two MSWI plants Based on these results, the hydrodynamic behavior of hyperbranched PEI was studied in the operation of a membrane ultrafiltration pilot plant. The technical scale retention, enrichment, purification, and regeneration of Cu(II) was thoroughly investigated and is discussed
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