Preparation and performance of a novel composite as a reactive resin for copper retention

A novel magnetic nano-resin was fabricated by supporting nickel hexacyanoferrate on Fe3O4 nanoparticles and immobilizing them within PAN matrix. The prepared composite was characterized using FTIR, TG–DTA, XRD, SEM and BET-N2 measurements. The textural properties indicated the existence of slit-shaped pores and showed larger pores formed between plate-like particles. FTIR analysis suggested the presence of both hexacyanoferrate (II) and hexacyanoferrate (III) anions in the nano-composites. Further, data clarified a typical face-centered cubic structure with the molecular formula K2Ni[Fe(CN)6]·3H2O. The resins were relatively fine, homogeneous with presence of little irregular clusters and had 15–25 nm average size. The kinetics of copper retention followed pseudo-second-order expression with k2 values 3.81 × 10−5 g mg−1 min−1. Copper sorption was pH-dependent and qmax was attained at pH 6.0 suggesting sorption by single Cu2+ species through molar exchange with either H+ or K+ ions at low pH values. In neutral solution, Cu2+ ions were retained by surface complexation besides ion exchange and hydrogen bonding interactions, while precipitation was the relevant mechanism taking place in basic medium. Intra-particle diffusion played a significant role at the initial stage of sorption and presence background electrolyte significantly reduced Cu2+ removal. Freundlich model appropriately described the removal of Cu(II) through a favorable sorption process.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Nickel hexacyanoferrate loaded on nanoscale iron ferrite was synthesized. ► The nano-resins had homogeneous geometric shapes with 15–25 nm average size. ► Copper removal was attained through participation of different mechanisms. ► The background electrolyte played a significant role in the extent of sorption. ► Copper was retained through reversible process forming multi-linear formations.