Copper-Binding Properties of Polyethylenimine–Silica Nanocomposite Particles

Abstract

Increasing demand for copper resources, accompanied by increasing pollution, has resulted in an urgent need for effective materials for copper binding and extraction. Polyethylenimine (PEI) is one of the strongest copper-chelating agents but is not suitable directly (as is) for most applications due to its high solubility in water. PEI-based composite materials show potential as efficient and practical alternatives. In the present work, the interaction of copper ions with PEI−silica nanocomposite particles and precursor PEI microgels (as a reference) is investigated. It is hypothesized that the main driving force of the reaction is chelation of copper ions by amino groups in the PEI network. The presence of silica in the PEI−silica composites was shown to increase the copperbinding capacity in comparison with the parent microgel. The copper-binding behavior of etched (PEI-free "ghost") composite particles in comparison with the original composites and microgel particles shows that silica nanoparticles in the composite structure increase the number of copper-binding sites in the PEI network rather than adsorbing copper themselves. PEI−silica composites can be easily recycled after copper adsorption by simply washing in 1 M nitric acid, which results in complete copper extraction. Employing this recovery method, PEI−silica composite particles can be used for multiple, efficient cycles of copper removal and extraction.

Polyethylenimine–Silica–Magnetic Nanoparticle Composites for Efficient Extraction of Dissolved Copper from Aqueous Solutions and Multiphase Mixtures

“…Magnetic PEI–silica particles are expected to strongly bind copper and allow its complete extraction by soaking in 1 M nitric acid in the same way as their precursor, PEI–silica nanocomposites . These were benchmarked in detail against existing commercial- and research-grade materials for copper adsorption, indicating PEI–silica nanocomposites as prominently effective material. , Furthermore, the high level of magnetic response of the designed MC particles allows copper retrieval after dispersion in copper-containing mixtures, enabling copper extraction in a practical and effective recycling process that is schematically outlined in Figure A.…”

“…The quantity of bound copper q (binding capacity in mg g –1 ) was calculated according to the equation: q = ( C 0 − C e ) V m normalc normalo normalm where C 0 is the initial concentration of Cu(II) in solution in mg L –1 , C e is the equilibrium Cu(II) concentration in solution in mg L –1 , V is the sample volume in liters (L), and m com is the mass of the nanocomposite particles in the sample in grams (g). From the obtained copper-binding isotherms, values of the maximal binding capacity ( q max ) for each cycle were calculated according to the method described in previous work. , …”

“…For a comprehensive analysis of the process, results of each copper binding/extraction cycle were obtained as isotherms (binding capacity q versus equilibrium copper concentration C e ) in accordance with a procedure developed earlier. 30 The copper binding process was observed in two representative background solutions, chosen as the most relevant for the proposed application of MC particles in environmental remediation procedures. (1) Pure water without any intentional ionic strength and pH control, which would be representative of low or nonacidified pollution cases, and where PEI−silica particles, as any PEI-based materials, shift the pH level to 8−9.…”

“…(1) Pure water without any intentional ionic strength and pH control, which would be representative of low or nonacidified pollution cases, and where PEI−silica particles, as any PEI-based materials, shift the pH level to 8−9. 30 The 3 g L −1 concentration of the MC particles used in these experiments resulted in a pH of 8.4. (2) 0.1 M KNO 3 aqueous solution at pH 5 that is relevant to acidified contamination cases.…”

“…In the present study, magnetic PEI−silica nanocomposite microparticles (PEI−silica−magnetic nanoparticle composites) have been developed to obtain an efficient copper-binding material that is easy to disperse in, and then separate from typical aqueous mixtures. The presence of a silica network entwined with a PEI network at the nanoscale within this composite provides a maximum copper-binding capacity of around 55 mg g −1 at pH = 5 30 and necessary chemical and physical stability of the composite particles. 31 Entrapment of magnetite nanoparticles (MNPs) of size <35 nm within the composite matrix produces a strong magnetic response of the final material, in line with expectation.…”