Removal of sulfide-bound copper from white wine by membrane filtration

Sulfide-bound copper (Cu) in wine may act as a potential source of hydrogen sulfide. The aim of this study was to understand how the white wine matrix can influence the filterability of sulfide-bound Cu. Methods and Results: Sulfide-bound Cu was formed in situ with addition of copper(II) sulfate and sodium sulfide to white wine and model wines. The amount of subsequent Cu passing through membrane filters was measured by flame atomic absorption spectroscopy or inductively coupled plasma with optical emission spectroscopy. Nanoparticle tracking analysis was utilised to measure the size of particles generated after copper (II) and sulfide addition. The majority of the particles were around or below 0.2 μm, and polyethersulfone and nylon membranes remove up to 40-90% of sulfide-bound Cu from white wine. The regenerated cellulose, Teflon and glass fibre membranes removed minimal sulfide-bound Cu. Conclusions: Membrane filtration removed sulfide-bound Cu by adsorption rather than by particle size discrimination. Polysaccharides and proteins were the components of white wine that most inhibited adsorption. Significance of the Study: The addition of copper(II) to wine with hydrogen sulfide results in products that cannot be removed by filtration on the basis of their particle size but instead may be partly removed by adsorption onto membrane filters to an extent impacted by the wine composition and the filtration medium.