Electrically-conductive microfiltration membranes effectively separate model proteins through selective electrosorption and release

Electrically conductive membranes (ECMs) have emerged as promising tools for fouling mitigation in recent years. In this work, we present a novel approach utilizing ECMs for the electrosorptive separation of proteins. However, the adsorption behavior of proteins at charged surfaces is complex and not solely governed by electrostatics. Hence, we predict interfacial forces and the strength of electrostatic interactions using XDLVO models and validate the calculations through adsorption isotherms under various degrees of double-layer screening. BSA and Lysozyme serve as model anionic and cationic protein, respectively. When a positive potential of +1 V vs. Ag/AgCl is applied, BSA adsorption increases by 113 % compared to the open circuit potential, while Lysozyme adsorption decreases by 73 %. Upon reversing the potential, we recover the electrosorbed proteins efficiently (up to 78 %) without active alteration of the mobile phase and with Lysozyme retaining > 82 % of its biological activity. The electrosorption of both proteins is reversible and the protein behavior closely linked to the surface charge. Separation factors can be modulated in favor of either protein by one order of magnitude during the adsorption and desorption phase, while the energy consumption remains below 5.9 x 10⁻² kWh g⁻¹ protein m⁻² membrane. This work highlights the mechanisms of protein electrosorption on ECMs and demonstrates their potential in adsorptive applications, offering a versatile and energy-efficient approach for selective protein binding.