Jovana Bošnjaković

This study reports the development, optimization and mechanistic evaluation of bio-based cellulose/lignin–tannin membrane adsorbents for the removal of representative inorganic and organic water pollutants: Cr(VI), Pb²⁺, difenoconazole (DFC) and bisphenol A (BPA). Waste cellulose fibers (wCF) from cigarette-package paperboard were converted into reactive membrane constituents by amino/ester and epoxy functionalization and subsequently cross-linked with epoxy-modified kraft lignin (EpKL), with or without tannic acid (TA), yielding wCF/EpKL and wCF/EpKL/TA membranes. Response surface methodology was used to optimize formulation parameters, while structural, morphological, and physicochemical analyses supported successful functionalization, cross-linking, and formation of porous, structurally modified surfaces. At 298 K, the Langmuir adsorption capacities of wCF/EpKL/wCF/EpKL/TA reached 85.37/88.78 mg g⁻¹ for Cr(VI), 155.6/163.9 mg g⁻¹ for Pb²⁺, 51.80/84.49 mg g⁻¹ for DFC, and 194.4/195.4 mg g⁻¹ for BPA, respectively. Isotherm, kinetic, and thermodynamic analyses indicated favorable, heterogeneous, and spontaneous adsorption involving specific surface interactions and diffusion-related contributions. Spectroscopy-supported mechanistic interpretation suggested that metal species are retained mainly through complexation with amino, phenolic, and oxygen-containing groups, together with electrostatic interactions, whereas DFC and BPA adsorption involves hydrogen bonding, hydrophobic interactions, and π–π interactions with lignin/tannin aromatic domains. Fixed-bed experiments confirmed the applicability of the membranes under continuous-flow conditions, while regeneration, stabilization/degradation, and soil-burial tests supported their potential within a more sustainable water treatment cycle. Overall, the results demonstrate that waste-derived cellulose/lignin–tannin membranes are promising regenerable sorbents for the adsorption of chemically diverse inorganic and organic pollutants.

The oxygen-evolving IrO₂-Ta₂O₅/Ti anode (OEA), primarily used in electrolyzers for plating, metal powder production, electrowinning (EW), and water electrolysis, is analyzed. This study focuses on the distribution of oxygen evolution reaction (OER) activity and the associated operational loss over the randomized OEA texture. The OER activity and its distribution across the IrO₂-Ta₂O₅ coating surface are key factors that influence EW operational challenges and the lifecycle of OEA in EW processes. To understand the OER activity distribution over the coating’s randomized texture, we performed analyses using anode polarization in acid solution at both low and high (EW operation relevant) overpotentials and electrochemical impedance spectroscopy (EIS) during the OER. These measurements were conducted on anodes in both their as-prepared and deactivated states. The as-prepared anode was deactivated using an accelerated stability test in an acid solution, the EW simulating electrolyte. The obtained data are correlated with fundamental electrochemical properties of OEA, such as structure-related pseudocapacitive responses at open circuit potential in the same operating environment. OER and Ir dissolution kinetics, along with the physicochemical anode state upon deactivation, are clearly characterized based on current and potential dependent charge transfer resistances and associated double layer capacitances obtained by EIS. This approach presents a useful tool for elucidating, and consequently tailoring and predicting, anode OER activity and electrolytic operational stability in industrial electrochemical applications.

The electrochemical performances of an oxygen-evolving anode produced by the reactivation of waste Ti substrate by a typical IrO₂-Ta₂O₅ coating are correlated to the textural (non)uniformities of the coating and its exhaustion state. Coating degradation is considered operational loss of the activity in a metal electrowinning process. It was found that (pseudo)capacitive performances can vary over the coating surface by 20–30% and depend on the type of dynamics of the input perturbation: constant through cyclic voltammetry (CV) or discontinuous time-dependent through electrochemical impedance spectroscopy (EIS). CV-EIS data correlation enabled profiling of the capacitive properties through the depth of a coating and over its surface. The correlation was confirmed by the findings for the analysis of coating activity for an oxygen evolution reaction, finally resulting in the reliable proposition of a mechanism for the operational loss of the anode. It was found that the less compact and thicker coating parts performed better and operated more efficiently, especially at lower operational current densities.