"Biomass to Membrane": Sulfonated Kraft Lignin/PCL Superhydrophilic Electrospun Membrane for Gravity-Driven Oil-in-Water Emulsion Separation

Activated char embedded in biodegradable film for antimicrobials removal: Towards sustainable water purification

The development of sustainable materials toward efficient pollutant removal is crucial for water remediation. Following a waste-to-wealth approach, we report a novel preparation of biodegradable film embedded with a biomass-derived activated char and its effective application for the removal of fluoroquinolones from aqueous solutions. The presence of these antimicrobials contributes to the worrying increase of environmental antimicrobial resistance and ecotoxicity since they are emerging and harmful pollutants, and requires effective solution for their removal. The impact of different parameters on the sorptive performance was evaluated (e.g., type of polymeric support and char, amount of char), revealing that the removal process strongly depends on the type and amount of activated char used, whereas the polycaprolactone only acts as a support immobilizing the char and facilitating the sample treatment. By simply suspending the film in the aqueous sample, it is possible to adsorb the target contaminants, with removal efficiency up to 80 % in 240 min and satisfactory cumulative sorption capacity (Q up to 14,000 μg g-1) in competitive conditions. The sorption process obeys second-order kinetics in all the water samples tested (potable water, river water and wastewater). Notably, the film demonstrated continued stable removal capabilities over multiple uses (up to five). This work provides a new strategy for exploring a novel and efficient film for water purification.

Mitigation of Membrane Fouling in Lignin Recovery from Black Liquor via Surface-Patterned Ceramic Membrane

Among the various methods for recovering lignin from black liquor, membrane separation has gained prominence in the paper industry due to its advantages of uniform molecular weight distribution, high recovery rates, and absence of secondary pollution. However, over time, lignin particles tend to deposit and form a cake layer on the membrane surface, leading to membrane fouling and a decline in filtration flux. To address this issue, this study investigates the construction of ceramic membranes with radial rib patterns, and examines the effects of different trans-membrane pressure differences and radial rib patterns on membrane surface shear force and particle deposition. The research findings indicate that at a trans-membrane pressure difference of 0.5 bar and a blade rotation speed of 1000 r/min, the membrane surface experiences the highest shear force. Compared with those without patterns, ceramic membranes with radial rib patterns can more effectively delay the deposition of particles. Furthermore, it was observed that ceramic membranes combining coarse and fine rib patterns exhibit a more pronounced increase in membrane surface shear force.

Lignin and Nanolignin: Next-Generation Sustainable Materials for Water Treatment

Water scarcity, contamination, and lack of sanitation are global issues that require innovations in chemistry, engineering, and materials science. To tackle the challenge of providing high-quality drinking water for a growing population, we need to develop high-performance and multifunctional materials to treat water on both small and large scales. As modern society and science prioritize more sustainable engineering practices, water treatment processes will need to use materials produced from sustainable resources via green chemical routes, combining multiple advanced properties such as high surface area and great affinity for contaminants. Lignin, one of the major components of plants and an abundant byproduct of the cellulose and bioethanol industries, offers a cost-effective and scalable platform for developing such materials, with a wide range of physicochemical properties that can be tailored to improve their performance for target water treatment applications. This review aims to bridge the current gap in the literature by exploring the use of lignin, both as solid bulk or solubilized macromolecules and nanolignin as multifunctional (nano)materials for sustainable water treatment processes. We address the application of lignin-based macro-, micro-, and nanostructured materials in adsorption, catalysis, flocculation, membrane filtration processes, and antimicrobial coatings and composites. Throughout the exploration of recent progress and trends in this field, we emphasize the importance of integrating principles of green chemistry and materials sustainability to advance sustainable water treatment technologies.

Sustainable nanofibrous membranes for air filtration, water purification and oil removal

The increasing demand for sustainable solutions to address environmental and energy challenges has driven the development of advanced materials. Among them, nanofibrous membranes have emerged due to their high surface area, tunable porosity and versatile mechanical properties. However, traditional nanofibrous membranes, made from petroleum-based synthetic polymers, pose significant environmental concerns due to their non-biodegradability and reliance on fossil resources. This paper reviews recent advancements in the development of sustainable nanofibrous membranes, focusing on the use of biobased and biodegradable materials, and circular design approaches aimed at reducing environmental impact throughout the membrane life cycle. Challenges associated with improving the mechanical strength and stability of biopolymer-based nanofibers and expanding application areas are discussed. By highlighting strategies to overcome these limitations, this review aims to provide insights into the future direction of sustainable nanofibrous membranes, paving the way for their broader adoption in eco-friendly technological solutions.

Lignin- and Cellulose-Derived Sustainable Nanofiltration Polyelectrolyte Membranes

Nanofiltration (NF) polymeric membranes are typically made from fossil fuel-derived feedstocks and toxic solvents, requiring a shift to more sustainable materials. This study pioneers the use of two biopolymers-cationic lignin and sodium carboxymethyl cellulose-as polycation and polyanion, respectively, to fabricate a polyelectrolyte membrane (PEM) via the layer-by-layer method with water as the sole solvent and on a poly(ether sulfone) (PES) support. At a transmembrane pressure of 2 bar, the pure water permeance was 6 LMHB (L/m2 h bar) for 5 bilayers with a 96% rejection for positively charged methylene blue and 93% for negatively charged reactive orange-16, with a mass balance above 90%, indicating minimal adsorption on the membrane surface. The molecular weight cutoff (MWCO) of the PEM ranged from 300 and 620 Da, corresponding to a loose NF membrane. Additionally, the PEM demonstrated excellent stability after 30 days in deionized water, attributed to strong electrostatic interactions between the polyelectrolyte layers. This study demonstrates that effective NF membranes can be produced using sustainable biopolymeric materials and benign solvents. The efficient rejection of small, charged molecules makes the PEM membrane promising for protein removal, wastewater treatment, biotechnology, and pharmaceutical applications.

Research progress on biomass-based materials for oil/water separation: Designing strategy and efficiency mechanism

The treatment of water contaminated with oil or organic solvents has always been a thorny challenge, considering the complexity of water pollution, the susceptibility to secondary pollution and the consequent depletion of resources. Biomass is a versatile, green and self-circulating natural material that shows important potential in designing high-performance oil/water separation materials. This review highlights the recent research progress on biomass-based materials (BBMs) in the field of oil-water separation. Firstly, related properties for displaying definitions, sources and specificities on biomass materials are introduced, and the basic wetting theory of interfacial wettability is discussed. Secondly, representative nature-inspired designing strategies for oil-water separation materials are summarized. Finally, the current development prospects, future challenges and trends on BBM for oil-water separation are discussed as well. Hopefully, this review will provide some essential guidelines for the researchers to design novel oil/water separation materials with green, self-degradable, low-toxicity and readily available raw materials.

A Hydrogel-coated Wood Membrane with Intelligent Oil Pollution Detection for Emulsion Separation

Considering the potential threats posed by oily wastewater to the ecosystem, it is urgently in demand to develop efficient, eco-friendly, and intelligent oil/water separation materials to enhance the safety of the water environment. Herein, an intelligent hydrogel-coated wood (PPT/PPy@DW) membrane with self-healing, self-cleaning, and oil pollution detection performances is fabricated for the controllable separation of oil-in-water (O/W) emulsions and water-in-oil (W/O) emulsions. The PPT/PPy@DW is prepared by loading polypyrrole (PPy) particles on the delignified wood (DW) membranes, further modifying the hydrogel layer as an oil-repellent barrier. The layered porous structure and selective wettability endow PPT/PPy@DW with great separation performance for various O/W emulsions (≥98.69% for separation efficiency and ≈1000 L m-2 h-1 bar-1 for permeance). Notably, the oil pollution degree of PPT/PPy@DW can be monitored in real-time based on the changed voltage generated during O/W emulsion separation, and the oil-polluted PPT/PPy@DW can be self-cleaned by soaking in water to recover its separation performance. The high affinity of PPT/PPy@DW for water makes it effective in trapping water from the mixed surfactant-stabilized W/O emulsions. The prepared eco-friendly and low-cost multifunctional hydrogel wood membrane shows promising potential in on-demand oil/water separation and provides new ideas for the functional improvement of new biomass oil/water separation membrane materials.

An Innovative Surface Modification Technique for Antifouling Polyamide Nanofiltration Membranes

In this study, we developed a novel surface coating technique to modify the surface chemistry of thin film composite (TFC) nanofiltration (NF) membranes, aiming to mitigate organic fouling while maintaining the membrane's permselectivity. We formed a spot-like polyester (PE) coating on top of a polyamide (PA) TFC membrane using mist-based interfacial polymerization. This process involved exposing the membrane surface to tiny droplets carrying different concentrations of sulfonated kraft lignin (SKL, 3, 5, and 7 wt %) and trimesoyl chloride (TMC, 0.2 wt %). The main advantages of this surface coating technique are minimal solvent consumption (less than 0.05 mL/cm2) and precise control over interfacial polymerization. Zeta potential measurements of the coated membranes exhibited enhancements in negative charge compared to the control membrane. This enhancement is attributed to the unreacted carboxyl functional groups of the SKL and TMC monomers, as well as the presence of sulfonate groups (SO3) in the structure of SKL. AFM results showed a notable decrease in membrane surface roughness after polyester coating due to the slower diffusion of SKL to the interface and a milder reaction with TMC. In terms of fouling resistance, the membrane coated with a polyester composed of 7 wt % SKL showed a 90% flux recovery ratio (FRR) during Bovine Serum Albumin (BSA) filtration, showing a 15% improvement compared to the control membrane (PA). PE-coated membranes provided stable separation performance over 40 h of filtration. The sodium chloride rejection and water flux displayed minimal variations, indicating the robustness of the coating layer. The final section of the presented study focuses on assessing the feasibility of scaling up and the cost-effectiveness of the proposed technique. The demonstrated ease of scalability and a notable reduction in chemical consumption establish this method as a viable, environmentally friendly, and sustainable solution for surface modification.