Tree transpiration-inspired 3D-printed wastewater processors with hybrid nanocellulose for a broad range of oil-based effluents

Abstract

The rise in industrial and domestic activities has led to increased oily wastewater generation and illicit discharge, posing a serious threat to clean water resources. Traditional water treatment methods, though scalable, consume fossil fuels and cause secondary pollution, necessitating safer, more efficient solutions. Here, we developed hybrid nanocellulose (HNC) inks by combining cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs) to fabricate advanced oily wastewater processors. These HNC inks enable 3D printing of tailored processor structures with high shape fidelity. By incorporating polydopamine (PDA) and chitin nanofibers (ChNFs), we created 3D-printed HNC scaffolds with exceptional hydrophilic-submerged oleophobicity and photothermal conversion properties. The HNC/PDA/ChNF (HAC) filter sheets achieved a 98.87 % separation efficiency and a high flux of 1646.96 L·m-2·h-1 for immiscible oil-water mixtures. For miscible mixtures, a 3D-printed C-HAC@HNC evaporator with a “bowl-shaped” layer achieved a 1.52 kg·m-2·h-1 evaporation rate and 96.61 % photothermal efficiency, excelling in oil-in-water emulsion treatment. It also demonstrated potential for seawater desalination and oily seawater purification, producing water that meets WHO drinking standards. This study offers innovative strategies for addressing critical challenges in water and energy resource management through efficient oily wastewater treatment.