Two-dimensional membrane and three-dimensional bulk aerogel materials via top-down wood nanotechnology for multibehavioral and reusable oil/water separation

Abstract

Traditional oil/water separation materials can be divided into two types on the basis of their separation behavior: filtration materials (e.g., meshes, textiles, membranes, etc.) and absorption materials (e.g., sponges, foams, and aerogels). Both types of materials have advantages and disadvantages. Combining the filtration and absorption functions into one and the same material for oil/water separation applications presents a challenge. Prompted by the highly oriented porous structures and anisotropic architectures of wood and its hygro-responsive characteristic, two-dimensional (2D) membrane and three-dimensional (3D) bulk aerogel materials with water-responsive shape memory function, anisotropy, robustness, and superhydrophobicity are prepared using top-down wood nanotechnology for multibehavioral (absorption and filtration) and reusable oil/water separation. Wood aerogel is obtained by partially removing hemicellulose and lignin. Further, it is superhydrophobically treated using a polydimethylsiloxane (PDMS)/curing agent system. As-prepared wood aerogel/PDMS bulk materials possess high oil absorption capacity (about 20 g/g) and can be reused because of their fast water-responsive shape memory function. The prepared wood aerogel/PDMS membrane materials can efficiently separate oil/water mixtures with high separation efficiency (99.5%) and flux (around 2.25 × 104 L/m2·h) by only the driving force of gravity. Top-down wood nanotechnology is low-cost, facile, scalable, green, and efficient, exhibiting potential for application in multibehavioral oil/water separation and ability to handle industrial oily wastewater and oil spillage accidents.