Fabrication Of Wood-based Filter Loaded With Ag Nanoparticles And Its Performance In Wastewater Treatment

With the rapid development of modern industry,water pollution has become one of the most serious environmental problems facing the world.Wastewater from the chemical industry and daily life often contains insoluble oils and water-soluble contaminants like organic dyes.High-performance functional materials capable of simultaneously separating oil from water and removing water-soluble contaminants are critically demanded for wastewater treatment but remain highly challenging.Currently,superwetting materials can quickly and efficiently separate oils from water,but were ineffective for the removal of water-soluble organic dyes accompanying oily wastewater in most cases.Wood,a renewable,biodegradable and eco-friendly natural material with an ordered hierarchical structure and abundant porosity,may serve as a desirable scaffold for the development of novel filtration materials and devices for wastewater treatment.In this study,by in situ deposition of silver nanoparticles（Ag NPs）in the mesoporous structure of balsa wood,we developed dual-functional Ag/wood composite filters.With the synergistic effects of the hydrophilicity of the porous wood structure and the catalytic activity of Ag NPs,the Ag/wood composite filter can be used for simultaneous oil/water separation and organic dye removal from water in a one-step process,offering a promising solution for multifunctional water treatment.The main results are as follows:（1）The Ag/wood filter became dark in contrast with the natural yellowish wood after loading Ag NPs inside the wood matrix,and the content of Ag in the wood filter was 4.78 wt%.The wood cell wall components,especially lignin,contain many functional groups（such as hydroxyl and carbonyl groups）;these functional groups can reduce Ag（NH₃）₂⁺ions in situ to metallic Ag that were eventually anchored to the surface of the wood channels.The unique 3D porous structure of natural wood was well preserved in the Ag/wood filter after decoration with Ag NPs,which were uniformly distributed on the channel surfaces of wood vessels,with a size range of 5～20 nm.（2）Owing to its superhydrophilicity and underwater superoleophobicity,The Ag/wood filter can selectively separate various oil-water mixtures such as n-hexane,toluene,olive oil,motor oil with a high efficiency（～99%）.The Ag/wood filter exhibited different breakthrough pressures for different oils and organic solvents,showing a certain stability for oil-water separation.（3）The Ag/wood filter could effectively remove methylene blue（MB）in the presence of Na BH₄ from water during the filtration process due to the catalytic activity of Ag NPs anchored to the vessel channels,and the MB removal efficiency and water flux were highly dependent on the thickness of the wood-based filters.Specifically,the gravity-driven Ag/wood filter with a thickness of 6 mm showed desirable performance with a high MB degradation efficiency of94.03%and a water flux of 2600 L·m^-2·h^-1.The vessels connected by the perforation plates can serve as both liquid transport pathways and ideal catalytic reaction microchannels for catalytic degradation of organic dyes.The proposed Ag-decorated wood-based filters feature renewable,inexpensive raw materials,facile processing and scale-up potential,displaying great potential for wastewater treatment.