Preparation Of Silver-loaded Wood Nanocomposite For Water Treatment Application

Water is the source of life.The progress of society,the rapid development of industry,and the rapid growth of population have caused a series of serious water pollution problems,such as the release of organic dyes and cleaning agent pollutants,oil leakage,etc.,which seriously threaten the environmental safety of the earth.Alleviating the global problem of the shortage of clean fresh water supply is urgent.In this paper,the multi-scale hierarchical structure of balsa wood is effectively used to make the wood loaded with Ag NPs and covered with a thin layer of pyrrole(PPy)to prepare a multi-functional silver-loaded wood-based nanocomposite material,which has the ability to catalyze the degradation of organic dyes and oil-in-water emulsions.Separation,oily substance adsorption and other functions can also realize seawater desalination,which solves the defects of single function and pollutant treatment,narrow application area,low treatment efficiency,and insufficient strength when traditional membranes are used in water treatment processes.(1)Natural wood has a three-dimensional pore structure.Ag NPs particles are modified in the wood pores by the in-situ reduction method of silver ammonia solution to prepare an Ag@Wood filter.The loading of Ag NPs does not affect the pores of the wood,and still maintains a high water flux and a good sewage treatment effect.The results show that Ag@Wood filter has multifunction,which can carry out oil-water separation and remove organic dyes in water by one-step method;Ag@Wood filter has super-hydrophilic-underwater super-oleophobicity,and can separate water-in-oil emulsions.A recovery rate of over 97.2%is achieved.In addition,the Ag@Wood filter can effectively remove methylene blue(MB)from water and catalyze the degradation of rhodamine B(Rh B)under simulated sunlight conditions.The MB removal efficiency largely depends on the thickness of the wood-based filter.Specifically,the use of a 7 mm thick Ag@Wood filter for atmospheric filtration shows a high MB degradation efficiency of 94.4%and with a high water flux of 4577 L·m^-2·h^-1,the catalytic degradation of Rh B can reach an efficiency of 81.3%under 10 hours of sunlight.The multifunction Ag@Wood filter provides a new idea for wastewater treatment.(2)In order to realize the multi-function of the filter,Ag@Wood polymerizes a thin layer of polypyrrole(PPy)in situ on the surface of Ag@Wood to give it the function of seawater desalination,and at the same time realize the application of wood catalytic degradation of organic dyes and oil-water emulsion separation.Through SEM,XPS and FT-IR analysis,it is known that Ag NPs and Ag Cl are evenly distributed in the wood pores,and a thin layer of polypyrrole covers the wood surface without affecting the fluid transmission.The results show that,thanks to the generation of Ag Cl,the effect of PPy@Ag@Wood photocatalytic degradation of Rh B is greatly improved(photocatalytic degradation of Rh B>92%within 10 h),and the optimization of dye degradation efficiency is achieved.The PPy thin layer does not affect the pores of the wood,the water flux is 4276 L·m^-2·h^-1,and the recovery rate of various oil-in-water emulsions is above 96.2%.In addition,wood's porous structure,high hydrophilicity,and thermal insulation characteristics combined with the advantages of PPy(broadband and high solar absorption capacity)can quickly generate steam,which makes PPy@Ag@Wood an ideal solar evaporation The generator has high evaporation capacity(1.31 kg·m^-2·h^-1)and high evaporation efficiency(93.8%)under simulated 1 solar irradiation conditions.In addition,the purified water obtained by using PPy@Ag@Wood as a solar steam generator shows low ion concentration(in the water after desalination,Na⁺is 22.3 mg·L^-1,K⁺is 9.6mg·L^-1,and Ca²⁺is 12.6 mg·L^-1,Mg²⁺is 48.9 mg·L^-1),indicating that PPy@Ag@Wood has excellent capabilities in seawater desalination and wastewater treatment.(3)The 7 mm thick PPy@Ag@Wood is hydrophobically modified with stearic acid,and then a simple treatment is carried out to scrape off the hydrophobic surface and the polypyrrole thin layer on one side of the sample to expose the superhydrophilic-underwater super-oleophobic Ag@Wood inner layer,thus making Janus type special wettability wood film.Studies have shown that using normal pressure to filter a variety of oil-in-water emulsions with the hydrophilic side facing up has a significant effect,and the recovery rate is greater than 97%.Using the hydrophobic side for oil adsorption,the oil absorption capacity can reach up to 8.5times its own weight.In addition,under one sunlight condition,the hydrophobic layer can prevent the sample from being completely wetted.The same conditions make the surface temperature higher than PPy@Ag@Wood,thereby increasing the evaporation rate.Janus wood film is used as a solar evaporator for seawater desalination,with an evaporation rate of 1.32 kg·m^-2·h^-1and a heat conversion efficiency of 95.33%.