Preparation Of Cellulose Aerogel And Wood Evaporator For Water Treatment

Freshwater scarcity is a serious challenge facing modern society and causes problems for more than two billion people worldwide.At the same time,the rapid developments of industry lead to an increasing number of water pollutants such as dyes,antibiotics and heavy metals entering the environment.In this context,scientists urgently need to develop new materials and technologies to obtain freshwater resources.The high specific area and controllable chemical properties of the nanomaterials have attracted the attention of scientists and are used in sewage purification and seawater desalination processes.However,the above materials often exist in the form of powder,which has poor molding processability,easy to agglomerate and difficult to recycle,which greatly limits its industrial application.Usually need to find a suitable carrier to construct composite materials(e.g membrane,aerogel,microspheres),so as to improve its recycling performance.Cellulose aerogels and natural wood have a three-dimensional porous structure,which is a kind of green and renewable carrier.At the same time,it can disperse nanomaterials.Aerogels and wood can solve the difficult problem of recycling nanomaterials.Based on this,this paper designed three kinds of composite materials using cellulose or fast-growing wood as a carrier,and used to adsorb and remove ionic pollutants in water and solar water desalination process:(1)GO/nanocellulose aerogels were fabricated via simple solution blending and freeze-drying method.Water purification abilities of hybrid aerogels were tested by the adsorption of methylene blue and tetracycline.(2)UiO-66 nanoparticles were integrated into cellulose network through self-crosslinking interactions without chemical binders and surface modifications.Lightweight and flexible hybrid aerogels with hierarchical porosity are fabricated without any chemical binders and tested it adsorption capacity for anionic methyl orange(MO)and cationic methylene blue(MB).(3)Based on the photothermal transformation ability of ink and the water transport function of wood,a self-purification solar interface evaporation device was designed for desalination of sea water.The main studies of this thesis are as follows:(1)Composite grapheme oxide(GO)/nanocellulose aerogels were prepared by dispersing GO nanosheets into cellulose nanofibrils solution prepared by mechanical method.GO is well dispersed in the aerogel,high dispersion of GO was attributed to the promotion of the unfolding and peeling of the two-dimensional GO sheet under the effect of steric hindrance and electrostatic repulsion.The adsorption capacity of the composite aerogel was performed by using methylene blue(MB)and tetracycline(TC)as model pollutants.The test results showed that the aerogel loaded with 25(wt%)GO had the best adsorption capacity,and the adsorption capacity for MB was 174.8 mg/g,TC was 118.0 mg/g.The composite aerogels obeyed the pseudo-second-order model and Langmuir adsorption isotherm.The adsorption mechanisms were mainly ascribed to electrostatic attraction andπ-πinteraction.Moreover,the aerogels exhibited excellent reusability and recyclability.The development of this work helps to promote the preparation of GO composite gel and its application in the process of water pollution treatment;(2)Composite UiO-66/nanocellulose aerogel with hierarchical porosity and low density were prepared through a self-crosslinking method.The nanocellulose acted as the structural skeleton supporting and dispersing the UiO-66 particles.FT-IR and XPS results show that the hydroxyl groups in UiO-66 can form new hydrogen bonds with the hydroxyl groups on cellulose,thereby improving interface compatibility.The prepared aerogel is lightweight and has a multi-level pore structure,and the pores of UiO-66 have good accessibility.The composite aerogels that loaded with 50(wt%)UiO-66 demonstrated high adsorption ability towards both anionic methyl orange(71.7 mg/g)and cationic methylene blue(51.8 mg/g).The development of this work can effectively promote the deviceization and industrial application process of MOF,and provide new ideas for the combination of MOF and biomass-based carriers.(3)The main component of traditional Chinese ink is nano-carbon,which has a spectrum of sunlight absorption and is an excellent light-to-heat conversion material.The main components of wood are cellulose,hemicellulose and lignin,which have the characteristics of well-developed pores,strong hydrophilicity,good thermal insulation and fast water transmission rate,and are excellent base materials for evaporation devices.Based on the above two points,this work adopts a top-down strategy,selects block wood as the base,and coats ink on the surface to construct a double-layer solar interface evaporation device.In addition,through the introduction of millimeter-scale man-made holes,a multi-directional salt transmission channel is constructed inside the wood by the capillary effect,thereby effectively preventing the deposition of salt on the surface.The wood-based evaporator(H-C-Wood)shows a stable solar thermal conversion efficiency of 74%and an evaporation rate of 1.6 kg/m~2/h under simulated 1 sun irradiation.The development of this work can provide a useful reference for the development of low-cost,high-efficiency and strong continuity solar evaporation devices.The above work by choosing renewable cellulose and natural wood base,surrounding ascension carbon materials(graphene,ink)and MOF material formability and recyclability,construct the composite material can be used for water purification process,and the composite process,composite mechanism and water treatment effect has carried on the detailed investigation,help to promote new environmental protection compound material and the development of water treatment technology.