Studies On Construction Of A Self-healing Photothermal Water Evaporation System And Synergistic Catalysis

Solar water evaporation（SWE）is a technology that uses solar energy to produce clean steam from dirty water.The heat energy is produced by a photothermal conversion material from the light energy of the sun,which thereby drives water to evaporate to achieve desalinating seawater and purifying sewage.Solar absorption,photothermal conversion efficiency,heat control and water supply are optimized to gain high-efficiency SWE performance.However,there are two questions that SWE is not durable and the complex pollutants in dirty water fluence the evaporation performance,which are waiting to be solved urgently.In order to solve the above problems,this paper designs photothermal driven water evaporation membranes based on hydrogel,then self-healing ability and photo catalytic degradation ability are introduced in the hydrogel,so the solar driven water evaporation hydrogel membrane is produced,which realizes high-speed water evaporation,and further realizes the degradation of organic pollutants.These are as follows:First,because the solar evaporation hydrogel reported cannot be used after damaged,a self-healing solar evaporation hydrogel is designed.The hydrogel achieves high-efficiency light absorption through the inverted pyramid structure of high light-trapping.The dynamic reversible coordination interaction between Fe³⁺and-COOH leads to the self-healing ability,and the photothermal conversion ability of acetylene black leads to solar water evaporation ability,so the hydrogel of P（AM-co-AA）is constructed.Physical blending and the dispersion of PVP is used to disperse acetylene black in the hydrogel precursor fluid.And then the hydrogel membrane is obtained by heat curing.During the curing process,the Si pyramid is used as a template for soft imprinting to obtain an inverted pyramid structure.The solar water evaporation hydrogel membrane is obtained finally.Through experimental exploration,it is found that the water evaporation rate of the hydrogel membrane reaches to 1.58 kg m^-2 h^-1,which can meet the needs of efficient clean water generation.The breaking elongation of hydrogel is 1580%,which can cope with severe deformations rather than damaged.Even damaged,it can self-heal without external assistance within 1 h after contact,and can be stretched to 3 times its original length after self-healing,while the solar water evaporation capacity does not reduce,indicating its excellent stability.The self-healing solar water evaporation hydrogel membrane provides a new idea for continuous and stable clean water generation in harsh outdoor environments.Second,the solar water evaporation hydrogel reported currently cannot cope with organic sewage,and will cause the enrichment of organic pollutants,which will affect the water evaporation effect.In order to solve this problem,the Ag-disulfide bond interaction is used to fix the Ag₂O/Ag into the hydrogel,which realizes the photocatalytic degradation of methyl orange（MO）in cooperation with solar water evaporation,then the hydrogel of P（AM-co-AA）is obtained.Ag₂O/Ag that is used as a photothermal conversion material replaces acetylene black.The ability of charge separation is enhanced because of the heterostructure,which leads to the ability of photocatalytic degradation MO enhanced.The N,N’-Bis（acryloyl）cystamine grafted to the surface of Ag₂O/Ag not only fixes silver Ag₂O/Ag in the hydrogel network,but also participates in the construction of the hydrogel as a cross-linking agent.The dynamic reversible coordination interaction between Fe³⁺and-COOH is used to obtain a high light-trapping self-healing solar-driven degradation MO synergistically evaporation hydrogel membrane with soft imprinting technology.Through experimental exploration,it is found that the water evaporation rate of the hydrogel membrane reaches to 1.2 kg m^-2 h^-1 and MO removal rate after 3 h is 96%,which can be used to generate clean water from MO sewage.The breaking elongation of hydrogel is 1320%and the breaking stress is 0.35 MPa,which can cope with severe deformations.The self-healing solar water evaporation hydrogel membrane provides a new idea for stably obtaining clean water from organic sewage.Third,the self-healing hydrogel has the ability of photocatalytic degradation MO to synergize water evaporation,but it needs additional support materials to avoid sinking during use.In order to solve this problem,the reaction of Ca CO₃ dissolution in HCl is used to construct a self-floating PVA hydrogel.Then the solar-driven Photo Fenton synergistically evaporation hydrogel is obtained by repeated freezing and thawing combined with layer-by-layer assembly.The self-floating porous bottom hydrogel is prepared firstly,then the middle layer of Photo Fenton and the top layer of solar water evaporation is assembled on the bottom layer.Through experimental exploration,it is found that the hydrogel has an evaporation rate of up to 1.5 kg m^-2 h^-1,and can achieve up to 99%of MO removal rate in 3 h.In addition,the hydrogel has an elongation at break of 780%and a stress at break of 1.0 MPa,and can be self-floating.This self-floating solar-driven Photo Fenton synergistically evaporation hydrogel provides a broad idea for one-step portable generation of clean water from organic sewage.