| Solar-driven interface seawater desalination technology has many significant advantages,including environmental protection,energy saving as well as low cost.It provides a novel solution for solving the global freshwater crisis,and is one of the research hotspots in seawater desalination field.However,most,if not all,of the existing solar-driven interface evaporators have disadvantages of low evaporation rate and salt accumulation,which is difficult to meet the actual demand.In this paper,the three-dimensional solar-driven interface evaporation system with high-efficiency desalination property and salt resistance was obtained via the integrated study of structure design,preparation and modification of the solar-driven interface evaporator.This work could provide a theoretical basis to well promote the practical development of solar-driven desalination technique.Based on the geometrical optics theory,radiation energy conduction theory and heat transfer theory,the structure of three-dimensional light absorber was optimized via using virtual simulation methods of Trace Pro optical simulation and COMSOL Multiphysics thermal simulation.The three-dimensional hollow thin-walled cone-shaped light absorber was fabricated via the 3D printing technique using black ASA resin as the raw material.Then,Air-laid paper/ASA three-dimensional solar-driven interface evaporator featuring spatial separation of water-evaporating surface and light-absorbing surface was constructed,in which the inner surface of ASA cone worked as light-absorbing surface and the outer surface coated with Air-laid paper as water-evaporating surface.The influence of 3D printing parameters upon the photothermal response and mechanical properties of the ASA absorber was studied.Through photothermal seawater evaporation tests,the structure-activity relationship between evaporator structure and evaporation performance was discussed,and the solar-driven interface evaporation mechanism was also analyzed.Results indicated that when printing temperature,printing speed and printing layer thickness were240°C,30 mm s–1 and 0.10 mm,respectively,the ASA absorber can reach the steady-state temperature of 57.2°C within 120 s,as well as the interlayer adhesive strength and buckling load were 10.56 MPa and 128.18 N,respectively,implying sharp photothermal response and high mechanical strength.And when the cone apex angle is 30°,the corresponding evaporator showed optimal seawater evaporation performance,the evaporation rate and photothermal conversion efficiency were1.723 kg m–2 h–1 and 107.85%,respectively.This is due to the narrow space formed in 30°cone-shaped evaporator could force the incoming sunlight to reflect multiple times,which increased the light absorption rate to 99.80%;the spatial separation of light-absorbing surface and water-evaporating surface weakened the influence of water film and steam on light absorption,improved the stability of light absorption;the ratio of the projected area of the light-absorbing surface to the actual water-evaporating surface area was as low as 0.27,which could form full cold evaporation.To sum up,the 30°evaporator made full use of the energy captured from sunlight and surroundings in conjunction with Marangoni effect,synergistically improving photothermal conversion efficiency and seawater evaporation performance.PEI-PDA/ASA three-dimensional solar-driven evaporator was obtained by in-situ growing PEI-PDA film on the surface of ASA light absorber instead of the Air-laid paper.The effects of preparation process on micro-morphology and wettability of the surface-modified PEI-PDA film were discussed by SEM and contact angle test.Seawater evaporation of the three-dimensional evaporator was studied,and the solar-driven interface evaporation enhancement mechanism was also revealed.Results showed that when the co-deposition time was 36 h,the PEI-PDA modified film showed uniform and dense nano-porous structure,and the surface water contact angle was close to 0°;the evaporation rate was up to 2.682 kg m–2 h–1 during 168 h ongoing seawater evaporation process,which was 55.66%higher than that before surface modification.This is due to the introduction of polar groups such as amino groups and hydroxyl groups improved the wettability of water-evaporating surface,reduced the thermal resistance of the solid-liquid interface,and thus improved the heat utilization rate;the nanopores of the PEI-PDA film reduced the curvature radius of the liquid film to be evaporated upon water-evaporating surface to effectively reduce the energy required for evaporation,promoting the significant improvement of seawater evaporation performance.Using the PEI-PDA/ASA as evaporator and modified Air-laid paper as water conveyance belt,the PEI-PDA/ASA three-dimensional evaporation system was constructed.The capillary effect of the water conveyance belt was applied to draw seawater to the top of evaporation surface to provide water supply for photothermal evaporation.The influences of water conveyance capacity modification of Air-laid paper upon seawater evaporation performance and self-desalting behavior of such evaporation system towards treating seawater with different salinities were studied.Moreover,the long-term service stability of the obtained evaporation system was explored,and outdoor experiments were also carried out to evaluate its application feasibility under the real working conditions.The results suggested that when the surface laying density of long-staple cotton fiber on Air-laid paper increased to 8.25g m–2 and 25.80 g m–2 respectively,there was no salt deposition on the active water-evaporating surface during 30-day cycle evaporation testing process of 3.0%real Yellow seawater and 20%simulated hypersaline seawater,the average evaporation rates were 2.680 kg m–2 h–1 and 2.560 kg m–2 h–1,respectively.This is due to the introduced long-staple cotton fiber improved the water supply capacity of the Air-laid paper.When water supply was greater than the evaporation water,the excess seawater dripped out of the water-evaporating surface under the action of gravity,which removed the excess salt on evaporating surface,inhibited salt deposition,as well as improved long-term service stability.Furthermore,in outdoor desalination experiment,freshwater collection rate of such an evaporation system was as high as1.069 kg m–2 h–1,and the desalinated water well met the requirements for drinking,demonstrating broad practical application potential. |
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