Carbon Black-based Salt-ressisting Solar Evaporator For Efficient And Durable Seawater Evaporation Based On Interfacial Solar Heating

Desalination is regarded as one of the most promising solutions to the shortage of fresh water.However,the current desalination technologies such as multi-effect distillation,multi-stage flash and reverse osmosis are plagued by energy consumption and high cost.Furthermore,they also require large centralized installations and advanced supporting infrastructure,which are unsuitable for rural and remote areas.Recently,solar seawater desalination technology based on "air-water interface heating"has emerged in order to solve these problems.This technology has attracted significant attention because of its high evaporation efficiency,low energy consumption,simple operation,low cost,etc.In order to further improve the efficiency of solar seawater evaporation,the photothermal materials,water absorbing materials and insulation materials are assembled into integrated distillation modules.However,the use of evaporator will lead to salt clogging.In this paper,commercial carbon black(CB),air-laid cloth(ALC),air-laid paper(ALP),expandable polyethylene(EPE)foam and melamine foam(MF)were employed as raw materials to design two integrated distillation components:EPE/ALP/ALC/CB and EPE/MF/ALC/CB.The evaporation efficiencies and salt-rejecting properties of these two evaporators were studied respectively.The water evaporation rates of the EPE/ALP/ALC/CB(AFC-I)and EPE/MF/ALC/CB integrated modules under 1 sun irradiance are 1.46 kg·m-2·h-1 and 1.24 kg·m-2·h-1 respectively which were 3.75 and 3.18 times of the direct evaporation of seawater.And the photothermal conversion efficiency was 91.7%and 77.7%respectively.The direction of water transport has a decisive effect on the location of salt precipitation.In EPE/ALP/ALC/CB integration component,in different salinity,light intensity,water transport area and materials,the salt accumulation law was consistent,namely when the water transport from the center to the periphery,salt accumulated only on the surface of the EPE foam which shows good salt resistance and when the water transport from the periphery to the center,salt crystallization will occur on the surface of the photothermal conversion membrane.As a result,the water evaporation rate will be reduced due to the blocked vapor transport channel and reflected solar light.The EPE/MF/ALC/CB integrated module has excellent salt-rejecting due to the outstanding water absorption capacity of MF,which can effectively prevent the brine on the evaporation surface from reaching saturation and precipitation.Even if it is used for desalination of high-concentration brine(14%),there is still no salt accumulation during the whole evaporation process.In the meanwhile,when the light intensity and photothermal conversion materials are changed,the components still show excellent salt resistance.The water evaporation rate under 1 sun irradiance of AFC-I in 16 cycle experiments fluctuated between 1.43-1.48 kg·m-2·h-1 and the corresponding photothermal conversion efficiency varied from 89.7%to 92.9%.The water evaporation rate and photothermal conversion efficiency under 1 sun irradiance of the EPE/MF/ALC/CB integrated module during the 20-day continuous test fluctuated around 1.23kg·m-2·h-1 and 77.5%respectively.Both distillation components have good durability and stability,and the device is simple and effective which have great potential for application in poor,remote and sunny areas.