Interfacial Photothermal Distillation Desalination Study Of Superhydrophilic Honeycomb Activated Carbon

The new solar photothermal distillation desalination technology based on gas-liquid interface heating has been considered one of the effective ways to address the shortage of freshwater resources in islands with tight electricity supply.How to synchronize the distillation components to achieve anti-salinization（long-lasting operation）and control volatile contaminants into the condensed desalinated water is the hot and difficult point of the new technology research.In this paper,a super hydrophilic honeycomb activated carbon（denoted as SHHAC）distillation module was designed and assembled to prevent salt accumulation and control contaminants entering condensed freshwater simultaneously.The effectiveness and mechanism of water evaporation rate,photothermal conversion rate,and salt-rejection property,efficiency and mechanism of pollutant removal by the SHHAC distillation module were analyzed in depth.The SHHAC is the key component of the SHHAC distillation module,which can be used as a water transport channel.The channel can transport bottom seawater to the top layer and deliver the concentrated seawater back to the bottom seawater,thus realizing the salt-rejection property of the SHHAC distillation module,which in the next step enhance the effect of long-term operation.At the same time,it adsorbs the pollutants were adsorbed by the SHHAC during the seawater transport process result in the inhibition of the pollutants from entering the condensed freshwater.The optimal seawater evaporation rate of the SHHAC distillation module was 1.50kg·m^-2·h^-1under 1 solar irradiation intensity,corresponding to a photothermal conversion efficiency of 94.2%.The optimal conditions were:CB dosage of 12 g·m^-2,SHHAC pore aperture of 1.5 mm with iodine value of 800,EPE foam thickness of 10 cm,and three layers of dust-free paper.A 3.5 wt%Na Cl solution was used to prepare phenol,naphthalene and rhodamine B with a concentration of 1 mg·L^-1to simulate slightly contaminated seawater.The distillation rate（R_D）values for direct light distillation of the three contaminants were 75%,6.25%and0%,respectively,and the R_Dvalues for all three decreased to 0%after using the SHHAC distillation module.（Distillation rate R_D:the ratio of the concentration of contaminants in the condensed freshwater to the initial seawater.A smaller R_Dvalue indicates that fewer contaminants enter the condensed freshwater）After 15 cycles of use under 1 solar light intensity,the SHHAC distillation module had no salt accumulation,indicating the good salt-rejection performance.Meanwhile,the evaporation rate of seawater in the range of 1.45-1.50 kg·m^-2·h^-1within 15 cycles,and the R_Dvalues of phenol were all lower than 3%,indicating the good durability and stability of the SHHAC distillation module.Finally,with the actual East China Sea seawater as the feedwater,25 SHHAC distillation modules were assembled to carry out outdoor photothermal distillation seawater desalination experiments.The freshwater water quality indexes such as turbidity,conductivity（salinity）,conventional cations(Na⁺,K⁺,Ca²⁺,Mg²⁺,B³⁺)and some anions(F^-,Cl^-,NO₃^-,SO₄^2-)were all below the limit value of the U.S.Drinking Water Quality Standards（EPA）,Drinking Water Quality Guidelines（WHO）,and Sanitation Standards for Drinking Water（GB5749-2022）.