Interfacial Photothermal Properties Of Polypyrrole@Pulp Fiber Composite Paper And Its Application In Wastewater Purification And Seawater Desalination

The shortage of fresh water resources and energy is a huge challenge facing us today.The recovery technology of light and hot water resources based on green energy and solar energy is an important solution to solve the contradiction between water resources and energy.However,traditional light-to-heat conversion materials such as metal-based plasma solids,semiconductors,and carbon-based materials are easy to drop and disperse in water due to weak interface adhesion,which can easily cause water pollution.Cellulose fiber is a green and sustainable biomass material with abundant resources,superhydrophilicity,and low thermal conductivity,which can be used to fabricate solar-driven evaporation systems with many advantages.（1）In this study,pulp fiber（PF）was used as the substrate,and polypyrrole（PPy）was first loaded on it by in-situ polymerization method,and then the polypyrrole@pulp fiber（PPy@PF）composite photothermal fiber with high light absorption capacity and good water transfer efficiency was prepared by traditional papermaking technology.During the preparation process,the amount of pyrrole added and the amount of oxidant will affect the loading of polypyrrole on the fiber,and then affect the physical properties and photothermal performance of the photothermal paper.The quantification of photothermal paper and the deposition rate of PPy increase with the concentration of pyrrole monomer and the amount of oxidant in the reaction system.When the concentration of PPy monomer is 5 g·L^-1 and the molar ratio of monomer to oxidant is 1:2,the deposition rate of PPy was 39.61%;the tensile strength and tightness of PPy@PF photothermal paper decreased with the increase of the concentration of pyrrole monomer and the amount of oxidant;the water absorption and air permeability of the paper increased with the increase of the concentration of pyrrole and the amount of oxidant.Photothermal experiments have proved that PPy@PF has excellent photothermal conversion ability.When the concentration of pyrrole is 5 g·L^-1 and the molar ratio of monomer to oxidant is 1:2,the water evaporation rate of photothermal paper is 1.37 kg·m^-2·h^-1.（2）The excellent photothermal conversion ability of PPy@PF was then used to activate PDS to degrade MO and simultaneously produce clean water.The results of quenching experiments showed that both SO₄^-·and HO·participated in the reaction during the experiment.The degradation rate and degradation rate of MO increased with the increase of initial PDS concentration,light intensity,and PPy loading,and decreased with the increase of initial MO concentration.In addition,the degradation of MO was not greatly affected by the p H of the system,indicating that the activation of PDS can be carried out under a wide range of p H conditions.The common anions Cl^-,H₂PO₄^2-and HCO₃^-in natural water will have certain influence on the degradation of MO.The addition of Cl^-generally promotes the degradation of MO;a small amount of H₂PO₄^2-can promote the degradation of MO,but when the concentration of H₂PO₄^2-increases further,the degradation of MO will be inhibited;HCO₃^-will inhibit the degradation of MO,and the degradation effect will decrease with the increase of HCO₃^-concentration.Finally,Rh B was used as a representative of cationic dyes,and the results showed that MO and Rh B had similar removal rates,indicating that the degradation of PDS had a certain universality.The photothermal activation system still has a high water evaporation capacity(1.31kg·m^-2·h^-1,88.92%),and the PPy@PF photothermal activation persulfate system still has good stability and recyclability.（3）Finally,the application of PPy@PF photothermal paper in seawater desalination is discussed.By creating a one-dimensional water transmission channel,the evaporation effect of simulated seawater is improved.The devices 5.0PPy@PF/EPE-1,5.0PPy@PF/EPE-2,and5.0PPy@PF/EPE-3 with three different water delivery channels were compared（the water delivery channels are absorbent cotton cores,a diameter of 2.5 cm sponge,lower surface of photothermal paper）,the photothermal effect:5.0PPy@PF/EPE-1>5.0PPy@PF/EPE-2>5.0PPy@PF/EPE-3.The Evaporation rate of 5.0PPy@PF/EPE-1 is 1.56 kg·m^-2·h^-1,and the evaporation efficiency is 88.49%,which is slightly lower than that of pure water(1.63 kg·m^-2·h^-1,93.14%).The evaporation experiment was carried out continuously for 5 h with 3.5 wt%Na Cl solution,and the evaporation rate and evaporation efficiency showed a trend of increasing first and then decreasing.The increase of the heat-insulating foam thickness is conducive to improving the evaporation performance of light and hot water.When the thickness of the heat-insulating foam is 1.5 cm,the light-heat evaporation effect is the best.When the foam thickness continues to increase,the evaporation effect will slightly decrease.The evaporation rate of5.0PPy@PF/EPE-1 increased with the increase of light intensity,while the evaporation efficiency decreased,but the evaporation efficiency was greater than 81.73%.The evaporation rate and evaporation efficiency of PPy@PF/EPE-1 gradually decreased with the increase of salt concentration.