Preparation And Performance Of Functionalized Polyacrylamide-Based Gels For Photothermal Conversion And Environmental Treatment

The energy crisis and fresh water shortage pose a huge threat t to human life,so there is an urgent need to develop environmentally friendly methods of water purification.As a water purification technology with low energy consumption and zero pollution,solar photothermal drive water evaporation technology converts solar energy into heat energy through photothermal materials to generate water vapor at a temperature below the boiling point.However,in practical applications,most photothermal evaporators are prone to damage when exposed to strong sunlight and require high energy for evaporation.Traditional photothermal conversion materials have a single function and need to be compounded with materials with different characteristics to expand their application fields.In view of the above problems,this paper takes polyacrylamide as the basic material and compounds it with hydrophilic materials by different synthesis method to obtain gel-based evaporators,and introduces different types of photothermal materials to improve the light absorption performance of the gel evaporators,so as to expand the application scope of the evaporators while realizing high efficiency solar water evaporation rate.The main research contents are as follows:（1）Nickel/Cerium dioxide based sponge/polyacrylamide composite hydrogel evaporator.Polyacrylamide/agar was loaded on porous melamine sponge by hydrothermal method to prepare sponge based composite hydrogel.The morphology of the sponge-based composite hydrogels were regulated by adjusting the addition of acrylamide and agar monomers.A new type of Ni/Ce O₂ composite photothermal material was developed by two-step annealing method,which was introduced into gel to enhance the light absorption of gel.The evaporation rate of the sponge-based composite gel could reach up to 2.55 kg m^-2 h^-1 at one solar light intensity and the evaporation rate steadily increased without damage under high light intensity irradiation.The composite hydrogel not only showed excellent evaporation ability in salt solutions and strong acid and alkali solutions,but also has remarkable effect on the removal of organic dye solutions.（2）The strongly robust agar/polyacrylamide dual network hydrogel for efficient solar vapor generation.The agar/polyacrylamide double network hydrogels were synthesized by introducing agar with abundant hydroxyl groups into polyacrylamide through one-pot hydrothermal method.A unique hydroxyl structure was designed on the long chain of the polymer,which not only improved the hydrophilicity and mechanical properties of the sample but also regulated the content of intermediate water inside the hydrogel,reducing the evaporation enthalpy of water in the hydrogel to 1117 J g^-1.After compounding 100μL of carbon nanotube dispersion with the hydrogel,the absorbance of the composite hydrogel reached an optimum of 96.3%.The agar/polyacrylamide/carbon nanotube composite hydrogel could achieve an evaporation rate of 3 kg m^-2 h^-1 and an efficient heat utilization rate of 86.2%at 1 k W m^-2 light intensity.In addition,the composite hydrogel can effectively reduce the ions concentration in simulated seawater,and produce 17.68 kg m^-2 of fresh water under natural sunlight irradiation for 7 hours.（3）Multifunctional PPy/Mo S₂ film-based gel evaporator based on photocatalytic and photothermal effects.The PPy/Mo S₂composite powder with both photocatalytic ability and photothermal effect was synthesized by chemical oxidation and hydrothermal methods.Adjusting the light intensity to 1 k W m^-2,the removal rate of Rh B by PPy/Mo S₂ composite powder was increased by 15%compared with pure PPy powder under the same time condition.In order to solve the problem that the powder catalyst tends to remain in the water,PPy/Mo S₂ composite powder was deposited on filter paper by ultrasonic method to prepare PPy/Mo S₂photothermal filter paper film,and the removal rate of Rh B by this photothermal film was 37%in two hours,and the evaporation rate could reach 1.46 kg m^-2 h^-1 under one light.The film-based double-sided gel evaporator was obtained by assembling polyacrylamide/polyvinyl alcohol composite aerogel prepared by freeze-drying with PPy/Mo S₂ photothermal filter paper film.Benefiting from the increase of the evaporation area and the gain of environmental energy,the evaporation rate of the film-based Janus evaporator could be increased to 2.20 kg m^-2 h^-1 at one light intensity.