Study On Solar Interface Water Evaporation System Of Sludge And Biomass Based Composites

With the development of society,the problem of water shortage is becoming more and more serious.Among many water treatment technologies,solar interface evaporators are attracting attention because of their green and low energy consumption.Photothermal materials have been widely studied as one of the key components of solar interface evaporation systems.Among the photothermal materials,biomass materials have received attention because of their low cost and easy preparation,but the low light absorption conversion efficiency is still a problem for them.In contrast,sludge,as a by-product generated from wastewater treatment plants,contains metal substances with the ability to catalyze the pyrolysis of biomass materials,which can promote the pyrolysis of biomass at low temperatures and is expected to improve the light absorption efficiency.Compared with the use of conventional catalysts,sludge as a catalyst can not only save cost but also be used as a waste.Therefore,in this study,sludge and biomass-based composite photothermal materials were prepared to enhance the photothermal conversion efficiency of solar energy,interfacial evaporation rate and effective removal of pollutants from water as the research objectives,and the results of the study are as follows:（1）Corn cob carbon block HCCS was prepared by co-hydrothermal carbonization of sludge and corn cob to study the effect of sludge on the photothermal evaporation of corn cob carbon.The experimental results showed that the evaporation rate of the material was influenced by the amount of sludge added,the concentration of citric acid,hydrothermal carbonation temperature and time.Under the optimal preparation conditions,the material evaporated water up to 2.48 kg·m^-2·h^-1 under the light condition of 1 KW·m^-1 with an evaporation efficiency of 93.75%and purification rate of salt ions and dye molecules of more than 99.9%.Moreover,it was found in experiments on the treatment of wastewater containing volatile organic compounds that the addition of sludge（loading of metal oxides）could activate persulfate（PMS）in the solution to produce free radicals,thus in-situ degradation of phenol at the solar evaporation interface.（2）CDs@PDA@SA gels were synthesized by using dialysate of sludge and corn cob co-hydrothermal carbonation solution with dopamine hydrochloride and sodium alginate polymerization.The addition of dialysate was able to promote the polymerization of dopamine hydrochloride and improve the evaporation rate at the same time.The evaporation rate could reach 2.15 kg·m^-2·h^-1 under the light condition of 1 KW·m^-1 with an evaporation efficiency of 90.6%.In keeping the salt ions and the premise of dye molecules purification rate,further improve the evaporation rate,build a cup of concentrated within the system,make CDs@PDA@SA surface receives the PDA of radiation doubled,the evaporation rate of 3.92 kg·m^-2·h^-1.（3）SC@SA@PVA gels are prepared by gelation of carbon powder obtained by pyrolysis of sludge and corn cobs.The evaporation rate could reach 2.25 kg·m^-2·h^-1 under 1 KW·m^-1 light conditions with a solar evaporation efficiency of 91.2%.To further increase the evaporation rate,a 6 V solar cell was used as a compensation and current was passed on both sides of the material,and the generated Joule heat made the synergistic effect of photothermal and electrical heat,and the evaporation rate could reach 3.21 kg·m^-2·h^-1,and the synergistic effect with the in-cup concentrator mentioned above could make the evaporation rate reach 4.19 kg·m^-2·h^-1.To solve the problem of salt crystallization due to rapid evaporation,an evaporation base was designed by 3d printing,which can effectively block the precipitation of salt particles.In addition,multiple energy bands in the polymetallic oxides provide several conduction band（CB）-valence band（VB）pairs to inhibit charge carrier complexation and increase the generation of reactive oxygen species（ROS）,which contribute to effective photoinduced charge separation and electron leap and enhance photocatalytic activity,and SC@SA@PVA is able to remove volatile organic compounds（phenols）without the addition of persulfate.