Design And Application On Solar Water Evaporation System Of Biomass Fiber-loaded Carbon Dots Hybrid Gel

In order to ameliorate the both shortage of energy and water resources,solar-driven gas-liquid interface water evaporation technology,that is,using solar energy to drive gas-liquid interface water evaporation,is a new practical photothermal technology proposed in recent years,using cheap and clean solar energy.Efficient production of large quantities of clean water is the main feature and advantage of solar-driven gas-liquid interface water evaporation technology.Although this is a promising energy utilization method,However,in the practical application process,the salt and pollutants in the water will block and contaminate the photothermal evaporator,resulting in its damage and failure.Also,ma ny kinds of solar evaporators with self-cleaning ability that have appeared at present mostly realize the self-cleaning function at the cost of complex structure,increased cost and reduced efficiency.Cellulose nanofibers(CNFs)are a new type of nanomaterials extracted from natural plants.They have strong hydrophilicity,good thermal insulation,and are rich in nano-pores.They are an ideal material for solar water evaporators.Using CNFs as the photothermal material carrier and coal pitch carbon dots(CDs)as the photothermal material,an efficient solar water evaporator was fabricated,and its solar water evaporation performance was tested and studied in different application scenarios.Variation in tolerance and performance to seawater and contaminants.These contents can be summarized from the following two aspects.(1)A purely chemical method is demonstrated to treat a variety of biomass wastes for extracting cellulose nanofibrils(CNFs)with a consistent property.By hydrothermal reaction,carbon dots(CDs)can be easily grafted on the surface of CNFs.The polyvinyl alcohol(PVA)aqueous solution fills the voids between the CNFs@CDs.After gelation,the CNFs@CDs were firmly bound together,and the repeated freezing-thawing process was carried out to form a stable pore structure in PVA,and the strength and toughness of the CNFs@CDs hybrid gel were improved at the same time.Through the characterization results of SEM,it can be clearly understood that many holes and wrinkles can be found on the surface of CNFs fibers;while on CNFs@CDs,it can be observed that the loaded CDs are assembled on the surface of CNFs.By comparing the UV-vis results of CNFs and CNFs@CDs,it was found that loading CDs significantly enhanced the light absorption capacity of CNFs@CDs.The gel-treated CNFs@CDs have high mechanical strength,which is sufficient for practical production.Under one sun irradiation,the CNFs@CDs hybrid gel system enabled a high water evaporation rate(2.5 kg m-2 h-1)with a high Solar-vapor efficiency(96.45%).Based on the excellent recyclability,the CNFs@CDs hybrid gels exhibit excellent tolerance to salts(5 wt%,10 wt%,20 wt%)and acidic and alkaline(1 M,HCl,NaOH).(2)Experiments show that the CNFs@CDs evaporator is a multifunctional solar evaporator that can be used for seawater desalination and sewage purification.The CNFs@CDs hybrid gel system not only has good solar water evaporation performance,but also has adsorption performance for dyes in water,good salt resistance and excellent resistance to salt durability.Experiments confirmed that the CNFs@CDs evaporator had an adsorption effect on methylene blue(MB)in solution,and the adsorption could be greatly enhanced by solar irradiation.In addition to the solar enhanced adsorption capacity,the CNFs@CDs evaporator also exhibits resistance to salt precipitation when operating in brine.At the same time,its salt resistance can be further developed by opening millimeter-scale channels on the surface.Finally,we also verified that biomass nanofibers are a rich source of renewable CDs carriers.Efficient photothermal water purification equipment can be produced according to the conditions of local biological species.These fully demonstrate its possibilities in practical applications.