Research On Construction Of Eggplant Based Porous Carbon Materials And Its Application In Printing And Dyeing Wastewater Treatment

With the growth of population,industrial development and the expansion of agricultural irrigation area,the water crisis is increasingly severe.At the same time,the discharge of urban sewage and industrial wastewater has caused serious water pollution problems.Compared with other water treatment technologies,adsorption technology is widely used in sewage treatment and clean water production because of its simple operation,high efficiency,no byproducts,and its advantages of clean,rapid and sustainable development.Biomass porous carbon materials have rich pore structure,high specific surface area and high absorbance,and are commonly used as excellent adsorbent and photothermal conversion materials.Therefore,access to cheap,efficient and sustainable biomass porous carbon materials for sewage purification and clean water production is an effective way to alleviate the water crisis.Eggplant materials（Eggplant Materials,EMs）have a low cost and a wide range of sources,with rich three dimensional interconnected pore structures composed of natural spongy fiber sheets.From the perspective of physical adsorption and solar photothermal evaporation,this micron-sized porous structure is very favorable for the adsorption of dye molecules and the evaporation of water.Therefore,this project has successfully constructed a porous carbon material with eggplant as the base through pretreatment,freeze-drying and carbonization process（Eggplant Porous Carbon Materials,EPCMs）,the dye wastewater adsorption properties and photohot water evaporation properties were further studied.The main content has the following three parts:1.Construction and performance characterization of biomass eggplant-based porous carbon materials.（1）Natural porous EMs were obtained by one-step method（eggplant after peeling）.According to EDS and SEM characterization,eggplant is mainly composed of cellulose,hemicellulose and lignin,and is composed of micron-scale irregular porous structure,and the sheet surface is smooth,relatively flat,and the fold distribution is less.（2）The EPCMs obtained by alkali treatment,activation,pre-oxidation and carbonization have a more developed pore structure,and the surface is no longer smooth and slightly wrinkled.The BET-BJH method revealed that the EPCMs-500℃showed the best performance,with a specific surface area and pore volume of 516.0060m²/g and 0.6379 cm³/g,respectively.The infrared spectrum and X-ray diffraction analysis show that EPCMs have rich groups and produce a disordered microcrystalline carbon structure.（3）The EPCMs obtained by alkali treatment,pre-oxidation and carbonization have a honeycomb porous structure with a carbon content of 70.86%.The XRD and Raman analysis showed that the internal carbonization forms a disordered graphitization-like carbon structure.Static contact angle testing showed that the EPCMs are superhydrophilic.The excellent sunlight capture ability makes the light absorption rate of EPCMs nearly 100%.Moreover,compression strength and pressure tests show that EPCMs have good compression modulus and compression resistance.2.The adsorption performance of printing and dyeing wastewater of eggplant-based porous carbon material.Rhodamine B（Rh B）was used as the main simulation dye for EPCMs.The results show that the EPCMs can achieve 100%removal of the Rh B solution.The adsorption isotherm conforms to the Langmuir adsorption model and is an ideal monolayer adsorption process,and the theoretical maximum adsorption capacity can reach 263.16 mg/g.In addition,adsorption experiments showed that EPCMs also have good adsorption performance for other dyes including methyl orange（MO,acid anionic dye）,methylene blue（MB,alkaline cationic dye）and metaqing B（YB,reactive dye）and actual printing and dyeing wastewater.The adsorption mechanism of EPCMs is further analyzed:excellent hydrophilicity and high specific surface area make EPCMs fully contact with dye molecules,developed pore structure is conducive to the adsorption and storage of dye molecules,rich groups effectively capture dye molecules,the synergistic effect of the three makes EPCMs have fast and efficient adsorption performance.3.Photohot water evaporation properties of eggplant-based porous carbon material.EPCMs have a high evaporation rate for pure water,reaching 2.18 kg·m^-2·h^-1,which is 5.1 times that of pure water evaporation(0.42 kg·m^-2·h^-1).Water evaporation experiments show that EPCMs with different carbonization temperatures have some effects on the evaporation performance,while the thickness of EPCMs is less affected.In addition,dye wastewater evaporation experiments showed that EPCMs have excellent water evaporation performance for different dyes such as MB,MO,active yellow Y-3rs and actual wastewater(over2.01 kg·m^-2·h^-1).Circular evaporation experiments with 7 wt%,20 wt%saline and actual wastewater showed that EPCMs exhibit excellent salt resistance and stability during photothermal processes.In the process of water evaporation,the excellent water replenishment ability of EPCMs not only improves the evaporation efficiency,but also makes the material surface cannot reach the concentration of salt precipitation,and then has salt resistance and water evaporation stability.In conclusion,based on the natural porous structure of eggplant,this topic constructs EPCMs with rich pore structure.The EPCMs have rich groups,excellent hydrophilic and light absorption capacity,thus showing excellent dye wastewater adsorption and photohot water evaporation performance.This paper broadens the source of biomass carbon materials,and at the same time,lays a certain practical and theoretical foundation for the high value and diversified utilization of eggplant.