Preparation Of Shrimp Shell-based Activated Carbon And Its Adsorption Performance For Printing And Dyeing Wastewate

Textile printing and dyeing is a pillar industry in China.As a result,a large amount of dye-containing wastewater is discharged into natural water bodies.Printing and dyeing wastewater has the characteristics of extremely high toxicity,difficult decomposition and extremely complex chemical composition.If it is discharged into the environment at will,it will cause serious pollution to the waters.Printing and dyeing wastewater will be transmitted along the food chain and food web,and will eventually have a great impact on human life and health,with incalculable tragic consequences.Therefore,the efficient purification of printing and dyeing wastewater is of great significance to green ecology.At present,there are many alternative methods for the treatment of printing and dyeing wastewater,but the adsorption method has become the most effective treatment method because of its unique characteristics such as simple operation,efficient adsorption,and avoidance of secondary pollution and reusability of adsorbents.Among many adsorbents,activated carbon has attracted great attention from many scholars and environmental protection workers as an adsorbent with low cost,wide material source and environmental friendliness.However,biomass functional material activated carbon is facing a series of serious problems in the field of printing and dyeing wastewater treatment,including low adsorption efficiency,tight supply of high-quality raw materials and relatively insufficient scientific and technological content of products.These factors restrict its application in printing and dyeing wastewater treatment to a certain extent.In view of the above reasons,based on the in-depth investigation of the structure,physical and chemical properties,preparation technology,improvement research status of activated carbon and its application in printing and dyeing wastewater treatment,shrimp shell based activated carbon（SSBC）adsorbent was successfully developed by using shrimp shell as raw material and zinc chloride impregnation one-step activation method.The physicochemical properties of SSBC were systematically and comprehensively characterized by Zeta potentiometer,scanning electron microscope（SEM）,energy dispersive spectrometer（EDS）,Fourier transform infrared spectrometer（FTIR）and X-ray photoelectron spectroscopy（XPS）.Methylene blue（MB）was used as a typical dye.Through systematic and comprehensive experimental investigation,the effects of various activation conditions,including initial concentration of pollutants,reaction temperature,p H value,adsorbent dosage and adsorption time,on the adsorption effect were investigated.Finally,the optimal adsorption conditions were determined.Finally,with the help of adsorption kinetics,adsorption isotherm and adsorption thermodynamics,the adsorption mechanism of MB removal by SSBC was studied by SEM+EDS,FTIR and XPS.The research contents and results of this thesis can be summarized in the following three aspects:（1）Shrimp shell based activated carbon（SSBC）was prepared by using cheap and readily available shrimp shell powder（SSP）as raw material and zinc chloride as activator.The preparation conditions were optimized by single factor and response surface method,and the equilibrium adsorption capacity of MB was used as the response value.According to the results of adsorption kinetics and isothermal adsorption,the adsorption process of MB on SSBC surface conforms to the quasi-second-order kinetics and Langmuir adsorption isotherm model.Therefore,we can conclude that the adsorption of MB by SSBC is a chemical adsorption,which occurs on the monolayer.The adsorption rate is fast,accompanied by a certain degree of intraparticle diffusion process.Langmuir isotherm fitting results showed that the maximum adsorption capacity of MB by SSBC was 916.55 mg/g.Compared with other similar biomass activated carbon,the adsorption performance of MB is obviously better.（2）In this thesis,diffrent from the traditional two-step preparation of activated carbon by carbonization and activation,the activator is zinc chloride,and the activated carbon is prepared by one-step activation.At the same time,the author also fully considered the factors such as zinc chloride impregnation ratio（Zn Cl₂:SSP）,zinc chloride impregnation time,activation temperature and activation time,and finally obtained a low-cost and high-efficiency shrimp shell activated carbon adsorbent.According to the analysis results of SEM+EDS,FTIR and XPS,it can be concluded that the adsorption process of MB on SSBC surface has both physical adsorption and chemical adsorption.Among them,physical adsorption is mainly achieved by pore diffusion,while chemical adsorption mainly depends on the oxygen-containing functional groups on the surface of SSBC.In addition,it was also found that the-OH group on the surface of SSBC can also interact with MB molecules,forming hydrogen bonds to cause MB adsorption and removal.（3）The physical structure and chemical properties of activated carbon were characterized by various testing techniques.It was observed that the pores of the optimized SSBC were fine and presented a’coral reef-like’porous structure.After EDS test,its carbon content is as high as 93.16%,and these characterization results are very significant and rigorous.It can be proved by infrared spectroscopy that there are functional groups such as hydroxyl,carboxyl and amino groups on the surface of shrimp shell activated carbon.The specific surface area of SSBC obtained by BET is741.75 m²/g.Compared with common activated carbon materials,SSBC has higher specific surface area and MB adsorption capacity,which can be used for industrial treatment of printing and dyeing wastewater.