Preparation Of Lignite Modified By Loaded Copper Ion And Its Adsorption Performances For Direct Yellow Brown Dyes

The rapid development of Chinese industry is also facing the hard situation of water pollution.There are a large number of organic pollutants and heavy metals in industrial wastewater,which cause certain harm to the environment.Therefore,finding an economical and effective way to deal with pollution is a common concern at home and abroad.As a natural mineral,lignite is rich in resources and low in price.The lignite itself has a large specific surface area,a well-developed pores,and extremely rich oxygen-containing functional groups,and has strong characteristics of ion exchange and adsorption.Therefore,the preparation of the lignite-based adsorbent to treat the wastewater not only saves energy,but also achieves the purpose of waste treatment.In this paper,lignite was used as raw material,which was modified by ultrasonic impregnation method,and the experimental parameters of the prepared metal ion lignite were studied.At the same time,the loaded modified lignite was applied to the treatment of dye wastewater.The direct yellow-brown dye was used as a target to study the adsorption performance of raw lignite and modified lignite on the anion dye containing azo structure,and achieved the purpose of joint treatment of lignite,heavy metal and dye wastewater.Firstly,using the adsorption capacity of direct yellow brown as the index to measure the load modification condition parameters.The orthogonal experiment and single factor experiment method were used to determine the significance of various factors in the preparation process of loaded metal ion lignite,and then the optimal preparation conditions were obtained.Selecting copper nitrate trihydrate(in place of copper ion wastewater)for the impregnation solution,the concentration is 0.1 mol/L,the ultrasonic immersion time is 30 minutes,the temperature of the immersion liquid is 45°C,and then the loaded ion modified lignite and the raw lignite are subjected to roasting for 2hours at the temperature of 400°C in a fixed bed reaction device.The physical and chemical properties of lignite and modified lignite were analyzed by X-ray diffractometer,plasma emission spectrometer,scanning electron microscope,infrared spectrometer,TG analysis,X-ray photoelectron spectroscopy and specific surface area and pore analyzer.It was found that the surface of lignite modified by ultrasonic impregnation becomes smooth,and the loaded copper element mainly existed in the form of divalent copper ions.The specific surface area was slightly reduced from the original 7.15 m~2/g to 5.36 m~2/g.The types and properties of surface functional groups of lignite remained unchanged.The calcination process greatly reduced the specific surface area of lignite by about 1.89 m~2/g,which the surface showed large cracks,and the micropores disappeared.At the same time,the divalent copper was reduced and the number of surface functional groups was reduced.Combined with the characterization results,the loading process was mainly the ion exchange between the copper ions in the solution and the active groups on the surface of lignite,and the roasting of lignite at400°C was mainly the drying and desorption stage of lignite.Finally,the prepared modified brown coal was used as adsorbent to adsorb the direct yellow-brown dye.The effects of initial concentration,dosage,reaction temperature,initial pH of the solution and reaction time on the adsorption performance were investigated.Pseudo-first-order kinetic model,the second-order kinetic model and the intra-particle diffusion model were used to fit the adsorption kinetics.The adsorption thermodynamics process was fitted by Langmuir,Freundlich and Langmuir-Freundlich isotherm adsorption models and thermodynamic parameters calculations.The results showed that the initial concentration of 100 mg/L of direct yellow brown dye was 50 mL,coal sample dosage was 0.1 g,and the adsorption temperature of modified lignite to direct yellow brown could reach 31.39 mg/g.It was nearly double that of the original coal,and the adsorption kinetics process accorded with pseudo-second order kinetic;the adsorption isotherms were consistent with the Langmuir-Freundlich adsorption model.The results of kinetic and thermodynamic data show that the lignite adsorption of the direct yellow-brown dye is a spontaneous exothermic reaction,and the adsorption process is not controlled by a single adsorption rate.In this paper,the lignite with abundant resources is used as the adsorbent raw material to load metal ions to enhance the adsorption capacity of lignite to anionic dye wastewater.This method is simple in operation,low in process cost,and can treat two types of polluted wastewater at the same time,which provides a new way for lignite utilization.The paper has 39 figures,16 tables and 109 references.