Study On Hydrothermal Carbonation Of Lignin And Adsorption Of Hydrothermal Coke

Water resources are an indispensable and important material in human life.However,with the rapid development of social industry,more and more water resources have been destroyed,and how to effectively solve the problem of water pollution has attracted people’s attention.Because lignin is renewable,degradable,and environmentally friendly,and contains a rich structure of functional groups,it is used by researchers to prepare carbon materials.The hydrothermal coke prepared by the hydrothermal method has good adsorption performance,and can effectively remove heavy metal ions from water,which provides a new way to solve the problem of water pollution.In this paper,hydrothermal coke was prepared by low-temperature hydrothermal carbonization with lignin and glucose as raw materials.The influence of factors such as reaction time,temperature,lignin addition amount and glucose concentration on its preparation was explored.By orthogonal experiment,it was found that at 180℃,adding 1.0 g/100 mL glucose solution to 10 g lignin for 10 h,the yield of hydrothermal coke could reach 72.6%.SEM,XRD,BET,FT-IR characterization showed that:the appearance of hydrothermal coke is massive and belongs to the microporous structure,with a specific surface area of 13.5 m2/g,and no obvious crystal structure.The static adsorption method was used to adsorb Cr(Ⅵ)in the solution,and the influnce of reaction time,reaction temperature,pH value,and hydrothermal coke amount on the adsorption of Cr(Ⅵ)were probed,under optimal conditions,and the maximum adsorption capacity of hydrothermal coke for Cr(Ⅵ)is 4.7 mg/g,and the removal rate was 40.5%.Through the fitting analysis of the two isothermal adsorption models,it is found that the Langmuir adsorption isotherm model has a better fitting effect.The adsorption of Cr(Ⅵ)by hydrothermal coke belongs to monolayer adsorption.After analyzing the two adsorption dynamics models,the fitting degree of the pseudo-second-order dynamics model is higher than 0.9653,and the adsorption of Cr(Ⅵ)by hydrothermal coke is mainly chemisorption.The prepared hydrothermal coke is put into muffle furnace and heat treated at different temperatures(500℃,600℃,700℃).At 700℃,the specific surface area of the hydrothermal carbon increased to 287.7 m2/g,and its appearance changed from a block to a small particle carbon microsphere.For the prepared hydrothermal carbon,the static adsorption method was used to adsorb Cr(Ⅵ)in the solution.When the pH value was 2～3 and the temperature was 45℃,the maximum adsorption capacity of 1.0 g hydrothermal carbon on Cr(Ⅵ)could reach 8.7 mg/g in 180 min,the removal rate reached 87.7%,and the adsorption effect was doubled.The adsorption isotherm of Cr(Ⅵ)by hydrothermal carbon after high temperature heat treatment still conforms to the Langmuir model with a fitting degree of 0.9997,and the pseudo-second-order dynamics model with a fitting degree of 0.9996.