Study On Electrochemical Regeneration Mechanism Of Mushroom Residue Activated Carbon Adsorbing Aniline And Methylene Blue

Activated carbon(AC)has the characteristics of high specific surface area,rich pore structure,and diverse surface chemical groups.As the most widely used adsorbent,it is widely used in water treatment process.Now the mainstream AC raw materials are mainly coal and some high-value agricultural and forestry materials.The high cost of these materials limits the application of AC in my country.Mushroom residue(MR),as agricultural waste,has the characteristics of loose,porous and low cost.It is one of the excellent precursors for the production of biomass AC.The use of MR to prepare mushroom residue activated carbon(MRAC)is the resource utilization of agricultural waste and reduces the production cost of AC.In the process of wastewater treatment,with the increase of treatment time,the adsorption capacity of AC will reach saturation and the adsorption capacity will be lost.If the waste AC is not handled properly,it will cause secondary pollution to the environment and waste resources.Therefore,restoring the adsorption capacity by regeneration is an effective way to deal with the waste AC.As a new regeneration technology,electrochemical regeneration has the advantages of low carbon loss,high regeneration rate,and environmental friendliness.It got people’s attention and was researched a lot.In this study,MRAC was prepared to remove aniline and methylene blue(MB),the common pollutants in wastewater.The adsorption properties of MRAC were investigated by adsorption isotherms,kinetics and thermodynamic experiments.On this basis,the waste MRAC is treated by electrochemical regeneration technology.During the electrochemical regeneration process,the effects of single factor conditions such as current intensity,electrolyte type and concentration,regeneration time,and p H on regeneration were explored.The optimal regeneration conditions were determined by orthogonal experiments or response surface experiments.The adsorption mechanism and regeneration mechanism of MRAC were studied by FT-IR,BET,SEM,masking experiment and TOC experiment.Follows are main findings.1.Using agricultural waste MR as raw material,MRAC is prepared by zinc chloride activation method.When 5 g/L MRAC was added to the 100 mg/L aniline solution,the adsorption capacity was 80.43 mg/g;when 1 g/L MRAC was added to the 100 mg/L MB solution,the adsorption capacity was 92.27 mg/g.The adsorption process of aniline and MB was more in line with the pseudo-second-order kinetic model.The adsorption isotherm conforms to the Langmuir isotherm model,and the RL are between 0 and 1 at different temperatures,indicating that the adsorption is favorable.Thermodynamic experiments proved that the adsorption processes of aniline and MB were both spontaneous endothermic reactions and were subject to the combined effect of physical adsorption and chemical adsorption.The intra-particle diffusion model indicated that the adsorption process of MRAC was affected by the combined effect of external membrane diffusion and intra-particle diffusion.2.After comprehensively considering energy consumption and regeneration effect,the optimal regeneration conditions for electrochemical regeneration of MRAC saturated with aniline are: p H 5,current 300 m A,Na Cl concentration 15 g/L,and regeneration time 1.5 h.Adding 0.5 g of saturated MRAC,the regeneration rate was as high as 98.43%.After 6adsorption-regeneration cycles,the MRAC regeneration rate did not decrease significantly,and the sixth regeneration rate could reach 87.53%.Characterization analysis showed that after regeneration,the active groups represented by hydroxyl groups on the surface of MRAC were recovered,the specific surface area increased from 902.70 m2/g to 986.83 m2/g,the average pore size increased,and the pore volume increased.During the adsorption process,aniline was mainly adsorbed on the MRAC surface through hydrogen bonding and intermolecular interactions.During the regeneration process,the aniline on the surface of MRAC was removed by the electrodesorption of electric current and the oxidation of oxidative groups such as hypochlorite and hydroxyl radicals.3.In the experiment of electrochemical regeneration and adsorption of MB-saturated MRAC,the optimal regeneration conditions were determined by response surface methodology:the current was 300 m A,the regeneration time was 2 h,the Na2SO4 concentration was 10 g/L,and the p H was 8.4.Under the optimal conditions,the regeneration rate of 0.1g MRAC was as high as 98.43%.After 6 cycles of regeneration,the regeneration rate of MRAC can still reach84.36%,and the adsorption capacity does not decrease significantly.Characterization analysis showed that after electrochemical regeneration,the active groups on the surface of MRAC were recovered,such as hydroxyl groups,and the ester groups generated by adsorbing MB disappeared.After regeneration,the specific surface area of MRAC increased from 902.70 m2/g to 908.57 m2/g,the average pore size increased,and the pore volume increased.During the adsorption process,MB was mainly adsorbed on the MRAC surface through π-π bonds,hydrogen bonds and intermolecular interactions.During the regeneration process,the aniline on the surface of MRAC was removed by the electrical desorption of current and the oxidation of oxidative groups such as hydroxyl radicals,and the MRAC was regenerated.