Preparation Of Activated Carbon From Cotton Stalk And Its Adsorption Capability

In this study,cotton stalk-based activated carbon was prepared by orthogonal test with sodium hydroxide,zinc chloride and nitric acid as the activator.The activation temperature,the activation time and the ratio of the ratio of the agent to the activated carbon of the cotton stalk were studied by single factor experiment.The surface microstructure,specific surface area and pore size of the cotton-based activated carbon were determined by means of scanning electron microscopy,specific surface area analyzer,Fourier transform infrared spectroscopy,X-ray diffraction and X-ray photoelectron spectroscopy.Pore size,element composition,surface functional groups and the content of the physical and chemical properties of characterization analys is.The effects of different initial concentration,time,pH and dosage on the adsorption of cotton stalk on the adsorbate in water were studied by static experiment.Based on the above results,the Langmuir and Freundlich isotherm models,quasi-first-order kinetics and second-order kinetics model were used to analyze the adsorption kinetics curve.The mechanism and kinetics of adsorption of heavy metal ions by modified activated carbon were analyzed.This study provides theoretical guidance for the utilization of waste cotton stalks and the treatment of heavy metals and organic matter in waste straw by activated carbon.The main conclusions of this paper are as follows:(1)Different activators had significant differences in the pore structure and surface canopy groups of the activated carbon obtained by direct activation of the activated carbon and the pyrolysis of the activated carbon.When the sodium hydroxide was used as the activator,the pore structure of the activated carbon has some damage,but the type and content of the surface functional groups of the activated carbon are increased,especially the content of the hydroxyl crown can be increased obviously;When the nitric acid is used as the activator,the activated carbon and the direct pyrolysis,the surface pore structure of the activated carbon was signif icantly increased,and the type and content of the surface of the activated carbon were signif icantly increased.With the increase of carbonization activation temperature,the yield of cotton-based activated carbon is gradually reduced,and when the pyrolysis is carried out at a low temperature of 250?,the carbon ratio is 40.57%,but the cotton straw The adsorption of activated carbon is poor.Considering the adsorption effect and carbonation rate of cotton-based activated carbon on different adsorbents,the carbonization rate was 350? and the carbonization time was 120 min,and the carbon ratio was 37.62%.When the activator is nitric acid,the carbonization temperature is 450? and the carbonization is 180 min,the adsorption capacity is up to 1500mg/g;the surface area is 194.43m2/g;the specific surfac e area is 100.74m2/g,and the specific surface area of the pores is 26.38m2/g with an average pore size of 4.97 nm.(2)The adsorption capacity of the activated carbon on the adsorbate was better than that of the activated carbon under the direct pyrolysis c onditions,which indicates that the activator could effectively improve the adsorption capacity of the activated carbon of cotton stalk,and combine the experimental results of the previous two chapters.The sodium hydroxide activator could effectively inc rease the content and type of oxygen-containing crowns on the surface of the cotton-straw-based activated carbon by Fourier spectroscopy and X-ray diffraction pattern analysis,and the content of hydroxyl groups increased obviously.Under the conditions of pyrolysis temperature of 400? and pyrolysis time of 150 min,the adsorption ratio of the activated carbon prepared in the ratio of 1 to 1 was pH4,the adsorption of heavy metal was best at the adsorption temperature of 25?.Among these the maximum adsorption of copper was 8.439mg/g,and the maximum adsorption capacity of zinc was 10.13mg/g.The adsorption of heavy metal copper and zinc was consistent with the Lagrang quasi-second adsorption kinetics model and the Freundlich isothermal adsorption model,whic h indicated that the adsorption process of copper-based activated carbon on heavy metal copper in water was a dynamic adsorption process involving the combined action of multiple processes.(3)Nitric acid as an activator could effectively improve the specific surface area and pore structure of cotton-based activated carbon.The optimum conditions for the adsorption of organic carbon(phenol and methylene blue)were as follows: the pyrolysis temperature was 400? and the pyrolysis time was 150 min.Among these the maximum adsorption capacity of phenol was 227.36mg/g,and the maximum adsorption capacity of methylene blue was 202mg/g.The adsorption of phenol and methylene blue by cotton stalk-based activated carbon was in accordance with the quasi-second-order kinetic model.The adsorption equilibr ium experiment showed that the adsorption of phenol and methylene blue by cotton-straw-based activated carbon was in accordance with Langmuir model.The above results showed that the pore structure and specific surface area were the main factors influencing the adsorption of phenol and methylene blue by the activated carbon of cotton stalk.