Study Of Activated Carbon Prepared From Different Plant Wastes

Active carbon is one of the most widely used porous materials in the world.It’s excellent physical and chemical properties are widely used in environmental protection,chemical industry,food and pharmaceutical industry,and more coal,fruit shell and wood are used as production sources.In order to expand the range of raw materials and clean production,people are more inclined to choose renewable plant waste,in order to orientate the physical and chemical properties of activated carbon to obtain specific types of activated carbon,people have changed more in the process of activation or reformed activated charcoal for twice.The study of the relationship between the properties of plant raw materials and the directional change of activated charcoal is still less.In the experiment,the most commonly used two kinds of raw materials were selected,and the common fruit skin and harmless plants were added.The KOH activation method was used to make the best preparation conditions:the alkali carbon ratio was 3:1,the activation temperature was 750 temperature 1h,and the difference of the properties of the activated carbon from different plant sources was compared.It is found that(1)the yield of woody plants is higher than that of herbaceous plants.The yield of the selected raw material is almost equal.(2)It is generally considered that the micro pore ratio of the plant with high lignin content is higher and the iodine adsorption is higher,but the iodine adsorption value of the bamboo shoot shell is higher than that of the wood chips.(3)The specific surface areas of all activated carbons with the iodine adsorption value upon 1500mg/g were determined.The results showed that the specific surface area of bamboo shoots was the largest,higher than that of sawdust and husk.Two kinds of herbaceous raw materials(Alternanth.era philoxeroides,bamboo shoot shell)and three kinds of wood raw materials(lignin from low to high:sago cycas leaves,poplar sawdust,choerospondias stone)were selected for further analysis to explore the composition of different kinds of wood raw materials on the pore structure and adsorption properties of activated carbon formation.The results show that(1)yield is affected by ash content.(2)Neither the samples with lowest or highest lignin content can obtain highest surface area or best performance.(3)High content of total cellulose also has important contribution to high specific surface area.We select the common water plant waste Trapa bispinosa husk,use the anaerobic atmosphere self-activation method to make the activated carbon,and optimize the preparation process by orthogonal test.For the activated carbon prepared under the optimum conditions,the pyrolysis process of the activated carbon is analyzed by thermogravimetric analysis.N2 absorption and desorption,X ray diffraction and Fourier transform infrared spectrum are used.The structure and properties of the activated carbon prepared by the best process were characterized with SEM.The results are as follows:(1)the optimum preparation conditions are carbonization/activation at 800℃ for 2 hours,and the adsorption perform ance and yield of activated carbon are better.The activated charcoal prepared under this condition is microporous activated carbon,the specific surface area is 1254.46m2/g,the total pore volume is 0.69cm3/g,the micro-pore rate is 69.4%and the porosity is high.The structural stability is good,and the functional groups are not detected on the surface of activated carbon,indicating that the adsorption process is physical adsorption.(2)The adsorption value of phenol can reach 355.8mg/g and the higher the concentration of phenol,the greater the adsorption capacity.The higher the amount of the activated carbon,the increase of the phenol removal rate.The decrease of the adsorption capacity,and the adsorption equilibrium at the low concentration and high concentration at about 15min.The adsorption process of phenol conforms to the Langmuir isotherm model,indicating that the adsorption process is a single molecular layer.It indicates that the Trapa bispinosa husk is a good raw material for the preparation of activated carbon under the preparation conditions.(3)The adsorption value of the activated carbon is 1531.5mg/g and the adsorption value of methylene blue is 165mg/g,which is higher than the quality standard of the two grade of the activated charcoal for wood water purification in China.It is known that the activated charcoal of the diamond shell has a certain application value in the actual production.In summary,Lignin contents do not determine the yield,specific surface area and adsorption capacity of the corresponding activated carbon.A certain medium porosity can greatly increase the specific surface area.Ash has a greater impact on the yield of activated carbon.Activated carbon with good structure and function can be prepared by self-activation method from Trapa bispinosa husk,which shows that it is feasible to produce excellent activated carbon without adding activator.