Preparation Of Corn Cob Activated Carbon And Removal Of Cr(?)and Aniline From Water

China is a corn-producing country,producing as much as 200 million tons of corn each year,and there will be a lot of corn cob waste during the corn production and processing.However,there are no systematic corn cob treatment methods presently in China.Corn cob are roughly disposed,incineration or landfill,by the farmer.In these ways,utilization rate of the corncob are extremely low,and the pollution to the environment due to SO2,CO2 discharged by incineration is severe.In particular,the haze is severe currently,so incineration are disadvisable.Cr(?)and aniline in wastewater can be removed by treated corn cobs,which not only solves the problem of excessive residual corn cobs,but also reduces the environmental pollution of wastewater containing Cr(?)and aniline.In this paper,corn cob activated carbon(CCAC)was prepared by H3PO4 activation method,and the optimal preparation conditions were screened by orthogonal experiments.The adsorption performance of CCAC was studied using Cr(?)in water as determine contaminant.The effect of the solution p Hvalue,reaction time,CCAC dosage and initial concentration of hexavalent chromium(Cr(?))on it was study as well.The CCAC was modified by KMn O4 to generate Mn-modified corn cob activated carbon(Mn-CCAC)for the removal of aniline in water.The best Mn-CCAC was screened by orthogonal experiment,and CCAC was compared with Mn-CCAC.All samples were characterized by FTIR,XRD,BET,SEM,EDS and other test methods.The experimental results showed that the best preparation conditions for CCAC were: After adding corn cob 10 g,the ratio of corn cob and H3PO4 was1:2,and 10 m L of 5%H3BO3 was added,and immersed for 45 min.The carbonization temperature was 500°C.When the reaction was carried out for 1h,CCAC had the best Cr(?)adsorption effect.The optimal modification conditions for Mn-CCAC were: When 50 m L of 0.06mol?L-1 KMn O4 solution was added and soaked for 24 h,the calcination temperature was 400?and the calcination time was 1h,Mn-CCAC had better adsorption effect on aniline.CCAC characterization results: SEM showed that the surface of CCAC had a more porous structure,and the distribution was more developed and more uniform;XRD showed that CCAC had the structure that can promote the adsorption of Cr(?)by CCAC;FTIR showed that the surface of CCAC had oxygen-containing functional groups such as hydroxyl O-H bond,C=O bond,C-O single bond,C-O-C ether bond and-COOH carboxylic acid bond,which can promote the occurrence of adsorption;BET showed that single-site specific surface area,BET specific surface area and pore volume of CCAC and CSACwere significantly higher than CAC;EDS showed that the C content of CCAC was more than half.Mn-CCAC Characterization results: SEM showed that the surface of Mn-CCAC had more acidic oxygen-containing functional groups through modification of KMn O4,and the surface pores were finer and more uniform.The surface pore diameter of CCAC was larger than that of Mn-CCAC;XRD showed that after the KMn O4 solution was modified,the diffraction peaks became flat and the other impurity peaks weakened;XRD showed that after the KMn O4 solution was modified,the diffraction peaks became flat and the other impurity peaks weakened;FTIR showed that after the oxidation of CCAC by KMn O4,the acidic oxygen-containing functional groups on the surface increased,the-OH bond was oxidized to-C=O bond,and the oxygen-containing functional groups such as lactone and phenolic hydroxyl groups increased;BET showed that the single-point specific surface area,BET specific surface area and pore volume of Mn-CCAC were significantly higher than those of CCAC;EDS showed that the C content of CCAC and Mn-CCAC both were very high,accounting for about 70%,and the content of O accounted for 24%~25%.The best adsorption conditions for CCAC were: When the solution p H?9,temperature was 35?,rotation speed was 150r·min-1,reaction time was60 min,CCAC dosage was 1g·L-1.The Cr(?)removal rate can reach over 98%,the maximum adsorption amount was 9.985 mg?g-1,and the residual Cr(?)concentration in the water is less than 0.05 mg?L-1.It complied with China's"Sanitation Standards for Drinking Water(GB5749-2006)" and "Emission Standards for Pollutants for Municipal Wastewater Treatment Plants(GB18918-2002)".The best adsorption conditions for Mn-CCAC were: When the solution p H was 3~11,temperature was 25?,speed was 150r?min-1,reaction time was 10 min,CCAC dosage 3g?L-1.The aniline removal rate can reach more than 98%,the remaining aniline concentration in the water is less than 0.5mg?L-1.It complied with China's "Emission Standards for Pollutants for Municipal Wastewater Treatment Plants(GB18918-2002)".Adsorption of Cr(?)by CCAC was in accordance with pseudo-second order kinetics.The adsorption isotherm was in accordance with the Langmuir model and was monolayer adsorption.The adsorption reaction was an endothermic reaction,and the higher the temperature,the greater the spontaneous degree of the reaction.Adsorption of aniline on Mn-CCAC accorded with pseudo-second-order kinetics.The adsorption isotherm conformed to the Langmuir model.It belongs to monolayer adsorption and the adsorption reaction was exothermic.The lower the temperature was,the greater the degree of spontaneous reaction.