The Preparation Of Porous Carbon Composite Materials And The Adsorption Of Hexavalent Chromium

Activated carbon(AC)can adsorb Cr(VI)effectively.However,the density of AC is small,and the spent AC containing the adsorbed Cr(VI)can cause secondary pollution to the environment if it is not handled properly.In order to solve this problem,AC was coated on silica sand or waste glass fiber fabric,obtaining porous carbon-silica sand/glass fiber composite material.After the adsorption of Cr(VI),the composite materials were used as colorants to melt color glasses.In this paper,the samples were characterized by TEM,XRD,SEM,XPS,FTIR and N2-sorption.The effects of reaction components and experimental conditions on the preparation of porous carbon composites were studied.The effects of the experimental conditions on the adsorption of Cr(VI)were also investigated.The main contents and conclusions are as follows:1.We explored the effects of different proportions of AC-chromium and the feeding method on the coloration of glass,and confirmed the feasibility of using activated carbon to adsorb chromium ions for glass colorization.With the increase of the amounts of colorant added,the glasses gradually change from black-brown to green.When the amounts of Cr ions are same,AC itself helps affect the glass colorization.The feeding method has little effect on the colorization of the glass.2.Glucose was used as carbon source to prepare the porous carbon-silica sand composite materials(AC@sand)by hydrothermal reaction.The amount of coke coated on the sand formed via the hydrothermal reaction first increases and then decreases with the increase of ethylenediamine.And the optimal dosage of ethylenediamine is 0.5 mL.The specific surface area increases with the increase of SDS,because SDS is used not only as a soft template agent of AC@sand but also secondary carbon source.With the increase of the amount of KOH,the specific surface area first increases and then decreases followed an increase,because KOH and carbon layer or silica sand react under high temperature,respectively.With the increase of the activation temperature,the specific surface area increases first,then decreases.With the increase of the deliquescence time from the first day to the seventh day,the specific surface area increases obviously,and the specific surface area increases less with further extending the deliquescence time.The optimal experimental conditions for prapairng AC@sand determines as: 0.5 m L ethylenediamine,0.2 g SDS,0.1 g KOH,activation temperature of 700 ? and deliquescence time of 7 days.The specific surface area of the AC@sand is 59 m~2 / g,which is 80 times that of the original silica sand.The optimal conditions for adsorbing Cr(VI)ions with AC@sand are: pH of 2.0,the concentration of Cr(VI)ion of 20 mg / L,contact time of 2 h and temperature of 75 ?.Under these conditions,all Cr(VI)is removed,among which the adsorbed Cr accounts for 76.91% with the balance reduced.The adsorbed Cr(VI)on per unit mass of AC@sand is 1.5382 mg / g.The adsorption of Cr(VI)on AC@sand follows the Freunedlich adsorption model and the second-order kinetic model.3.PVP was used as carbon source to prepare the porous carbon-glass fiber composite composite materials(AC@GFF).The specific surface area of the sample increases with the increase of the activation temperature,the amount of PVP and KOH,respectively.PVP acts as both a carbon source and a binder.KOH is not only a activator but also increase the adhesion of the PVP to the surface of the glass.The optimal conditions for preparing AC@GFF are determined as: 5 g pvp,0.8 g KOH and activation temperature of 700 ?.The specific surface area of the AC@GFF is 248 m~2 / g,which is 248 times that of the glass fiber fabric.The optimal conditions for the adsorption of Cr(VI)ions by AC@GFF are: pH value of 2.0,concentration of Cr(VI)ion of 50 mg / L,contact time of 2 h and temperature of 45 ?.Under these conditions,the removal rate of Cr(VI)is 96.54%,among which the adsorption of Cr is 90.47% with the balance reduced.The adsorbed Cr(VI)on per unit mass of AC@GFF is 22.6170 mg / g.The adsorption of Cr(VI)on AC@GFF follows the Langmuir adsorption model and the second-order kinetic model.4.Under the best adsorption conditions,the green glasses are obtained with the colorants of spent AC@sand and AC@GFF containing the adsorbed Cr(VI),respectively.The proportions of AC@sand and AC@GFF in the glass batches are 44.07% and 3.00%,respectively.