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The Preparation Of Biological Carbon Composite Material Modified By Graphene Oxide And Its Adsorption Mechanism Of Cr(?)

Posted on:2018-08-18Degree:MasterType:Thesis
Country:ChinaCandidate:M R ShangFull Text:PDF
GTID:2321330542961747Subject:Environmental Engineering
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In recent years,heavy metal pollution in water body has attracted extensive attention at home and abroad,of which chromium pollution is the most common.Chromium mainly exists in two stable forms in water:Cr(III)and Cr(VI).However,Cr(VI)is especially poisonous,which was 100 times greater than Cr(III)in toxicity.Due to Cr(VI)long-term exposure to the environment,hexavalent chromium can cause many serious health problems for human beings(e.g.,skin irritations,lung cancer,and viscera damage).Therefore,it is an important environmental issue to develop an effective method to remove Cr(VI)from effluent.At present,adsorption is one of the most popular and effective option,due to its cost effectiveness,simple operation and least waste generation.Biochar has high adsorption characteristics for heavy metals,which contains rich functional groups,high specific surface area,loose porous structure,high charge density and so on.Common adsorbents such as carbon fiber material,clay mineral,zeolite and resin have the disadvantages of small adsorption capacity and low adsorption efficiency,which are limited application in many fields.Nowadays,graphene oxide(GO)as a new type of adsorbent has attracted vast technological and scientific interest due to its specific properties,such as rich functional groups,large specific surface areas,loose porous structure,biocompatibility,easy dispersion ect.Due to the above-mentioned excellent properties of graphene oxide,it is believed that it could be used as coating material to functionalize various adsorbent.In this study,a novel functional adsorbent,graphene oxide coated biochar,was prepared by slow pyrolysis in tube furnace,and applied to the removal of Cr(VI)ions in polluted water.The WHB-GO was characterized by many technologies,such as SEM,FTIR,XPS and BET.The experimental results indicated that the data were better fitted by the pseudo-second-order and Freundlich models.Thermodynamic experiments showed that the adsorption process of Cr(VI)in aqueous solution was a spontaneous endothermic reaction.The maximum adsorption of the WHB-GO was obtained at pH 2.0 and 50? with the sorption capacity of 150.02 mg g-1.The main adsorption mechanisms were electrostatic adsorption and complexation reaction.Besides,the adsorption process was significantly affected by the solution pH and ionic strength.Additionally,the adsorbent had a good stability during the adsorption-desorption cycles without significant reduction of the adsorption capacity.In summary the composite had excellent physical and chemical properties,which can effectively and economically remove Cr(VI)ions from aqueous solution.
Keywords/Search Tags:Biochar, Graphene oxide, Cr(?), coated, adsorption
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