Adsorption And Bioavailability Behavior Of Organic Contamintants On Carbonaceous Materials

With the fast development of carbon chemistry and materials technology,many scientists have focused on practical application of engineered carbon nanomaterials and porous carbonaceous materials.Owing to their stable physical and chemical properties,large specific surface area,abundant pore structure and surface functional groups,especially its adsorption properties,these carbonaceous materials are widely used in environmental field.Therefore,it is necessary to continue to study the interface process of organic pollutants on carbonaceous materials.It will help to form the microscopic mechanism and meticulous system understanding of adsorption behaviour on carbonaceous materials,controll the key factor of adsorption properties of carbonaceous material,ascertain the environment process of organic pollutant,predict the transport and fate of organic pollutant and its biological effects,and provide a theoretical basis on the economic efficiency removal techniques for organic pollutants.This dissertation focused on the adsorption process and its microcosmic mechanism of organic pollutants on engineered carbon nanomaterials(single-walled carbon nanotubes and multi-walled carbon nanotubes and graphene)and porous carbonaceous material(activated carbon,mesoporous carbon,black carbon)such as medium,investigated the adsorption behavior of the typical organic pollutants in the environment(monocyclic aromatic compounds,polycyclic aromatic hydrocarbons,tetracycline antibiotics?organochlorine pesticide,and aliphatic hydrocarbons)on the above two kinds of carbonaceous materials.Influences of chemical properties of organic pollutants and composition,surface chemical properties,pore size distribution of carbonaceous material,as well as the solution chemistry condition on the interface process and the microscopic mechanism.The main conclusions of chapters are as follows:(1)Our study indicate that the effectiveness of carbon-based adsorbents is highly adsorbate-specific and depends on the synergistic contributions of several factors.First,for compounds that can induce strong ?-? interaction(4-nitrochlorobenzene),the degree of carbon graphitization of the adsorbent is a critical factor controlling adsorption.Hence,compared with porous carbonaceous materials,the engineered carbon nanomaterials are superior adsorbent;micropore-filling can also be a significant mechanism,whose significance depends on how well the molecular geometry of the adsorbate molecules matches the pores of the adsorbent.Hence,for nonplanar aliphatic compounds(trans-1,2-dichlorocyclohexane),porous carbonaceous materials have better adsorption effect;Second,we add another two planar aromatic componds with different physical forms,our results verify that the micropore-filling mechanism is more pronounced for cubic molecules(trans-1,2-dichlorocyclohexane)than planar molecules;Finally,the model results and molecular model calculation results reaffirms these conclusion.(2)Our study first to point out that non-uniform structure of black carbon/BC(such as leachable pyrogenic organic carbon/LPyOC and hard carbon coexistence)could be the one of the important key fators of the nonideal sorption(e.g.,sorption irreversibility and slow kinetics).After removing the fraction of LPyOC,sorption of these sorbates(nitrobenzene,naphthalene and atrazine)to BC was enhanced.The sorption enhancement was positively correlated with sorbate molecular size.The removal of LPyOC also accelerated sorption kinetics and reduced sorption irreversibility.These observations were attributed to increased accessibility of BC micropores initially clogged by the LPyOC.Consistently,the sorption of nitrobenzene and atrazine to template-synthesized mesoporous carbon(CMK3),a model sorbent with homogeneous pore structures,showed decreased kinetics,but increased irreversibility by impregnating sorbent pores with surface-grafted alkylamino groups and by subsequent loading of humic acid.These findings indicated an important and previously unrecognized role of LPyOC(i.e.,micropore clogging)in the nonideal sorption of organic contaminants to BC.These results can assess accuratly the effect on the fate of organic pollutants on the BC and will provide a scientific basis on the environmental remediation technology.(3)Our study first to point out that the sorbed-tetracycline in biochar was bioavailable to bacteria mainly through desorption.However,the desorption may not be a prerequisite,because the tetracycline sorbed by low temperature produced biochar(C400)still showed higher bioavailability than high temperature produced biochar(C500)at the same dissolved tetracycline concentration,indicating that the tetracycline sorbed by biochar via surface sorption can be utilized by the bacteria simultaneously.Another finding in our study was that the bioavailability of tetracycline sorbed by C400 was also affected by incubation under different relative humidity.Our results can help us accurately evaluate the potential risks associated with tetracycline antibiotics in the environmental ecosystems.