The Preparation Of Novel Multifunctional Adsorbent Materials And Application In Water Treatment

The increasing worldwide contamination of water resources with thousands of inorganic and organic pollutants,such as toxic metals,dyes,pharmaceuticals,pesticides,and endocrine disrupting chemicals,has raised more and more serious environmental problems facing humanity in almost all part of the world.Nowadays,they are the common contaminants in water systems,and most of them are hazardous or carcinogenic.In this thesis,the recent development of adsorbent materials as well as the application of cross-linked polysaccharide biosourced polymers were briefly reviewed,and a series of novel multifunctional adsorbent materials were prepared and their application in water treatment were conducted,as summarized as followed:1.A novel adsorbent was synthesized by functionalizing chitosan with ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid(EGTA)ligands.The adsorption capability of EGTA-modified chitosan was investigated by the removal of Cd(?)and Pb(?)from aqueous solutions.The adsorption and regeneration studies were performed by batch techniques.The effects of pH,contact time,and ini-tial metal concentration were studied.Metal uptake by EGTA-chitosan was 0.74 mmol mmol g-1 for Cd(?)and 0.50 mmol g-1 for Pb(?).The adsorption mechanism,that the adsorbent formed octahedral chelate structures with bivalent metal ions,was proposed tentatively based on the experimental results of FTIR and the theoretically calculated data of point charges.The kinetics of Cd(?)and Pb(?)on EGTA-chitosan complied with the pseudo-second-order model and the adsorption rate was also influenced by intra-particle diffusion.BiLangmuir isotherm model was well fitted to the experimental data of one-compo-nent adsorption suggesting the surface heterogeneity of the novel adsorbent.The extended form of the BiLangmuir model was tested for the modeling of two-component adsorption equilibrium of Cd(?)and Pb(?)on EGTA-chitosan.In the two-component solution,both competitive adsorption and positive syn-ergy of chelation between metal ions occurred and the novel adsorbent showed higher affinity toward Cd(?).2.We described a green and economic approach to explore EDTA/DTPA-functionalized magnetic chitosan as adsorbents for the removal of aqueous metal ions,such as Cd(?),Pb(?),Co(?),and Ni(?).EDTA and DTPA play roles not only as cross-linkers but also as functional groups in chelating metal ions.The morphology,structure,and property of the magnetic adsorbents were characterized by SEM,TEM,XRD,EDS,FT-IR,TGA,and VSM techniques.Their adsorption properties for the removal of metal ions by varying experimental conditions were also investigated.The kinetic results revealed that the transportation of adsorbates from the bulk phase to the exterior surface of adsorbents was the rate-controlling step.The obtained maximum adsorption capacities of magnetic adsorbents for the metal ions ranged from 0.878 to 1.561 mmol g-1.Bi-Langmuir and Sips isotherm models fitting well to the experimental data revealed the surface heterogeneity of the adsorbents.More significantly,the resulting EDTA-/DTPA-cross-linked magnetic chitosan adsorbents had selectivity to Cu,Pb,Zn,Fe,and Ni from a practical industrial effluent.Furthermore,their good reusability and convenient magnetic separation makes them viable alternatives for real wastewater treatment.3.The discharge of metals and dyes poses a serious threat to public health and the environment.What is worse,these two hazardous pollutants are often found to coexist in industrial wastewaters,making the treatment more challenging.Herein,we report an EDTA-cross-linked ?-cyclodextrin(EDTA-?-CD)bifunctional adsorbent,which was fabricated by an easy and green approach through the polycondensation reaction of ?-cyclodextrin with EDTA as a cross-linker,for simultaneous adsorption of metals and dyes.In this setting,cyclodextrin cavities are expected to capture dye molecules through the formation of inclusion complexes and EDTA units as the adsorption sites for metals.The adsorbent was characterized by FT-IR,elemental analysis,SEM,EDX,?-potential,and TGA.In a monocomponent system,the adsorption behaviors showed a monolayer adsorption capacity of 1.241 and 1.106 mmol g-1 for Cu(?)and Cd(?),respectively,and a heterogeneous adsorption capacity of 0.262,0.169,and 0.280 mmol g-1 for Methylene Blue,Safranin O,and Crystal Violet,respectively.Interestingly,the Cu(?)-dye binary experiments showed adsorption enhancement of Cu(?),but no significant effect on dyes.The simultaneous adsorption mechanism was further confirmed by FT-IR,thermodynamic study,and elemental mapping.Overall,its facile and green fabrication,efficient sorption performance,and excellent reusability indicate that EDTA-?-CD has potential for practical applications in integrative and efficient treatment of coexistenting toxic pollutants.4.The separation and recovery of Rare earth elements(REEs)from diluted aqueous streams has attracted great attention in recent years because of ever-increasing REEs demand.In this study,a green synthesized EDTA-cross-linked ?-cyclodextrin(EDTA-?-CD)biopolymer was prepared and employed in adsorption of aqueous REEs,such as La(?),Ce(?),and Eu(?).EDTA acts not only as cross-linker but also as coordina-tion site for binding of REEs.The adsorption properties for the adsorption of REEs by varying experimental conditions were carried out by batch tests.The kinetics results revealed that the surface chemical sorption and the external film diffusion were the rate-determining steps of the adsorption process.The obtained maximum adsorption capacities of EDTA-?-CD were 0.343,0.353,and 0.365 mmol mmol g-1 for La(?),Ce(?)and Eu(?),respectively.Importantly,the isotherms fitted better to Langmuir than Freundlich and Sips models,suggesting a homogenous adsorption surface for REEs on the adsorbent.Moreover,the multi-component adsorption,which was modeled by extended Sips isotherms,revealed adsorbent's selectivity to Eu(?).More significantly,the successful recoveries of the studied ions from tap water and seawater samples makes EDTA-(3-CD a promising sorbent for the preconcentration of REEs from diluted aqueous streams.5.The global contamination of inorganic and organic micropollutants,such as metals and pharmaceuticals,poses a critical threat to environment and human health.Herein,we report a chitosan-EDTA-?-cyclodextrin(CS-ED-CD)trifunctional adsorbent,which was fabricated via a facile and green one-pot synthesis method by using EDTA as a cross-linker,for adsorption of inorganic and organic micropollutants.In this system,chitosan chain is considered as the backbone of this novel polymer,and the immobilized cyclodextrin cavities capture organic compounds via host-guest inclusion meanwhile EDTA-groups complex metals.The adsorbent was characterized by FT-IR,elemental analysis,SEM,?-potential,and TGA.The amounts of active EDTA-groups and cyclodextrin cavities on CS-ED-CD were defined by conductometric-potentiometric titration and photometric titration,respectively.The adsorbent showed a monolayer adsorption capacity of 0.803,1.258 mmol g-1 for Pb(?)and Cd(?)respectively,while a heterogeneous sorption capacity of 0.177,0.142,0.203,0.149 mmol g-1 for bisphenol-S,ciprofloxacin,procaine,and imipramine,respectively.The adsorption mechanism was verified by FT-IR and elemental mapping.Importantly,the adsorbent perform an effective and simultaneous removal of inorganic and organic pollutants at environmentally relevant concentrations.These findings demonstrate the promise of CS-ED-CD for practical applications in the treatment of micropollutants.6.A novel magnetic hydroxamic acid modified polyacrylamide/Fe3O4 adsorbent(M-PAM-HA)was prepared with acrylamide by microemulsion polymerization and then nucleophilic substitution of hydroxamic acid.The morphology,structure of the magnetic adsorbents before(M-PAM)and after modification(M-PAM-HA)were characterized and their adsorption properties for the removal of metal ions by varying test conditions were also investigated.The modified M-PAM exhibited lower swelling property and less magnetic leaching than M-PAM.Their adsorption kinetics followed the pseudo-second order model.The maximum adsorption capacities of metal ions ranged from 0.11 to 0.29 mmol g-1 for M-PAM and 0.88-1.93 mmolg-1 for M-PAM-HA,respectively.Sips model fitting well to experimental data revealed the surface heterogeneity of the prepared adsorbents.In multi-metal systems,M-PAM-HA showed the relative selectivity toward Pb(II),although Pb(II)wasadsorbed the least in their corresponding one-metal systems.The adsorption mechanism was proposed based on the results of FTIR and density functional theory(DFT)calculation.