Preparation Of Novel Materials For The Adsorption Of Heavy Metal Ions And Dyes

With the rapid development of modern industry, factories always discharge effluentcontaining heavy metal ions and dyes, which can bring about serious environmentalthreats and serious hazards to ecosystem and human health, respectively, due to theirtoxicity. If not promptly and effectively remove those toxic contaminants will directlythreaten human survival. Therefore, it is urgent to effectively deal with the wastewatercontaining toxic heavy metal ions and dyes. In this thesis, a series of novel magneticnanocomposite materials were synthesized and their adsorption performances towardheavy metal ions and photocatalysis performances toward organic dyes wereinvestigated. The details are as follows:1. The hyaluronic acid (HA) functionalized magnetic nanoparticles(Fe3O4@SiO2-HA) were synthesized and firstly used as adsorbent for potentialapplication in water treatment. Fe3O4@SiO2-HA nanoparticles have uniform sizes,legible spherical shapes and obvious core-shell structures. The Fe3O4@SiO2-HAnanoparticles have super-paramagagnetic property, which can make thesenanoparticles easily separated by an external magnetic force after adsorptionaccomplished. Effects of Cu (II) ions initial concentration and aqueous pH value onthe adsorption efficiency have been discussed. The adsorption isotherms and kineticshave also been investigated. The results showed that the optimum pH value for Cu (II)uptake studies was selected as6.8. The maximum adsorption capacity of thesynthesized Fe3O4@SiO2-HA was found to be13.5mg/g. Freundlich isotherm modelgave better fittings the adsorption equilibrium data. Kinetic experiments clearlyindicated that adsorption process of copper ions on the Fe3O4@SiO2-HA was followedpseudo-second-order kinetic models.2. Magnetic carbonaceous polysaccharide nanoparticles (Fe3O4@CPS) weresynthesized through hydrothermal process by using sesbania gum (SG) served ascarbon resource, and their structure, morphology, and component were characterizedsubsequently. Fe3O4@CPS nanoparticles have legible spherical shapes and obvious core-shell structures. Effects of adsorbent dosage, initial concentration, pH value andadsorption time on the adsorption capacity for heavy metal ions have been discussed.The adsorption isotherms and kinetics have also been investigated subsequently.When the initial concentration of heavy metal ions varing from50mg/L to250mg/L,the maximum adsorption capacities of Fe3O4@CPS towards Cd (II), Cu (II) and Pb (II)ions were found to be50.1mg/g,27.5mg/g, and23.4mg/g, respectively. Thedifference in adsorption capacities can be well explained because the “hard” metalions (Cd (II) and Cu (II)) had a higher complexation affinity than the “soft” metal ions(Pb (II)). Magnetism study displayed that Fe3O4@CPS nanoparticlas havesuper-paramagnetic property and strong magnetic response at room temperature,which can make these nanoparticles easily separated by applying the externalmagnetic force. The results showed that the Fe3O4@CPS have above91.2%for Cu(II),96.7%for Cd (II) and87.6%for Pb (II) ion desorption efficiency after theregeneration process.3. Poly(barbituric acid) functionalized magnetic nanoparticles (PBA-MNPs) weresynthesized through one-step oxidation polymerization method. Their microstructure,morphology, and functional groups were characterized in detail. The nanoparticleshave spherical shape. These spherical functional particles were formed by smallerspherical agglomerates of dimension~15nm. The synthesized PBA-MNPs used asadsorbents for potential application in water treatment. When the initial concentrationof adsorbates varing from50mg/L to300mg/L, the PBA-MNPs nanoparticles havethe adsorption capacities toward Cu (II) and Pb (II) ions were95.2mg/g and130.5mg/g, respectively. Recycling adsorption/desorption experiments revealed that thePBA-MNPs shown above87.1%for Cu (II) and82.7%for Pb (II) ions desorptionefficiency after the three regeneration cycle process. PBA-MNPs showed potentialapplication as recyclable adsorbent for heavy metal ions.4. A facile sol-gel method and sequential calcination treatment was utilized tofabricate alumina (Al90-600) with hierarchical hollow structure and high surface area.The as-prepared Al90-600was characterized by a series of measurement. Effect ofreaction temperature on the morphology of alumina was studied. The as-obtainedAl90-600exhibited a large BET surface area of320.6m2/g and expected that willpresent excellent adsorption behavior towards organic dyes. The as-obtained Al90-600was used as adsorbents for Congo red and Methyl orange removal. The results showed that the optimum pH value for CR uptake studies was selected as5.0. Todescribe how adsorbate molecules interact with the adsorbent surface, the adsorptionisotherms and kinetics were applied to analysis equilibrium adsorption data. Themaximum adsorption capacities of Al90-600obtained from the equilibrium adsorptionvalue were found to be CR (835.0mg/g) and MO (26.0mg/g), which are nearly closeto the adsorption capacity of adsorbent calculated from Langmuir adsorption isotherm.The adsorption experimental results showed that the maximum adsorption capacity ofCR by Al90-600was much higher than the maximum adsorption capacity for the MO.This is indicated that the as-synthesized Al90-600with hierarchical hollow structuremay is beneficial for enhancing adsorption intensity relatively large organic molecule.This is indicated that the adsorption capacity of an adsorbent is not only determinedby the specific surface area of materials, but correlated with structure and themolecular size distribution of adsorbate molecule.5. A facile homogeneous precipitation method and sequential calcination treatmentwas utilized to fabricate zinc oxide (Z-400) with hierarchical hollow structure. Theprepared Z-400can be utilized as efficient adsorbent/photocatalyst for CR removal.The factors affecting the adsorption/photocatalytic degradation capacity towards CRand the corresponding mechanisms were investigated in detail. In order to evaluate theadsorption/photocatalysis efficiency of Z-400, the removal experiments of CR withTiO2P25and commercial ZnO were also selected as the reference under the identicalreaction conditions. The adsorption data of the Z-400were well fitted with theLangmuir model, whereas for those of the TiO2P25and commercial ZnO, simulationwith the Freundlich model was better than those with Langmuir model. The maximumsorption capacity (qm) of Z-400, commercial ZnO and TiO2P25toward CR were97.0mg/g,41.5mg/g and7.2mg/g, respectively. The photocatalytic result showed that thedegradation percentiles of each sample were65%for Z-400,41%for TiO2P25, and31%for commercial ZnO within2h irradiation time. Based on the experimentalresults, Z-400is combined adsorbent and catalyst materials for removal of CR fromwaterbodies.