| Economic development benefits to society while also brought pollution, for example, a huge amount of wastewater discharged from industrial factory. The wastewater discharged from plating, electronics, leather, mining and metallurgy, chemical industry, printing, machinery manufacturing and some other industrial contain large quantities of heavy metals. These heavy metals would get into human body or animals by drinking water or ingesting living creature in the water. On the other hand, the heavy metals would also get into body by crops and harm to human and animal health if they discharged into soil. Nearly half a century, heavy metal pollution occurred frequently, such as "Minamata disease","Itaiitai disease". Recent years with the rapid development of industry in China, heavy metal pollution was also perplexing us. The media have reported lead poisoning cases of children or villagers and cadmium poisoning many times. Heavy metal pollution has become a serious problem.With the rapid development of science and technology, nanotechnology became gradually visible to us. Compared to common materials, nano-materials present many advantages, such as large surface area, lower melting point, superparamagnetic and so on. Nano-materials have been widely used in various fields for those advantages as well as environment protection. Recently, many researchers used cheap natural mineral and organic substance to synthesize excellent adsorbent due to their abundant supply, low cost, readily availabilityand simple handling. Therefore, magnetic nano-adsorbents, including hematite, limonite, chitosan, hydroxyapatite, which have high surface area, high adsorption capacity and separate convenience can be prepared using these cheap natural materials and appropriate methods. To enhance the adsorption capacity of hematite and other magnetic nano-absorbent, many researchers used organic substance containing functional groups coated magnetic nanoparticles to form new adsorbent. This method can greatly increase the adsorption sites of adsorbent. For instance, the magnetic nanoparticles coated with chitosan was used as a great nano-adsorbent for removing heavy metal resulting from chitosan complexating with heavy metal ions for the functional groups such as carboxyl, hydroxyl, amino. The use of natural minerals and natural organic to synthesis new adsorbents has become a hot research topic. In this thesis, we have used shellac modified magnetic iron oxide and obtained a new adsorbent called shellac coated magnetic nano-adsorbent (SCMN). Furthermore, we have also used Fourier transform spectrometer, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometer (EDX), Zeta Sizer and Nano series equipped with a microprocessor unit, Nitrogen adsorption BET surface area and pore size distribution tester and vibration sample magnetic field meter instruments to characterize the adsorbent, and have a cost evaluation for the SCMN. Moreover, we have taken cadmium as an example to explore the possibility of heavy metal ions. We have investigated the factors, which may affect the adsorption of heavy metal ions such as pH, Contact time, salt concentration, etc. we also studied the desorption of adsorbent and stability of SCMN in soulution. Experiments showed that the shellac modified magnetic nano-adsorbent can effectively remove cadmium ion. Furthermore, we can conclude that the adsorption mechanism between SCMN adsorbent and cadmium (II) was electrostatic attraction as well as chemisorptions. From the TEM photo and SEM photos we know SCMN adsorbents were core-shell structure. The size of SCMN and the thickness of shellac shell were about20nm and5nm, respectively. XPS analysis shew SCMN mainly composed of Fe, C and O. The zeta potential of SCMN and BMN (Bare magnetic nanoparticles) decreased with increase of pH gradually (from positive to negative), the isoelectric point are pH=4.6and pH=5.0, respectively. The BET specific surface area of SCMN is56.95m2/g; Production price of SCMN is＄670per ton in accordance with the current raw material cost. The adsorption processes fitted pseudo-first-order model well, correlation coefficient is R2=0.9994; adsorption isotherms data of shellac modified magnetic nanoparticles were well fitted by both Langmuir model and Frenudlich model, the correlation coefficient is R2=0.9832and R2=0.9879respectively. The maximum absorption capacity is18.80mg/g. The equilibrium time is about one hour. The adsorbance increased with the rise of pH when the pH is3～8, the optimal pH is7～8. The adsorb process influenced by salt solution. Moreover, the adsorbent can easily desorbed by low concentrations of EDTA solution, the desorption efficiency was86.75%. The adsorbent synthesis in this thesis has great stability, magnetism is well (Saturation magnetization is39.1emu/g) and can easily separated from aqueous solution... |
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