Preparation And Heavy Metal Ion Adsorption Properties Of Diatomite-Based Hybrid Adsorbent

Diatomite or diatomaceous earth, mainly composed of the remains of ancient diatom deposition, inherits diatom's porous structure and multilevel pore size distribution. Diatomaceous earth has a series of advantages, such as chemical stability, high specific surface area and strong adsorptive. As the large quantity of the diatomite resource in our country,people now begin to realize the grat value of diatomaceous earth, and are willing to apply this mineral into the ecological environment improvement. However, at present, most of the diatomite are used as low value-added products, such as low-grade filter aid. Therefore, developing the diatomite in environmental protection can not only increase the value of diatomite, but also can be of great significance in protecting the earth and purifying the human living space.The characteristic of diatomite from different mining were analyzed. After some modification, we chose the one with less impurities and high grade, according to the application features. It was mainly focused in developing diatomite-based composite materials for environmental applications. A two-step method was proposed and applied to grow functional sorbent material (MnO2) on surface of porous diatomaceous earth. The hybrid adsorbent was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and infrared spectroscopy. The concentration of Pb(II) was tested by inductively coupled plasma mass spectrometry. Sorption experiment showed that the hybrid adsorbent can effectively remove the Pb(II) in aqueous solutions. Then the influence of different adsorption conditions on the adsorption effect was discussed. Results are as follows:1. The surface morphology, chemical composition, specific area and pore size distribution features of diatomite from different regions are quite different. The more impurities diatomite are, the deeper color they will show, and the specific area and pore size distribution features are more likely influenced by surface modification such as calcinating, acid leaching.2. MnO2 nanocrystals were uniformly coated on the DE surface via an in situ redox reaction over the carbonized DE powder. The load rate of MnO2 can be adjusted by varying the concentration of glucose.3. The composite material MnO2@DE showed a strong adsorption of heavy metal ions of Pb. According to the equilibrium studies, the adsorption capacity of DE for adsorbing lead ions is increased more than six times after MnO2 modification. The influencing factor of the adsorption was discussed by changing the adsorption conditions, including contacting time, the amount of adsorbent, the load rate of MnO2, the initial concentration of Pb(?), and the initial pH of the Pb2+ solution. The adsorption of Pb2+ on the MnO2 surface is based on ion-exchange mechanism. The adsorbent also has a certain anti-interference ability.4. The dynamic adsorption experiment platform was designed, which was used for the dynamic adsorption of Pb2+ by raw diatomite and MnO2@DE. The preliminary experiment results provide the theoretical basis for the real application.