| Mercury is ranked first in the heavy metal pollution “top five”. It is a serious threat to human when it reaches a certain level contamination. Removal of bit, trace, and even ultra-trace mercury becomes very important because of the trace mercury can accumulate in the role of microorganisms and the food chain in the water. However, the general adsorbent is better for higher concentrations of mercury-containing wastewater, and the adsorption capacity is small, low adsorption efficiency. But the metal-organic framework materials to be the best choice as an adsorbent, because it has a larger surface area and pore size, diversity, adjustable surface properties and other characteristics, and it is already a hot spot as adsorbent in the field of handing mercury.In the paper, different preset aromatic carboxylic acid groups were selected to prepare a series of cell wall material functionalized MOFs: Zn(ip)(L), Zn(hip)(L) and Zn(nip)(L), in order to break through the low capacity of small and inefficient of the adsorbents when they adsorb the trace mercury. Three kinds of MOF materials are characterized by XRD, FT-IR, SEM, TG and other methods. The effects of factors of Metal-organic framework materials adsorb Hg2+ under the different kinds of group, the solution p H, adsorption time, Hg2+ initial concentration and temperature. Discusses the law of thermodynamics adsorption, adsorption kinetics and adsorption isotherm. Study the effects of trace Hg2+ adsorption.The results of Hg2+ adsorption of Zn(ip)(L) and Zn(hip)(L) and Zn(nip)(L) showed that the adsorbents are affected by the solution p H, concentration and temperature. The result is that the processes of these adsorbents adsorb Hg2+ conform to a quasi-second-order kinetic equation in the adsorption kinetic, and they are also chemical adsorption. It can be seen that their adsorption process are spontaneous and an exothermic from thermodynamic studies. The Hg2+ adsorption process of them meets the Langmuir isotherm model after studying the adsorption temperature model, this shows that these reactions are the monomolecular layer adsorption, and the adsorption capacity is respectively 62.62mg·g-1,335.57mg·g-1 and 129.97mg·g-1.In the case of the low initial concentration(c0=5 ng·m L-1), the removal efficiency of Zn(nip)(L) exceeds 70%, about 66 % is the removal efficiency of Zn(hip)(L), while the removal efficiency of sample is lower than 50%. In the case of the low initial concentration(c0=10 ng·m L-1), there are subtle difference in the removal efficiency of Zn(hip)(L) and Zn(nip)(L), respectively 75.53% and 78.09%. Unfortunately, the removal efficiency of Zn(ip)(L) is obviously poor, and the rate is less than 60%. With the increase of initial concentration(c0=20 ng·m L-1), the removal efficiency of Zn(hip)(L) and Zn(nip)(L) is more or less to 80%, the removal rate of Zn(ip)(L) is still less than 60%. So we put the concentration increased to 50 ng·m L-1, the removal rate of Zn(ip)(L) is still about 60%, the removal efficiency of Zn(hip)(L) and Zn(nip)(L) has been over 80%. These results suggest that MOF materials have a better performance for Hg2+ because of they contain hydroxyl and nitro group. |
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