The Synthesis Of Porphyrin-functionalized Polyacrylonitrile Fiber And The Highly Selective Colorimetric Detection For Mercury(?)

Mercury is one of the most toxic metals to human health as it is not biodegradable and has strong bioaccumulation. The water soluble divalent mercuric ion(Hg2+) is one of the most stable and widespread inorganic forms of mercury pollution. Therefore,selective determination of Hg2+in the environmental samples has become increasingly important. In this thesis, porphyrin derivative was immobilized on to the polyacrylonitrile fiber(PANF) to realize the selective colorimetric detection of Hg2+.In this thesis, polyacrylonitrile fiber was used as supporting material and reacted with ethylenediamine to produce the aminated fiber(PANAF). Then, PANAF was treated with 5,10,15-Tris[4-(3,5-dichlorotriazinyl)aminophenyl]-20-phenylporphyrin(CTAPP) to produce porphyrin-functionalized polyacrylonitrile fiber(CTAPPPANAF). The produced fiber was characterized by elemental analysis, scanning electron microscopy, fourier-transfer infrared spectroscopy and X-ray diffraction spectroscopy.The colorimetric properties and mechanism of the fiber have been systemically studied. Upon addition of Hg2+, CTAPP-PANAF shows a remarkable visual color change from red-brown to dark-green and excellent selectivity towards Hg2+over other common metal ions(Pb2+, Ba2+, Cd2+, Ag+, Zn2+, Cu2+, Ni2+, Co2+, Fe3+, Mn2+,Cr3+, Ca2+, Al3+ and Mg2+). The selectivity of the sensor can also be performed by the significant detectable changes in the FT-IR, UV and FL spectra of CTAPP-PANAF.The naked-eye detection limit is as low as 20 ppb(1×10-7 mol/L), which is below the maximum contamination level of 50 ppb for mercury containing wastewater in China.When CTAPP-PANAF was soaked in a solution of 1×10-3mol/L Hg2+, distinctive color change was observed within 5 s. CTAPP-PANAF works well over a wide pH range from 3.0 to 11.0. The successful detection of Hg2+ dissolved in the Weijin river water sample confirms the practical application of this fiber sensor. Though the high stability of [EDTA-Hg]2-, [HgI4]2- and [Hg(S2O3)4]6-, color change was observed as before when the fiber was immerged into these solutions, which indicates that this colorimetric fiber has strong complextion ability for Hg2+. In a word, this facile, low cost and solid-state Hg2+ detecting sensor represents a great advance for the in-situ monitoring of Hg2+ in environmental applications.