Fabrication And Application Of Nanomaterials For Heavy Metal Ions Determination

Heavy metal ions pollution is a serious environmental problem which was caused by the development of industry.Among various heavy metal ions,Cd(II)and Pb(II)were reported to be highly toxic even in low concentrations.Cd(II)and Pb(II)always come from industrial wastes,phosphate fertilizers,smelting and fuel combustion.Bismuth film modified electrodes can act as electrochemical sensors for detection of Cd(II)and Pb(II)due to excellent reproducible stripping responses,low background current and high hydrogen evolution.However,bismuth film modified electrodes have disadvantages of poor stability and single structure,which limit their applications.Synthesis of novel structure of bismuthbased materials has been the focus in the field.Three kinds of nano-bismuth-based modified CPE have been constructed for electrochemical analysis of Cd(II)and Pb(II)in this paper.The main contents were as follows:(1)Bismuth nano-needle,nano-rod,nano-sheet,and nano-flower were synthesized using a facile one-step solvothermal method by adjusting the volume of ethylenediamine.The prepared Bi nano-particles were characterized by scanning electron microscope(SEM)and X-ray diffraction(XRD)analysis and their formation mechanism was discussed.It was shown that Bi nano-flower modified electrode displayed the highest detection sensitivity to Cd(II)on account of its particular three-dimensional structures.The stripping peak currents of Cd(II)at “bulk” and “drop coating” Bi nano-flower modified CPEs were compared with those of Bi film modified CPEs using “in-situ” and “out-situ” plating methods.The optimized detection conditions were Bi nano-flower bulk modified CPE at pH 4.4,deposition potential of-1.2 V and deposition time of 200 s.The linear range,sensitivity and detection limit were 0.05~1 ?M,27.5 ?A/?M,and 2.4 nM,respectively.The proposed Bi nano-flower bulk modified CPE was conveniently usable in the trace Cd(II)analysis for environmental water samples with the recovery rang of 91.1%-105.6%.(2)Mg/Bi-LDH was synthesized using a facile one-step solvothermal method.The prepared Mg/Bi-LDH was characterized by scanning electron microscope(SEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and Fourier transform infrared(FT-IR).The stripping peak currents present an obvious enhancement compared to bare CPE,stripping Cd(II)peak current was nearly three times than that of bare CPE,the Pb(II)stripping response was twice larger than that of bare CPE,which can be correlated with high affinity of Mg/Bi-LDH for the target heavy metal ions and the nanosphere characteristic ensures the maximum exposure of surface active sites.The optimized detection conditions were Mg/Bi-LDH bulk modified CPE at pH 4.4,deposition potential of-1.2 V and deposition time of 200 s.The linear range,sensitivity and detection limit for Cd(II)and Pb(II)were 0.03~1 ?M,17.54 and 24.22 ?A/?M,6.2 and 1.4 nM,respectively.Meaningfully,the proposed electrochemical sensor showed excellent anti-interference capability,the relative stripping signal deviations for both Cd(II)and Pb(II)were less than 10% in the absence or presence of other metal ions at a concentration of 100-fold as much as that of Cd(II)and Pb(II).(3)Bi-MOF was synthesized using a facile one-step solvothermal method,and then calcinated at 300 ?.The Bi-MOF and Bi-MOF-300 were characterized by scanning electron microscope(SEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and Fourier transform infrared(FT-IR).Compared with bare CPE,the stripping peak currents of Bi-MOF/CPE and Bi-MOF-300/CPE presented obvious enhancement.The stripping Cd(II)peak current was nearly 2 times and 3 times than that of bare CPE,the Pb(II)stripping response was 2 and 2.3 larger than that of bare CPE.Bi-MOF-300/CPE exhibited the highest and sharpest stripping currents toward Cd(II)and Pb(II),which was due to the porous structure,the increase of the effective group ratio and the more transparent pores after calcination.The optimized detection conditions were Bi-MOF-300 bulk modified CPE at pH 4.4,deposition potential of-1.0 V and deposition time of 200 s.The linear range,sensitivity and detection limit for Cd(II)and Pb(II)were 0.05~1 ?M,20.71 and 26.23 ?A/?M,10.9 and 4.5 nM,respectively.Meaningfully,the proposed electrochemical sensor shows excellent anti-interference capability,could be used in the trace Cd(II)and Pb(II)analysis for environmental water samples with the recovery rang of 93.33%-105.71%.