| For there were less materials for detection of nmol·L-1level of heavy metal ions concentration,biomass carbon materials which have large specific surface area and abundant functional groups and LDHs composite which has the larger inter lamellar spacing and good adsorption performance were selected to preparation of the modified Mg/Al-LDHs@BC and Mg/Fe-LDHs@BC materials,XRD,FT-IR,BET,SEM,TEM,XPS and other methods were used for characterization and testing,and the electrochemical method were used for heavy metal ions detection,the obtained results were much better.Firstly,biomass materials were prepared by pyrolysis of biomass hamma bar under high purity nitrogen gas.According to the TG-DSC characterization analysis,the pyrolysis temperature of modified materials Mg/Al-LDHs@BC and Mg/Fe-LDHs@BC were set at 600?.Secondly,the modified materials Mg/Al-LDHs@BC with different molar ratio were prepared by urea hydrothermal method.In the synthsized process,biomass carbon material mixed with Mg/Al-LDHs precursor solution,taking biomass carbon material as template and urea as precipitator.XRD test showed that Mg/Al-LDHs@BC modified material had characteristic diffraction peak in?0 0 3?,?0 0 6?and?1 1 0?,which proved the existence of LDHs lattice structure.FT-IR test showed that Mg/Al-LDHs were connected to the surface of biomass charcoal by chemical bonds.SEM and TEM tests confirmed that LDHs were grown on the surface of tubular biomass carbon in nanosheet state.Electrochemical methods of modified electrodes materials used for heavy metal ion Cd???,Pb???,Cu???,Hg???detection proved much better results,and the limit of detection were 1.258×10-10mol·L-1,8.464×10-11mol·L-1,1.546×10-10mol·L-1,7.892×10-11mol·L-1,respectively.Mg/Fe-LDHs@BC modified materials with different molar ratios were prepared by using the same urea hydrothermal method as Mg/Al-LDHs@BC.In this process,just changing aluminum nitrate into iron nitrate in original raw materials.XRD results showed that LDHs lattice existed in the modified materials.FT-IR test proved that Mg/Fe-LDHs and biomass charcoal were bonded by chemical bonds.SEM and TEM tests proved that Mg/Fe-LDHs were growing on the surface of tubular biomass carbon with nanometer particles.The electrode modified by materials used for electrochemical test for heavy metal ions Pb???,Hg???were 1.001 x 10-10mol·L-1,1.642 x 10-10mol·L-1,respectively.In experimental range,the square wave stripping voltammetry method?SWVSV?used in electrochemical workstation for different heavy metal ions detection results showed that the detection limit was less than 1×10-9mol·L-1,below the level of nmol·L-1.This attributed to the nano flake LDHs evenly distributed on the surface of tubular biochar,and the unique interlayer structure of LDHs made the specific surface area of the modified material much larger.Simultaneously,the interaction between oxygen-containing functional groups and hydroxyl groups on the surface increased the oxygen defects and enriched the effective adsorption sites.This all further proved that the modified materials has good testing performance,and it expected to be widely used in the actual environment detection. |
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