| Based on the problem that there are few materials with ultra-low detection limit in the current heavy metal ion detection materials.Peanut shell carbon（BC）was prepared by using peanut shell as carbon source.Modified NiFe（Al）-LDHs@BC was synthesized by a simple one-step hydrothermal method.To solve the problem that there are few heavy metal ion detection materials with the concentration of nmol·L-1 in the market at present,peanut shell was used as carbon source to prepare peanut shell carbon（BC）,and modified NiFe-LDHs@BC and minor materials were synthesized by a simple one-step hydrothermal method.The morphology and structure of the modified materials were analyzed by XRD,FT-IR,BET,SEM,TEM and XPS characterization tests.And the optimum hydrothermal conditions were determined.The four heavy metal ions of Zn（Ⅱ）,Cd（Ⅱ）,Pb（Ⅱ）and Cu（Ⅱ）in water were detected by electrochemical method,and the detection effect is good.Firstly,modified NiFe-LDHs@BCmaterials with Ni-Fe layered dihydroxides were synthesized by one-step hydrothermal method with urea as precipitator.Then modified materials NiFe-LDHs@BC with different molar ratios were prepared by using peanut shell as biomass and pyrolytic biochar as the component.XRD results confirmed that the modified NiFe-LDHs@BC material with the ratio of nickel salt and iron salt of 2:1 had the best performance.Infrared detection confirmed that there were abundant functional groups in NiFe-LDHs@BC.SEM and TEM further verified that NiFe-LDHs grew on the surface of honeycomb peanut shell carbon material in form of nanosheets.The thickness of the sheets was about 10 nm,and there were many mesoporesuniformly distributed on the sheets,and the pore size was concentrated at 3.46 nm.The results showed that the limit of concentration were 2.048×10-10mol·L-1、3.179×10-11mol·L-1、1.975×10-10mol·L-1、2.253×10-10mol·L-1,respectively.Secondly,series modified materials NiFe Al-LDHs@BC were prepared doped with aluminum salt by changing the hydrothermal temperature,hydrothermal time and the molar ratio of Ni-Fe-Al salt,and the material with molar ratio of Ni-Fe-Al salt 6:1.5:1.5had the best properties and morphology under the conditionsby using urea as precipitator.As described above,the electrode prepared by the modified materials were used for the detection of four heavy metal ions,and the results showed that the limit of detection concentration of Zn（Ⅱ）,Cd（Ⅱ）,Pb（Ⅱ）and Cu（Ⅱ）were 3.742×10-11mol·L-1、4.530×10-10mol·L-1、8.430×10-10mol·L-1、3.859×10-11mol·L-1,respectively.The detection limits of the electrodes modified by the modified materials for the four heavy metal ions are all less than nmol·L-1 range.This is due to the orderly growth of LDHs on the surface and pores of honeycomb peanut shell carbon,which plays the purpose of increasing the specific surface area of peanut shell carbon.When Al ions are doped into the modified materials,the number of functional groups of the modified materials increases significantly,and the specific surface area also increases,thus providing a large number of vacancies for the adsorption of heavy metal ions,and showing excellent performance in the detection of heavy metals in water.In summary,NiFe（Al）-LDHs@BC modified electrode material synthesized by one-step hydrothermal method had excellent detection performance for heavy metals in water.This high-performance of the material not only presented on detecting a single metal ion,but also realized the simultaneous detection of four kinds of heavy metal ions in mixed solution.This materials were expected to be widely used in commercial applications. |
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