Determination Of Lead And Cadmium In Wastewater From Coal Preparation And Lead-zinc Polluted Water Using Porous Carbon Nanofiber Composites

Heavy metal ions,such as Cd???and Pb???,are discharged from wastewater with industrial processes and cause great environmental pollution,because of heavy metal ions are highly toxic and stable in the environment.They propagate through food chains and cause severe damage to the human body even at very low concentrations.Therefore,how to quickly and effectively detect lead and cadmium content is particularly important.There are numerous traditional methods used for heavy metal detection,including atomic absorption spectrometry?AAS?,atomic fluorescence spectrometry?AFS?,inductively coupled plasma mass spectrometry?ICP-MS?,and inductively coupled plasma atomic emission spectrometry?ICP-AES?.However,the above-mentioned methods are expensive,time-consuming,inconvenient,and require complicated pretreatment.In contrast,electrochemical techniques are simple,inexpensive,sensitive,and selective for monitoring trace amount of Cd???and Pb???.Carbon matrix materials are regarded as one of the most important electrode materials for heavy metal detection.But even so,optimization procedures of carbon nanofibers?CNFs?for tracing Cd???and Pb???remains challenging.Here,zeolitic imidazolate framework?ZIF-8?/polyacrylonitrile?PAN?-derived nitrogen-doped porous carbon nanofibers?N-PCNFs?and trithiocyanuric acid,silica nanospheres and polyacrylonitrile-derived nitrogen,sulfur co-doped porous carbon nanofibers?N,S-PCNFs?were investigated as a new electrode material for determining the concentration of Cd???and Pb???in coal preparation waste water and lead-zinc mine polluted water.By optimizing electrochemical conditions such as deposition potential,deposition time,pH of buffer solution,and quantity of N-PCNFs loaded on a glassy carbon electrode?GCE?,the linear response curves of Cd???and Pb???could be obtained.Due to the unique structural feature and N content,the N-PCNFs possess excellent detection limits of 0.8?g L^-11 for Cd???and 0.3?g L^-1 for Pb???.To manifest the practical use of the sensor platform the concentration of Cd???and Pb???in normal tap and waste water were monitored.According to the ICP-MS results,the calculated recovery?97.0–107%?indicates that N-PCNFs have potential as a candidate material to monitor the concentration of Cd???and Pb???in Coal preparation waste water and Lead-zinc mine polluted water.Compared to a bare GCE and a Nafion modified GCE,the GCE modified with N,S-PCNFs shows improved sensitivity for Cd???in differential pulse anodic sweeping voltammetry.The stripping peak current?typically measured at 0.81 V?increases linearly in the 2.0–500?g?L?1Cd???concentration range.This is attributed to the large surface area?109 m2?g?1?,porous structure,and high fraction of heteroatoms?19.3 at.%of N and 0.75 at.%of S?.The method was applied to the determination of Cd???in lead-zinc polluted water where it gave recoveries that ranged between 95 and 103%.