Fabrication Of Porous Carbon Materials Derived From Pomelo Peels For The Detection Of Heavy Metal Ions

So far,heavy metals such as Cadmium?Cd?,lead?Pb?and copper?Cu?in water environments have created a huge threat to the balance of the ecosystem and human health in the world,and a new enormous challenge for scientists and analytical chemists.Due to heavy metals are highly toxic,widely available,non-biodegradable,persistent,widely distributed and biomagnified,it is especially important to detect the content of heavy metals in water environment with an accurate,rapid and convenient method.Among those detection methods,the square-wave anodic stripping voltammetry?SWASV?is proved to be a simple,fast and efficient method with high sensitivity,high selectivity and low detection limit.For the electrochemical analysis method of detecting trace metal ions,one of the most important way to improve the sensitivity of detection is to choose suitable catalytic carriers and high catalytic nanoparticles.Due to their renewable and sustainable,highly compatible,highly absorbent,fast electron transfer rate and high specific surface area,biomass-derived carbon materials have shown great potential in catalytic application.Therefore,in the present investigations waste pomelo peels were employed as raw material to prepare porous activated carbon derived from pomelo peels materials with chemical activation method and thermal carbonization process,which was directly used as catalyst or loaded metal nanoparticles and jointly used as SWASV catalytic material for the detection of heavy metal ions.The main point are as follows:?1?Used waste pomelo peels as raw materials,porous activated carbon derived from pomelo peels materials?PAC?was prepared via KOH activation method and thermal carbonization process,the morphology and structure of PAC were studied by scanning electron microscope?SEM?and transmission electron microscope?TEM?and it is shown that PAC possess honeycomb-like porous structure and high specific surface area(1055.46 m²g^-1)and high graphitized carbon degree.PAC is directly used as a working electrode for the simultaneous detection of heavy metal ions.The detected concentration of Cd²⁺,Pb²⁺and Cu²⁺can as low as 0.1?M,and it has excellent sensitivity and low detection limit.The optimal condition for simultaneous detection:deposition voltage-2.1V,deposition time 240 s.Meanwhile,it has excellent stability in the detection process,and the detection in the real water sample also shows excellent detection performance.?2?To further improve the electrochemical activity,palladium nanoparticles loaded on porous activated carbon?Pd@PAC?was successfully prepared by in-situ thermal reduction technique.The microstructure and structure were researched and it indicated that palladium nanoparticles?Pd NPs?were successfully loaded into PAC throughout the whole porous material,and the size of the nanoparticles is about 20-30 nm.Pd@PAC/GCE is used as the working electrode for the single and simultaneous detection of heavy metal ions.The results showed that the minimum detection concentration of Cd²⁺,Pb²⁺and Cu²⁺can reach up to 25 nM,and it has excellent sensitivity and low detection limit.Meanwhile,it showed good stability and repeatability.In addition,Pd@PAC/GCE detection of heavy metal ions in real water samples shows its potential application in real environment detection.?3?To reduce the cost and improve the detection activity,a transition metal Co was substituted for part of Pd to form an alloy structure,and palladium cobalt nanoparticles loaded on porous activated carbon?PdCo@PAC?was prepared by in situ thermal reduction process.And its microstructure and structure analysis showed that material has three-dimensional porous structure and palladium cobalt nanoparticles?PdCo NPs?evenly dispersed on the surface,with nanoparticles size of about 30-50 nm.Simultaneous detection of heavy metal ions at different concentrations by SWASV revealed that the detection concentrations of Cd²⁺,Pb²⁺and Cu²⁺detection minimum concentration can be up to 5??and showed good detection performance.