Studies On The Electrochemical Sensors For COD Based On The Enhancement Effect Of Nano-Ni And Functionalized Glassy Carbon

As environmental pollution problems becoming more and more serious, it is extremelyimportant to establish rapid, sensitive and simple methods for the environmental monitoring.COD (Chemical oxygen demand) is an important indicator of the extent of water pollution,which defined as the number of oxygen equivalents consumed in the oxidation of organiccompounds using strong oxidizing agents. This work aims to research novelelectrochemical sensors for COD, and to develop rapid, sensitive and simpleelectrochemical methods for the detection of COD. Main work is as follows:1. Using NiSO4as the precursor, nickel nanoparticles were in situ prepared on thesurface of glassy carbon electrode via potentiostatic reduction. The shape of nano-Ni andthe catalytic activity for the oxidation of glycine were successfully tunned by variation ofreduction potential, deposition time, pH value, and concentration of Ni2+. After that, theapplication of the nano-Ni in the electrochemical detection of COD was investigatedselecting glycine as the standard reagent for evaluation of COD. As a result, nano-Niremarkably improved the electrochemical response of COD. Over the range from0.24to480mg L-1, the response signal of COD on nano-Ni modified electrode increased linearlywith its concentration. The limit of detection was as low as0.14mg L-1. Finally, this newmethod was used to detect COD values of real water samples, and the results were in goodagreement with those obtained by conventional dichromate method.2. The glassy carbon electrode (GCE) was successfully functionalized viapotentiostatic oxidation method. After300s oxidation at1.8V in0.1M Na2HPO4,three-dimensional structures were introduced on the surface of the GCE. Micro-FTIRproved that hydroxyl group was also introduced on GCE surface after oxidation. It wasfound that the functionalized GCE exhibited considerable enhancement effect on theresponse signal of COD. As a result, the functionalized GCE greatly increases thesensitivity of COD detection. Using real lake water samples as research target, the influences of electrolyte, activation potential and activation time were studied on theresponse signal of COD. Finally, a sensitive, simple and convenient electrochemicalmethod was developed for the detection of COD. The linearity is from3.74to67.13mg L-1,and the limit of detection is0.33mg L-1. It was used to detect COD values of various watersamples and the results consisted with the values that obtained by dichromate method.