Preparation Of Au/mpg-C₃N₄ Nanocomposite And Its Application In The Electrochemical Detection Of Cr(?)

The content of inorganic chromium species in the environment is much higher than organic chromium,mainly in two valence states of Cr(III)and Cr(?).Different chromium species show significant differences in toxicity and ecological environmental effects.Cr(III)is an essential trace element for the human body;Cr(?)is a highly toxic substance,and its toxicity is more than 100 times that of Cr(III).Polluted water of Cr(?)can cause liver damage,kidney failure,nervous system damage,and even death.According to relevant wastewater discharge standards,the content of hexavalent chromium in industrial wastewater cannot exceed 0.5 mg/L.Therefore,to achieve strict control of chromium pollution and effective early warning of its ecological environmental behavior,it is urgent to develop a simple,fast,and highly sensitive on-site inorganic chromium speciation analysis method.As an analytical method with the typical advantages,the electrochemical method is one of the most promising methods for the rapid and high-sensitivity analysis of inorganic chromium species in water,and exploring materials with excellent electrocatalytic properties to construct electrochemically sensitive interfaces is the key to improving the performance of electrochemical sensors.Following the guidance of green chemistry,we prepared the Au/mpg-C₃N₄ nanocomposites via photocatalysis method,which were used as the modification material for constructing the Cr(?)electrochemical sensor.Its electrochemical performance on Cr(?)detection was systematically evaluated based on the optimized experimental parameters.The feasibility of applying the as-constructed electrochemical sensor for the field analysis of Cr(?)in industrial wastewater(such as leather wastewater and electroplating wastewater)was also studied.The research contents are as follows:(1)Preparation of Au/mpg-C₃N₄ nanocomposite via photocatalytic reduction method.The material was characterized by SEM,TEM,XRD,XPS,FT-IR,and Raman.The results show that gold nanoparticles with an average diameter of about 50 nm are uniformly dispersed on the surface of mesoporous carbon nitride without significant agglomeration.(2)The Au/mpg-C₃N₄ nanocomposite material was modified on the surface of a glassy carbon electrode(GCE),and its electrochemical properties were characterized by CV and EIS.The linear sweep voltammetry(LSV)and chronoamperometry methods were adopted to detect Cr(?)in the water environment,and the sensitivity and minimum detection limit of the sensor were obtained based on the optimized detection conditions,such as p H and electrolyte solution.At the same time,the properties of anti-interference,stability,and repeatability were evaluated.The results show that under optimized conditions,the sensitivity of the sensor towards Cr(?)is 0.002196?A/ppb in a wide linear range of Cr(?)(100-1000 ppb),and the lowest detection limit is 14.7ppb(3?method),and the sensor has good repeatability,reproducibility,and anti-interference performance.(3)The Au/mpg-C₃N₄ nanocomposite was modified on the surface of the commercial screen-printed electrode(SPE)with industrial mass production,to evaluate the practical applications of Au/mpg-C₃N₄ nanocomposite for Cr(?)detection,especially for on-site monitoring of Cr(?)in the industrial waste liquid.The results show that the Au/mpg-C₃N₄/SPE sensor has a high sensitivity towards Cr(?)(0.0307?A/ppb),and the Cr(?)in real leather wastewater and plating wastewater can also be accurately detected,and the RSDs are 94.1%,98.2%,respectively.