Study On Colorimetric Detection Method Of Metal Ions In Metallurgical Wastewater Based On Nobel Metal Nanozyme Catalysis

There are many products in the metallurgical industry,and the production processes are in series.The discharges of wastewater in these processes are large and diverse wastewater,and its water quality is complex and changeable.The Large amounts of heavy metals contained in the wastewater,especially lead,cadmium,mercury,arsenic,chromium,copper,etc.,are the main sources of heavy metal pollution in water and are likely to cause environmental pollution and permanent harm and threaten human health.Therefore,the effective detection of heavy metal ions is not only a guarantee for the maintenance of human health,but also an important support for the reasonable treatment of metallurgical wastewater and the healthy and sustainable development of metallurgical industry.Nanoenzyme is a kind of nanomaterial with high enzyme-like activity.Because of its unique physical and chemical properties,it can be used to establish various complex catalytic systems.The heavy metal ion detection methods based on nanoenzymes are simple to operate,the detection results are quick and easy to obtain,the detection accuracy is high,the detection limit of heavy metals can reach the sewage discharge standard or even the drinking water standard,and can meet the heavy metal detection in water under more severe conditions,conform to the green and sustainable technology strategy,and are of great significance to the prevention and control of heavy metal pollution,the rational use of resources and the protection of the environment.In this thesis,a variety of precious metal nanoenzymes were developed for the purpose of highly sensitive detection of heavy metals in water,the effects of different modified ligands on the properties of nanoenzymes were studied;the catalytic activity of precious metal nanoenzymes and the mechanism of the mechanism of using nanoenzymes to detect heavy metal ions was explored;combined with the properties of nanomaterials such as enzyme-like activity,a variety of detection methods that can effectively detect trace heavy metal ions in water were established.The specific content is as follows:1.An assay is proposed for the photometric determination of Cr⁶⁺by employing polyethylenimine-stabilized Ag nanoclusters（PEI-Ag NCs）as an oxidoreductase-like mimic.Firstly,Cr⁶⁺with a certain oxidizing property can react specifically with 3,3’,5,5’-tetramethylbenzidine（TMB）,and can trigger the oxidation of TMB to TMBox,which causes the color of the solution system to change from colorless to blue.When PEI-Ag NCs is added,it can be used as a kind of oxidoreductase to greatly promote the above reaction,thereby establishing an optical detection method for toxic Cr⁶⁺.By using PEI-Ag NCs as nanoenzymes,the constructed method achieves the purpose of rapid and convenient detection of Cr⁶⁺,and the detection limit is as low as 1.1μM.Additionally,the proposed assay exhibited excellent selectivity.Other ions,including Cr³⁺,hardly affected the determination of Cr⁶⁺.2.This work proposes a catalytic colorimetric assay of arsenite based on the analyte inducing the aggregation of citrate-stabilized Au nanoparticles（Au NPs）with promoted peroxidase-mimicking activity.Highly dispersed Au NPs with a mean size of～20 nm show negligible enzyme-like activity.When a small amount of arsenite is added,it triggers the rapid aggregation of Au NPs by interacting with the stabilizer citrate on Au NP surface,and it is further observed that the formed Au NP agglomerate can exhibit significantly accelerated peroxidase-mimetic activity to catalyze the 3,3’,5,5’-tetramethylbenzidine chromogenic reaction with the participation of H₂O₂.Based on this phenomenon,a facile colorimetric strategy with catalytic signal amplification was established for the efficient sensing of arsenite and the arsenite in a wide range（0.01─11.67 mg/L）was linearly determined.3.A copper ion detection method based on the regulation of cysteine-coated silver nanoclusters（RSH-Ag NPs）enzyme activity is proposed.RSH-Ag NPs have weak peroxidase-like activity and can catalyze the decomposition of hydrogen peroxide into hydroxyl radicals,which further oxidize colorless TMB into colored TMBox.When copper ions are added,they can interact specifically with cysteine on the surface of RSH-Ag NPs,causing cysteine to detach from the surface of silver nanoparticles.On the one hand,the silver nanoparticles agglomerate due to the detachment of cysteine;on the other hand,the catalytic sites in the silver nanoparticles covered by cysteine are exposed.The colorimetric detection method based on this principle can realize the high-efficiency detection of trace copper ions.