Application Of Nano-metal Oxides In The Analysis And Degradation Of Environmental Pollutants

Organic dyes have been widely utilized as color-imparting agents in hair-coloring,textile and printing industries for many years.However,a growing number of studies have showed that organic dyes have the potential carcinogenic and genotoxic.So releasing dyes-containing industrial and domestic wastewater arbitrarily will cause serious environmental pollution and damage to mammal and human health.On the other hand,a large amount of dye pollutants in wastewater are difficult to be degraded,which deteriorate the water quality and hinder the photosynthetic activity of aquatic organisms by decreasing the penetration of solar light.How to efficient degrade or remove organic dye pollutants in the wastewater for environment protection and public security is of great significance.Thus it has attracted great attention.In recent years,many methods have been applied for treating dye pollutants,including adsorption/precipitation-based physical approaches,oxidation-based chemical approaches,and aerobic/anaerobic biological approaches.However,most of these methods require expensive instruments and complex procedures,which may inevitably restrict their wide application.Hence,it is particularly important to find a simple and effecient method to handle the problem of organic dye pollutants for environmental protection.Organophosphorus pesticides?OPs?are mostly used as pesticides in agriculture.In addition,it can act as a main kind of chemical warfare agents in military activities and terrorist attacks because of its large toxicity.The toxicity of OPs poses instant and lethal effects on human and mammal due to the nonreversible phosphorylation and inactivation of acetylcholine esterase in central nerve system.The inhibition of ace-tylcholinesterase?AChE?could cause the accumulation of neurotransmitter acetylcholine,thus inducing serious clinical complications including respiratory tract,fibrillation and ultimately leading to death.So far,literatures have reported a variety of methods to detect the OPs,such as gas chromatograph-mass spectrometry?GC-MS?,liquid chromatography?LC?,enzyme activity inhibition methods,and several immunoassays.Laboratory-based GC/LC/MS analytical techniques are commonly used and show detection limits in the nanomolar concentration range.However,these methods also have some shortcomings such as high-costs,time-consuming and usually require highly trained technicians,which are not suitable for rapid analysis under field conditions,especially in emergency cases.Based on the above facts,it is urgent to develop an effective quick and easy analysis method to detect OPs.Hydrogen peroxide?H₂O₂?is a colorless,odorless liquid.It played an effective role in "three wastes" treatment,bleaching pulp and fabric,chemical synthesis,disinfection,anticorrosive deodrization etc.Generally,the H₂O₂ solution concentration is between 0.01 and 3%?w/w0?.A large amount of H₂O₂ is released into the environment.At the same time it can also exist in atmosphere and sea.Studies found that H₂O₂ released into the environment can cause oxidative damage of kinds of cells.Long-term exposure H₂O₂ in the environment could affect human health.So it is especially important to detect the H₂O₂ concentration changes before and after released into the environment.So devopling a simple,portable and sensitive method can bring great convenience for the dection of H₂O₂.Nano metal oxides have excellent physical and chemical properties?such as enzyme activity,etc.?due to their particular structures.In recent years,it has a wide application prospect in chemical industry,electronics,food,environment,biology,medicine and other fields.In this study,we synthesized the novel polymer-coated nano metal oxides by efficient one-step method.Based on this material,we established a new method of highly efficient degration of organic dye pollutants,and developed a rapid,sensitive and effective method for detection of OPs residues and developed a simple and effective new device for testing H₂O₂.This thesis was made up of four parts:Chapter 1.IntroductionIn this chapter,the actualities,harm and detection methods of organophosphorus pesticide and the degradation of organic dyes were introduced.Then we introduced the environment impact and main detection methods of hydrogen peroxide.Finally,the characteristics,preparation methods and application fields of nano metal oxides were outlined.Chapter 2.One-Step Facile Synthesis of Polyacrylic Acid-Coated Co3O4 and the Application Research in the Degradation of Organic Dye PollutantsThe use of organic dyes not only made our lives more colorful but also brought a lot of waster water containing organic dye pollutants.This waste water discharged into rivers can cause water transparency declines,dissolved oxygen falls and so on a series of problems,which can seriously interfere the normal growth of aquatic organisms.At the same time,the health of humans and animals was damaged caused by ingestion of water contaminated with organic dyes.The degradation of organic dye pollutants in water can not only reduce the harm to the environment,but also can recycle the water resources.So it has important and far-reaching significance.A novel and facile strategy has been established for the synthesis of well-distributed polyacrylic acid-coated cobaltosic oxide nanoparticles?PAA-Co3O4 NPs?in this part.This material has small size,large special surface area,excellent catalytic activity,which can be used in the degradation of organic dyes pollutants.At the same time,we made a simple reactor,the proposed reactor could be readily acted as a new versatile platform for the decontamination of dye pollutants in industrial and domestic wastewater.Chapter 3.Synthesis of Polyacrylic Acid-Coated CeO₂ and the Application Research in the Detection of organophosphorus pesticides?OPs?Our county is an agricultural country.A large quantities use of organophosphorus pesticides?OPs?not only brought huge benefits for agricultural production,but also led to serious environmental problems and food safety problems.Thus,the development of rapid and convenient detection of OPs residues analysis methods has been a research hot spot.In this study,we developed a novel colorimetric assay for the detection of OPs utilizing polyacrylic acid-coated cerium oxide nanoparticles?PAA-CeO₂?as an oxidase mimic and OPs as inhibitors to suppress the activity of acetylcholinesterase?AChE?.The sensing system for the OPs assay is constructed by composing of PAA-CeO₂,AChE,acetylcholine?ATCh?and a colorimetric substrate?e.g.3,3',5,5'-tetramethylbenzidine,TMB?.Firstly,we prepared PAA-CeO₂ with well water-solubility,which could catalyze the oxidation of TMB to produce a color reaction from colorless to blue.The enzyme of AChE was used to catalyze the substrate of ATCh to produce TCh,which can cause a decreasing catalytic oxidation of TMB by PAA-CeO₂ oxidase mimic.Upon incubated with OPs,the enzymatic activity of AChE was inhibited and produced less TCh,resulting in more TMB catalytically oxidized to show an increasing blue color.A substantial color change of the sensing system was observed in a concentration-dependent manner,upon AChE incubated with various centrations of OPs.In this assay,two OPs were tested:dichlorvos and methyl-paraoxon.As low as 8.62 ?g/ml dichlorvos and 26.73 ?g/ml methyl-paraoxon are easily detected in a colorimetric format.By employing such oxidase-like activity of PAA-CeO₂,our proposed colorimetric assay has great application potential,which can provide effective detection means for daily life.Chapter 4.Based on the PAA-CeO₂ Colorimetric method and the Application on the Detection of Hydrogen PeroxideHydrogen peroxide?H₂O₂?played an important role in daily production and living.However,incorrect discharge of H₂O₂ into the environment can cause serious environment problems and affect human health.So it is necessary to detect and control the concentration of H₂O₂ in the environment.In this study,we used polyacrylic acid-coated cerium oxide nanoparticles?PAA-CeO₂?with reducibility as a colorimetric probe.When adding H₂O₂,colorless Ce3+ of PAA-CeO₂ was oxided to yellow Ce4+.By using this response characteristics,we achieved the colorimetric analysis of H₂O₂.Combined with our developed portable colorimetric detection divice based on the Arduino microcontroller and TCS230 sensor,it could make the transition from the color of the solution to the RGB values displayed on the screen.This not merely greatly reduced the volume of colorimetric test instrument,but also realized testing H₂O₂ conveniently with easy and inexpensive equipments in the scene.