Study On The Detection Of Iron In Water Based On LIBS Technology

Water is the foundation of all living beings.In recent years,due to the acceleration of urbanization,a large amount of waste garbage,industrial and agricultural wastewater are discharged indiscriminately,which has led to an increasingly prominent problem of heavy metal pollution in water.A large number of metal elements converge in the surface water body through surface runoff and other methods,and eventually accumulate in the human body as the food chain flows,thereby threatening human health.Therefore,this thesis uses chelating resin as the enrichment material to adsorb divalent iron(Fe(?))and trivalent iron(Fe(?))from the liquid phase to the solid matrix,and then apply Laser-Induced Breakdown Spectroscopy(LIBS)technology for qualitative and quantitative analysis.In this thesis,chelating resin is selected as the solid phase matrix,and the Fe(?)and Fe(?)in the solution are adsorbed based on the enrichment method to prepare the LIBS analysis sample required for the experiment.In the experiment,the sequential test method was used to analyze the influence factors of the emission spectrum such as the flow rate of the standard solution,the p H value,the laser energy and the detection delay.The optimal experimental parameters were set,and the Fe(?)and Fe(?)calibration models were established by the external standard method.The linear fits were 0.9903 and 0.9914,respectively,and the limits of detection were calculated to be 0.120 mg/L and 0.142 mg/L.The experimental results show that this thesis uses chelating resin assisted LIBS technology to analyze Fe(?)and Fe(?)in solution with high detection sensitivity.Next,in order to verify the accuracy of the calibration model established,actual water samples were collected to study the spike recovery rate,and the results of Fe(?)and Fe(?)were97.73%?105.79% and 98.82%?101.45%,it turns out that the method proposed in this thesis is suitable for actual water sample analysis.Finally,according to the adsorption threshold of the chelating resin to the p H of the solution,the valence states of Fe(?)and Fe(?)in the mixed solution were separated,and then the experimental results of the single valence and mixed valence solutions of the same concentration were compared and analyzed.The relative error ranges of Fe(?)and Fe(?)were 0.25%?1.12% and3.05%?7.24%,respectively.The above results indicate that this article provides a new method for the separation of metal ions in solution.In order to improve the detection stability and quantitative analysis capabilities of LIBS technology,this thesis builds a laser beam expander and a lateral imaging system to optimize the LIBS experimental device,and writes two image definition evaluation programs based on the energy gradient algorithm and the Tenegrad gradient algorithm.Through the method of plasma image quality evaluation,the focus position of laser pulse on Fe(?)and Fe(?)samples is explored.Next,this article evaluates the detection stability and quantitative analysis ability of the optimized LIBS experimental system.The experimental results show that the detection stability and quantitative analysis ability of the system have been improved.Finally,this thesis studies the time-resolved characteristics of laser-induced chelating resin plasma,and verifies the establishment of the local thermodynamic equilibrium state.