Determination Of Heavy Metal Content In Wastewater By USN-ICP-OES And Interference Factors Research

With the development of modern industry and increasing the people's living standards, more and more heavy metal pollutants various waste discharge into surface water, causing the surface water heavy metal content seriously overweight, and serious harm to human health. Accurately test the content of heavy metals in a variety of waste water is an important part of how to choose suitable treatment programs, evaluate treatment results and guide to carry out follow-up work.Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) is widely used in various fields of elemental analysis as an element analysis technology. ICP-OES coupled with ultrasonic nebulizer (USN) can further lower detection limit of the elements to improve detection capability. The main contents of this paper are as follows:By changing the power of high-frequency generator, the plasma gas flow, nebulizer pressure, peristaltic pump speed and auxiliary gas flow five conditions respectively to finding the best working conditions of USN-ICP-OES. Read spectral line intensities of each element and the change of signal-background ratio to optimize the analysis conditions, and ultimately choose the optimum analytical conditions for the high-frequency generator power 1.3KW, nebulizer pressure 280 KPa, plasma gas flow rate 18 L/min, the peristaltic pump speed 17 rpm, the secondary gas flow of 2.25 L/min.To establish a test method for determination of lead, cadmium, chromium, arsenic, selenium, copper, nickel, mercury at same time, by using USN-ICP-OES for analysis and microwave digestion method for pre-treatment. Selecting 2.5mL hydrochloric acid+2.5mL nitric acid+ 2mL hydrogen peroxide as digestion solution, and selecting "heat up to 180? within 15 minutes then keep temperature for 15 minutes" as the best microwave digestion procedure by experiments. The recoveries of elements are between 83.8% to 101.8% and the relative standard deviations between 1.0% to 6.8% and the detection limit between 0.002 to 0.025 mg/L, meet the analysis requirements. For each element concentration of 0.2mg/L of sample solution, which combined uncertainty are between 0.010 to 0.038mg/L.The results show that ICP-OES combined with an ultrasonic nebulizer can significantly lower detection limits, improved detection capabilities.And microwave digestion pretreatment consumes less reagents, short reaction time, high efficiency, good recovery and less secondary pollution compared with hot plate method.