Verification And Optimization Of The Analytical Method Of Heavy Metal In Sewage Sludge And Fly Ash By Means Of FAAS

The credibility of measurement result is very important to chemical measurement, quality assurance which could increase the reliability of the analytical results are used in chemical measurement. This paper verified the reliability of FAAS method which determinate the heavy metals depending on the principles of quality assurance at ICEEE laboratory, and optimized this method.First, the accuracy, precision, sensitivity, limit of quantification, limit of detection, the standard curve and linear range of the determination of heavy metals by means of AAS using municipal sewage sludge certified reference material (CRM) BCR-144R as the standard samples was assessed. The results show that the recoveries of this method amounted to 90 to 110 %, the relative standard deviations were less than 3 %, the limits of quantification were less than the lowest concentration of standard solution, except Zn, the uncertainties were smaller than required of CRM. This method had good accuracy, precision, sensitivity, linear range and the limit of detection.Secondly, this method of determination the concentration of heavy metal in the sludge (sludge 1 and sludge 2) from Shenyang northern sewage treatment plant, fly ash and slag was applied. We found that the concentrations of Zn were completely and those of Cu partly higher than the respective Chinese national threshold values for application to agricultural land of 1000 and 500 mg/kg dm, respectively, So, the sludges from Shenyang northern sewage treatment plant were not suitable for farming; The concentrations of Cd but not Pb in air-cooled thermally stabilized fly ash were higher than the Danish threshold value of 10 mg/kg for reuse of the material. In the cases of Ni and Cu, water-cooling of the stabilized fly ash led to higher proportions of the metals remaining in the slag than air-cooling, but in the cases of Pb and Zn the opposite effect occurred. The Cd proportion fixed in the stabilized fly ash did not show a clear relation to the cooling method. Finally, In order to assess the potential for saving energy, work time and material resources, varying conditions such as microwave digestion times, acid volume and heating pre-treatment times were studied to find the best digestion condition.