Shan Qing

A new Am-Be PGNAA setup for element determination in aqueous solution

A new prompt-gamma neutron activation analysis (PGNAA) setup has been designed for element determination in aqueous solution with a 300 mCi 241Am-Be neutron source and a 4in.×3in. (diameter×height) BGO detector, uncooled. A polyethylene cylindrical sample container approximately 40cm in outer radius and 80cm in height was used. To reduce the neutron dose in the detector, a block of 5cm thickness Li2CO3 was placed between the source and the detector for separation, but no gamma-blocker was used. By adjusting the position of the detector and optimizing the geometrical conditions of the setup, the element detection limit with a low activity neutron source was further improved. This methodology was checked by simulations with chlorine, mercury and cadmium determination and by experiments with chlorine determination in aqueous samples. The results show a good linear relationship between chlorine concentration and the count of its characteristic peak, and the detection limit of chlorine can reach 41.7mg/L with a collection time of 3600s for each spectrum. Additionally, a linear relationship was identified between mercury concentration and the count of its characteristic peak, but for cadmium, a non-linear relationship was observed in the simulations.

Development of an online X-ray fluorescence analysis system for heavy metals measurement in cement raw meal

ABSTRACT Particulate matters, gaseous chemicals, and heavy metals emitted from industrial processes into the environment could be directly transmitted to humans through air inhalation. In order to accurately estimate health risk and control the source of pollution caused by cement raw meal, an online X-ray fluorescence analyzer system, consisting of an X-ray fluorescence analyzer with data acquisition software and a laser rangefinder, was developed to carry out the measurement of heavy metals in cement raw meal. The X-ray fluorescence analyzer was mounted on a sled, which can effectively smooth the surface of cement raw meal and reduce the impact of surface roughness during online measurement. The laser rangefinder was mounted over the sled for measuring the distance between cement raw meal sample and the analyzer. Several heavy metals and other elements in cement raw meal were online measured by the X-ray fluorescence analyzer directly above a conveyor belt. The limits of detection for Pb, Cr, Fe, Ti, Ca, and S by the analyzer were 47 ± 1, 33 ± 1, 37 ± 1, 44 ± 1, 246 ± 4, and 118 ± 1 mg kg−1, respectively. The relative standard deviation (RSD) for the elements mentioned was less than 10.7%. By comparison with the results by inductively coupled plasma mass spectrometry (ICP-MS) and CHNS/O elemental analyzer, relative deviation (D) of the online X-ray fluorescence analyzer was less than 7.4% for Fe, Ti, Ca, and S, between 1.71% and 12.10% for Pb and Cr.

Online X-ray Fluorescence (XRF) Analysis of Heavy Metals in Pulverized Coal on a Conveyor Belt

Heavy metals in haze episode will continue to threaten the quality of public health around the world. In order to decrease the emission of heavy metals produced from coal burning, an online X-ray fluorescence (XRF) analyzer system, consisting of an XRF analyzer with data acquisition software and a laser rangefinder, was developed to carry out the measurement of heavy metals in pulverized coal. The XRF analyzer was mounted on a sled, which can effectively smooth the surface of pulverized coal and reduce the impact of surface roughness during online measurement. The laser rangefinder was mounted over the sled for measuring the distance between a pulverized coal sample and the analyzer. Several heavy metals and other elements in pulverized coal were online measured by the XRF analyzer directly above a conveyor belt. The limits of detection for Hg, Pb, Cr, Ti, Fe, and Ca by the analyzer were 44 ± 2, 34 ± 2, 17 ± 3, 41 ± 4, 19 ± 3, and 65 ± 2 mg·kg–1, respectively. The relative standard deviation (%RSD) for the elements mentioned was less than 7.74%. By comparison with the results by inductively-coupled plasma mass spectrometry (ICP-MS), relative deviation (%D) of the online XRF analyzer was less than 10% for Cr, Ti, and Ca, in the range of 0.8–24.26% for Fe, and greater than 20% for Hg and Pb.

The treatment of aniline in aqueous solutions by gamma irradiation

Abstract A laboratory investigation of the radiation-induced degradation of aniline by gamma irradiation is the subject of this paper. During the inquiry, several aqueous samples with aniline concentrations of 25, 50, 75, 100 and 200 mg/L were irradiated for 5, 10, 15, 20, 25 and 30 h, respectively, by a 60Co source with an absorbed dose rate of 0.78 kGy/h at the core channel. After the testing, the project authors scrutinized the aqueous samples to determine the effects of their irradiation by analyzing the pH, the hydroxyl radical and the H2O2 of the individual initial concentrations. The findings showed that gamma irradiation is effective in removing aniline from aqueous solutions and, in the process, tends to remove the chemical oxygen demand (COD). Among other findings, the tests revealed that at a 25 mg/L aniline concentration, up to 100 % removal is possible after only 5 h of exposure. The authors explained that kinetic studies have shown that the degradation of aniline follows a pseudo first-order reaction. They have also shown that pH plays a significant role in aniline-removal efficiency. The tests in this study revealed that with a dose of 7.8 kGy, the removal efficiency of COD in an alkaline environment is higher than that of an acidic environment. With the absorbed dose increases, the authors learned that an acidic environment is helpful for the removal efficiency of COD. They also found that by adding 50 g/L of sodium bicarbonate as the hydroxyl radical scavenger, there was an 8 % decrease in the removal efficiency of COD at the absorbed dose of 23.4 kGy. This indicates the importance of using a hydroxyl radical in the gamma irradiation process. Also, a 1 g/L H2O2 addition increases the COD removal rate from 31 % to 55 %. This percentage-point jump shows a synergistic effect in the use of gamma irradiation. The authors also identified several major decomposition products by GC/MS which are useful in the radiation-induced degradation of aniline by gamma irradiation process. Finally, they present proposals of possible pathways for successful aniline decomposition.