Characterization of Nanoparticles Produced from a Spark Discharge System with Manganese and Iron Alloy Electrodes

1721 

Student Poster 

M Theis¹, J Park¹

¹Purdue University, West Lafayette, IN

Mishael Theis, GSP  
Purdue University

Dr. Jae Park, Ph.D./CIH  
Purdue University

Welding fumes typically consist of high concentrations of metallic particles smaller than 300 nm. The small particle size and presence of metals, such as manganese (Mn), contribute to the toxicity of welding fumes. Mn nanoparticle exposure from welding fumes is associated with slower reaction time, hand tremors, and Parkinson's disease-like symptoms, referred to as manganism. To evaluate the toxicity of welding fumes in the lab, a welding fume generation system is required. The ability to control welding fume concentrations is critical in toxicological studies. Only a few welding fume inhalation exposure systems have been developed due to the numerous different types of welding processes employed in the workplace, and the difficulties with generating a fume with stable output over extended periods. Recently, a spark discharge system (SDS) has been used to simulate the welding fumes. In this study, Mn and Iron (Fe) electrodes were used to simulate welding fumes in the SDS. Various electrodes were used to simulate different metal contents and particle size distributions.

Welding fume exposures present negative health effects for workers due to their metal contents and particle size. The hazardous metals in the fumes may translocate from the lungs to other organs in the body, such as the brain, after inhalation. Due to these adverse health effects, welding fumes have been a well-studied research topic. However, collecting welding fumes can be difficult. In the past, researchers would use real welders to gather fumes and then re-aerosolize them. In more recent decades, newer models such as robots and rotating cylinders have been used. The issue with these methods is they are costly, take up a large space, time -consuming, and a stable/continuous difficult. The Spark Discharge System (SDS), a novel technology for simulating welding fumes, can mitigate these issues. The SDS is cost-effective, timely, and provides a stable output for welding fume nanoparticle generation. In this study, the SDS is used to generate nanoparticles to simulate welding fumes with various iron (Fe) and manganese (Mn).

In this study, the spark discharge system (SDS) was used to simulate welding fumes. A scanning mobility particle sizer (SMPS) and field-portable X-ray fluorescence analyzer (XRF) were used to develop the particle size distributions and analyze metal contents. The SDS generates welding fumes using an electric current between two metal electrodes. Particle free compressed air flows through the system at 2 L/min which brings the generated particles to an aerosol neutralizer, which removes the electrostatic charge. The air-flow, with an additional 2 L/min of dilution air, is then directed to one of three portals: (1) exhausted air after passing through a HEPA filter; (2) SMPS which captures real-time particle concentration and size statistics at 0.3 L/min; (3) 25 mm mixed cellulose ester filter for XRF analysis at 3 L/min. The filters used, as well as the electrodes, undergo XRF analysis to determine metal content percentages, concentrations, and the generation rate. The operational conditions of the SDS are 5 kV of applied voltage and 0.5 mA of loading current. The electrodes used in this specific study were pure iron (Fe), pure Manganese (Mn), Fe 50% + Mn 50%, and Fe 90% + 10% Mn. The running time for every experiment is 2 hours.

The total number concentrations and geometric mean diameter ranged from 7.13 × 106 - 8.60 × 106 particles/cm³ and 46.3 - 67.4 nm, respectively, with the highest statistics produced by pure Manganese (Mn). The generation rate, which was calculated from the metal contents in the X-ray florescence (XRF) analysis, ranged from 0.85 – 1.74 µg/min, with the highest generation rate produced by pure Mn. Increasing Mn content also leads to the higher total mass (µg) and concentration (µg/m³). Additionally, the XRF analysis showed the compositions of the particles were consistent with the electrodes.

These results indicate that higher Mn content produces higher particle concentration, geometric mean diameter, and generation rate. Additionally, generated metal contents are correlated with the relative concentrations in electrodes. Further analysis of the simulated welding fumes using transmission electron microscopy, as well as future tests using various other metals, will enhance the scope of this study. This information may be useful in future toxicology studies on welding fume exposure.

Aerosols

Technology

Toxicology