Abstract No:
1698
Abstract Type:
Student Poster
Authors:
M Van Houten-Armstrong1, C Lungu2, J Oh3
Institutions:
1University of Alabama at Birmingham, Birmingham, AL, 2The University of Alabama at Birmingham, Birmingham, AL, 3UAB, Birmingham, AL
Presenter:
Maya Van Houten-Armstrong
University of Alabama at Birmingham
Faculty Advisor(s):
Claudiu Lungu
The University of Alabama at Birmingham
Jonghwa Oh
UAB
Description:
Many workers are exposed to environments containing harmful gasses such as volatile organic compounds (VOCs), increasing their risk of harmful health effects including asthma, kidney damage, and some cancers [1]. To protect against VOCs, respirator cartridges containing adsorptive media, such as activated carbon (AC) in granular form, are often used. While the granular activated carbon has the necessary characteristics for VOC adsorption such as a high surface area and microporosity, because of friction the granules can degrade overtime lowering its performance. Developing activated carbon materials manufactured via stereolithographic (SLA) 3D printing could help improve upon the current granular activated carbons by mitigating internal friction through complex stationary structures. The present work sought to improve upon activated carbon manufacturing techniques through the development of precursor photo resins compatible with SLA 3D printing to produce materials with favorable adsorptive properties for VOC capture.
Situation/Problem:
The purpose of this study is to explore the role of various thermal treatments in the activation of carbonaceous materials prepared from experimental SLA resin, achieving a 3D printed activated carbon media. Before an AC precursor material can be produced via SLA 3D printing, a suitable photoresin must be developed. Previous work identified the acrylate monomer, poly(ethylene glycol) diacrylate (PEGDA), as a favorable candidate for 3D printing materials with a high surface area and porosity, but there has been little work investigating the adsorptive characteristics of 3D printed carbons [2]. Although this material was not designed for VOC capture, due to its morphological characteristics, it shows promise for VOC adsorption in this present study. These characteristics led us to investigate the following research questions:
1. Do 3D printed precursor materials respond to thermal activation to achieve high surface areas and porosity characteristics matching industry standard activated carbons?
2. What effect do the thermal activation stages have on the material's carbon yield regarding mass retention?
Methods:
To create the experimental resin, an industry standard photoinitiator, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) was combined with the polymer poly(ethylene glycol) diacrylate (PEGDA) in a ratio of 10 mg/mL. To mimic conditions of an SLA printer, samples were cured under a 405 nm UV source at a distance of 20 cm. The time of polymerization was evaluated based on the speed of observed solidification. This process was performed in quadruplicate for the experimental resin. The speed of solidification was compared to SLA resin standards to establish compatibility.
To activate the material, samples were subjected to three sequential thermal treatments carried out in a tube furnace under varying gasses. Three thermal treatments were conducted: oxidative stabilization, pyrolysis, and CO2 activation. The cured samples underwent oxidative stabilization first, with a peak temperature of 300 °C heated under a nitrogen atmosphere (400 mL/min), once at peak temperature the gas supply was changed to synthetic air (450 mL/min) and samples were held for a duration of 6 hours before cooling. The oxidized samples then underwent pyrolysis with a peak temperature of 900 °C under a nitrogen atmosphere (450 mL/min), once at peak samples were held for 15 minutes before cooling. The samples where then subjected to additional CO2 activation with a peak temperature of 860 °C heated under nitrogen gas (400 mL/min), once at target temperature the gas was changed to CO2 (450 mL/min) and samples were held for 6 hours to complete activation. Surface area characteristics were taken before and after every thermal treatment to establish a baseline for the untreated material and show the effect of oxidative stabilization, pyrolysis, and CO2 activation.
Results / Conclusions:
The average cure time was 33.3 s ± 2.1s per layer. Prior to thermal treatment, the precursor material had a very low Brunauer-Emmett-Teller (BET) surface area of 0.9450 m2/g. Oxidized samples had a slightly higher BET surface area of 2.2474 m2/g. Pyrolyzed samples had a high BET surface area of 1221.5974 m2/g. Samples that underwent CO2 activation had the highest BET surface area of 2295.8028 m2/g. Oxidation resulted in a 27.6% carbon mass loss, pyrolysis resulted in a 90.9% loss, and CO2 activation resulted in a 32.1% loss. From the precursor material to the final thermal treatment, there was a total of 96.2% mass loss with a 3.3% carbon yield.
The experimental PEGDA resin had a cure rate that was slower than commercial resins but is within the range of SLA compatibility. While the untreated precursor and oxidized samples appeared primarily non-porous, subjecting the material to the high temperature thermal treatments (pyrolysis and CO2 activation) resulted in high BET surface areas and favorable adsorptive characteristics. Samples that underwent CO2 activation had BET surface areas similar to commercially available activated carbons, suggesting the thermally treated material would be suitable as an adsorptive media for VOC capture. These initial findings provide insight on the role of thermal treatment to activated 3D printed carbon materials, but further work must be done to address the high degree of mass loss across each treatment. It is normal for activated carbons to lose between 10-50% mass during activation, but the 96.2% loss observed in these experimental trials poses a challenge for future work. Next steps of this research should target mitigating mass loss, potentially by cross-linking the PEGDA with a vinyl polymer, and testing the material's adsorptive capacity with a VOC challenge.
Core Competencies:
Personal Protective Equipment
Secondary Core Competencies:
Chemical Hazards
Choose at least one (1), and up to five, (5) keywords from the following list. These selections will optimize your presentation's search results for attendees.
Personal protective equipment
Respiratory Protection
Based on the information that will be presented during your proposed session, please indicate the targeted audience practice level: (select one)
Professional: Professional is a job title given to persons who have obtained a baccalaureate or graduate degree in IH/OH, public health, safety, environmental sciences, biology, chemistry, physics, or engineering or who have a degree in another area that meets the standards set forth in the next section, Knowledge and Skill Sets of IH/OH Practice Levels, and has had 4 or more years of practice. One significant way of demonstrating professional competence is to achieve certification by a 3rd party whose certification scheme is recognized by the International Occupational Hygiene Association (IOHA) such as the Board of Global EHS Credentialing (BGC).
Was this session organized by an AIHA Technical Committee, Special Interest Group, Working Group, Advisory Group or other AIHA project Team?
No
Are worker exposure data and/or results of worker exposure data analysis presented?
No
How will this help advance the science of IH/OH?
The development of customizable adsorptive media contributes a significant advancement in the field of IH as it expands the degree of protection offered to workers by tailoring the fit and protection level provided by respirators. Due to the speed offered by 3D printing, this media could allow for the production of fast customizable respirators. Additionally, through resin templating, this material could be manipulated to have various levels of porosity to better capture the specific VOCs. This could have applications for industry, but also for first responders as a tailor-made respirator could be quickly manufactured to offer specific protection for emergency response.
Have you presented this information before?
No
I have read and agree to these guidelines.
Yes