End-of-life waste management of chromatography operations includes the disposal of the stationary phase media and solvents (water and organic additives). Our previous blog discussed the sustainability impact of solvents used in reverse-phase process chromatography workflows. This blog discusses the ecological impact of two stationary phase media– the widely used Silica C18 and our NanoPak-C graphitic carbon chromatography media.
The use of reverse-phase chromatography has significantly increased due to the rising production of peptide pharmaceuticals. A frequently asked question is: What happens to reverse-phase media after they fulfill their role in pharmaceutical output?
Landfill and incineration are the two most prevalent end-of-life disposition methods.
Landfill disposal is the process of discarding waste in a specific area where it will break down over time. Incineration involves burning waste materials, which turns them into ash, heat, and flue gas. Both methods are widely used around the world, but some countries choose one method over the other based on their specific needs.
Sustainable waste management is a central part of a broader circular economy.
Sustainable waste management focuses on minimizing, reusing, and recycling end-of-life materials to reduce waste production. The goal is to keep these materials in circulation for as long as possible, decreasing waste disposal.
The preferred method for disposing of Silica C18 media is to either discard it in a sanitary landfill or incinerate it in a controlled manner with flue gas scrubbing [1].
When disposed of in landfills, the alkyl components of the media (C18 and other small alkyl groups used for end-capping) slowly undergo aerobic degradation, breaking down into carbon dioxide (CO2) and water. The underlying silica gel will dissolve into silica when exposed to alkaline water sources.
Silica is another name for silicon dioxide, a common chemical compound. You can find it in minerals like quartz, sand, and agate. These materials are widespread and unlikely to react chemically to other environmental substances. However, Silica does not break down further.
Controlled incineration of Silica C18, combined with flue gas scrubbing, involves high-temperature heating in the presence of oxygen, which converts the alkyl components into CO2. The resultant gas, known as flue gas, is chemically treated to limit particulate pollution, carbon dioxide emissions, and other harmful byproducts.
Since silica will not decompose, it must be appropriately disposed of to prevent accumulation in landfills or water systems over time.
NanoPak-C graphitic carbon media can be reclaimed, recycled, and reused for chromatography and other applications where graphite is used as a functional component.
Graphitic carbon media is porous. Its pores foul with increased use, leading to a decrease in its chromatography performance. Once the performance is below a certain threshold, it is disposed of.
This disposed porous carbon material can be reclaimed by:
Treating it with a strong alkaline solution (e.g., sodium hydroxide (NaOH) could regenerate the material. The solution will degrade the components that are the cause of fouling.
Heat treatment is the second method to regenerate the porous graphitic microbeads. The materials could be moderately heated (up to 200◦C) to carbonize the fouling components, followed by washing out the carbonaceous material with dilute solutions of strong acid (e.g., sulfuric acid) or base (e.g., NaOH).
In both methods, care is taken not to destroy the crosslinkers that hold the graphitic carbon together in microbeads to maintain their mechanical integrity.
Applications of reclaimed porous graphitic carbon media.
Chromatography.
Water treatment and filtration. The heat treatment of porous graphitic microbeads could increase their surface area and, thus, their adsorption capacity, making them practical for water treatment applications. It can be used in filters to remove contaminants and impurities from water, improving its quality.
Electrochemically modulated liquid chromatography. The electrical conductivity of the porous graphitic carbon can be harnessed for electrochemically modulated liquid chromatography, a more gentle and sustainable method for separating charged molecules and macromolecules such as ionic compounds and proteins.
Other applications.
Energy. Porous graphite is widely used in electrochemical applications such as electrodes for batteries, fuel cells, and capacitors.
Thermal management. Due to its thermal conductivity and lightweight nature, porous graphite is used in heat exchangers, thermal insulators, and cooling systems where efficient heat dissipation is crucial.
Composite materials. Materials with enhanced mechanical, thermal, and electrical properties can be developed by incorporating porous graphite into composite materials with polymers or other substances.
The bottom line. SiC18 media waste management adheres to the principles of a linear economy, where products are produced, utilized, and eventually disposed of. In contrast, the end-of-life management of
NanoPak-C graphitic carbon microbeads emphasize sustainable waste management and support a circular economy. This approach prioritizes actions that ensure the most efficient use of resources, placing renewable practices and waste reduction at the forefront of the sustainable waste management hierarchy, as illustrated in Figure 1.
For more information on how our NanoPak-C All Carbon media can address your peptide purification challenges or or to request samples, please email us at inquiry@millennialscientific.com, call us at 855 388 2800, or fill in our online form.
References
3. Srinivasa Kannan, Exploring the World of Porous Graphite: Properties, Applications, and Future Prospects, Advanced Materials Science Research, 7, 2024
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