The ever-increasing levels of carbon dioxide (CO₂) emissions have become a pressing global concern, contributing significantly to climate change and its adverse effects. To combat this problem, the development of efficient and sustainable methods for CO₂ capture is paramount. Among the various techniques, solid sorbents, and more specifically solid, carbon-based sorbents have emerged as one of the most promising and effective approaches.

Common examples of solid sorbents considered for CO₂ capture include:

1. Amine-based sorbents: These sorbents contain amines, such as monoethanolamine (MEA), diethanolamine (DEA), or their derivatives. Amine-based sorbents chemically react with CO₂ to form stable compounds and have high CO₂ selectivity and capacity. However, they suffer from corrosion issues, are energy-intensive to regenerate, and can degrade over time, all leading to high costs of capture.

2. Zeolites: Zeolites are crystalline aluminosilicate minerals. They are porous materials with a well-defined structure, high surface area, and good thermal stability. They adsorb CO₂ through physical adsorption, due to their microporous structure.

However, zeolites are sensitive to moisture and can lose their adsorption capacity when exposed to high humidity conditions. This limits their applicability in environments where humidity levels are significant, such as flue gases. They effectively capture the water from the flue gas, dramatically reducing their CO₂ capture capacity after relatively few capture cycles.

Zeolites can also be prone to fouling and deactivation due to the presence of impurities in the CO₂ source, such as sulfur compounds or trace contaminants. These impurities can interact with the zeolite structure and reduce its effectiveness over time, requiring more frequent regeneration or replacement.

3. Metal-organic frameworks (MOFs): MOFs are crystalline materials composed of metal ions connected by organic ligands. They are tunable and demonstrate high porosity and surface area, providing high CO₂ selectivity and adsorption. However, MOFs are prone to degradation under the cyclic industrial conditions encountered during CO₂ capture, such as high temperatures, humidity, and the presence of impurities.

The synthesis of MOFs can be complex and expensive, involving multiple steps and the use of high-purity precursors. This can significantly increase their production cost, making them less economically viable for large-scale CO₂ capture applications.

MOF scalability has also not been proven. MOF synthesis and activation often involve batch-processes, which can be challenging to scale up for large-scale CO₂ capture applications. The need for continuous and cost-effective production methods remains an area of active research.

Also, some MOFs may contain toxic or environmentally harmful components, such as heavy metals. The safe handling, disposal, and long-term environmental impact of MOFs is also an important consideration.

4. Silica-based sorbents: Silica-based sorbents, such as amorphous silica or mesoporous silica, have shown promise for CO₂ capture. They can be functionalized with amine groups or other reactive species to enhance CO₂ adsorption. While they offer some advantages, there are also significant drawbacks associated with their use.

Silica-based sorbents typically have lower CO₂ capture capacities compared to other sorbents. This means that a larger amount of sorbent material is required to capture the same amount of CO₂, leading to higher capital and operational costs.

Regeneration of silica-based sorbents requires high temperature levels, also making it an energy-intensive and costly process.

While silica-based sorbents have been studied extensively in research laboratories, their scalability and commercial availability are relatively limited compared to other CO₂ capture technologies. This can also hinder widespread adoption and deployment in large-scale industrial applications.

5. Calcium-based sorbents: Calcium-based sorbents, such as limestone or calcium oxide (lime), react with CO₂ to form stable calcium carbonate. These sorbents can be used in carbonation/calcination cycles, where they capture CO₂ when exposed to the gas and release it when heated. However, calcium-based sorbents typically require high temperatures to achieve efficient CO₂ capture. On the other hand, the calcination process, which releases the captured CO₂ from the sorbent, also requires a substantial amount of energy input. These high-temperature requirements increase the energy consumption of the overall process, making it less economically viable.

6. Dotz Earth activated carbon sorbent: The Dotz Earth sorbent is a highly porous carbon material with a large internal surface area that can physically adsorb CO₂ due to surface interactions. Dotz Earth holds several key advantages over competing solid sorbents:

Abundant and Renewable:

It is synthesized using a well known and technically mature process (pyrolysis) and using an abundant feedstock, waste plastics. The proprietary process of pyrolyzing waste plastics with certain potassium salts also leads to the production of pyrolysis oils and gases, which can be reused to power the process and drive down the cost of synthesis, making the Dotz Earth sorbent economically feasible and readily accessible. Unlike some other sorbents, the production of the sorbents does not rely on rare or limited resources, ensuring a sustainable supply for large-scale CO₂ capture operations.

Tailorable Surface Properties:

The surface characteristics of a sorbent play a vital role in capturing CO₂. Dotz Earth possesses a highly tunable surface, allowing for modifications to enhance its affinity for CO₂ adsorption. Techniques like chemical activation, surface functionalization, and pore size engineering have been employed to tailor the Dotz Earth sorbent's surface properties, thereby optimizing its CO₂ capture capacity and selectivity.

High Adsorption Capacity:

The Dotz Earth sorbent exhibits good CO₂ adsorption capacities due to its unique structure of micropores and mesopores which provide a large surface area for CO₂ molecules to interact and be captured. This high adsorption capacity makes carbon-based sorbents highly efficient in capturing CO₂ from flue gases and other emission sources.

Regenerability and Reusability:

An effective CO₂ capture process must not only capture the gas but also enable its subsequent release or conversion for storage or utilization. Carbon-based sorbents offer excellent regenerability, allowing them to be used in cyclic CO₂ capture processes. After adsorbing CO₂, these sorbents can be regenerated by applying heat, pressure, or a combination of both, enabling the release of CO₂ for storage or utilization purposes. This feature enhances the economic viability and environmental sustainability of carbon-based sorbents.

Versatility and Compatibility:

Carbon-based sorbents exhibit compatibility with a wide range of CO₂ sources and capture conditions. They can be applied to capture CO₂ from various emission sources, including power plants, industrial facilities, and even the atmosphere. Furthermore, carbon-based sorbents are robust and are not normally subject to degradation, so they can function effectively under diverse temperature and pressure conditions, making them versatile and adaptable to different CO₂ capture scenarios.

In conclusion, the urgent need to address carbon dioxide (CO₂) emissions and combat climate change has driven the search for efficient and sustainable methods of CO₂ capture. Among the various solid sorbents considered, carbon-based sorbents, particularly the Dotz Earth activated carbon sorbent, have emerged as an advantageous solution. Dotz Earth offers several key benefits, including its abundant and renewable production process using waste plastics, the tailorable surface properties that enhance CO₂ adsorption, high adsorption capacity facilitated by its unique structure, regenerability and reusability for cyclic capture processes, and its versatility and compatibility with diverse CO₂ sources and capture conditions. These characteristics make carbon-based sorbents, such as Dotz Earth, a promising and effective approach for large-scale CO₂ capture, paving the way for a more sustainable future and mitigating the adverse effects of climate change.

About Michael Shtein, Ph.D., MBA, Co-Founder & CTO , Dotz Nano Limited

Entrepreneur with over 15 years of managerial and R&D experience, Dr. Shtein is an expert in commercializing academic concepts to products and is a co-founder of several Nanotech and Biomed companies.

Dr. Shtein holds a Ph.D. in Nano technology interdisciplinary studies from Ben-Gurion University, together with an M.Sc in Chemical Engineering and an MBA.

Before founding Dotz, he was the Chief Material Engineer for the Israeli Ministry of Defense and has developed several new materials and compounds. 

About Dotz Nano Limited

Dotz Nano Limited (ASX: DTZ) is a technology company specializing in high-value advanced materials. Dotz develops and commercializes innovative solutions addressing global environmental & industrial changes, utilising its carbon-based nano technology. Two main areas of focus are:

• In-product tagging solution for anticounterfeiting and monitoring, primarily for the oil & gas and chemical sectors

• Carbon-based sorbent technology for industrial decarbonisation & sustainability

To learn more about Dots, please visit the website via the following link https://dotz.tech/

By Dr. Michael Shtein, CTO – Dotz Nano Limited