(180x) Design and Evaluation of an Energy-Efficient Direct Air Capture System with Lab-Synthesized Zeolite 13X

Direct Air Capture (DAC) technology is quickly being recognized as one of the crucial climate change mitigation technologies. However, direct capture of CO₂ from air remains a problematic technical and economic challenge. In our study, Zeolite 13X was synthesized from bentonite raw material by alkaline fusion followed by hydrothermal treatment in the absence of an external silica or alumina source. Under controlled laboratory conditions, the performance of the material in a compact and energy-efficient DAC system was evaluated.

The DAC unit, with a modular design in a 1 ft³ casing, facilitates repeated CO₂ uptake by adsorption. Two vertically aligned 3D-printed columns of 15 cm length and 6 mm inner diameter were filled with 20 grams of the prepared Zeolite 13X. Airflow through the apparatus was regulated by a compact compressor and channeled by a series of solenoid valves, which were operated based on commands from an Arduino microcontroller. The system alternated airflow between the columns every 5 seconds, and the integrated sensors were continuously monitored the CO₂ concentration, pressure, airflow, and temperature.

The system was semi-automated, with real-time data acquisition and sensor readings recorded every 5 seconds and exported for post-processing. Although adsorbent regeneration was not performed, the ability for manual control provided efficient data collection and operation flexibility. Experiments were conducted using ambient air with the initial CO₂ concentration ranging from 671 to 782 ppm (average ~719 ppm). The system consistently maintained 0 ppm CO₂ at the outlet, confirming complete CO₂ removal in each adsorption cycle. Each cycle last for 10 minutes, during which airflow rates were maintained in the range of 0.42–0.45 L/min. Overall energy consumption was extremely low at 1.4 Wh, proving the efficacy of the combined mechanical and electrical subsystems.

The system captured an average of 0.315 mL/min or a total captured volume of 3.15 mL (approximately 6.2 × 10^-3 g CO₂) throughout the 10-minute operation. Although the capture rate per unit mass of adsorbent was relatively low, the system was extremely energy efficient as an active DAC system. The estimated cost to capture one ton of CO₂ was approximately $88,641, highlighting the need for optimization towards greater scalability and cost-effectiveness.

Future improvements, including increased airflow rates and regeneration cycles for the adsorbent, will greatly improve capture capacity and cost of operation. The successful use of low-cost bentonite-derived Zeolite 13X for low-energy CO₂ capture, combined with the low energy requirements of the system, provides a solid starting point for next-generation DAC technology advancement. This work establishes a basis for further engineering development to scalable, cost-effective carbon removal technologies. Full details and more results will be addressed comprehensively and presented during the 2025 AIChE Annual Meeting.