(425h) Direct Capture of Carbon Dioxide from Seawater Via Novel Hollow Fiber Contactor

Greenhouse gas contributions to global climate change have generated interest in separating carbon dioxide (CO2) from the atmosphere. Oceanic seawater behaves as a natural sink for CO2 and absorbs approximately 40% of atmospheric CO2 dating back to the industrial revolution. Once absorbed into seawater, CO2 primarily exists as bicarbonate ions. Direct ocean capture of CO2 has much potential in the carbon capture space when considering CO2 concentration is 140 times higher in the ocean compared to the atmosphere. Most CO2 seawater removal technologies being researched utilize electrochemical approaches that are energy-intensive and require expensive capital and operational costs. A scalable, cost-efficient process is needed to advance the direct ocean capture space and achieve net-negative carbon emissions. To bridge this gap, a scalable, energy-efficient, hollow fiber sorbent (microporous polyvinylidene fluoride (PVDF)) contactor-based process was designed with low-cost and high surface area to provide high interfacial area for effective CO2 capture from oceanic seawater. To effectively remove bicarbonate ions from seawater, PVDF hollow fibers are first functionalized with bicarbonate selective groups to effectively adsorb bicarbonate ions from solution and achieve this separation. To measure CO2 removal, a carbon dioxide ion selective electrode was utilized. Upon saturation of bicarbonate ions, a pH swing mechanism was employed to regenerate the hollow fibers by desorbing the ions back into solution, allowing for further adsorption. This regeneration process allows for repeated, recycled use of the contactor in a cost-friendly and energy-efficient manner. Results from this work underscore the importance of utilizing bicarbonate selective PVDF hollow fibers in HFMC-based separation processes for effective direct ocean carbon capture and provides a pathway toward practical deployment.