A novel, robust, and innovative electrolytic cation exchange process has been used to efficiently extract large quantities of CO2 in the form of bicarbonate and carbonate from natural seawater, and to simultaneously produce H2 gas in quantities and ratios intended for possible future production of hydrocarbons. This indirect approach acidifies seawater by using the protons electrolytically produced by electrolysis at the anode. Electrons concurrently produced with these protons are subsequently consumed at the cathode forming hydrogen gas. The ability to degas and recover 92% [CO2]T from natural seawater was demonstrated. The potential detrimental effects of mineral deposits on the module’s electrode surfaces were successfully mitigated by cyclically changing the module electrode’s polarity. This feasibility study marks the first time that CO2 has been successfully extracted on a continuous basis from natural seawater. In addition, there is no energy or economic penalty to extract CO2 from the seawater matrix, above the energy needed to produce hydrogen.

An electrolytic cation exchange process has been developed to extract large quantities of carbon dioxide (CO 2 ) from natural seawater where it is in the form of bicarbonate and carbonate, and to simultaneously produce H 2 gas in quantities and ratios (3:1 H 2 to CO 2 ) intended for future synthesis of hydrocarbons. During the early stages of development, optimizing the energy efficiency and CO 2 production efficiency of the process is key to its future practical implementation. Both efficiencies are impacted specifically by the amount of time needed to re-establish equilibrium conditions in the module after a polarity reversal. Three electrolytic cation exchange module (E-CEM) configurations were tested and evaluated to determine the parameters that had the most significant effects on shortening the re-equilibration times after polarity reversal. From these evaluations, a new fourth custom E-CEM was designed, built, and tested that lowered seawater pH 65% faster so that carbonate and bicarbonate in the seawater were re-equilibrated to CO 2 gas for recovery and the electrical resistance was reduced by 31%. These results are important for the future scale-up and implementation of such a process.

Based on continuous electrodeionization (CEDI) technology, a novel hybrid electrochemical acidification process has been developed to extract large quantities of CO 2 from seawater. This indirect approach acidifies seawater to recover CO 2 from bicarbonate. The electrolytic regeneration of cation exchange resin allowed simultaneous and continuous ion exchange and regeneration to occur within the cell along with control of the seawater pH. Lowering seawater pH was found to be proportional to the applied current to the cell, and the CO 2 in the acidified seawater was readily removed at pH less than 6.0. In addition, the cell produced a portion of hydrogen gas without additional energy penalties.

A novel electrochemical acidification process has been developed in a successful feasibility attempt to extract large quantities of CO 2 in the form of bicarbonate and carbonate from seawater for potential use as a source of carbon for hydrocarbon production at sea. This indirect approach acidifies seawater by the electrolytic production of acid. Lowering seawater pH was found to be proportional to the applied current to the cell. Spontaneous degassing and recovery of CO 2 below pH 4.5 was reduced from 92% in synthetic seawater to 30% in natural seawater. The effects of increased operational time, flow rate, current, and natural seawater's complex equilibrium buffer on process performance and CO 2 recovery have been shown to be essential for further improvements in future cell design, efficiency, and scale-up.

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