Using Magnesium Hydroxide for Ocean Alkalinity Enhancement: Elucidating the Role of Formation Conditions on Material Properties and Dissolution Kinetics
Abstract
Mg(OH)2 holds potential as an alkalinity source for Ocean Alkalinity Enhancement (OAE). It is a
current byproduct of desalination treatment through the alkalinity exchange of
electrochemically derived NaOH to the Mg-rich reverse osmosis reject brine. Characterization
found no chemical composition difference among seawater-precipitated and industrial sourced
Mg(OH)2 with both having high (>98%) purity. Differences were found with the crystallinity with
industrial sources containing a higher degree of crystallinity of 0.83-0.85 compared to 0.16-0.33
for seawater-precipitated paste. Mg(OH)2 with a higher degree of crystallinity (>80%) had
significantly slower dissolution rates than Mg(OH)2 with a lower degree of crystallinity (<20%).
Results revealed that there is a strong inverse relation between degree of crystallinity and
dissolution rate of both seawater-precipitated and industrial sourced Mg(OH)2. Seawater39 precipitated Mg(OH)2, with its similar purity to industrial sources yet faster and more complete
dissolution and alkalinity release, could hold an advantage over other alkalinity sources for OAE
applications with its seemingly tunable dissolution kinetics.
current byproduct of desalination treatment through the alkalinity exchange of
electrochemically derived NaOH to the Mg-rich reverse osmosis reject brine. Characterization
found no chemical composition difference among seawater-precipitated and industrial sourced
Mg(OH)2 with both having high (>98%) purity. Differences were found with the crystallinity with
industrial sources containing a higher degree of crystallinity of 0.83-0.85 compared to 0.16-0.33
for seawater-precipitated paste. Mg(OH)2 with a higher degree of crystallinity (>80%) had
significantly slower dissolution rates than Mg(OH)2 with a lower degree of crystallinity (<20%).
Results revealed that there is a strong inverse relation between degree of crystallinity and
dissolution rate of both seawater-precipitated and industrial sourced Mg(OH)2. Seawater39 precipitated Mg(OH)2, with its similar purity to industrial sources yet faster and more complete
dissolution and alkalinity release, could hold an advantage over other alkalinity sources for OAE
applications with its seemingly tunable dissolution kinetics.
