10:45 AM - 12:15 PM
[SCG58-P17] Natural chelating agents enhance mineral dissolution and its effect to potential carbonation
Keywords:Chelator, Mineral dissolution, Plant metabolite, Silicates
Mineral dissolution process contributes to many geochemical characteristics and phenomena, such as soil fertility, reservoir porosities, ore deposits formation and global carbon cycle. In recent years, the dissolution of Ca- and Mg-silicates is receiving increasing attention due to its potential contribution to atmospheric CO2 removal/storage. To enhance the dissolution of silicate minerals, which is considered slow in water, thermal or chemical approaches such as using artificial chelating agents have been suggested. In natural, organic agents that have potential chelating ability, can be plentily secreted by organisms and are considered have crucial role in mineral dissolution promotion. The purpose of this study is to verify these positive effects through batch experiments.
Dissolution experiments were conducted at room temperature (~20°C) and ambient pressure using olivine [(Mg0.91Fe0.09)2SiO4] and wollastonite (MgSiO3) powders, and solutions of amino acids glycine, L-serine, L-glutamic acid with a concentration of 0.1 mol/L, and humic acid with a dosage of 10 g/L, all these compounds have potential chelating ability to Mg and Ca. At pH 8, the ocean pH, all the amino acids and humic acid significantly promoted the extraction of Mg from olivine and Ca from wollastonite. Ca extraction from wollastonite was enhanced by 12 times in L-glutamic acid solution compares to that in water in 168 hours. With the increased extraction of Ca or Mg, more CO2 was captured from the atmosphere to HCO3-. Moreover, dissolution experiments using wollastonite and L-glutamic acid at different pHs show that, with the increase of pH from 3.8 to 7.0, less Ca was extracted due to the presence of less proton, which is expected. However, the Ca extraction ratio at pH 8 was not lower than that at pH 4, probably due to the stronger chelating ability to metals under weak alkaline conditions.
This study verified the role of some natural chelating agents in the promotion of mineral dissolution especially in weakly alkaline environments, and this enhanced dissolution further contributed to the removal of atmospheric CO2.
Dissolution experiments were conducted at room temperature (~20°C) and ambient pressure using olivine [(Mg0.91Fe0.09)2SiO4] and wollastonite (MgSiO3) powders, and solutions of amino acids glycine, L-serine, L-glutamic acid with a concentration of 0.1 mol/L, and humic acid with a dosage of 10 g/L, all these compounds have potential chelating ability to Mg and Ca. At pH 8, the ocean pH, all the amino acids and humic acid significantly promoted the extraction of Mg from olivine and Ca from wollastonite. Ca extraction from wollastonite was enhanced by 12 times in L-glutamic acid solution compares to that in water in 168 hours. With the increased extraction of Ca or Mg, more CO2 was captured from the atmosphere to HCO3-. Moreover, dissolution experiments using wollastonite and L-glutamic acid at different pHs show that, with the increase of pH from 3.8 to 7.0, less Ca was extracted due to the presence of less proton, which is expected. However, the Ca extraction ratio at pH 8 was not lower than that at pH 4, probably due to the stronger chelating ability to metals under weak alkaline conditions.
This study verified the role of some natural chelating agents in the promotion of mineral dissolution especially in weakly alkaline environments, and this enhanced dissolution further contributed to the removal of atmospheric CO2.