Changes of Silica Species in Sodium Chloride Solution by Fast Atom Bombardment Mass Spectrometry: Silicate Complex Substituted by Sodium Ion

Abstract

The types of chemical species of silicate complex ion exchanged with sodium ions (silicate-Na þ complex) with increasing concentration of sodium chloride (NaCl) and their numbers of chemical species of silicate-Na þ complexes formed were examined. Silicate-Na þ complexes in several concentrations of NaCl were identified by fast atom bombardment mass spectrometry (FAB-MS). The basic structures of silicate species are not complexes with Na þ , such as the dimer, trimer, cyclic tetramer, linear tetramer, cyclic pentamer, linear pentamer, cyclic hexamer and linear hexamer, were identified. When the peak intensity ratios of silicate-Na þ complexes were plotted against the concentration of NaCl, the changes with increasing concentration of NaCl were mainly classified into two patterns. One is the linear silicate-Na þ complex pattern (dimer-Na þ complex, trimer-Na þ complex and linear tetramer-Na þ complex), and the other is the cyclic silicate-Na þ complex pattern (cyclic tetramer-Na þ complex and cyclic pentamer-Na þ complex). In the linear silicate-Na þ complex pattern, the peak intensity ratios of the linear silicate-Na þ for the basic structures vary largely between 0.001 and 0.1 mol dm À3 (M) NaCl, and they become constant at above 1 M NaCl. In the cyclic silicate-Na þ complex pattern, the peak intensity ratios of the basic structures of cyclic silicate-Na þ change slightly between 0.001 and 0.1 M NaCl and change considerably above 1 M NaCl. The basic structure of cyclic silicate has a stable structure and hydrophobic part. By substituting Na þ , the hydrophobicity of the cyclic silicate complex increases. The linear silicate complex is not as stable as the cyclic silicate complex and it possesses a higher degree of hydration than the cyclic silicate. The hydrophobicity of the linear silicate also increases by the substitution of silanol groups by Na þ . These changes of the hydrophobicity of the linear silicate due to the substitution of Na þ are larger than those for the cyclic silicate. The dissolution system of the silicate species in NaCl solution should be elucidated by considering the relationship between the stabilities of the basic structure and Na þ -containing silicate complexes, and their hydration effect.

Study on chemical speciation in aluminum chloride solution by ESI‐Q‐MS

“…Speciation is required in environmental chemistry as well as in solution chemistry. For example, ‘chemical speciation’ of silica has been extensively discussed 1–7. As a new tool for speciation of elements, the progress in the development of electrospray mass spectrometry (ESI‐MS) has been reviewed 8.…”

Release of Si from Silicon, a Ferrosilicon (FeSi) Alloy and a Synthetic Silicate Mineral in Simulated Biological Media

“…These bonds reduce the number of silanol groups available for interactions with hydroxyl ions, thereby reducing the total silicon release. Alkali cations such as Na + have been reported to promote dissolution of silica [17] , [22] , [23] . As this effect not could be observed for PBS at pH 1.7 (containing 8.8 g NaCl/L) when compared with GST (no Na) it is likely that the hindering effect of surface-linked phosphates is stronger than the accelerating effect of Na.…”

“…The mechanism of Fe in combination with silica has not been as thoroughly investigated as for Al, but has shown a similar, albeit weaker, effect on the dissolution rate [4] . Other cations such as Mg 2+ , Ca 2+ , Ba 2+ , Na + , K + and Li + also have a strong effect on the dissolution of silica particles, however addition of these ions to pH neutral solutions increase dissolution of quartz [23] , [24] , [31] , [32] . Other compounds that commonly are in contact with silica are organic acids, for example citric acid [27] – [30] .…”