Report
Adsorption isotherm and mechanism of $\mathrm{Ca^{2+}}$ binding to polyelectrolyte
| العنوان: | Adsorption isotherm and mechanism of $\mathrm{Ca^{2+}}$ binding to polyelectrolyte |
|---|---|
| المؤلفون: | Mantha, Sriteja, Glisman, Alec, Yu, Decai, Wasserman, Eric, Backer, Scott, Wang, Zhen-Gang |
| سنة النشر: | 2023 |
| المجموعة: | Condensed Matter |
| مصطلحات موضوعية: | Condensed Matter - Soft Condensed Matter |
| الوصف: | Polyelectrolytes, such as polyacrylic acid (PAA), can effectively mitigate $\mathrm{CaCO_3}$ scale formation. Despite their success as antiscalants, the underlying mechanism of $\mathrm{Ca^{2+}}$ binding to polyelectrolyte chains remains unresolved. Through all-atom molecular dynamics simulations, we construct an adsorption isotherm of $\mathrm{Ca^{2+}}$ binding to sodium polyacrylate ($\mathrm{NaPAA}$) and investigate the associated binding mechanism. We find that the number of calcium ions adsorbed $[\mathrm{Ca^{2+}_{ads}}]$ to the polymer saturates at moderately high concentrations of free calcium ions $[\mathrm{Ca^{2+}_{aq}}]$ in the solution. This saturation value is intricately connected with the binding modes accessible to $\mathrm{Ca^{2+}}$ ions when they bind to the polyelectrolyte chain. We identify two dominant binding modes: the first involves binding to at most two carboxylate oxygens on a polyacrylate chain, and the second, termed the high binding mode, involves binding to four or more carboxylate oxygens. As the concentration of free calcium ions $[\mathrm{Ca^{2+}_{aq}}]$ increases from low to moderate levels, the polyelectrolyte chain undergoes a conformational transition from an extended coil to a hairpin-like structure, enhancing the accessibility to the high binding mode. At moderate concentrations of $[\mathrm{Ca^{2+}_{aq}}]$, the high binding mode accounts for at least a third of all binding events. The chain's conformational change and its consequent access to the high binding mode is found to increase the overall $\mathrm{Ca^{2+}}$ ion binding capacity of the polyelectrolyte chain. Comment: 10 pages of main manuscript, 5 figures, and a supplementary document with 5 figures |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1021/acs.langmuir.3c03640 |
| URL الوصول: | http://arxiv.org/abs/2311.11404 |
| رقم الانضمام: | edsarx.2311.11404 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1021/acs.langmuir.3c03640 |
|---|