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<p>Salts and transition metals commonly co-occur with phenolic co-pollutants in impacted aquifers and treatment reactors, yet their combined effects on phenol speciation, transport, and removability remain poorly constrained. Here we examine how chloride and sulfate salts of Na, Zn, Fe, and Cu alter the mixing behavior of m-cresol and p-cresol in water and the downstream consequences for mobility and filtration. Bottle tests and optical microscopy show that 0.1–0.5&#xa0;M electrolytes decrease cresol miscibility and generate polydisperse cresol-rich droplets. Conductor-like Screening Model for Realistic Solvation (COSMO-RS) calculations support salt-driven increases in cresol activity consistent with salting out. Beyond phase separation, metal identity and counter-ion strongly influence cresol association: attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) reveals isomer-dependent new bands (815&#xa0;cm⁻¹ for m-cresol; 775&#xa0;cm⁻¹ for p-cresol) in selected systems, indicating formation of salt- and isomer-specific cresol–metal species, particularly in chloride media, while sulfate salts suppress or alter these signatures. Density-based “perfect cresol-water separation” predictions indicate that most divalent brines at 0.5&#xa0;M should buoy cresol. However, observed flotation/sinking deviates systematically where metal association and iron (oxyhydr)oxide floc formation promote droplet densification and entrainment. Using Stokes–Einstein scaling and a geometric straining model, we show that salt-induced droplets shift cresol transport from purely molecular diffusion to size-dependent particle mobility, with multi-micron droplets increasingly susceptible to pore-throat exclusion in finer media. Collectively, these results link electrolyte-driven demixing and complexation to cresol migration pathways, which should inform the management of impacted sites.</p>

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Cresol salting out and complexation with metal salts influence their migration in impacted aquifers

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月16日

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  • Renato Souza Lima Sant’Anna,
  • Alejandro G. Marangoni,
  • Erica Pensini

摘要

Salts and transition metals commonly co-occur with phenolic co-pollutants in impacted aquifers and treatment reactors, yet their combined effects on phenol speciation, transport, and removability remain poorly constrained. Here we examine how chloride and sulfate salts of Na, Zn, Fe, and Cu alter the mixing behavior of m-cresol and p-cresol in water and the downstream consequences for mobility and filtration. Bottle tests and optical microscopy show that 0.1–0.5 M electrolytes decrease cresol miscibility and generate polydisperse cresol-rich droplets. Conductor-like Screening Model for Realistic Solvation (COSMO-RS) calculations support salt-driven increases in cresol activity consistent with salting out. Beyond phase separation, metal identity and counter-ion strongly influence cresol association: attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) reveals isomer-dependent new bands (815 cm⁻¹ for m-cresol; 775 cm⁻¹ for p-cresol) in selected systems, indicating formation of salt- and isomer-specific cresol–metal species, particularly in chloride media, while sulfate salts suppress or alter these signatures. Density-based “perfect cresol-water separation” predictions indicate that most divalent brines at 0.5 M should buoy cresol. However, observed flotation/sinking deviates systematically where metal association and iron (oxyhydr)oxide floc formation promote droplet densification and entrainment. Using Stokes–Einstein scaling and a geometric straining model, we show that salt-induced droplets shift cresol transport from purely molecular diffusion to size-dependent particle mobility, with multi-micron droplets increasingly susceptible to pore-throat exclusion in finer media. Collectively, these results link electrolyte-driven demixing and complexation to cresol migration pathways, which should inform the management of impacted sites.