Elucidating the Role of Sulfide on the Stability of Ferrihydrite Colloids under Anoxic Conditions

• DOI: 10.1021/acs.est.8b05694
• Publication Date: 2019-03-14T23:04:10Z
• Authors: Leiyu He; Lin Xie; Dengjun Wang; Wenlu Li; John D. Fortner; Qianqian Li; Yanhua Duan; Zhenqing Shi; Peng Liao; Chongxuan Liu
• Keywords: Ferrihydrite

While the reaction mechanisms between ferrihydrite and sulfide are well-documented, role of redox reactions on particle–particle stability colloids is largely overlooked. Such critical for a number (bio)geochemical processes governing ferrihydrite-based colloid processing their associated in nutrient contaminant subsurface dynamics. Taking fundamental chemistry approach, along with complementary suite characterization techniques, here, we explore over wide range environmentally relevant concentrations at pH 6.0. Results show that lowered both concentration-dependent fashion. At lower (15.6–62.5 μM), apparently stable, but coagulation concentration (CCC) NaCl linearly decreases increasing concentration. This attributed to formation negatively charged elemental sulfur (S(0)) nanoparticles surfaces positively ferrihydrite, intensifying electrostatic attractions oppositely regions adjacent surfaces. Further generates more S(0) attaching surface. results effective surface charge neutralization then subsequent reversal, leading extensive aggregation (core) colloids. Interestingly, higher hydrodynamic diameter, rates from 156.3 312.5 μM, which likely due substantial amounts FeS. Findings highlight significance sulfidation products controlling sulfidic environments.