title: Hydration interactions and stability of soluble microbial products in aqueous solutions.
abstract: Soluble microbial products (SMP) are organic compounds excreted by microorganisms in their metabolism and decay and the main constituents in effluent from biological wastewater treatment systems. They also have an important contribution to the dissolved organic matters in natural aqueous systems. So far the interactions between SMP colloids have not been well explored. In this work, the interactions between SMP colloids in water and salt solutions were studied by using a combination of static and dynamic light scattering, Fourier transform infrared spectra, Zeta potential and acid-base titration techniques. The second osmotic virial coefficient had a larger value in a 750-mM salt solution than that in a 50-mM solution, indicating that repulsion between SMP colloids increased with an increase in salt concentration, which is contrary with the classic Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory. Such a repulsion was attributed to water structuring and enhanced by the accumulation of hydrophilic counter ions around SMP colloids and the formed hydration force. The repulsion and hydration effect led to the dispersing and deeper draining structure, accompanied by a decreased hydrodynamic radius and increased diffusion coefficient. This hydration force was related to so-called ion specific effect, and electrolyte sodium chloride had a more substantial effect on hydration force than KCl, CsCl, NaBr and NaI. Our results provide an experimental approach to explore the SMP structures, inter-colloid interactions and confirm the non-DLVO forces.
authors.affiliation: Department of Chemistry, University of Science & Technology of China, Hefei 230026, China.
authors.forename: Ling-Ling
authors.initials: LL
authors.lastname: Wang
authors.forename: Long-Fei
authors.initials: LF
authors.lastname: Wang
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Ye
authors.forename: Han-Qing
authors.initials: HQ
authors.lastname: Yu
mesh_terms: D012542:Scattering, Radiation; D012996:Solutions; D014867:Water; D014871:Water Microbiology
chemical_list: D012996:Solutions; D014867:Water
keywords: Hydration force; Interaction; Second osmotic virial coefficient; Soluble microbial products (SMP); Static and dynamic light scattering