Dr. Martin Rudolph
Head of the Processing Department

Phone: +49 0351 260 - 4410

Investigating Interfacial Phenomena

When in water immersed particles adhere to gas bubbles, three different phases are in contact: a solid, a liquid and a gaseous phase. By precisely characterizing their properties at microscopic scale, HIF scientists aim at improving the general understanding of interfacial phenomena. A better understanding will thus help to improve controlling the flotation processes. For example, by using amphiphilic molecules - flotation reagents that are soluble in both polar solvents (e.g., fats) and nonpolar solvents (e.g., water).

Gedankenexperiment zur Hydrophobierung von Mineraloberflächen und dadurch erfolgreiche Anhaftung an Gasblasen
Mental experiment: Hydrophobization of a mineral surface and the successful attachment of a gas bubble

Important questions the Processing Department is tackling:

  • Which fundamental physical parameters describe the particles wettability the best?
  • How do hydrophobic interactions work?
  • What is the impact the heterogeneity of a surface has on its functionality and particle-bubble interactions?
  • What role do water structure effects play in particle-bubble interactions of hydrophilic and hydrophobic phases?
  • Why do some depressant reagents have an additional promoting effect on hydrophobized particles?

Surface energy determination
Surface energy determination
Photo: HZDR/Detlev Müller

The following methods are being used in order to address those questions:

  • Tensiometry (static und dynamic) using a bubble pressure tensiometer and the pendant drop method
  • Wettability measurements with contour analysis
  • Film compression measurement using a Langmuir-Blodgett trough
  • Adsorption measurements using a quartz crystal microbalance
  • Streaming potential determination with an automatic titration and a Zeta potential analysis
  • Dynamic frothing analyses
  • Surface energy determination using the inverse gas chromatography (iGC) technique

Selected Publications

  • Rudolph M.; Hartmann, R.
    "Specific Surface Free Energy Component Distributions and Flotabilities of Mineral Microparticles in Flotation – An Inverse Gas Chromatography Study", Colloids and Surfaces A: Physicochemical and Engineering Aspects, 513 (2017) 380-388
    DOI-Link: 10.1016/j.colsurfa.2016.10.069
  • Knüpfer, P.; Fritzsche, J.; Leistner, T.; Rudolph, M.; Peuker, U. A.
    "Investigating the removal of particles from the air/water-interface – Modelling detachment forces using an energetic approach", Colloids and Surfaces A: Physicochemical and Engineering Aspects 513(2017)
    DOI-Link: 10.1016/j.colsurfa.2016.10.046