Hydrophobicity of Minerals Determined by Atomic Force Microscopy – A Tool for Flotation Research

Abstract

The mineral separation process flotation is fundamentally relying on hydrophobic interactions, which are still not entirely understood and heavily discussed in literature. Here, various possibilities to determine hydrophobic properties of mineral surfaces in water using the concept of colloidal probe atomic force microscopy are introduced. The method is based on the accepted theories of the hydrophobic effect of hydrophobic surfaces in water. Additionally, the hydrophobic parameters are correlated with microflotation experiments for magnetite and quartz surfaces.

Fast preparation and recycling method for colloidal probe cantilevers in hydrophobic mapping applications

“…Colloidal probe atomic force microscopy (CP-AFM) was first reported by [1,2] and is nowadays used in multiple applications in various fields of research. One possible application are adhesive force mappings on a variety of samples including biological [[3], [4], [5]], mineral [6,7], ceramic [[8], [9], [10]] or wooden samples [3,11]. Beside possible sources of contamination during storing in ambient conditions as summarized by [12], the main source of colloidal probe contamination in an adhesive force mapping application on mineral surfaces experienced by the authors are inorganic particulate contaminations [13], as given in Fig.…”

“…A variety of methods for cantilever or colloidal probe functionalization have been reported in literature, the same applies for possible colloids attached to the cantilever like glass spheres [18], polystyrene particles [6,7,19], silica microspheres [14,19,20] Al 2 O 3 particles [[8], [9], [10]] or gold particles [14]. A broader overview of the colloidal probe method was compiled by [18], listing more possible probes like TiO 2 , MgO, ZnS, poly-(methyl methacrylate) and polyethylene.…”

“…As this process is not reversible under standard lab conditions, this paper focusses on the utilization of glues for probe fixation. Previously reported glues are Norland Optical UV-adhesive NOA63 [23], Araldit® Rapid glue [14], Epikote 1004 [15] or other types of epoxy glues [6,7]. The application of UV glue seems favorable in terms of glue handling and reduction of curing times, both does not apply to rapid glues or epoxy based glues with a problematic handling or extensive times for curing respectively.…”

Modeling the Separation of Microorganisms in Bioprocesses by Flotation

“…Repulsion and attractive forces depend heavily on the process conditions and can be influenced by the addition of chemicals that tailor surface properties of cells or bubbles. They can either be modeled using the DLVO theory extended by Born repulsion forces [41], or be computed using molecular dynamics simulations [42], which requires knowledge of the surface of the particles, or be measured using atomic force microscopy [43]. Recently, Ditscherlein et al [44] introduced a new AFM method to quantify the micro-sized bubble-yeast interactions depending on the conditions of the surrounding medium such as pH, ethanol and salt concentration Using those methods to infer P A,0 , the effect of chemical addition on separation efficiency should become predictable with a suitable aggregation model.…”

Modeling the Separation of Microorganisms in Bioprocesses by Flotation

“…Repulsion and attractive forces depend heavily on the process conditions and can be influenced by the addition of chemicals that tailor surface properties of cells or bubbles. They can either be modeled using the DLVO theory extended by Born repulsion forces [36] or be computed using molecular dynamics simulations [37], which requires knowledge of the surface of the particles, or be measured using atomic force microscopy [38]. Using those methods to infer P A,0 , the effect of chemical addition on separation efficiency should become predictable with a suitable aggregation model.…”