Temperature, pH and photo-responsive polymers as responsive flocculants

Project Leader: George Franks
Staff: Luke Connal
Student: Will (Wei-Sung0 Ng
Primary Contact: George Franks (gvfranks@unimelb.edu.au)
Keywords: mineral processing; polymeric materials; stimulant responsive polymers
Disciplines: Chemical & Biomolecular Engineering
Domains: Optimisation of resources and infrastructure
Research Centre: Particulate Fluids Processing Centre (PFPC)

Stimuli-responsive polymers are an exciting class of materials that undergo reversible hydrophilic-hydrophobic transitions following changes in environmental conditions. The most well-studied example is poly(N-isopropyl acrylamide) (PNIPAM), a smart polymer with extensive applications in drug delivery, sensor technologies and minerals separation based on its temperature-responsive properties. These polymers have been shown by our group to be useful in solid-liquid separations in the minerals industry.  [1]

Spiropyrans (SP) are a group of compounds which display varying colour,  structural configurations and solubility under different light, pH, and solvent conditions. Recent investigations into SP-functionalised PNIPAM copolymers have yielded multi-responsive materials sensitive to temperature, light, and pH, with the goal of enhancing the current targeting properties and sensing capabilities of PNIPAM.

The aim of this project is to evaluate how these new polymers can be used in solid liquid separations in the mineral industry.  A polymer which can switch between flocculant and dispersant by exposure to sunlight would be an incredibly powerful reagent to improve minerals tailings handling.  Initial investigation involves looking at how changing pH, light, ionic strength, and solvent conditions influence the temperature-responsive phase transition behaviour of the SP-functionalised PNIPAM copolymers. This will be achieved through heating and cooling of the polymers in light and dark at different pH. The results are expected to improve our understanding of how each factor interacts with the conformation and structure of the polymer. Further investigation involves applying the polymers to solid liquid separation via sedimentation tests at different temperature and in light and dark. The goal would be to improve recovery and reuse of water from mineral tailings.

[1] G. V. Franks, J.-P. O’Shea, E. Forbes, “Controlling Thickener Underflow Rheology Using a Temperature Responsive Flocculant”, AIChE Journal, 60 [8] 2940-2948 (2014).