Flocculation of kaolinite clay suspensions using a temperature‐sensitive polymer

Abstract

in Wiley InterScience (www.interscience.wiley.com).A temperature-sensitive polymer, poly(N-isopropylacrylamide) [poly(NIPAM)], was tested to flocculate kaolinite clay suspensions. Settling tests at both room temperature and 408C were carried out. The results show that settling at 408C resulted in significantly higher settling rates and smaller sediment volumes. This behavior indicates that the polymer molecules changed from a stretched structure to a coil-like conformation with increasing temperature. It is the change in conformation that induced more compacted flocs, thus resulting in faster settling. To understand the role of temperature in the flocculation, the long-range interaction and adhesion forces between kaolinite clay particles in the polymer solutions at both room temperature and 408C were measured using an atomic force microscope (AFM). The measured adhesion forces correlated well with the settling characteristics: a stronger adhesion led to a higher initial settling rate. The retraction force profiles obtained at different temperatures confirmed the conformational change of the polymer with temperature.

Current state of fine mineral tailings treatment: A critical review on theory and practice

“…Introduction of additional coagulant and/or flocculant that specifically binds to particle surfaces of different nature (Figure 5), offers the opportunity to increase the compactness and size of the solids-polymer aggregates, both of which further improve the rate of slurry clarification (Yuan & Shaw, 2007;Alagha, et al, 2013). Changes in adsorption conformations via external inputs are also possible for "smart" flocculants such as poly-NIPAM, whose hydrophobicity is found to be heavily influenced by slurry temperature (Franks, et al, 2009;Li, et al, 2007). Thus below the hydrophobic transition temperature, poly-NIPAM is hydrophilic and can be deployed similarly as a PAM.…”

What is the significance of pore pressure in a saturated shale layer?

“…[15] The last experimental method to measure surface forces at the microscopic scale uses the atomic force microscope [see, e.g., Li et al, 2007]. The force between two microscopic spherical samples (few micrometers) placed at a certain distance are measured.…”

Estimating thermo-osmotic coefficients in clay-rocks: I. Theoretical insights

“…A substantial structural force was inferred from the comparison between DLVO calculations and measurements. The data of Li et al [52] together with Eq. (29) was used to determine the structural component of the disjoining pressure at 10 À3 mol L À1 .…”

“…SFA experiments provide values of the ratio F/R as a function of the surface spacing. More recently, an atomic force microscope (AFM) was used to measure the interaction force F between microscopic spherical probes of radius R in electrolytic solutions [52]. While the first apparatus provides direct estimates of the disjoining pressure, the two other ones (SFA and AFM) require some algebraic treatment in order to obtain an equivalent disjoining pressure for a plane-parallel geometry.…”

“…In a simplified manner, since the analysis carried out in the previous section suggests the dominance of the structural specific excess enthalpy DH s , this later was considered alone. The only reliable surface force data for kaolinite is from Li et al [52]. The authors used AFM measurements to identify the total surface force between two spherical probes covered with kaolinite in a KCl solution at 10 À3 mol L À1 .…”