Structure and sedimentation characterisation of sheared Mg(OH)2 suspensions flocculated with anionic polymers

Flotation using sodium dodecyl sulphate and sodium lauroyl isethionate for rapid dewatering of Mg(OH)2 radwaste suspensions

“…For 0 mM collector dose, the PSD may be considered as pseudo-bimodal, with a small peak at 0.3-2 mm of magnitude $2 vol% and a major peak at 2-20 mm of magnitude $8 vol%. The smaller peak is likely the size of the primary particles, which were determined by Lockwood et al 12 to be $0.3 mm via SLS, whereas the larger peak is likely the equilibrium particle size achieved by sonication (with some initial particle-cluster aggregation as discussed in Fig. 2C and D).…”

“…60 Similar mineral pseudo-hexagonal platelet material, such as aluminium hydroxide, have also been found to have correspondingly high BET surface areas, ranging from 1.5 m 2 g À1 , as observed by Adekola et al, 61 up to 91 m 2 g À1 measured by Rosenqvist. 62 The low surface potential of magnesium hydroxide (of $12 mV, as noted in the methodology 12 ) has implications when considering colloidal stability of particulates, suggesting they may naturally aggregate. 63 Aggregation may affect the accessible surface area in aqueous media, resulting in consequences for adsorption density.…”

“…greater shear reduces equilibrium particle size). 12,17,[70][71][72][73] Collector adsorption and effect on particle aggregation…”

“…Chord length number distributions were then computationally translated to volume percentage spherical equivalent diameters, assuming oc sphericity, as outlined by Rhodes 55 and used in the current authors previous work. 12 Collector adsorption onto Mg(OH) 2 Suspensions of 2.5 vol% Mg(OH) 2 and varying concentrations of collector ranging from 0.82 mM to 1000 mM, were prepared in centrifuge tubes of 15 mL with the required collector concentration of SDS or SLI diluted from the stock solutions. The suspensions were then agitated using a carousel mixer (Compact Star CS4) for 24 hours, to ensure equilibrium adsorption of the anionic collectors on the Mg(OH) 2 , before being centrifuged at 500 rpm for 4 hours to separate the particulates from the supernatant liquor.…”

“…To accelerate dewatering, there is current research into the application of polymeric occulants to enhance suspension zonal settling rates, which have been shown to signicantly decrease residence times in thickening operations. [11][12][13][14][15] However, these processes have a number of drawbacks, in terms of their modication to waste structure and related downstream issues. 1 In particular, the resultant fractal nature of these polymeric ocs can increase settled bed volumes, which may reduce the solid waste capacity of intermediate level waste containers for nal geological disposal.…”