John-Paul O'Shea

Temperature-Responsive Solid–Liquid Separations with Charged Block-Copolymers of Poly(N-isopropyl acryamide)

Temperature responsive charged block-copolymers of poly(N-isopropylacrylamide) (PNIPAM) have been used in the solid-liquid separation of alumina mineral particles from aqueous solution. The effects of temperature, polymer charge-sign and fraction of charged segment have been investigated. Batch settling and adsorption studies showed that rapid sedimentation results for suspensions with polymers of opposite charge-sign to the particle surface-charge (counterionic) at 50 °C. Cooling the suspensions after flocculation at 50 °C was found to increase the final solids volume fraction of the sediment beds formed through a mechanism related to partial desorption of polymer and the reduction of the hydrophobic attraction. Suspension stability results after dosing with polymers of similar charge-sign to the particle surface-charge (co-ionic) at both 25 and 50 °C. Increasing the amount of polymer charge increased the influence of polymer charge-sign on the adsorption and solid-liquid separation behavior. The performance of the charged block copolymers are compared to that of the random charged copolymer and neutral homopolymer PNIPAM structures.

Beneficiation of Coarse Coal Ore in an Air-Fluidized Bed Dry Dense-Medium Separator

The beneficiation of different size fractions (+5, −31 mm) of coal using an air-fluidized bed dry dense-medium separator with silica/zircon sands as the fluidizing-bed medium has been studied. Particle size and bed height were found to strongly influence the efficiency of separation with the dry dense-medium separator. An increase in bubble size associated with increase in bed height to 15 cm results in density variations within the bed that increase the probable error for deeper fluidized beds for the smaller particles up to 0.19 from 0.06 for the shallower 10 cm bed. Good agreement was found between the theoretical yield and ash content obtained from washability curves (produced from conventional float/sink tests) and the actual yield from the dry fluid bed separation for the bulk coal sample. A comparison with industrial coal-washing unit operations indicates that dry dense-medium separations are a strong candidate as an energy- and resource-efficient alternative process.