Department of Chemical & Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia.
J Colloid Interface Sci. 2010 Aug 1;348(1):9-23. doi: 10.1016/j.jcis.2010.04.063. Epub 2010 Apr 28.
The effects of temperature and molecular weight of the temperature-responsive polymer, poly(N-isopropylacrylamide) (PNIPAM) were investigated in the solid-liquid separation of silica and alumina mineral particles. Suspensions dosed with PNIPAM at 25 degrees C were stable and did not settle. When the temperature was raised above the polymer lower critical solution temperature (LCST) (>32 degrees C), the suspensions were found to have high settling rates, large particle aggregate sizes and high suspension shear yield stresses (tau(y)). The sediment bed solids volume fraction (phi(f)), of these suspensions was found to increase after a temperature decrease below the polymer LCST and was attributed to a decrease in the attractive particle-particle interactions as shown by a corresponding decrease in shear yield stress, with decreasing temperature. Settling rates were found to increase with molecular weight when suspensions were dosed at 25 degrees C and settled at 50 degrees C. Increasing polymer molecular weight resulted in increased molecular polymer adsorption at 25 degrees C. Greater initial adsorbed amounts of polymer on the surface produced more nucleation sites for deposition of additional polymer as the temperature was increased from 25 degrees C to above the LCST where polymer phase separation occurred. When the polymer was dosed at 50 degrees C, the rate of sedimentation was very low. Under these conditions, the polymer molecules associate with each other to form polymer aggregates of typically 1250 nm diameter. These colloidal polymer aggregates do not readily deposit on the particles surfaces such that mineral particle aggregation does not readily occur.
温度和温敏聚合物分子量的影响，聚（N-异丙基丙烯酰胺）（PNIPAM）在二氧化硅和氧化铝矿物颗粒的固-液分离中进行了研究。在 25°C 下加入 PNIPAM 的悬浮液稳定且不沉降。当温度升高到聚合物低临界溶液温度（LCST）以上（>32°C）时，发现悬浮液具有高沉降速率、大颗粒聚集尺寸和高悬浮剪切屈服应力（τ(y)）。发现这些悬浮液的沉积床固体体积分数（phi(f)）在温度降低到聚合物 LCST 以下后增加，这归因于随着温度的降低，颗粒间吸引力的减小，如剪切屈服应力相应减小所示。当悬浮液在 25°C 下投加并在 50°C 下沉降时，发现沉降速率随分子量的增加而增加。当聚合物在 25°C 下投加时，增加聚合物分子量会导致更多的聚合物分子在 25°C 下吸附。在温度从 25°C 升高到 LCST 时，聚合物相分离发生，由于聚合物在表面上的初始吸附量增加，产生了更多的沉积额外聚合物的成核点。当聚合物在 50°C 下投加时，沉降速度非常低。在这些条件下，聚合物分子相互缔合形成直径通常为 1250nm 的胶体聚合物聚集体。这些胶体聚合物聚集体不易沉积在颗粒表面上，因此矿物颗粒聚集不易发生。
