Chapter 1 Recent Drifts in pH-Sensitive Reverse Osmosis

Preparation of some smart PAm-ZTS pH-responsive membranes, via reactions between ZTS and PAm under different conditions, was conducted for testing pressure-driven reverse osmosis membranes (PDROMs) in active rejection of Ce, Pr, Sm, Gd, Dy, and Ho ionic lanthanide species in their 3 and 4 states. Recent theoretical models to designate the membrane operations were mathematically itemized, after selective characterization of the PDROMs. The pH scale response of the membrane was confirmed using static adsorption and hydraulic pervasion result estimations. The flux across the PAmZTS membrane decreased with the lowering pH value, with drastic decreases between pH 4 and 7, and was both reversible and durable with pH shifts between ~3 and ~8. At lower pH 3, the individual pores were in a closed-state due to the prolonged structure of the amide chains on the porous surfaces. In contrast, at pH 8, the higher pH value, the membrane pores were in an open-state format, because of the collapsed structures of the amide chains. This grants a clear possible approach for manufacturing some pHresponsive composite membranes and inspires further design for their stimuli-responsive actions by incorporating molecularly designed macromolecules, synthesized by controlled polymerization.