Triptycene and triphenylbenzene-based polymers of intrinsic microporosity (PIMs) for the removal of pharmaceutical residues from wastewater

This study aims to investigate the adsorptive removal of three TCAs; imipramine (IMI), nortriptyline (NOR) and desipramine (DES) using four polymeric networks based on triptycene (TRIP) and triphenylbenzene (TPB). For the first time, these polymeric networks have been used as a pure hydrocarbon (TRIP-HC and TPB-HC) and as their sulfonic acid derivatives (TRIP-SO₃H and TPB-SO₃H), for the decontamination of TCAs from wastewater. The effect of the initial TCAs concentration was investigated, and it was found that sulfonic acid modified polymers tolerated higher TCAs concentrations than their pure hydrocarbon-based counterparts. Furthermore, the adsorption kinetics and isotherms were studied, which indicated that the four polymers followed pseudo-second-order kinetics and Langmuir isotherm models, respectively. The adsorption capacities values for TRIP-SO₃H and TPB-SO₃H were between 196.0 and 384.6 mg g⁻¹, whilst for TRIP-HC and TPB-HC were between 133.3 and 175.4 mg g⁻¹. The effect of the presence of coexisting ions such as Cl⁻, NO₃⁻ and SO₄²⁻ was also examined and the adsorption affinities of IMI, NOR and DES were slightly lowered using TRIP-SO₃H and TPB-SO₃H, on the other hand, a greater decrease was observed using TRIP-HC and TPB-HC. Furthermore, IMI in a tablet formulation was dissolved in tap water and TRIP-SO₃H and TPB-SO₃H were employed, and it was found they exhibited excellent adsorption efficiencies of 96.96 and 98.78%, respectively. Regeneration of these two polymers was tested by performing five adsorption-desorption cycles and TPB-SO₃H showed better stability in comparison to TRIP-SO₃H. Finally, a potential mechanistic pathway for the adsorption of theses pharmaceuticals by the polymers was also proposed.