Sustainable tetracycline transportation using greener PIM: nanoindentation, prolonged stability, and process kinetics modelling studies

The industrial application of Polymer Inclusion Membranes (PIMs) for pharmaceutical wastewater remediation is often limited by the extraction–stripping trade-off and carrier-mediated transport kinetics. To bypass these limitations, this study introduces a highly efficient, liquid-plasticizer-free, self-plasticizing bi-continuous network PIM system and employs a 1 M NaCl strip phase. This transition provides mobile chloride (Cl⁻) counter-ions that trigger an accelerated, continuous ion-exchange “hopping” mechanism, breaking the low transport efficiency ceilings typical of traditional receiving chemistries. Scanning electron microscopy and nanoindentation modeling confirm that this optimized engineered PIM created a vertically aligned finger-like matrix channel, induced a ~92% reduction in nanomechanical stiffness, and a ~39% increase in elastic recovery. Process kinetics modeling demonstrates a well-balanced mass transport regime, splitting the kinetic diffusion share ( D m = 48%) and thermodynamic sorption share ( S = 52%) to drive a synchronized surge in the kinetic rate constant ( k = 0.09169 h⁻ 1 ) and effective diffusivity (8.48 × 10⁻ 10 m 2 s⁻ 1 ). As a result, the membrane exhibits 100% quantitative tetracycline extraction and an exceptional transport efficiency of ~99.5% at a peak initial flux ( J 0 ) of 3.98 × 10⁻ 10 mol · m⁻ 2 · s⁻ 1 . Long-term process stability trials confirm matrix integrity and a sustained high-flux transport environment across the initial four phases, maintaining membrane structural integrity across 10 consecutive cycles totaling 450 h of continuous runtime without chemical regeneration. This offers a robust, eco-friendly framework that aligns with Global Sustainable Development Goal 6 (SDG 6).