Processing of water regenerable PLA@HNT nanocomposite via melt extrusion for selective adsorption of aqueous phase tetracycline

Abstract

Emerging water pollutants pose a serious threat to the ecosystem function. To avert this, efficient remedial and preventive measures that also protect the environment are required. The use of sustainable materials as alternatives to water treatment systems has become a global focus due to their ‘fit-for-purpose’ potential. This study reports on a process engineered water regenerable nanocomposite (PLA@HNT) from polylactide (PLA) and Halloysite (HNT) for the removal of aqueous phase Tetracycline (TC). PLA was surface etched with NaOH to activate carboxylates, hydroxyls and enhance hydrophilicity. HNT was hydrothermally treated with CO(NH₂)₂ for basal spacing as well as access to activated inner Al–OH and Si–OH functional groups. The modified materials were reacted via melt extrusion to obtain a surface responsive PLA@HNT which was subsequently applied as an adsorbent for selective TC adsorption in a fixed bed column system at 1 ml min⁻¹ and 2 ml min⁻¹ flow rates. The maximum capacity (q_bed) was found to be 0.05 mmol g⁻¹. Hyphenations of Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometer (UHR FT-ICR-MS) and other analytical techniques were used to investigate aspects of PLA@HNT before and after application. Collision induced dissociation (CID) analysis found only residual TC and no degradation products in the effluent after removal studies. Furthermore, PLA@HNT can be reused over 4 adsorption cycles with water as eluent.