Novel magnetic gellan gum hydrogel nanocomposite with polydopamine and functionalized halloysite nanotubes for efficient butylparaben adsorption from wastewater.

This study addresses the challenge of efficiently removing butylparaben (BP), an endocrine-disrupting preservative that persists in conventional wastewater treatment streams. A magnetic gellan gum (GG) hydrogel nanocomposite incorporating polydopamine (PDA) and functionalized halloysite nanotubes loaded with Fe₃O₄ (GG hydrogel/PDA/HNT@Fe₃O₄ beads) was synthesized as a novel adsorbent designed for BP capture and easy magnetic recovery. The beads were synthesized via ionic crosslinking. Characterization confirmed porous morphology, thermal stability, and superparamagnetic properties. Response surface methodology (RSM) optimized adsorption parameters: pH 6.74, contact time 52 min, initial BP concentration 12.27 mg/L, adsorbent dosage 0.78 g/L, and temperature 28 °C, achieving 99.12 % removal (15.59 mg/g capacity) in deionized water and 91.5 % (14.38 mg/g capacity) in real wastewater. Equilibrium data followed the Freundlich isotherm, and kinetics were best described by the Elovich model, indicating multilayer chemisorption on a heterogeneous surface via hydrogen bonding, π-π stacking and hydrophobic interactions. The beads showed high swelling (≈1400 % at pH 7), antibacterial activity against Escherichia coli and Staphylococcus aureus, and retained 88 % of their initial removal efficiency after six adsorption-desorption cycles using ethanol as eluent, highlighting their practical potential for BP removal from wastewater.