Bismuth ferrite (Bi2Fe4O9) nanosheets: an efficient adsorbent for triclosan

Abstract

Triclosan (TCS) is the most common antimicrobial agent used in personal care products. Even a small concentration of TCS (<0.3 mg L⁻¹) in water poses a potential threat to human and aquatic lives. We investigated TCS adsorption from aqueous solutions using hydrothermally synthesized bismuth ferrite (Bi₂Fe₄O₉) or BFO materials. Different compositional variations of bismuth ferrite were obtained by altering the mole ratio of bismuth and iron precursors (Bi/Fe ratio) and NaOH concentration. The synthesized BFO materials were then analyzed using XRD, FESEM, BET, FTIR spectroscopy and zeta potential analysis. Moreover, batch adsorption experiments were conducted to investigate the influence of different BFO materials, pH and adsorbent loading on the TCS adsorption equilibrium. We examined the efficacy of TCS adsorption by different BFO materials and fitted the experimental data to different isotherms. The Redlich–Peterson model was the most suitable for describing the TCS adsorption on BFO. Furthermore, the mean free adsorption energy obtained from the D-R isotherm indicated that physical adsorption played a key role in the adsorption process. The adsorption kinetic fitting revealed that TCS adsorption followed a pseudo-second-order kinetic model. Our experimental results showed that altering the solution pH drastically affected the adsorption behaviour. The interaction mechanism revealed a high TCS adsorption rate attributed to hydrogen bonding and electrostatic interactions. The BFO sample with a 1 : 1 Bi/Fe mole ratio and 5 M NaOH concentration demonstrated the maximum TCS adsorption capacity, reaching 903 mg g⁻¹ at pH 3, with a 0.2 g L⁻¹ adsorbent loading at 298 K. This remarkable adsorption capacity of BFO nanosheets with minimal adsorbent loading and material stability validates its strong potential as a sustainable adsorbent for the efficient removal of emerging contaminants, like TCS, from wastewater.