• Rahman, Mohammad Mahmudur
• Paul, Santosh Kumar
• Biswas, Bhabananda
• Deb, Amal Kanti
• Naidu, Ravi

Abstract

<p>Groundwater contaminated by arsenic (As) is a serious concern because it poses a significant threat to millions of people reliant on both drinking and irrigation of farms. Hence, the low-cost and efficient treatment of these waters is of utmost importance. This study presents the ecofriendly synthesis of magnetite nanoparticles (Fe₃O₄NPs)-immobilized halloysite nanotube (HNT) composite (Fe₃O₄@HNT) for remediating arsenate [As(V)] from water. High-resolution transmission electron microscopy confirmed that ultrasmall Fe₃O₄NPs (4.52 ± 1.63 nm) were immobilized on the interior surface of HNT. Fe₃O₄@HNT possesses a larger surface area (82 ± 0.23 m²/g) and a higher thermal stability (7.1% weight loss at 950 °C) than a pristine HNT (47.23 ± 0.14 m²/g and 12.6%, respectively). Adsorption kinetics were best fitted with pseudo-second-order and intraparticle diffusion, while the isotherms results were best supported with the Freundlich model (R²= 0.99 in each case). Therefore, it could be surmised that multiphase rate-controlling chemisorption occurred during adsorption. The thermodynamics data revealed the endothermic nature of As(V) adsorption by Fe₃O₄@HNT. Fourier transform infrared and X-ray photelectron spectroscopy analyses confirmed chemical bonding between As and Fe. In addition, Fe₃O₄@HNT was easily separable by an external magnet (the saturation magnetization value was 20 emu/g), which is an additional benefit of the material to be used on an industrial scale. The material was also reusable after regeneration for five rounds of consecutive sorption-desorption with excellent efficiency and no substantial loss of structural integrity. Furthermore, Fe₃O₄@HNT removed more than 99% As(V) from the groundwater, signifying its viability in real-case implementation. Cost-benefit analysis ensured that Fe₃O₄@HNT was cost-effective, while its biocompatibility test confirmed no detrimental impact on soil bacterial growth once the spent material had been disposed. Consequently, cheap, easily separable, reusable, and biocompatible Fe₃O₄@HNT may be a prospective composite for the sustainable eradication of As and other metallic toxicants from wastewater.</p>

Topics

• nanoparticle
• impedance spectroscopy
• surface
• nanotube
• composite
• transmission electron microscopy
• magnetization
• saturation magnetization
• biocompatibility
• Arsenic