Adsorption of As (III) from contaminated water on activated carbon-supported nanoscale zero-valent iron particles

Abstract

Arsenic (As) contamination is a major concern due to its toxicity and tendency to accumulate and bio-magnify within the food chain, causing wider damage to the ecosystem. In the current study, activated carbon-supported nanoscale zerovalent iron (AC-nZVI) particles, were produced using chemical reduction of ferric chloride hexahydrate in the presence of activated carbon as a scaffold to avoid agglomeration and improve their dispersity. Detailed transmission electron microscopy (TEM), and scanning electron microscopy (SEM) characterization of the as-synthesized nanoparticles showed monodispersed nanoparticles of approximate size 45 ±10 nm. Their potential application for removal of As(III) from contaminated water was investigated in batch adsorption experiments at various adsorbent dosages and pH values. The results of the study demonstrated that AC-nZVI particles exhibited 82.5% removal of As (III) ions (initial concentration 100 mg/L) at an adsorbent dosage of 2 g/L. The adsorption performance increased with increasing adsorbent dosage and removed 99% As(III) at an adsorbent dosage of 5g/L. The Langmuir and Freundlich adsorption models were fitted to the experimental data, and it was found that the Langmuir isotherm fitted the data better than the Freundlich isotherm with a maximum adsorption capacity of 27.83 mg/g of adsorbent. In the current study As(III) exists predominately as uncharged species H3AsO30 under the designed pH range of 4-8, therefore the effects of solution pH on As (III) adsorption were hardly observed. The results of the study demonstrated that activated carbon-supported zerovalent iron particles can have tremendous potential application for the effective removal of As(III) from industrial wastewaters.