Starch-assisted facile gel formation method for the synthesis of Fe–Mn binary oxide for the simultaneous removal of As(iii) and As(v)

Abstract

Researchers have significantly focused on eco-friendly methods for nanomaterial synthesis to reduce the reliance on hazardous chemicals. In light of this, this study presents an eco-friendly, straightforward, alkali-free method for synthesizing iron–manganese (Fe–Mn) binary oxide (FMBO) and their single oxides by adopting a direct gel formation approach using starch. The synthesized materials were characterized through FTIR, FESEM, EDX, and XRD. Based on the characteristics of the synthesized materials, the probable formation mechanism of nanomaterials within the starch matrix via gel formation was comprehensively investigated. The presence of MnO₄⁻ resulted in faster gelation than Fe³⁺ owing to its stronger oxidizing properties, leading to a more robust gel network that could stabilize nucleation, control the growth of nanoparticles, and thereby reduce particle agglomeration. The synthesized materials were further employed for the adsorptive removal of arsenic, and the findings demonstrate that FMBO was much more effective than the individual oxides in simultaneously eliminating arsenic species (III and V) with an adsorption capacity of 79 mg g⁻¹ for total arsenic (As(III) + As(V)) owing to its nanostructure, surface characteristics, and synergistic effects of Fe and Mn oxides. Our observation suggests that Mn oxide pre-oxidizes As(III) to As(V), which is then efficiently adsorbed by Fe oxide. This study underscores the potential of starch-based nanomatrices in developing efficient materials with enhanced properties.