Influence of calcination on magnetic honeycomb briquette cinders composite for the adsorptive removal of As(III) in fixed-bed column

• MHBC was successfully synthesized and calcined at 1000 °C under air and nitrogen.
• Dynamic nitrogen-flow calcination increased the adsorbent hardness and particle size.
• As(III) adsorption using un- and calcined MHBC was performed in fixed-bed column.
• As(III) adsorption process in fixed-bed column was well described by Thomas model.
• Selective calcination guaranteed phase transformation for enhanced arsenic removal.

Elevated concentration of arsenic in water supplies is detected worldwide and therefore becomes a global issue. Calcination process is known to increase the adsorbent hardness for its effective application in column-based treatment. In this study, magnetic honeycomb briquette cinders (MHBC) and its calcined products: MHBC(A) and MHBC(N) were employed for the adsorptive removal of As(III) in fixed-bed column. Characterizations revealed that the calcination at 1000 °C under nitrogen has significantly increased the adsorbent particles size; favored phase transformation and improved saturation magnetization (>20 emu g−1). Additionally, the new iron silicate phase (Fe2SiO4) in aqueous medium generated highly reactive iron oxide species (=FeOOH), which effectively bind As(III) from the influent water by ligand exchanges. In contrast, calcination under dynamic air drastically reduced the saturation magnetization (<1 emu g−1) and assisted to form segregated magnetite, quartz and hematite, as revealed in XRD patterns. The breakthrough curve of each column was compared with Thomas model and found that the model could be applied to estimate As(III) adsorption in fixed-bed column. Thomas model suggested parameters follow the order: MHBC(N) > MHBC > MHBC(A) and the maximum solid phase concentration (qT) was found to be about 56.07 mg g−1 for MHBC(N). The column beds could be successfully regenerated using 200 bed volume of 10% NaOH solution. This study suggests that the selective calcination process need to be integrated with the adsorbent development process for the efficient removal of As(III) from contaminated water using column-based treatment.

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