Removal of Arsenic from Water Using a Composite of Iron–Manganese Oxide Incorporated Active Rice Husk Silica

Abstract

AbstractLow‐cost adsorbents from agricultural by‐products are intensively studied in water treatment, especially in arsenic removal for obtaining safe drinking water. Here, it is reported that a cheap and effective nano‐composite of iron–manganese oxide incorporated active rice husk silica (FMRS) for efficient removal of arsenic (As(III) and As(V)) from water, which is fabricated using a one‐pot synthesis. Fe3+ and Mn4+ in their oxides supported silica structure are successfully characterized. The FMRS (qe = 11.9 mg g−1) shows a remarkable enhancement of arsenic removal compared with the original rice husk ash (qe = 0.4 mg g−1) at initial [As(V)] = 5 mg L−1. The As(III) and As(V) adsorption are in good agreement with both Langmuir and Freundlich non‐linear isotherm models (R2 > 0.98), where the maximum adsorption capacities at pH 7 are found up to 19.1 and 20.3 mg g−1, respectively. The role of Mn4+ in enhancing the As(III) adsorption is also discussed. The FMRS exhibits high selectivity toward arsenic under the influences of other co‐existing anions in water (e.g., chloride, sulfate, and bicarbonate) and sustains a good arsenic removal efficiency during four cycles of the reusability test, suggesting a high potential of the fabricated adsorbent for long‐term removal of arsenic in field application.