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

摘要

Low-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 (q(e) = 11.9 mg g(-1)) shows a remarkable enhancement of arsenic removal compared with the original rice husk ash (q(e) = 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 (R-2 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.