Teruhisa Hongo

Preparation and performance of arsenate (V) adsorbents derived from concrete wastes

Solid adsorbent materials, prepared from waste cement powder and concrete sludge were assessed for removal of arsenic in the form of arsenic (As(V)) from water. All the materials exhibited arsenic removal capacity when added to distilled water containing 10-700 mg/L arsenic. The arsenic removal isotherms were expressed by the Langmuir type equations, and the highest removal capacity was observed for the adsorbent prepared from concrete sludge with heat treatment at 105°C, the maximum removal capacity being 175 mg-As(V)/g. Based on changes in arsenic and calcium ion concentrations, and solution pH, the removal mechanism for arsenic was considered to involve the precipitation of calcium arsenate, Ca3(AsO4)2. The enhanced removal of arsenic for the adsorbent prepared from concrete sludge with heat treatment was thought to reflect ion exchange by ettringite. The prepared adsorbents, derived from waste cement and concrete using simple procedures, may offer a cost effective approach for arsenic removal and clean-up of contaminated waters, especially in developing countries.

Synthesis and Characterization of Nanostructured Tungsten Oxide by Hard Template Method

Nanostructured WO3 was synthesized by a hard template method using platelet-shaped mesoporous silica SBA-15. The nanostructured WO3 consisted of nanorod arrays comprised of mixed crystalline tetragonal and monoclinic phases with the diameter of 8.5 nm and the length of 170-300 nm. The specific surface area was 30 m2/g, which was about 6 times higher compared to that synthesized without the template.