Green conversion of hazardous red mud into diagnostic X-ray shielding tiles.

Red mud is a solid hazardous alumina industrial waste, which is rich in iron, titanium, aluminum, silicon, calcium, etc. The red mud contains 30-60% of hematite, which is suitable for shielding high energy X- and gamma rays. So, the iron rich red mud was converted into diagnostic X-ray shielding tiles through ceramic route by adding a certain weight percentage of BaSO4 and binders (kaolin clay or sodium hexametaphosphate) with it. The kaolin clay tile possess sufficient impact strength (failure point is 852 mm for 19 mm steel ball) and flexural strength of ~25 N/mm2, which is suitable for wall applications. The 10.3 mm and 14.7 mm thick red mud:BaSO4:kaolin clay tile possess the attenuation equivalent to 2 mm and 2.3 mm lead at 125 kVp and 140 kVp, respectively. No heavy elements were found to leach out except chromium and arsenic from the sintered tiles. However, the leaching of Cr (0.6 ppm) and As (0.015 ppm) was found to be well below the permissible limit. These tiles can be used in the X-ray diagnosis, CT scanner, bone densitometry, and cath labs instead of toxic lead sheet and thereby to protect the operating personnel, public, and environment from radiation hazards.