Chromium is used in many industries, including steel production, electroplating, pigments, and tanning. Discharge from these industries into waterways is a problem. In particular, Cr(VI) has a range of toxic biological and ecological effects due to its ability to diffuse through cell membranes and oxidize biological molecules. The Environmental Protection Agency (EPA) has set 0.01 ppm as the maximum level of chromium permitted in community water systems.
Antonio Alberto da Silva Alfaya and colleagues, Universidade Estadual de Londrina, Brazil, have found a cheap and simple way of removing Cr(VI) ions from contaminated water. They use natural cotton fibers coated in a ZrO2 surface film as an anion exchanger. The material was shown to be very effective at low Cr(VI) concentrations (as low as 0.0052 ppm). It has a high absorption capacity (69 mg/g) and fast absorption rates (8.66 × 10−3 g/mmol min) which make it very attractive for water purification purposes.
- Cotton Fiber/ZrO2, A New Material for Adsorption of Cr(VI) Ions in Water
A. A. Muxel, S. M. N. Gimenez, F. A. S. Almeida, R. V. S. Alfaya, A. A. S. Alfaya,
Clean Soil, Air, Water 2011, 39 (3), 289–295.