ORIGINAL PAPER Evaluation of metabisulfite and a commercial steel wool for removing chromium(VI) from wastewater Caio F. Gromboni Æ George L. Donati Æ Wladiana O. Matos Æ Eduardo F. A. Neves Æ Ana Rita A. Nogueira Æ Joaquim A. No ´brega Received: 9 June 2008 / Accepted: 25 November 2008 / Published online: 17 December 2008 Ó Springer-Verlag 2008 Abstract Efficiency of metabisulfite and a commercial steel wool as reducing agents in the removal of Cr(VI) from wastewaters was evaluated. Chromium(VI) was converted to Cr(III), precipitated with NaOH, and removed by filtration. A reduction of more than 1.0 9 10 5 and 4.0 9 10 5 fold in total Cr and the Cr(VI) concentrations, respectively, was observed by employing steel wool mas- ses as low as 0.4420 g to 30-mL solutions of wastewater. Chromium(III) hydroxide obtained after the treatment was recycled and used as marker in cattle nutrition studies. The liquid residue obtained after the treatment was reused as precipitation agent replacing NaOH. Keywords Total Cr  Cr(VI)  Wastewater treatment  Metabisulfite  Steel wool Introduction The most common chromium oxidation states are Cr(III) and Cr(VI). However, each of these species presents distinct characteristics. Chromium(III) is considered an essential nutrient and it is involved in the metabolism of glucose, lipids, and proteins. The deficiency of this mineral in the diet is related to high concentrations of glucose in the blood, high levels of cholesterol and triglycerides, and the reduction of HDL (high density lipoproteins) (Anderson 1998). On other hand, Cr(VI) is toxic to human beings, animals, and plants even at low concentrations, and it is related to several clinical problems such as nasal irritation and ulceration, skin hyper-sensitivity reactions, dermatitis, and even lung cancer. The toxic properties of Cr(VI) result from the free diffusion of this species through the cellular mem- brane (Shrivatava et al. 2002). Chromium compounds present different applications. They are mainly used as anti-corrosive, in the constitu- tion of pigments, and in the industry of refractories. Sulphochromic solution, for instance, is still used in standard methods to determine organic matter in soils, chemical oxygen demand (COD) in water quality studies, and laboratory glassware (Guillemont et al. 2006; Shervedani and Babadi 2006). These diversified and important applications make chromium compounds important sources of Cr(VI) contamination to the environment. According to the Environmental Protection Agency (EPA) and the European Environment Agency (EEA), the maximum chromium concentrations allowed for wastewa- ter for hexavalent [Cr(VI)] and trivalent chromium [Cr(III)] are 0.1 and 0.5 mg L -1 , respectively (US EPA 2003; I.C. Consultants 2001). The limits allowed for some This article is in memory of E. F. A. Neves. A. R. A. Nogueira (&) Embrapa Pecua ´ria Sudeste, Rodovia Washington Luı ´s km 234, P.O. Box 339, Sa ˜o Carlos 13560970, Brazil e-mail: anarita@cppse.embrapa.br URL: http://www.cppse.embrapa.br C. F. Gromboni  G. L. Donati  W. O. Matos  E. F. A. Neves  J. A. No ´brega Departamento de Quı ´mica, Universidade Federal de Sa ˜o Carlos, Rodovia Washington Luı ´s km 235, Sa ˜o Carlos 13565905, Brazil URL: http://www.dq.ufscar.br Present Address: G. L. Donati Department of Chemistry, Wake Forest University, Salem Hall, 7486, Winston-Salem, NC 27109, USA 123 Environ Chem Lett (2010) 8:73–77 DOI 10.1007/s10311-008-0194-6