Thermal and spectroscopic studies on sorption of nickel(II) ion on protonated bakerÕs yeast V. Padmavathy a , Padma Vasudevan b, * , S.C. Dhingra a a Department of Chemical Engineering, Indian Institute of Technology, Hauz Khas, Delhi, 110 016, India b Centre for Rural Development and Technology, Indian Institute of Technology, Hauz Khas, Delhi 110 016, India Received 11 June 2002; received in revised form 28 January 2003; accepted 4 February 2003 Abstract Protonated form (Hy) of yeast was subjected to thermal analysis (TGA and DTG) in the temperature range 60– 800 °C. Chemically bound water volatilizes around 200 °C and the matrix undergoes extensive oxidative decom- position at 450 °C, the weight loss reaching 75% at 800 °C. The sorption capacity of the matrix for nickel(II) ion increases on heat treatment from 60 to 200 °C (from 16.9 to 25.0 mg/g), but was reduced on heating to higher tem- peraturesataninitialnickel(II)ionconcentrationof1200mg/g.TheFTIRspectraofHyandnickel(II)ionsaturated yeast, indicated that biosorption occurs on the sugar and nucleic acid regions, possibly involving –COOH and –NH groups. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: TGA; FTIR studies; Nickel(II) ion; Biosorption; Yeast 1. Introduction Uptake of toxic and heavy metal ions from waste waters and industrial wastes by certain types of micro- bial biomass especially algae (Figueira et al., 2000; Wong et al., 2000; Aksu, 2001), fungi (Gadd, 1990; Kapoor and Viraraghavan, 1995), bacteria (Beveridge and Murray, 1980) and other materials (Billie and Wightman, 1983; Ho and McKay, 2000) has been the subjectofmanyrecentstudies.Biosorptionofdeadcells hascertainadvantagesoverthatonlivingcells.Inactive biomass does not require supply of nutrients for cell growth, can be procured easily as waste products from industrial fermentation processes and is not sensitive to operating conditions like pH and temperature. Kapoor and Viraraghavan (1995) reviewed various methods of killing living cells like heat treatment, autoclavingandvacuumdrying,usingdifferentchemical modifications with acids, alkalis, detergents, organic chemicals like formaldehyde, glutaraldehyde and also mechanical dispersion. Several methods of immobiliza- tion (Volesky, 1987; Jeffers et al., 1991) have also been employed. It has been observed (Nakajima and Sakaguchi, 1986; Volesky, 1987; Brady et al., 1994a) that killing ofcellsbyheatingenhancedbiosorptionbythebiomass. Further, the temperature of heating of biomass has a significant effect on sorption capacity of metal ions (Sakaguchi et al., 1979; Strandberg et al., 1981; Avery and Tobin, 1992; Rapport and Muter, 1995; Omar et al., 1997). Tsezos and Volesky (1982) reported that uranium uptake increased with increase in tempera- tureofheatingofthebiomassfrom20to50 °C. Muter et al. (2001) observed that a decrease of the initial cell residual humidity from 72.5% to 8.2% increased the sorption of Cr(VI) by Candida utilis cells from 0.12 to 0.60mggdw 1 . Also, the release of intracellular com- pounds (nucleic acid) increased from 0.73 to 15.2 mggdw 1 . Chemosphere 52 (2003) 1807–1817 www.elsevier.com/locate/chemosphere * Correspondingauthor.Tel.:+91-11-26591156;fax:+91-11- 26591121. E-mail address: padmav@rdat.iitd.ernet.in (P. Vasudevan). 0045-6535/03/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0045-6535(03)00222-4