Ž . Advances in Environmental Research 4 2000 6977 Solid-state 113 Cd NMR studies of metal-binding to a Datura innoxia biomaterial Hongying Xia, Gary D. Rayson  Department of Chemistry and Biochemistry, Box 30001 MSC 3C, New Mexico State Uni  ersity, Las Cruces, NM 88003, USA Accepted 13 March 2000 Abstract The use of both slurry and solid-state 113 Cd NMR has been applied to the investigation of the chemical moieties involved in cadmium ion binding to a biosorbent. This material was derived from fragments of cell walls cultured from the plant Datura innoxia. Comparison of the 14-ppm chemical shift of the bound metal ion with that of model ligands directly demonstrated the involvement of carboxylate-containing binding sites. The application of solid-state cross-polarization magic angle spinning techniques to the metal-bound material yielded a broad resonance. This was interpreted as indicative of the presence of a distribution of chemically similar sites.  2000 Elsevier Science Ltd. All rights reserved. Keywords: NMR; Biomaterials; Datura innoxia; Cadmium; Binding 1. Introduction The utility of algae and other biomaterials as possi- ble sources of inexpensive sorbents for the removal of environmentally significant inorganic metal ions from Ž aqueous solution has been studied Darnall et al., 1986; . Volesky, 1990; Drake and Rayson, 1996 . Even so, few applications of these biomaterials have been reported for the remediation of contaminated water. One expla- nation for the under-utilization of these biomaterials is a general inability to accurately predict their binding characteristics in complex real-world conditions. This requires understanding the fundamental chemistry of the metal binding process, including the identity of the functional groups responsible for the metal ion bind- ing.  Corresponding author. Tel.: 1-505-646-5839; fax: 1- 505-646-2649. Ž . E-mail address: garayson@nmsu.edu G.D. Rayson . Biomaterials typically have a very complex chemical composition. The binding of metal ions in solution by Ž . non-living biomaterials i.e. ‘biosorption’ has been proposed to involve functional groups associated with proteins, polysaccharides, lignin, and other biopolymers Ž in and on the biomass cell wall Crist et al., 1981; . Summers, 1988; Gardea-Torresdey et al., 1990 . Speci- fically, amino, thioether, sulfhydryl, carboxyl, carbonyl, imidazole, phosphate, phenolic, hydroxyl and amide functionalities have been indicated as possible moieties involved in the biosorption of metal ions. Although each of these functionalities is a plausible contributor to metal binding to plant materials, the involvement of only a small subset has been verified experimentally Ž through the use of luminescence Ke and Rayson, 1992; Ke et al., 1992, 1993, 1994; Drake et al., 1996, . Ž 1997 , NMR Majidi et al., 1990; Ke and Rayson 1992; Zhang and Majidi, 1993; Larive et al., 1996; Xia and . Ž Rayson, 1998 , and X-ray spectroscopy Watkins et al., . 1987; Gardea-Torresdey et al., 1999 . Europium-III luminescence has been extensively ap- 1093-019100$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. Ž . PII: S 1 0 9 3 - 0 1 9 1 00 00010-1