Use of X-ray Absorption Spectroscopy and Esterification to Investigate Cr(III) and Ni(II) Ligands in Alfalfa Biomass

Abstract

Previously performed studies have shown that alfalfa shoot biomass can bind an appreciable amount of nickel(II) and chromium(III) ions from aqueous solution. Direct and indirect approaches were applied to study the possible mechanisms involved in metal binding by the alfalfa biomass. The direct approach involves investigations of the metal-bound alfalfa shoot biomass by X-ray absorption spectroscopic analysis (XANES and EXAFS). Results from these studies suggest that nickel(II) and chromium(III) binding mostly occurs through coordination with oxygen ligands. Indirect approaches consist of chemical modification of carboxylate groups that have been shown to play an important role in metal binding to the alfalfa biomass. An appreciable decrease in metal binding resulted after acidic methanol esterification of the biomass, indicating that carboxyl groups are entailed in the metal binding by the alfalfa biomass. In addition, base hydrolysis of the alfalfa biomass increased the binding of these metals, which further indicates that carboxyl groups play an important role in the binding of these metal ions from solution. Therefore, by combining two different techniques, our results indicate that carboxylate groups are the major ligands responsible for the binding of nickel(II) and chromium(III) by alfalfa biomass.

Removal of heavy metal from industrial wastewater using chitosan coated oil palm shell charcoal

“…Above the pK a value the chitosan adsorbent will be negatively charged. X-ray photoelectron spectroscopy spectrum by Tiemann et al (1999) and Dambies et al (2001) of chitosan biomass after contact with chromium (VI) at pH around 5, reveals that about 55% of chromium (VI) gets reduced to chromium (III). Similar bioreduction process can also be accomplished using alfalfa, seaweed, and some lyophilized plant tissue (Wittbrodt and Palmer, 1996;Lytle et al 1998).…”

Biosensors for heavy metals

“…Conventional techniques to analyse metals include cold vapour atomic absorption spectrometry, inductively coupled plasma mass spectrometry, UV visible spectrophotometry and X-ray absorption spectroscopy (APHA 1995;Breuil et al 1998;Tiemann et al 1998;Townsend et al 1998). These techniques, although highly precise, suffer from the disadvantages of high cost, the need for trained personnel and the fact that they are mostly laboratory bound.…”

Binding of Silver(I) Ions by Alfalfa Biomass (Medicago Sativa): Batch PH, Time, Temperature, and Ionic Strength Studies

“…Previous studies have shown that alfalfa biomass has the capability to recover heavy metal ions, such as Cu(II), Cd(II), Zn(II), Pb(II), and Cr(III), from aqueous solutions. In addition, alfalfa biomass is also able to reduce the oxidation state of other metals such as Cr (VI) and Au(III) (Gardea-Torresdey et al, 1996;Tiemann et al, 1999;Gardea-Torresdey et al, 1997;Gardea-Torresdey et al, 2000). Alfalfa, a forage commonly found throughout the U.S., may be an efficient alternative to high-cost silver recuperation processes, and the use of a natural product would make the process more environmentally friendly.…”