An XAS study of the binding of copper(II), zinc(II), chromium(III) and chromium(VI) to hops biomass

XAS and XPS studies on chromium-binding groups of biomaterial during Cr(VI) biosorption

“…This result means that the coordination environment of the chromium on the biomasses was also similar to that of Cr(III)-acetate, where Cr(III) is in an octahedral geometrical arrangement. The bonding distances of the chromium oxygen atoms were approximately the same lengths (as shown in Table S1, 1.96 Å for the Cr(III)-acetate and 1.97-1.99 Å for the Cr(III)-and Cr-laden biomasses, respectively), which corresponds to the Cr-O bond lengths cited in the literature [26][27][28].…”

“…Cardea-Torresdey et al [27] reported that Cr(VI) could be bound to an oat byproduct, but was easily reduced to Cr(III) by positively charged functional groups, which subsequently adsorbed to available carboxyl groups. Parsons et al [28] also reported the reaction of Cr(VI) with the biomaterial of hops, which resulted in the reduction of Cr(VI) to Cr(III), with the Cr(III) bound to the biomaterial with the same geometry as Cr(III)-acetate. These studies reached the same conclusions as found in this study, i.e., Cr(III) resulting from the reduction of Cr(VI) was bound to the carboxyl groups present on the brown seaweed, Ecklonia, biomass.…”

Copper isotope fractionation during its interaction with soil and aquatic microorganisms and metal oxy(hydr)oxides: Possible structural control

“…Parsons et al (2002) reported that for Cu(II) bound to a hop plant (Humulus lupulus), Cu-O distances are longer at pH 2 as compared to pH 5. Since carboxylate functional groups play a critical role in the biosorption of Cu(II) by hop biomass (Hejazi, 2001), this indicates that the light isotope enrichment of organic surfaces is possible, which is consistent with the measurements of this study.…”

Determination of thermodynamic parameters of Cr(VI) adsorption from aqueous solution onto Agave lechuguilla biomass

“…Cr(VI) is much more toxic than Cr(III) and has been considered to be mutagenic and carcinogenic [3]. Due to the health hazards of hexavalent chromium, numerous studies concerning its removal from aqueous solutions have been performed using different processes [7][8][9][10][11][12]. However, few studies have analyzed the effect of temperature and reduction of Cr(VI) to Cr(III) in the bioadsorption process from the thermodynamic view point [13,14].…”