title: Use of ICP and XAS to determine the enhancement of gold phytoextraction by Chilopsis linearis using thiocyanate as a complexing agent.
abstract: Under natural conditions gold has low solubility that reduces its bioavailability, a critical factor for phytoextraction. Researchers have found that phytoextraction can be improved by using synthetic chelating agents. Preliminary studies have shown that desert willow (Chilopsis linearis), a common inhabitant of the Chihuahuan Desert, is able to extract gold from a gold-enriched medium. The objective of the present study was to determine the ability of thiocyanate to enhance the gold-uptake capacity of C. linearis. Seedlings of this plant were exposed to the following hydroponics treatment: (1) 5 mg Au L(-1) (2.5x10(-5) mol L(-1)), (2) 5 mg Au L(-1) + 10(-5) mol L(-1) NH4SCN, (3) 5 mg Au L(-1) + 5x10(-5) mol L(-1) NH4SCN, and (4) 5 mg Au L(-1) + 10(-4) mol L(-1) NH4SCN. Each treatment had its respective control. After 2 weeks we determined the effect of the treatment on plant growth and gold content by inductively coupled plasma-optical emission spectroscopy (ICP-OES). No signs of shoot-growth inhibition were observed at any NH4SCN treatment level. The ICP-OES analysis showed that addition of 10(-4) mol L(-1) NH4SCN increased the concentration of gold by about 595, 396, and 467% in roots, stems, and leaves, respectively. X-ray absorption spectroscopy (XAS) studies showed that the oxidation state of gold was Au(0) and that gold nanoparticles were formed inside the plants.
authors.affiliation: Environmental Science and Engineering PhD Program, University of Texas at El Paso, El Paso, TX 79968, USA. jgardea@utep.edu
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Gardea-Torresdey
authors.forename: Elena
authors.initials: E
authors.lastname: Rodriguez
authors.forename: Jason G
authors.initials: JG
authors.lastname: Parsons
authors.forename: Jose R
authors.initials: JR
authors.lastname: Peralta-Videa
authors.forename: George
authors.initials: G
authors.lastname: Meitzner
authors.forename: Gustavo
authors.initials: G
authors.lastname: Cruz-Jimenez
mesh_terms: D029402:Bignoniaceae / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D007202:Indicators and Reagents / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*; D013861:Thiocyanates / Q000737:chemistry*
chemical_list: D007202:Indicators and Reagents; D013861:Thiocyanates; D006046:Gold