Adsorption Behavior of Au(III) Complex Ion on Nickel Carbonate and Nickel Hydroxide

Autor: Daisuke Kawamoto, Hironori Ohashi, Hiroaki Ando, Yoshihiro Okaue, Takushi Yokoyama, Makoto Tokunaga, Tamao Ishida, Tetsuo Honma
Rok vydání: 2018
Předmět:
Zdroj: Colloids and Surfaces A: Physicochemical and Engineering Aspects. 537:383-389
ISSN: 0927-7757
DOI: 10.1016/j.colsurfa.2017.10.028
Popis: When preparing gold(Au) supported on NiO catalysts by the coprecipitation method, the chemical state of the coprecipitated Au differed when Na 2 CO 3 and NaOH were used as the coprecipitating reagents. In this preparation using Na 2 CO 3 and NaOH solutions, precursor of support metal was largely NiCO 3 and Ni(OH) 2 , respectively. Therefore, the different chemical states of Au may be controlled by the interaction between the [Au(OH) 4 ] − and precursor of support metal. The aim of this study is to elucidate why the chemical state of Au differs when using NiCO 3 and Ni(OH) 2 . Adsorption experiments of [Au(OH) 4 ] − onto NiCO 3 or Ni(OH) 2 were performed. The Au concentration in the filtrate was determined by atomic absorption spectrometry (AAS). The chemical state of the adsorbed Au was examined by X-ray absorption(XA) spectroscopy. The adsorption experiments suggested that the change in surface charge on NiCO 3 and Ni(OH) 2 electrostatically controls the adsorption of [Au(OH) 4 ] − . The XA analysis indicated that the chemical state of [Au(OH) 4 ] − adsorbed on NiCO 3 is maintained because of electrostatic interactions, while some of the [Au(OH) 4 ] − adsorbed on Ni(OH) 2 may be reduced to Au(0) due to specific adsorption-accompanying distortion of the square planar structure of the adsorbed [Au(OH) 4 ] − .
Databáze: OpenAIRE
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