Mechanisms of nickel sorption on pyrophyllite: Macroscopic and microscopic approaches

Journal Article · Fri Nov 01 04:00:00 EST 1996 · Soil Science Society of America Journal

DOI:https://doi.org/10.2136/sssaj1996.03615995006000060022x· OSTI ID:458669

Scheidegger, A M; Sparks, D L ^[1]; Fendorf, M ^[2]

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1. Univ. of Delaware, Newark, DE (United States)
2. Lawrence Berkeley National Lab., CA (United States)

A thorough understanding of the sorption mechanisms of heavy metals on soil mineral surfaces is of fundamental importance to the environment. This study examined Ni(II) sorption mechanisms on pyrophyllite. The removal of Ni from solution was studied as a function of pH (pH = 5-8.5), initial Ni concentration (1 x 10{sup -4} to 1 x 10{sup -2} M), and ionic strength (0.01-1 M). The data suggest that Ni sorption behavior can be divided into two distinct pH regions. In the lower pH region (i.e., pH < 7), relative Ni sorption increased with decreasing ionic strength and initial Ni concentration. The adsorption maximum at pH= 6 was significantly higher than the cation-exchange capacity (CEC) at the same pH. Based on these findings, we propose that both specific and nonspecific adsorption are involved. In the higher pH region (pH > 7), nickel sorption becomes slow and does not seem to be affected by the ionic strength and the initial Ni concentration. We employed high-resolution transmission electron microscopy (HRTEM) to ascertain whether any alteration in the surface structure of pyrophyllite could be detected after reaction with Ni at pH > 7. Surface deposits, not present on untreated samples, were found. We hypothesize that the formation of a mixed Ni-Al hydroxide phase on the pyrophyllite surface is responsible for the sorption behavior above pH 7. 56 refs., 8 figs.

• Sponsoring Organization: USDOE
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 458669
• Journal Information: Soil Science Society of America Journal, Journal Name: Soil Science Society of America Journal Journal Issue: 6 Vol. 60; ISSN 0361-5995; ISSN SSSJD4
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
40 CHEMISTRY
ADSORPTION
ADSORPTION ISOTHERMS
ALUMINIUM HYDROXIDES
KINETICS
NICKEL
NICKEL HYDROXIDES
PH VALUE
PYROPHYLLITE
SORPTION
TRANSMISSION ELECTRON MICROSCOPY
X-RAY SPECTRA