2134/3080
Peter Warwick
Peter
Warwick
Edu Inam
Edu
Inam
Nicholas D.M. Evans
Nicholas D.M.
Evans
Arsenic's interactions with humic acid
Loughborough University
2007
arsenic
humic substances
Speciation
ICP-AES
Chemical Sciences not elsewhere classified
2007-11-30 11:45:14
Journal contribution
https://repository.lboro.ac.uk/articles/journal_contribution/Arsenic_s_interactions_with_humic_acid/9394061
The environmental mobility of arsenic is primarily controlled by adsorption onto
metal oxide surfaces, particularly iron, aluminium and manganese. Humic acid (HA)
may interfere with this adsorption, thereby increasing arsenic mobility. This study has
characterised the interaction of arsenic with HA in a system consisting of HA with
As(III), As(V) and DMAA. Three sets of batch experiments were performed at
varying pH (3-12), ionic strength (I = 0 - 0.4), concentration of each arsenic species (0
- 100 mg dm-3) and HA concentration (0 - 10 g dm-3). Arsenic species were shown to
react with humic acid. The interaction is postulated to involve bridging metals and
deprotonated functional groups within the HA. The association is dependent on pH,
ionic strength and arsenic concentration. The extent of the interaction was greater in
the pH range 8 – 10 for As(V) and DMAA, while it extended to pH 12 for As(III).
The strong pH dependency is probably due to the aqueous speciation of arsenic. The logarithmic conditional association constants for the reactions were found to be 1.97 ±
0.02, 1.58 ± 0.07 and 1.50 ± 0.10 for As(V), As(III) and DMAA respectively. These
values indicate the formation of weak complexes with humic acid.